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INDIVIDUAL DIFFERENCES IN HEMISPHERIC SPECIALIZATION

A. Glass (Editor)

University of Birmingham

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DEC 0 4 1987 I

BASIC RESEARCH LABORATORY

Michael Kaplan, Director

U. S. Army

Research Institute for the Behavioral and Social Sciences

November 1987

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ARI Research Note 87-56

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4. TITLE (-«nd StiblHI.)

INDIVIDUAL DIFFERENCES IN

HEMISPHERIC SPECIALIZATION

7. AUTHONfa)

A. Glass (Editor)

t. PERFORMING ORGANIZATION NAME AND ADDRESS

University of Birmingham

Medical School, Department of Anatomy

Birmingham, England B15 2TJ

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U.S. Army Research Institute for the Behavioral

and Social Sciences, 5001 Eisenhower Avenue,

Alexandria, VA 22333-5600

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READ INSTRUCTIONS

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IB. SUPPLEMENTARY NOTES

Michael Kaplan, contracting officer's representative

Research note is the proceedings of a NATO ARW held in Maratea, Italy,

October 1984. >,. 4 i

It. KEY WORDS (Con(/nu» on ttrttm» »14» II n«. •••«ry mnd Idontlly by block number;

Cerebral Hemispheric Specialization Measurement

^Electrophysiological Asymmetries^ Gender , Anatomical/Circulatory Asymmetries • Handedness . -^-

Perceptual Behavioral Asymmetries^' Psychopatholoqy

Individual Differences.—

20. ABSTRACT rCmilmum om rmvmn I Idmttlfy »» 6l«cft numbm

Neurologists, psychologists, and neuroanatomists have lonq recognized that

>the left cerebral hemisphere is specialized fcr lanauaqe and possibly other

symbolic processes, and that the right hemisphere has a visuospatial specialization. Aphasia affecting the cerebral nemisphere on the same side as the

preferred hand has also long been understood.

Individual variation in degree and direction of specialization due to nender

and handedness has, until recently, been regarded as a barrier to the (OVER)

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ARI RESEARCH NOTE 87-56

20. ABSTRACT (continued)

investigation of lateral ization, and at the same time individual differences

have been used to explain differences in lateralization measurements on a

post-hoc, basis. ' / - '

Cross^comparisons of several methods for assessing hemispheric specialization, have been made in this volume,- methods such as perceptual/behavioral,

clinical/neurological, electrophysiological, and "real-time" techniques for

assessment of cerebral orientation. Errors of assessment should thereby be

differentiable from individual variations in hemispheric specialization.

It is the consensus of.those whose views are expressed in this research note

that hemispheric specialization may reemerge, not as a monolithic, absolute

structural concept, but as a dynamic process, modulating the utilization by

differential s^ategy, activation, and arousal, of a relative structural

specialization of the hemispheres in individual subjects.

The research note also considers the importance of these concepts for

psychopathology. u , „ _ _ .^ ^

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CONTENTS

Introduction 1

DEFINING THE ISSUES

Individual Differences in Healspherlc Specialization: Source«

and Measureaent 18

S.J. Segalowltz

Cerebral Laterallty: Rube Goldberg at the Bauhaus? 24

John C. Marshall

Inpllcations of the Right Shift Theory of Handedness for

Individual Differences in Hemispheric Specialization 32

Marian Annett

Is Cerebral Lateralization a Graded or a Discrete

Characteristic ? 43

John C. Marshall

INDIVIDUAL DIFFERENCES IN CEREBRAL ANATOMICAL ASYMMETRY AND

CIRCULATORY ASYMMETRY

Individual Differences in the Anatomy of the Corpus Callosum:

Sex, Hand Preference, Schizophrenia and Hemisphere

Specialization 46

Sandra F. Witelson and Debra L. Klgar

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Hemispheric Specialization and Regional Cerebral Blood

Flow

Ruben C. Cur and Raquel E. Gur

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INDIVIDUAL DIFFERENCES IN ELECTROPHYSIOLOGICAL ASYMMETRIES

Individual Differences in the Asymmetry of Alpha

Activation 93

Stuart Butler and Alan Glass

Age and Sex Related EEC Configurations in Normal

Subject Ill

Appendices

P. Flor-Benry, Z.J. Roles and J.R. Reddon

Attentional Factors and Individual Differences Reflected

In the EEC 139

Williaa J. Ray

Longitudinal Auditory Evoked Responses and the Development

of Language 159

Dennis L. Molfese and Victoria J. Molfese

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Differences between Anhedonlc end Control Subjects L>iV^

In Brain Hemispheric Specialization as Revealed

by Brain potentials 172 !>./>'.

Brigitte Rockstroh and Werner Lutzenberfer >''/vi

Hemispheric Differences in Relation to Sacking 184 /^'v|

Thomas Elbert and Niels Birbaumer i^i-^l;

Interval Histogram Analysis of EEC Hemispheric

Activity in Schizophrenie 196 S£v.<

Antonio E. Fuente and Lelon J. Peacock '•/vOv

INDIVIDUAL DIFFERENCES IN BEHAVIOURAL INDICES OF

CEREBRAL ORIENTATION

Organization 272

A.M. Weber and J.L.Bradshaw

ASYMMETRIES IN PSYCHOPATHOLOGY AND INDIVIDUAL DIFFERENCES

Individual Differences in Dynamic Process Asymmetries in the

Normal and Pathological Brain 291

John H. Gruzelier

The Evolving of the Homeostatic Brain: Neuropsychological

Evidence 320

Michael Miran and Este Hiran

An Argument concerning Schizophrenia: the Left Hemisphere

Drains the Swamp... 338

Rue L. Cromwell

Cerebral Laterality i Schizophrenia:

a Review of the Intcrhcmispneric Disconnection

Hypothesis 347

John H. Gruzelier

Individual Differences in Cerebral Laterallzatlon:

Homeostatic Brain Functions of

Schizophrenics 36e

Michael Miran and Esta Miran

Cerebral Laterality and Psychopathic

Disorders 382

E.A. Serafetinides

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Age and Sex Differences In Lateral Asymmetries ^^j

to Visual and Tactile Stimuli 205 Ü'-VW V.-A"

Andrew W. Young, Pamela J. Blon and Kathryn R. McWeeny ''.'J'\J\•'

Estimating Cerebral Asymmetry and Interhemlspheric

Transmission Time from Individual Differences in '"•"/v"

Bimanual Response to Lateral Ized Stimuli 222 ^V^'

W.N. Schofield {J"-">V

Self-report of Neuropsychological

Dimensions of self-control 256

Thomas R. O'Connell, Don M. Tucker and Thomas B. Scott

Handwriting Posture and Cerebral .\.1 W* -*

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Contributors 387

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INTRODUCTION: INDIVIDUAL DIFFERENCES IN HEMISPHERIC SPECIALIZATION

PREAMBLE

The "Thlnk-Tank"

At the outset of the Workshop (of which this volume is the record), it

was pointed out that the Workshop itself was, in current parlance, a sort of

transient "Think-tank", meaning an establishment or institute temporarily

housing the "thinkers"-the participants. It is interesting that this

expression evolved from the term "think-tank" signifying head or cranium.

This quotation can be taken as an example of the earlier meaning:

"... a roscoe said: 'Whr-r-rang!' and a lead pill split the ozone past

my noggin... Neon lights exploded inside my think-tank ..Kane Fewster was on

the floor. There was a bullet hole through his think-tank." (Perelman,

1951).

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The original meaning could also be associated with the Workshop,

theme might be encapsulated by the question: what models of cerebral

organization inside the "think-tank" can be inferred from measures of

individual differences in hemispheric specialization?

The

Since the earlier usage evolved, much of relevance to the Workshop has

occurred in the Neurosciences and related fields, but it could be argued

that among these, together with a greatly increased knowledge of cerebral

dominance, the development of the computer and the parallel appreciation

that human cognitive processes may be mimicked by it, may have been among

the most relevant. It could be speculated, perhaps, that the extension of

the meaning of "Think-tank" has in some way, symbolised these developments.

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Origin of the Workshop

This volume has its origin in a NATO Advanced Research Workshop on

"Individual Differences in Hemispheric Specialization" held in Maratea,

Italy in October, 198A.

The concept of the Workshop, in turn, sprang from a Round Table

entitled "Hemispheric Specialization and Lateral Asymmetries in the EEC"

given under the auspices of the Second European Winter Conference on Brain

Research, in Chamonix, France, in March 1982. The papers emanating from the

Round Table were later published as a Special Issue of Biological Psychology

(Glass, 1984). The earlier Round Table was divided Into two sections, one

dealing with normal lateralization of cognitive function and psychophysiological studies and the other concerned with EEC asymmetries as signs

of disturbed la.erality In psychiatric disorders. Insofar, as the plan of

the Workshop followed that of the Round Table, although it broadened and

extended the plan which the Round Table adopted, the contents of the

Workshop and Round Table correspond. After an initial section in which the

issues are defined, this volume is divided into three sections, dealing with

the normal brain, and corresponding to the first part of the Round Table.

The first of these three sections deals with individual differences in

hemispheric specialization from the viewpoint of cerebiil anatomical and

circulatory asymmetries (although the emphasis is upon hemispheric

specialization related to individual differences in the anatomy of the

corpus callosum). The second section covers hemispheric specialization in

respect of electrophysiologlcal asymmetries largely, but not exclusively, in

relation to asymmetries in the EEC alpha rhythm. The third section covers

behavlouial indices of cerebral orientation, in respect to lateral

asymmetries in visual and tactile stimuli and divided field studies. The

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second part of this volume which covert psychopathologlcal and psychiatric

aspects of individual differences in hemispheric apeclallzatlon, corresponds

to the second section of the Round Table.

Theme of Workshop

The original theme of the Workshop was to have encompassed the theme of

the Round Table, to Include not only EEC alpha and evoked potential (VER,

CNV, event-related potential studies) measures of lateral asymmetry in

relation to hemispheric specialization but also the cross-comparison of

these with other measures of assessment of hemispheric specialization

including imaging asymmetry techniques such as Positron Emission Tomography

(PET) (Raichle, 1985), blood flow studies such as those of Lassen, Ingvar

and Sklnhoj (1978) and Gur and Reivlch (1980), and Gur and Cur (this vo'.ume)

clinical and neurological evidence of latersllzatlon, together with the

behavioural perceptual techniques of dlchotlc listening (Rimura, 1967) and

divided field studies (Beaumont, 1982). The aim, with a methodological

emphasis was to cross-compare the results of assessment of laterallty by

these techniques in Individuals In specific clusters such as gender and

handedness groups and In clusters encountered in psychiatry and

psychopathology.

However, valuable such a methodologically based comparison of different

techniques might be, it would not have had the conceptual value appropriate

for a NATO workshop, so a new theme was evolved, in the formulation of the

new theme much was owed to the insight of my colleague Dr. S. R. Butler who

drew attention to a concept formulated by Segalowltz. The problem of

individual variation in lateralizatlon had been highlighted by Segalowltz

and Bryden (1983) who emphasized the importance of individual differences in

cerebral lateralizatlon for cognitive function. Evidence from brain

imagery, cerebral blood flow patterns of distribution, divided field studies

and dlchotlc listening studies together with clinical examination of the

effects of lateralized lesions indicated that the pattern of functional

specialization for language was not consistent across individuals. Some of

the differences were correlated with handedness some with gender, although

not to a sufficient extent to account for them all. Thus the same

"ingredients" (i.e. methods of laterallty assessment) could be used as for

the earlier formulation of the Workshop theme, but with a significant shift

of emphasis from the purely methodological to that of a fresh but related

concept, that of individual differences in hemispheric specialization. The

concept of individual differences in language lateralizatlon or functional

specialization was broadened to Include together with the conventional

cognitive functions of the "left" hemisphere, the cognitive functions of the

"right" hemisphere (Bogen, 1969), encapsulated in the term "hemispheric

specialization", that is, in individual differences in the cognitive

specialization of both cerebral hemispheres, including its variation in

geodet and handedness groups among other factors and in effect comparing

different methods of laterallty assessment.

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•' Thus, the proposal for Che Workshop was redrafted extensively drawing

on the original concept of individual differences in language lateralizatlon

(Segalowltz and Bryden, 1933, and Segalowltz, see this volume) to include

not only language but other lateralizable functions of both left and right

hemispheres. The basic idea in the original proposal of « comparison of the

different methods of assessment of hemispheric specialization in clusters of

individuals i.e. gender «nd handedness, familial laterallty groups,

developmental groups and, of course, psychiatric and psychopathologlcal

groups was retained and was implicit in the new context.

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"Crossed Aphasia" «nd Associated Factor»

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The problem of individual differences in hemispheric specialization had

emerged in the study of task-related EEC alpha asymmetries in different

groups of normal subjects, specifically gender and familial handedness

groups (Glass, Butler and Carter, 1984; Butler, 198A). But, to retrace the

steps, it was an important and challenging problem, generally, potentially

apparent since the time of Broca (1865). Indeed as early as the end of the

nineteenth century Bramwell (1899) used the term "crossed aphasia" to

describe individu&l patien s who differed from or vere exception;: to Broca's

generalization that, uniformly, the left hemisphere was specialized for

language and that aphasia or dysphasia rarely or never occurred after a

lesion of the right hemisphere. "Crossed aphasia" in both dextrals and

•inistrals (setting aside discussion of the aetiology) was defined as

aphasia or dysphasia occurring as the result of a cerebral lesion which was

ipsilateral not contralateral to the preferred hand. It was encountered in

inistral as well as dextral patients. Thus, in both right and especially

in left banders there is long established clinical evidence of individual

differences in language lateralization (reversed dominance) (Zangwill,

1982). This conclusion is supported by evidence derived from the use of

other techniques for assessing lateralization. Right banders, in a sample

of normal subjects, showed greater suppression of EEC alpha rhythm over the

left hemisphere when performing mental arithmetic, but left banders almost

no alpha asymmetry, suggesting that the verbal-symbolic cerebral function of

left banders was more strongly lateralized than that of right banders

(Butler and Glass, 1974) or that a greater proportion of left handed than

right banders had reversal cf dominance (see Butler and Glass, this volume;

and Marshall this volume, in regard to graded versus discrete effects of

lateralization). The conclusion regarding individual differences is

supported by evidence derived from earlier behavioural assessment of

lateralization. For example, in dichotic listening studies, Satz,

Achenbach, Pattishall and Fenncll (1965) showed that left and right ear

difference scores were twice as large for dextrals as sinistrals.

Sinistrals showed no LVF superiority for recognising dot patterns (Harcum

and Dyer, 1962) and no differences between sides to a unilateral auditory

stimulus (Frovins and Jeeves 1975).

The effects of familial laterality on cerebral dominance have also been

Investigated. Recovery from aphasia, for example, was faster if there were

left handed relatives (Zangwill, 1960). Sinistrals with left handed

relatives developed speech disorders with equal frequency after either left

or right sides lesions, sinistrals with only dextral relatives tended to

develop aphasia after only left sided lesions (Hecaen and Sauguet, 1971).

RVF superiority for verbal material was reduced in non-familial sinistral

right banders. A left banded relative reduced the probability of a left ear

superiority for the recognition of verbal material in right handers (Satz,

Achenbach and Fennell, 1967) and left banders (Zurif and Bryden, 1969).

Thus, a close sinistral relative Increases the probability of weak or even

reversed lateralisatlon of cerebral function. McKeever and VanDeventer

(1977) had shown a familial laterality effect in left banded subjects in

that left banders with left banded relative? produced a significant right

visual field superiority for tachistoscopically presented verbal material,

indicating a left hemisphere dominance for language, which left handed

subjects without left handed relatives did not. No such familial laterality

effect was found In right banders, however. Using dichotic listening

studies, Lishman and McMeekan (1977) found that a family history of

sinlstrality among left banders was associated with smaller ear difference

scores, indicating reduced lateralisatlon or bilateral representation of

language, equally in left dominant and right cerebrally dominant left

banders.

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AIMS OF THE WORKSHOP

Therefore, it must be appreciated that, to attempt to define the alms

of the Workshop In terms of the elucidation of the role of Individual

differences In hemispheric specialization, there would appear to be a single

key Issue. This appears to be that the lateral asymmetry of human cerebral

function is descrlbable at one extreme in terms of the variation in

cognitive strategies employing one healsphere rather than the other from one

Individual to another, or, from task to task performed by a single

Individual and the intrinsic "absolute" functional identity of the

hemispheres, what is termed the dynamic process model versus the fixed

structure model (see Gruzelier, this volume; Cohen, 1982). It is worth

clarifying the distinction between a fixed structure model of cerebral

asymmetry and a gross morphological feature of cerebral asymmetry, for

example, that between left and right plena temporales. A gross

morphological asymmetry can only be one component of the fixed structural

model, as Marshall, (this volume) points out, the relationship between size

and hemispheric specialization or local gross cerebral asymmetry is inferred

from an assumptive relationship between size and proficiency.

The models of hemispheric specialization that we shall consider have

been categorised (Cohen, 1982) as either absolute or relative fixed

structure models where a given cognitive function is completely laterallzed

to one hemisphere and relative models in which a given function is performed

preferentially, better, or more efficently, by one hemisphere than the

other.

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Until relatively recently, the possibility of individual variation in

hemispheric specialization had been regarded as stumbling-block in the

assessment of human cerebral functional organization. This has happened

because, as Segalowltz has pointed out, (Segalowitz and Bryden, 1983;

Segalowitz, see this volume), the analytical techniques for determining

laterallzable functions have been limited.

Analyses currently employed have not in general permitted us to

distinguish variation due to differences in individual hemispheric

specialization, related to expected biological or experiential variability

from the unavoidable errors of measurement made in the various types of

assessment of laterality in these individual subjects. Taking a specific

example, although one which is not necessarily the most familiar, in

measuring EEC alpha asymmetry during mental arithmetic, suppression being

greater over the more active hemisphere, the amplitude of the alpha rhythm

then, is lower during calculation over the left side of the brain in righthanders. However, analyses currently employed have not allowed us to

distinguish variation in asymmetry of the alpha rhythm, due to differences

in individual hemispheric specialization or even individual differences in

hemispheric usage or utilization from unavoidable errors of measurement made

in the electrophysiological and other types of assessment of cerebral

laterality. Bryden (1982), for example, has pointed to the existence of

factors which may be unrelated to the lateralization of language function or

even to hemispheric specialization and which may cause lateralization of the

perceptual measures of asymmetry in dichotic listening studies and in

divided field studies (split field tachistoscopy), factors such as

variation in strategies used to perform the tasks and attentional biases

which may contribute, it is suggested, to the variability in measurement of

lateralization. One could add another source of variance which might simply

be that due to asymmetries of function in the primary receptor organs or

their centripetal connections, which cannot always be controlled for

satisfactorily. These are valid points, for, as Cohen (1982) has pointed

out, a model of hemisphere asymmetry is essentially a neurological model.

This has the consequences that the model must incorporate all the relevant

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design procedures for rejection of sensory and motor asymmetries, among

other features, Into the proposed experiments.

The Inflation of the error of measurement by the biological variation

of Individuals has been an apparent stumbling block, because It has tended

almost outweigh the main outline of the "generalised" case, that the left

hemisphere Is specialized for language and the right for vlsuospatlal

function. Now that these main outlines have, apparently by consensus,

received clarification by the experimental efforts of the past decades and

because of the relative measure of agreement reached by perceptual,

clinical-neurological and "realtime" (Including EEC and evoked response)

indices of cerebral orientation. It may be profitable to take stock, as

attempted In this volume and to study the factors affecting variation In

hemispheric specialization between Individuals. At the same time. It must

be borne In mind that such Individual differences or variation may well tend

to undermine such generalisations concerning cerebral functional

organisation that have cost so much to achieve. Although Popper (1972) has

stated that the function of experimental test or trial can only result In

the disproof, not the proof of hypotheses. It Is a paradox that no prizes

are offered for negative results. Yet It may be that In this volume we are

approaching the point of dissolution of the paradigm where consensus give

way to dlssensus (Laudan, 1984) and a fresh paradigm may emerge. To quote

Schofleld (this volume) In the context of Individual differences in bimanual

response to laterallzed stimuli and referring to gender differences.

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"It Is one thing to find that males and females choose, possibly as set

by unnoticed situatlonal Influence, prior experience, or experimenter

reactivity, different task strategies, either linguistic or non-linguistic,

and quite another to propose that there are functional brain differences

between males and females".

Factors such as handedness, familial laterallty, gender, developmental

experience, literacy, diversity In the cognitive strategies adopted In

problem solving may each contribute to this Individual variation. Indeed,

It would not be surprising If one method of assessing specialization Is

more appropriate to a particular factor than to another. It was, at the

outset of the Workshop, the aim (or hope) that by the cross-comparison of

the various asymmetry measures, it should have been possible to develop

guidelines and future strategies for teaslng-out the relative contributions

of those factors affecting cerebral orientation. The reader will be able to

ascertain how far this hope has been fulfilled, bearing In mind some of the

caveats that have already been put forward. Nevertheless, to quote

Segalowltz and Bryden (1982): "The field of experimental neuropsychology

has not advanced beyond the stage where error of measurement and Individual

differences In brain organisation can remain confounded". The reverse side

of the coin is that the extent of non-pathological individual differences In

cerebral orientation may be far greater than was once suspected.

This need to find out at a fundamental level more about variation In

the functional asymmetry of the human brain must obviously be relevant to

understanding how the brain "works", which In turn is of Importance In

fields as diverse as computer science and psychiatry. In computer science,

for example, accounts of laterallzed function have sparked off an Important

and fruitful area of Investigation In current artificial Intelligence

studies of visual perception.

However, It Is to be hoped that these fields have. In turn, and will

continue themselves to contribute to the understanding of cerebral function.

Psychiatry and psychopathology are dealt with In the last Section of this

volume. Computer science, for example, through artificial Intelligence (or

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Defining the Issues

An attempt has been made to define the Issues In the discussion of the

theme and the aims of the Workshop, in this Introdurtion, and this is the

aim of the first Section.

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cognition) may have much to contribute. Marr (1982) has recently provoked ^v'*!-'

us to ask through his modular concept of localization, what is it exactly

that we consider is being lateralized? For example, the "shading" of a

three-dimensional object gives rise to the perception of its solidarity.

Each of these factors is what Marr terms a module, that ic, "tree

recognition" and three-dimensional viewing of the tree itself are each, in

cerebral terms, a separate module. Does this provide us with a clue as to

the way in which lateralization or hemispheric specialization proceeds?

BRIEF OVERVIEW

It will be helpful, in view of the foregoing discussion of the aims of »

The issues considered by Marshall, initially, is concerned with what he

terms the duality hypothesis. He draws an important distinction between

hypotheses that propose a difference between the functional capacity of left

and right hemispheres, and the concept of cerebral duality, th • one

hemisphere can function independently of the other, almost to the extent of

mental duality. These two hypotheses are evaluated critically and

separately and the concept of hemispheric specialization is contrasted wich

the crncept of focal specialization, localization, between and within

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the Workshop, to consider, in the light of this discussion, the '"v^v

contributions to this volume, to ascertain whether in the time intervening ''-/">/-

since the Workshop there has been a development of views „owards a change in

the theoretical stance of the contributors.

However, although three of the twenty three chapters were not in fact

presented at the Workshop, these contributors were invited to attend hut,

in the event, were unable to participate at Maratea. Their chapters, are,

however, relevant to the theme of the volume. The delay ensuing in

publishing the volume after the Workshop is to some extent valuable in that

the views expressed at the Workshop have thereby been considered and

matured. On the other hand, the chapters are, in some cases less up-to-date

than otherwise they might have jeen. In some instances, the delays have

been due to the tardiness of a few contributors and editorial flexibility

which did not disallow this! On the other hand, the delays have also been

due to the decision taken at the Workshop itself to referee the chapters

independently. This has been done in nearly all chapters and, hopefully,

has improved the quality of the contributions, tut has delayed their

publication.

I.

In the first chapter, Segalowitz defines what appears to be a central

problem for the Workshop, that is, the possible confounding of biological

differences in brain asymmetry with variation in the measurement of

asymmetry itself, whether by perceptual, neurological or clinical and "real

time" measures of cerebral orientation. Consideration Is given to the

factors which contribute variance to lateralization scores, whether or not

these factors relate to hemispheric specialization. The issue is whether

these variables correspond to variables other than those of the commonly

considered individual differences: for example, attentional bias and

hemispheric activation are considered. To resolve some of thise problems, a »

method of statistical analysis is developed which allows for variation in

lateralization, and this is illustrated by a repeated measures study on

visual half-field data and with single sei-ion EEC alpha asymmetries:

intersubject variation in asymmetry, whatever the source, can he isolated.

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hemispheres, not a duality of functional» lateralization but the concept of ',

a multiplicity of loci Is emphasized.

Individual differences in Cerebral Anatomical Asymm / and Circulatory

Asymmetry

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The chapter by Annett summarises Issues concerned with hemispheric

specialization, related to her well-known Right Shift theory of handedness,

based on analysis of her extensive left- and right- hand preference and -'*

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skill data (Annett, 1985). Individual differences in hemispheric /V'V

specialization are hypothesised to depend on a gene (the RS gene) which may 'V'NV

be present in single or double doses and which may promote the early control <

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of speech by the left hemisphere. A bias to right handedness is secondary. f'-^A

In the absence of the gene, there is a chance bias to either left or right

hemisphere or either hand preference, but In this case slight cultural

pressure and other factors, may cause a tendency towards right handedness.

It follows that testable predictions concerning hemispheric specialization

can be formulated in respect of sinistral tendencies among individuals and

their relatives and in respect to gender, as well as hyptheses specifying fflfcn-.

the consequences for improved interhenispheric cooperation in the absence of ". ".>" '"

the double RS gene. •*ik-

Marshall's second chapter rrises an issue germane to any discussion of AvOH

individual differences in hemispheric specialization, that of whether

lateralization can be considered a graded or a discrete characteristic.

Consideration of this problem, is essential to the study of individual

differences in lateralization. A metric is developed over which gradation

of lateralization can be measured to correspond to, or be compared to,

empirically derived measures of laterality, but, of course, it must be W

remembered that, overall, within a given group, the main metric will also be VKiJ

contributed to by individual variation, and this could in theory occur as a £

graded effect even if lateralization in the individual cases making up the ^ ^

group were discrete, not graded.

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t Uitelson and Klgar have addressed the problem of individual differences

in anatomical asymmetry not directly in relation to hemispheric

specialization, but to a related field, that of individual variation in the

morphology of the corpus callosum, that broad and extensive band of

myelinated fibres which link left and right hemispheres. A review of the

considerable literature which includes methodological considerations,

reveals variation in callosal morphology between handedness and age groups

and which is consistent across diverse studies. Earlier studies which

showed Increased callosal thickness In schlroph. nia arc not supported by

later work, although interactions with gender and handedness are ':'.''-.''•

possibilities. Such findings in regard to callosal topography may provide •.'-•". '-".

an anatomical substrate for individual differences in hemispheric

specialization, although it is not yet clear, of course, how such IM>J

differences could be incorporated in a fixed structure model of cerebral t -,.

.dominance. It must be remembered, as Marshall (this volume) has pointed out .yjS

that It Is an assumption, although a plausible one, that a larger cerebral

neurostructure is evidence of greater functional proficiency. SSj

Cur and Gur summarise their findings in relation to individual

differences in the direction and degree of hemispheric specialization.

Studies during cognitive function have been made in brain damaged and leftand right-handed normal subjects. Employing not only perceptual methods of

laterality assessment, dichotic listening and split field tachistoscopic

techniques, but also regional blood flow measures using 133-Xenon inhalation

techniques and local cerebral glucose metabolism studies with Positron -Vv'-j

Emission Tomography (PET), both of the latter techniques showing lateralized

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activity during standardised lateralIzatlon tasks. Also, the neuro-iaaging

studies have been used in the study of emotion and affect and have shown

individual difference effects in regard to handedness and gender. The main v'Ä^

focus of the results is on regional blood flow studies, however. S^OO

Individual Differences in Electrophysiological Asymmetries *£*& *

Butler and Class, in their chapter, review data on individual l-SWv

differences in EEC alpha asymmetries during cognitive tasks designed to ^'SS

engage either left or right heaispheres. Such asymmetries have already been iSKtf

shown to be associated with cognitive processes and not due to asymmetric ""v'v'v

motor or sensory loading (Butler h Glass, 1985). The results are ~

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interpreted using the assumption that suppression of alpha rhythm over

homstopic areas of one hemisphere compared with the other is an indication

of the activation of that hemisph re. Thus, this indicstes a relative ^y^V

increase in the utilization of that hemisphere during specific cognitive -"""-"v-'J

task performance. On this basis, individual differences in EEC alpha 'X-'Xf'S

asynoetry involving handedness and gender groups are interpreted in terms ?-«./ /

not of a fixed structure model of hemispheric specializaton, a model for Tvv v

which the results do not provide support, but a more labile, dynamic process ^N'J

of interhemispheiic functional organisation, which even perhaps, in part, V^vi

Involves cognitive strategy differences between groups. An example of this i-'v'-l-v

lability, the possible influence of dynamic processes and f cognitive

style, an investigation of the effect of a potential conversant on EEC alpha

asymmetries is presented (Butler, Glass and Fisher, 1986).

Flor-Henry, Koles and Reddon, in their chapter, report on the analysis

of the EEC from an eight-electrode montage in 57 males and 56 females, all •"^S'j^

right handed, whose ages ranged from 18 to 59. Recordings were made during

various cognitive tasks. Measures were made of EEC power, phase and

coherence. The details of this normative data are recorded in the

appendices to the chapter. EEC differences were found between males and

females, consistent with cognitive differences. The ageing brain in EEC

asymmetry terms was found to approximate more to the female pattern of

cerebral organization, than to the male, with EEC signs of a right

hemisphere preponderance.

Ray, in his chapter, ban summarised work in his laboratory which has r'v^vS

been directed towards understanding how individual differences occur in < '••>'/

psychophysiological measures (especially the EEC alpha rhythm) of cognitive ^'v'/ö

and emotional processes. He points out the basic, pioneering approach of ''>J/-J'SJ.

early EEC research into the alpha rhythm in his field. He then reviews

task-related EEC alpha asymmetry measures of hemispheric lateralization,

especially In relation to gender differences. However, the possibility of

there being apparently unresolved methodological isaues still complicating the

interpretation of EEC alpha asymmetries has led him to propose other lines -1 •'% %-

of research. The Investigation of factors such as emotionality, direction •"v"vN'j

of attention, intake and rejection tasks (the former requiring the use of .v^/v*.'

external information, the latter not requiring it) on the asymmetry of EEC *„

alpha activity arc described. Finally, in regard to the possibility Chat

Individual differences in personality outside those of gender and handedness

might influence hemispheric specialization, an EEC study in alpha rhythm and

other frequency bands of the introversion/extraversion dimension is MHM

described. Among other effects, these preliminary findings showed the JNÖG

importance of the resting EEC "baseline" condition in this field. nm

%' \ '" Molfese and Molfese, in their chapter, describe the use of the auditory ,.•%/

evoked response (AER) in studying the development of language and its NÄO^l

interrelationship with hemispheric specializaiton at different ages. The i^''^J

technique is described in a study in which the brain's electrical response N•./•/»

over left and right hemispheres to speech and non-speech syllables is I,

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recorded at birth. The results at birth especially from the left hemisphere

can be used to predict accurstely performance on two language tests in 3-

year-olds. Although the Individual differences here studied were those of

age or development and speech proficiency, it is considered that the

electrophyslologlcal parameters do not indicate laterallzatlon as the sole

factor involved. ££?

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Rockstroh and Lutzenberger describe experiments with event-related slow

brain potentials to provide evidence for hemisphere-specific processing in

anhedonic subjects. These subjects are characterised by a marked defect in

pleasure capacity, a personality trait which has for long been associated

with schizophrenia. Results of Contingent Negative Variation (CNV) and

post-imperative slow potential (SP) studies indicated significantly greater

post-imperative negativity (PIMV) in anhedonics than in controls, over the

left precentral region. Although a similar effect can be seen normally

(Butler, Glass and Heffner, 1981). This, together with other evidence

suggests greater compensatory left hemisphere activation in the anhedonic

group, to counteract for attentional and preparatory deficits in the group.

Elbert and Birbaumer describe experiments to investigate hemispheric

interaction in smokers and nor-saokers, using cigarettes with differing

nicotine concentrations. They presented tactile stimuli to both hands, the

left requiring pattern discrimination, the right simple enumeration. The

slow potentials (CNVs) recorded during task-performance showed a taskdependent asymmetry which developed earlier with nicotine. This, and

blofeedback evidence suggests that nicotine either interacts asymmetrically

with right hemisphere arousal or facilitates interchange between

hemispheres. Smokers with nicotine, were better adapted as a group, to

switching between hemispheres, but without nicotine were less well adapted

to switching.

Puente and Peacock describe, in their chapter, an EEC interval

histogram analysis (using half-wave duration) from occipital sites (01 and

02) in brain damaged and non-brain damaged schizophrenics and patients with

affective disorders, in EECs recorded while subjects rested, and performed

i multiplications and solved geometric problems. Relatively slow right

hemisphere activity is reported for the schizophrenic group during the

geometrical task. This and other evidence suggests, it is emphasised, the

dynamic nature of the hemispheric dysfunction in schizophrenia.

Individual Differences in Behavioral '..ndices of Cerebral Orientation

Toung, Bion and McWeeny report, in their chapter, on a series of

experiments involving right-handed children, in which stimuli (chiefly face

recognition and dot enumeration) were presented to left and right visual

fields and left and right hands respectively, to determine age and gender

differences in lateral asymmetries. No developmental changes in the size of

asymmetries are reported but gender differences in asymmetry across age

proved to be stable. However, as these gender differences could be induced

or eliminated by small procedural changes, the model of variation in

functional asymmetry in male or female brains is not well-supported, but,

instead, the concept of a gender difference in subjects' reliance on, or use

of, lateralized cognitive processes is affirmed. Possibly, these processes

could either be under voluntary control, or, what is considered to be more

likely, procedurally determined or material-specific.

Schofleld has provided, in his chapter, an extensive critical review of

divided field studies of cerebral laterallzatlon using manual reaction time

to dots and flashes of light, studies in which an attempt has been made to

measure intcrhemispherlc transmission times. Inconsistencies in the

reported findings could be explained by failure to take into account 9 j

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Individual difference« in processing strategy in relation to healspheric

specialization. A simple reaction time experiment in children is reported

and thoroughly analysed, in which biaanual responses to bilateral stimuli is

related to bimanual responses to unilateral stimuli. Gender differences tu

laterality to unilateral presentations are reduced to factors which may

represent individual hemispheric differences in processing strategies. Hand

differences (fasthand, alowhand) in reaction time and other measures are

suggested to relate not to the hemisphere of Initial visual projection but

the hemisphere in which the response is initiated.

(TConnell, Tucker and Scott present, In their chapter, a self-report

scale designed to measure accurately the constructs of emot:ional and

cognitive self-control, set in the context of individual differences in

lateralized cognitive style. The methodological and theoretical problems

encountered are discussed in respect of hemispheric activation particularly

in relation to direction of eye movement studies. Self-regulation and

emotional factors either traits or states are Involved in the dynamic

determination of asymmetric brain activation and, therefore, of cognitive

style which is not seen as synonymous with hemispheric specialization.

Following discussion of the self-report scale, the proposition that an

anterior-posterior dimension of cerebral organization may be at least as

important when considering activation and arousal as a 'hemispheric'

dimension, is put forward.

Weber and Bradshaw's contribution is devoted to a critical examination

of the evidence for Levy's revised hypothesis (Levy, 1982) and is a

rejoinder to it. The hypothesis is, of course, that the preferred writing

hand and, especially in left handed writers, hand posture; that Is, whether

the position of the hand in writing is inverted or normal, is an indication

of the direction of lateralization of cerebral function or hemispheric

specialization. This problem and the associated question of ipsilateral

motor control has received a great deal of experimental investigation.

Weber and Bradshaw make the point of general relevance, perhaps, based on

Levy's assertion of possible differences in educational methods, that if

hand posture is a "cultural" phenomenon (Levy, 1982) then it is less likely

to be an "important correlate of neurological organization". In general,

they claim to find little clear evidence to link writing posture with the

lateralization of cerebral function.

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Asymmetries in Psychopathology and Individual Differences '•^-yj

Gruzelier, in his first chapter, fully develops the concept of

Individual differences in lateralization of cerebral function applying to

the normal and pathological brain. He extends its scope from the widely

accepted forms of individual differences in hemispheric specialization,

gender and haodedness, to consideration of other differences. This he does

by enlarging the concept of hemispheric specialization beyond an exclusively

structural model of lateralization to a combined structural and dynamic

process model (Cohen, 1982). Evidence is presented from a variety of

conditions in both the normal and pathological brain. Assessment is mainly

through asymmetries in the rate of habituation of electrodermal responses

and non-specific electrodermal responses. Thus, a contribution is made

towards specifying the role of dynamic process asymmetries, with reference

to individual differences not only in gender and handedness but individual

differences in cases where hemispheric activation, in particular, may be a

factor.

Miran and Miran, in a wide-ranging contribution, gathe- evidence from a

variety of sources, to place what appears to be an increasingly appreciated

flexibility of lateralization of cerebral function in the context of an

integrated, homeostatic brain model, which they would argue is more

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realistic than other models. They draw on supporting but circumstantial

evidence from "hardwired" perceptual and motor systems; go on to consider

several lateralized, including cognitive, functions in the same framework

and adduce evolutionary and developmental dimensions to their theory. They

regard the homeostatic brain model as providing a model, based on

hemispheric specialization for understanding individual differences. They

propose that psychopathological conditions may be caused by a disruption of

homeostatic systems rather than site-specific deficits.

Cromwell, In his chapter, focuses provocatively on schizophrenia in

relation to hemispheric specialization. He emphasises the role of

hemispheric advantage, not of absolute hemispheric specialization, and a

sequential, dynamic rather than a static concept of cerebral lateralization.

A model of schizophrenia is put forward in which the processing of

Information is conceptualised as flowing from right to left hemisphere prior

to verbal or other responses. Left hemisphere hyperarousal is seen as a

secondary phenomenon, resulting from "faulty" information being transferred

to it, derived from an earlier, "preattentional" stage dysfunction in the

right hemisphere.

Gruzelier, in his second contribution, reviews the role of the

interhemlspheric disconnection hypothesis stemming from experimental

disconnection (Sperry, 1964) and clinical callosotomy (Bogen and Vogel,

1962) in schizophrenia in the context of hemispheric specialization. Two

initial influences on the concept of disturbed interhemlspheric integration

are described, that of left sided temporal lobe epileptic foci associated

with schizophrenia (Flor-Henry, 1969) and that of the enlarged corpus

callosum in schizophrenia (Rosenthal and Bigelow, 1972; however, see

Uitelson and Kigar, this volume). From this stanupoint, the evidence for

disordered interhemlspheric transfer is reviewed not on the basis of

callosal agenesis or callosal section, but of faulty transmission such as

might be involved by a reduced signal-to-noise ratio (Butler, 1979).

Evidence from auditory processing sources, haptic tasks involving

interhemlspheric transfer, visual processes (divided field studies) and

somatoseneory evoked potentials in schizophrenic patients are summarised.

The conclusion appears to be that although a consistent pattern of results

has emerged across studies, evidence is against the concept of frank,

functional disconnection as an aetiological factor. For example, a

lateralized deficit could also give rise to defective interhemlspheric

transfer. More questions than answers are said to emerge from the results

and the heuristic value of the callosal theory In future investigation of

the schizophrenic brain is emphasised.

Miran and Miran, In their second, penetrating contribution, focus on

the role of intrahemispheric and Interhemlspheric communication in

schizophrenia. They propose that typical schizophrenic deficits in

cognition and perception can be interpreted as breakdowns in internal

communication within a homeostatic brain. Studies of left and right

hemispheric dysfunction and callosal dysfunction in schizophrenia are

-evaluated and frontal lobe dysfunction (which has produced negative

findings) and deficits in parietal and occipital function are considered.

Schizophrenia is regarded as a dysfunction of the homeosratic brain and

implications for its assessment and treatment are examined. In conclusion,

a number of points are made in relation to the homeostatic brain model and

hemispheric specialization, but it is emphasised that to consider merely the

over- or under- activation of a dominant hemisphere is too simplistic.

Schizophrenia, in terms of psychopathology, is considered to be a breakdown

in both intra- and interhemlspheric feedback systems.

Serafetlnldes, in his chapter linking cerebral laterallty and

psychopathological disorders, has recalled his earlier evidence for

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agresslve behaviour in young, male temporal lobe Epileptics, the majority

having a left dominant hemisphere focus, and he reviews subsequent

supporting evidence that assaultive psychopathologlcal disorders are

associated with communication difficulties. It Is concluded that the role

of the verbal hemisphere In control of agresslve Impulses Is considerable

and that a similar sequence of dysfunction may hold for other hemisphere

specific Impairments. The need for constant redefinition of such testable

formulations of brain-behaviour relations Is emphasised.

CONCLUSIONS

It is hardly feasible to attain a complete synthesis of the

contributions to this volume and It would certainly be foolhardy to claim to

have done so. It is also difficult to represent a contributor's views with

much semblance of accuracy, but In spite of this it was felt worth risking

possible misrepresentation, if some form of synthesis were to be achieved.

The reader must judge whether this goal has been gained.

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A common thread can be discerned and appears to run through those

chapters In which what appears the central problem of the Workshop is

addressed. These chapters are to be found in each Section but perhaps

especially in the Psychopathology Section. There appears to be a detectable

gradient shift in the paradigm concerning hemispheric specialization. This

shift was perhaps just apparent at the time of the Workshop and has since

been consolidated in these contributions. There Is a tendency for a move

towards a greater lability in the concept of hemispheric specialization,

particularly in the area of individual gender and handedness but also in

other less well-studied areas of Individual difference. The move is in a

direction away from a fixed structure model towards one based on hemispheric

usage and activation. There is a growing realisation thai, there are factors

affecting the measurement of Isteralization other than tKose purely of

hemispheric or language lateralization, between those individuals making up

the commonly acknowledged groups of gender and handedness. The measures of

laterality are the perceptual/behavioural, and the "real-time" indices of

orientation, the electrophysiological asymmetries and brain Imagery. These

measures may contrast with, and, have to be reconciled, with the data

regarding individual differences in hemispheric specialization derived from

clinical/neurological sources.

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The paradigm has shifted, in the last decade, from perhaps a simple

"black and white" model of cerebral dominance (which, of course, was never

held in totality!) which had been essentially unchanged from the nineteenth

century, but with the more recent acknowledgement of the importance of right

hemisphere function. It was based on and invigorated by the split-brain

work of Bogen and Vogel and Sperry and Gazzaniga (1970). It has now moved

towards the formulation of a more complex model, less simplistic, perhaps,

but hopefully nearer "reality" in which differences in strategy may play

their role as part of a dynamic process in cerebral asymmetry. Strategy

differences (Butler & Glass, this volume) as a basis for individual

differences are not the whole component of the dynamic process (Gruzelier,

'this volume). Possibly, further insight be sought into dynamic processes of

hemispheric specialization by followlng-up the study of performance

indicators in relation to task-related EEG alpha asymmetries, as predictors

of laterallzed task performance (Fürst, 1976, for right hemisphere tasks;

Glass and Butler, 1977, for left hemisphere tasks). This change in the

paradigm is reflected in the application of hemispheric specialization to

psychopathology and psychiatry (See Gruzelier and Miran and Miran, this

volume).

It has been emphasised, however, and this should be taken as a warning

that the "best" hypothesis, a combined structural and dynamic model of

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hemispheric specialization (Cohen, 1982) is, perhaps paradoxically, least

cifective in forming predictions that can be tested experimentally. Also

unpredictable results are too easily explained by it. Its heuristic value

is limited by its underdetermination (See Laudan, 198V,.

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An example of a less than fixed model of specialization is that

involving differences of cognitive style, described as "a disposition to

adopt a particular processing strategy which effectively changes the

cognitive demands of Che task" (Cohen). Fixed structure and dynamic models

are not mutually exclusive, in fact they could be mutually dependent in a

"real" brain. A functional asymmetry, that is, a dynamic process, must be

combined with an underlying structural asymmetry (which is not necessarily

the same as a gross anatomical asymmetry, of the type of the asymmetrical

plenum temporale). Unless, of course, the structure model is like a

standard set of "pigeon holes", which are uniform in structure but have

different objects or messages inside them. To extend this analogy, let us

imagine two structurally identical microprocessors (PCs, or personal

computers), slde-by-side, representing left and right cerebral hemispheres,

with cables interlinking Inputs and outputs to represent the corpus

callosun. It is possible for these computers to vork together with

different operating systems, CP/M, MS-DOS, for example. Perhaps, each

microprocessor could support different languages, Fortran, Basic, for

example and which in turn could also support quite different functional

categories of software, let us say, a Wordprocessing program in one computer

and a Graphics program, in the other, for example. It is possible, in fact,

for the two microprocessors to have different structures and still be

functionally linked by the cable if their software Is compatible, or can be

made compatible. It is difficult to know how such an information processing

model or analogy, could be commensurate with those current theories of

cerebral organization seeking to account for lateral!ty findings and which

form the theme underlying the Workshop and its proceedings. Would it be a

fixed structure asymmetry? A dynamic process asymmetry? A function of

cognitive style or strategy? A verbal or visuospatial dichotomy? A

holistic or analytical process? It is interesting to speculate how, for

example, a heterarchical concept of hemispheric specialization could be made

to fit such a model. If is difficult to ascertain where in current models

of hemispheric specialization such an analogy could be fitted or at what

level. Intuitively, one feels that any such theories should be compatible

with an information processing model of this type, however simplistic it may

appear initially. Alte ra.ivcly, we should consider how current models

could be reconciled wltt such an analogy to give us more insight into

hemispheric specialisaa o.' in the "real" brain. There are difficulties here

which have not yet been ackled "head-on", but if they are may represent a

way forward into Individual differences in hemispheric specialization.

The final question we must ask Is, what we consider is being physically

later all zed when we say, for example, that "language" is lateralized to the

left hemisphere or visuospatial function is lateralized to the right

-hemisphere? Will this reduce to an asymmetry of neurotransmitter substances

(Reynolds, 1984), for example? When we are in a position to answer this

question we will be In a position to understand better the basis for

individual differences in hemispheric specialization and to evaluate their

significance.

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ACKNOWLEDGEMENT

Thanks are due to the NATO Scientific Affairs Division for their

generous support without which the Workshop would not have been possible,

and also to the Wellcome Foundation for their additional help with the

project.

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14

A. Glass,

University of Birmingham

REFERENCES

&s

Hy thanks must be expressed to the late Dr. M. dl Lullo, formerly

Director of the ARW Programme for his support and are also due to Dr. Tllo

and Mrs Barbara Kester for help in organizing the Workshop. Mr Guzrardl and »SjWy

his staff of the Hotel Villa del Mare at Maratea, Italy ably looked after -^M

the participants during the meeting. . 1

'. am deeply indebted to my colleague Dr. Stuart R. Butler for

stimulating and helpful discussion before, during and after the Workshop and ^v^'

also to Dr. Joseph E. Bogen for helpful discussion some years ago, and to

Professor Dietrich Lehmann for earlier discussion leading to the initial

suggestion of the Workshop and its later formulation. The support of

Professor J.J.T. Owen for allowing the facilities of the Department of

Anatomy, University of Birmingham to be used for preparation of the text is

greatly appreciated. Mr Roland A. Hill is thanked for help in organization,

preparation and support. Also the editorial support of Madeleine Carter of

Plenum Publishing Company Limited is gratefully acknowledged. I am

particularly grateful to Sue Burton and Claire Hundley for their patient and

unremitting work in processing the entire text of the volume.

The following are thanked for refereeing the chapters or for advice and

assistance with refereeing: M. Annett, S.R. Butler, D. Carroll, J.H.

Gruzeller, L.J. Harris, D.H. Ingvar, M.A. Jeeves, J.C. Marshall, M. ^'v'v'

Moscovitch, R. Obrecht, M.A.J. O'Callaghan, K.P.O'Connor, D.J. Parker, P. ^.--1

Prior, S. Segalowitz, J.C. Shaw and D.M. Tucker.

Especial thanks «re due to the Organizing Committee, Professor Pierre .-' "•'-">!

Flor-Henry and Dr. Michael Miran and I am deeply grateful to the -S-'v^

participants for their stimulating contributions. A!M3

Preparation for publication of the chapters in this volume has been iVlV"

made possible by Contract Number DA7 A45-85-M0184 from the U.S. Army

j Research Institute for the Behavioral and Social Sciences through its ! ." "^

European Science Coordination Office in London, England. The opinions

j expressed are those of the authors and do not necessarily represent those of

] the U.S. Army. In this connection, Dr. Michael Kaplan, Chief, European

Science Coordination Office, Army Research. Institute is thanked for his

patient support.

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r

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Gazzaniga, M.S. (1970). Bisected Brain. New York: Appleton-Century-Crofts.

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Hecaen, H. and Sauguet, J. (1971). Cerebral dominance in left handed

•ubjects. Cortex, 7, 19-48.

Klmura, D. (196777' Functional «symmetry of the brain in dichotic listening.

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Laudan, L. (1984). £>cience and Values. London: University of California

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Marr, D. (1982). Vision. A Computational Investigation into the Human

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W.H. Freeman & Co. $fiS

-,
16

McKeever, U.F. and VanDeventer, A.D. (1977). Visual and auditory language

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Perelman, S.J. (1951). Crazy Like a Fox. Harmondsworth: Penguin Books.

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3rd Edition.

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time to simple auditory stimuli. Neuropsychologia, 13, 207-211.

Raichle, M.E. (1985).

Reynolds, G.P. (1983).

Nature 317, 574-576.

lateral asymmetry of

1.

Progress in brain imaging.

Increased concentrations and

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Satz, P., Achenbach, K., Pattishall, E. and Fennell, E. (1965). Order of

report, car asymmetry and handedness In dichotic listening. Cortex,

377-396.

Satz, P.. Achenbach, K. and Fennell, E. (1967). Correlations between

assessed manual laterality and predicted speech laterality in a normal

population. Neuropsychologia, 5^, 295-310.

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341-372.

Sperry, R.W. (1964). The great cerebral commissure. Scientific American,

210. 42-52.

Zangwill, O.L. (1960). Cerebral Dominance and its Relation to Psychological

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Zangwill, O.L. (1982). On cerebral dominance. In R.N. Malatesha and L.C.

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differences in auditory and visual perception. Neuropsychologia, 7,

179-187.

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INDIVIDUAL DIFFERENCES IN HEMISPHERIC SPECIALIZATION: SOURCES AND

MEASUREMENT

S.J.Segalowltz, Ph.D.

Department of Psychology, Brock University,

St. Catharines, Ontario,

Canada L2S 3A1

INTRODUCTION

When we focus on Individual differences In hemispheric specialization,

we usually design our experiments to detect these differences as group

effects. For example, we may include factors such as those listed in Table

1 in any particular study, and, of course, the list can be expanded at will.

Although the factors nust, for reasons of statistical analysis, be applied

to groups of subjects, we often study them not because we are interested in

groups of left banders, or schizophrenics, etc. per se, but rather because

we want to make a statement about individuals. The individuals within the

group are assumed (or hoped) to be alike on all other variables important

for brain lateralization. For practical purposes, this is impossible since

it would be impossible to form a group of subjects representing each

intersection of all the factors listed. There are probably also sources of

individual variation in lateralization tests that are beyond any divisions

we have managed to make so far. With this perspective, each individual is

seen to be a group unto himself to some extent. An intensive case study of

the individual, although possible, and laudable (Dywan t Segalowitz, in

press), would not satisfy our curiosity about the factors under examination

(cf. Caramazza, 1986). We must remain with the traditional group paradigm,

but we are left in the traditional, awkward position of having to accept the

individual variation in lateralization not controlled for in our study as

error variance. Thus, if we measured cerebral specialization in a fully

crossed paradigm for the first three factors listed in Table 1, the others

would add error variance. In this chapter, I outline some of these sources

of uncontrolled varistion and discuss a paradigm that allows us to measure

it and separate such variation from the error variance measure.

SOURCES OF VARIANCE IN A LATERALITY TEST

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There are at lesst five factors that contribute variance to

lateralization scores. Some of these factors are relatively easy to

Incorporate into a research design and therefore to control. Others are

less amenable to experimental control and yet are documented adequately to

be a source of concern. The issue here is that whatever adds variance to

the scores obtained on a test of lateralization is of concern, whether or

not the particular factor relates to hemispheric specialization.

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Table 1. A list of variables that researchers have suggested influence the

asynmetry «hown on various tests of hemisphere specialization.

HANDEDNESS

SEX

FAMILIAL SINISTRALITY

SCHIZOPHRENIA

DEPRESSION

ANXIETY

FATIGUE

AGE

SMOKING

INTROVERSION/EXTRAVERSION

It

1. Functional Asymmetries Common to the Group

The individual differences commonly associated with variation in brain

lateralization are those due to handedness and sex. There is clear evidence

that whereas right banders have speech representation in the left hemisphere

to an overwhelming degree, left banders present a different distribution

(Segalowitz & Bryden, 1983). For example, Rasmussen 6 Mllner (1977) present

data from Wada testing that illustrate the most commonly-held view: that

whereas at least 96S of right banders are left-dominant for speech, only 70*

of left banders are clearly so, with the remainder evenly split between

right-dominant subjects and those bilaterally represented for speech.

Similar group differences have been documented for behavioural tasks with

normals, repeatedly (Zurif & Bryden, 1969; McKeever, VanDeventer & Suberi,

1973; Bryden, 1965). The issue of familial left-handedness is clear. Some

claim that if a subject has left handedness in the family, then that subject

is more likely to be bilaterally or right dominant for speech (Hannay &

Malone, 1976; Varney & Benton, 1975). Others do not find this a robust

effect (Bradshaw, Nettleton & Taylor, 1981; Bradshaw & Nettleton, 1979).

>:

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Sex differences in speech dominance have also been repeatedly reported

(Lake i Bryden, 1976; Bradshaw, Gates & Nettleton, 1977; McKeever 6 Jackson,

1979). The common assertion is that males are more likely to be left

dominant for speech, and that females, like left-banders, are more likely to

show bilateral representation for language. The evidence is both clinical

(McGlone, 1980; Inglis 6 Lawson, 1981) and experimental (Bryden, 1979).

This picture is somewhat clouded by studies that have examined the factors

of handedness, familial sinistrality and sex together. Piazza (1980), for

example, found that whereas for men handedness and ear advantage on a verbal

dichotic listening task interact (left banders being less asymmetric), the

women showed no main effect or Interaction. Women showed a significant

handedness by car Interaction on the environmental-sounds dichotic task,

while men showed no significant effects. A tachistoscopic face-recognition

task produced a triple interaction among the factors of visual field,

handedness and familial sinistrality, whereby only right banders with no

familial sinistrality showed the expected left visual-field advantage.

Thus, sex, modality, handedness and familial sinistrality interacted in this

study. The situation may very well be more complicated. It may be

necessary to include other factors in the equation such as the type of

language task being examined, e.g. expressive versus receptive (Moore &

Heynes, 1980; Orsini, Lewis & Satz, 1985), or possibly the witbin-bemisphere

organization of language representation (Klmura, 1980). However, whatever

the factors, as long as they can be catalogued and the subjects identified,

they can be incorporated into the research design as a group factor.

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2. Individual Differences in Neuropsychologic«! Organization Beyond the

Group Pattern

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There is always residual variation in lateralization even within a

supposedly homogenous group, e.g. of right-handed, non-schizophrenic,

university age males without familial sinistrality. Could some of this

remaining variation in laterallzatlon be in some part due to other

constitutional variables? There is good evidence that the temporal lobe

differs in size between the hemispheres, (Geschwind and Levitsky, 1968) as

indexed by the different directions of the curve of the Sylvian fissure

(Rubens, 1977). As well, however, there is considerable Individual

variation in this asymmetry and therefore in the shape and size of the

planum temporale, a key language area. Differences in dichotlc listening

scores could be related to such anatomical variations.

A number of workers have suggested that the asymmetries in size between

the two hemispheres are an indicator of aome gross functional differences in

language skills, specifically in dyslexia (Hier, Lemay, Rosenberger i Perlo,

1978; Galaburda & Kemper, 1979). Indeed, they suggest that this may be a

contributing factor to the syndrome of dyslexia. If specific language

difficulties were related to this anatomical variation, we would expect that

a group of subjects that otherwise appears homogeneous with respect to

lateralizatlor would on some measures (perhaps visual half-field reading

tasks) show considerable variation. Similarly, Vitelson (1985; this volume)

has shown that hand preference differences correlate with size of the corpus

callosum. There is every reason to expect that dichotlc listening

performance should be affected by auch variation, especially since it is the

anterior section of the corpus callosum that especially shows the effect.

There very well may be other constitutional factors that affect

performance on laterallzatlon tasks, factors that we may cot be aware of

yet. OJemann and his colleagues (1983) have presented such evidence from

their brain stimulation work in clinical patients. The specific posterior

areas that when stimulated lead to language disruption vary considerably,

although there is good consistency on the anterior area. Even within a

bilingual individual, each language can be disrupted by stimulation to

different areas.

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3. Lateral Attentional Biases not related to Hemispheric S^ecializatloa

Individual subjects may have attentional biases that predispose them to

respond more to stimuli on one side of their personal space. The source of

this bias could be due to central or peripheral factors, including some that

would be classified as dysfunctions. For example, there may be central

dysfunctions that promote some form of hemispatial neglect that is not

clinically serious but that can influence the result of *ny auditory or

visual vigilance task. Also possible are peripheral dysfunctions that could

be reflected in poorer visual acuity scores for one visual field or poorer

hearing in one tar. Although normal subjects are usually screened for such

factors, the procedure is usually relatively informal and often consists of

•elf-reports. It is entirely possible that the subject is unaware of the

•light perceptual asymmetry since It is only of interest in laboratory

tests. One general instance of such lateral biases is related to hand

preference. Bryden (1978) has pointed out that right banders have a

greater right ear advantage on a dichotlc listening task compared with left

banders independent of the side of the speech dominance as asses ed by Wada

testing. We do not know whether or not this is a generalized directional

bias that supersedes modality or is specific to listening tasks. The

modality of testing may be critical and hearing, vision and motor

asymmetries may cot be consistent within Individual subjects (Porac, Coren &

Duncan, 1980).

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4. Individual Differences In Hemispheric Activation

Just at the item above concerned «one generalized perceptual bias

because of some factor not related to hemispheric specialization

specifically, it is also possible, though more controversial, that

individuals may differ in asymaetric hemisphere activation. Asymmetries of

activation are presumed to be present whenever the subject engages in some

behaviour that requires the processes of one hemisphere more than the other

(Galln 4 Ornstein, 1972; Ornsteln, Johnstone, Herron & Swencionis, 1980; ^•'/s's*

Moore, 1979; Moore 4 Haynes, 1980). It is also possible that because of y>v^'

structural asymmetries (including minor damage), Individuals may differ in Xs^/V

how relatively active each hemisphere is. This source of differences has / /"^

not to my knowledge been documented, although one would suppose that frank

asymaetric damage would affect the EEC output (cf. Heilman, 1979). It is

clear, however, that within a group of subjects with left hemisphere speech,

there is a wide variation of hemisphere activation (as reflected in

asymmetric EEC alpha) across subjects performing a verbal task (Butler &

Class, 1976; thir. volum«).

vV*

More controversial is Che notion chat some individuals habitually have

asymmetric activation due to specific cognitive styles (Ornstein, 1972) or

personality traits (Tyler & Tucker, 1982; Smokier & Shevrin, 1979). The

suggestion is that while verbally oriented individuals and visuospatially '/N^T

oriented people are structurally similarly lateralized for speech as long as L^^S

they have the same handedness characteristics, one group will have come to "'S'S^

the testing situation with a heightened level of left hemisphere activation §

compared to the right, and the other group will have the opposite pattern. WMfl

This difference may predispose them to utilize differing strategies on the .'/'>'.'>!

lateral izar ion task, even on tasks where we try to control the task '*'/%']

requirements. Of course, there is no clear cause-and-effeet relationship ''

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here: the choice of strategy may produce the asymmetric activation rather slv'v'v

than any constitutional factor predisposing the subject towards one or the *

other. An example of this "henlspherlcity" is Illustrated in Levy, Heller, ^v'-lv

Banich & Burton (1983), who show that differences in VHF asymmetry can be «WM?

! attributed to strategy differences. 'fSS

\ >VN The strong hemisphericity hypothesis implies a long term effect: that

subjects have a long-lasting activation asymmetry, e.g. that some people are

chronically more verbal than others. It is also possible that any such

predisposition is temporary and may even be confined to the testing /;'

situation. For example, some subjects may react to being in a psychology

experiment by an increase in tension with, for some subjects, a concomitant /'

increase in verbal mediation, while in other subjects there may be a ^N>

decrease of the same proceses. The result would be a /ariation in * ,

lateralization scores that would look like an attcntional bias that is not V^T

stimulus-specific. This affect would ba hard to uncor.found from the type

of factor outlined in (3) above. For example, Levine, Banich and Koch-Ueser

(1984) found that the degree of asymmetry that subjects show in recognizing Ity/.

items that do not produce a VHF advantage among right banders (line drawings

of chairs) generally correlates significantly with the degree of VHF

advantage shown on lateralized taaks (e.g. recognising faces). This means

that whatever predisposes a subject to recognize more information in one

visual field on one task beyond the hemisphere-specific processing >i"Ä>Sfl

requirements generalizes to other tasks. They interpreted these results as ;-'/-/-V

indicating that subjects vary in their hemisphericity, i.e. asymmetry of ^vCvCl

sctivatlon. It could equally be the case that the stable asymmetry is due I {

to lateral biases from other more peripheral sources including visual !KR^J

asymmetries.

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5. Error Varlanct 22

Sine« Chtrt It • continual fluctuation in attention from internal and

external factors during any vigilance Cask, and most lateralization tasks

involvt such demanding processes, there will always be some variation in the

performance of any individual, even if the individual is tested repeatedly.

This, of course, leads to a certain degree of variance unaccounted for -

«rror variance - and adds to the unreliability of the tests (Segalowitz, in

press).

In most lateralization studies, factors 2, 3, and 4 are considered to

be nuisances, and the experimenters hope that a large sample size will

reduce them, cancel them out and increase the relative strength of factor 1

to get the desired result. Although It is true that many of these factors

will cancel themselves out given a large enough sample size, i.e. the

«symmetry devistion due to them averaged over the entire group will be

•mall, the variance they contribute is added to the error term. Not only

does this inflate the Type II error, that is, the chances of not finding s

•ignificant effect when one is present, but masks what may be interesting

facts about individual variation in hemispheric organization. The methods

outlined here separate factor 1 from 2 and both from factors 3 and 4.

<• V V V

As an illustration of the difference between factors 1 and 2 on the one

hand and factors 3 and 4 on the other, consider the following pair of

subjects (Segalowitz & Orr, 1981; Segalowitz, 1983): Subject J showed right

visual field advantages on both a verbal and on a spatial visual half-field

task consistently over 6 test sessions on different days. Subject L showed

a consistent LVF advantage. They both showed the expected trend for right

banders: the verbal task producing a relatively higher RVF score, the

spatial task a greater LVF score (see Figure I). Thus, one could conclude

that their pattern of hemispheric specialization is the same and conforms to

the common one for right banders: LH dominance for verbal functions and RH

dominance for visuospatial functions. This illustrates factors 1 and 2.

The widely differing absolute scores, however, illustrate factors 3 and 4:

whatever the pattern of hemispheric specialization, these subjects have VHP

biases. The consistency of these VHF biases suggests we are not dealing

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positive values indicate a RVF advantage and negative acores a P'F

advantage. Lambda is independent of total accuracy (see Bryden 4 Sprott,

1981). CVC stimuli are clcckface times balanced for left/right «symmetries,

The clockfaces have no digits on them. (Reproduced from Segalowitz 4 Orr,

1981).

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CEREBRAL LATERALITY: RUBE GOLDBERG AT THE BAUHAUS? JOÖÄV5

John C. Marshall 'i'^

Neuropsychology Unit,

The Radcliffe Infirmary,

Oxford, 0X2 6HE, U.K.

INTRODUCTION WWsH

HPH

What could be simpler than a dichotomy? A whole, obviously. Or as §

Pierre Flourens put it, quoting Rene Descartes and attacking Franz-Joseph '*'*>'/'''

Gall: SSW

s v •

"I remark here ... that there is a great difference W^-jky

between the mind and the body, in that the body is, Cl['iZ'i<

by its nature, always divisible, and the mind wholly §

Indivisible. For, in fact, when I contemplate it - ^v"v^

that is, when I contemplate my own self - and consider A/s""^'

myself as a thing that thinks, I cannot discover in ."v£"j«'S

myself any parts, but that I clearly know that I am '"-'"-">'

a thing absolutely one and complete" (Young, 1970, p.72),

i ]

0 happy days! Today, of course, wholes are out. Even the most committed of />

dualists (e.g. Eccles, 1985) know that the brain is the organ of mind, and fiy£

that the brain, like it or not, is not a unitary organ, either anatomically, /'^v'-J

physiologically, or functionally. For Eccles, the immaterial will can act jS'»*W

only via the supplementary motor area, not via the occipital lobes, for Vv,,vS

example.

The brain may be unified, in much the same sense that the (rest of the)

body (or an automobile) is unified ...but 'unified' does not mean 'having no JMj

parts' (in Descartes' sense). As one of Descartes' followers. La Forge,

elegantly phrased the matter: a machine is "a body composed of several

organic parts which being united conspire to produce certain movements of

which they would be Incapable if separate" (Marshall, 1980, p.172). Thus,

to pick an example at random, two separate hemispheres (with eyes closed) SföÄj

are incapable of making the movement "pen" when a pen Is held in the left >^"vv

hand, an enterprise that occasions no difficulty when the neocommissures are

intart (Bogen, 1983a). But long before such experiments were performed, the

anatomy of the brain had convinced many physicians, Hippocrates included, | t

that the brain was more akin to the kidneys or the lungs than to the heart: IHWM

".... the human brain, as in the case of all other WvrSl

animals, is double" (Chadwick and Mann, 1950, p.183). KvK -•

jwHHI

Yet the analogy with the other paired organs Of the body could not have been
exact ^veii for the ancients. For Lokhorst (1982) has recently drawn 25

attention to a theory of hemispheric specialization that can be traced back

to the Creek physician Soranus in the fourth-century B.C.E.:

•i •. •

HEMISPHERIC SPECIALIZATION

there are two brains in the head, one which gives

understanding, and another which provides sense perception.

That is to say, the one which is lying on the right side is

the one that perceives; with the left one, however, we

understand" (Lokhorst, 1982, p. 34).

Needless to say, Soranus' theory has no parallel in accounts of the vS-'v"^

functioning of the kidneys. As far as I know, no-one has ever hypothesized '^'^"li

Chat the left kidney had different functions fron the right. The position

taken by Soranus will, however, enable us to see why the further evidence

for cerebral laterallty, derived in the first place from study of the

effects of unilateral cerebral lesions, does not unequivocally lead one to

suppose that the mind-brain is dual (Benson and Zaidel, 1985). The relevant

question is now: What's so special about two? And, pertinently enough,

there are even two versions of what I shall call the duality hypothesis. In

an exceptionally clear account of 'the dual brain' Bogen (1983b)

distinguishes between hemispheric specialization and cerebral duality.

The firsr notion, hemispheric specialization, refers to the (putative) '. VJ

fact that the functional capacities of the left and the right brains are js^ftS

different (either quantitatively or qualitatively); the second, cerebral • "• -'•/

duality, implies that "each hemisphere can function to a significant extent £AV?V

independently of the other" (Bogen, 1985b, p.28), perhaps Indeed to such an

extent that we might be prepared to credit one (normal) person with two

minds (Wigan, 1844). Phrased in this fashion one can Immediately see that

both hypotheses could, in point of logic, be true (or false), or, more loSv>j

literestlngly, that either one could be true with the other one false. What -VV*^

seems to be critical is that the two hypotheses should not be conflated when

their empirical adequacy is assessed.

*•/• :

: •::-••

• >

The number two undoubtedly has a special affinity for •!■■''•!

neuropsychologists. Throughout the nineteenth century, physicians and "•'"'!

philosophers attempted to describe the functioning of the cerebral B )

hemispheres by such polar contrasts as intelligence/emotion, reason/madness, '.-/?/<*

male/female, and objective/subjective. (In each pair, the left hemisphere r'V'v',»

characterization Is given first). Harrington (1985) provides a masterly Mvu

survey of these dichotomies and the 'evidence' that was held to support fJW/S

them. Yet when one comes to the 'modern' work that supports our own central JW/vifij

dogma of 'complementary hemispheric specialization' (Geschwind and I (

Galaburda, 1984), one does not find Broca's children attempting to locate -'^"V

the faculties of reason and objectivity or madness and subjectivity (not

even understanding and sensation qua Soranus) In one hemisphere or the

other.

Rather, Broca (1965) argued that one aspect of the language faculty was

(usually) localized in the third frontal convolution of the left hemisphere; ?SMl

that component was "tne memory of the procedure that Is employed to

articulate language". And likewise for other (relatively) specific domains:

language comprehension (Wernlcke, 1874), and skilled praxis (Liepmann,

1908), for example. The association of deficits in these areas - expressive

and receptive aphasia, ideomotor and ideaCional apraxla - with left

hemisphere pathology contrasted with the apparent lack of any striking ^5558

cognitive deficits subsequent to unilateral right hemisphere pathology led WJCsÄi

directly to the first modern conceptualization of hemispheric

specialization: namely, that their relationship was that of master and

WSfQ
uwjwyrwvtnmiwirwn

26

slave. On this arcount, the left hemisphere was the source of all higher

ental functions; when bilateral action or unilateral action of the left

side of the body was required, it was the left hemisphere that determined

the course of action and instructed the right hemisphere (as a purely

executive organ) to act appropriately. Hemispheric specialization yes,

cerebral duality no, for the right hemisphere as a truly passive, fully

obedient slave clearly had 'no mind of its own'.

»'

This picture, of course, changed dramatically upon the rediscovery and

extension (Poetzl, 1928; McFie, Plercy, and Zangwlll, 1950) of John

Hughlings Jackson's work. Jackson (1676) had reported that a patient with a

large right temporal glloma (and smaller growths In the right hippocampal

region) could no longer find her way in familiar surroundings and had great

difficulty with the spatial component of dressing herself. These findings

led Jackson to propose that posterior areas of Che right hemisphere were

"the seat of visual Ideation". The right hemisphere now had a

specialization of its own. Jackson had also observed that even in cases of

very severe aphasia (consequent upon left hemisphere damage) some language

ability was usually retained. In particular, overlearned, 'automatic', and

emotional speech (including obscenity and blasphemy) was spared.

Accordingly, Jackson suggested that the left hemisphere was "leading" for

language and the right "more automatic" whereas the relationship was

reversed for visuo-spatial cognition. Thus was the notion of 'complementa'y

hemispheric specialization' born.

The question now become: In the light of subsequent research into the

effects of unilateral and bilateral brain injury, does this dichotomy indeed

serve to unify the respective functional specializations of the hemispheres?

VW

is

Certainly, the generalization has some force. Most, if not all, 'core'

linguistic functions are left-lateralized in the vast majority of (righthanded) adults. The gross Impairments of sentence structure, word finding,

segmental phonology, and language comprehension seen after unilateral damage

to the perisylvian region of the left-hemisphere sre not (usually) found

after comparable insult to the right. It would seem that the relevant

generalization must refer to an 'abstract' characterization of linguistic

form (grammar) rather than to a modality-specific form of speech processing

(i.e. auditory-vocal language). Thus the primary disorders of reading,

writing and spelling are consequent upon left-hemisphere damage (Patterson,

Marshall and Coltheart, 1985). Likewise, aphasic disorders of sign

languages (i.e. languages that have no surface features in common with

auditory-vocal languages) are found after left-hemisphere Injury, despite

the fact that sign-languages are executed in three-dimensional space and

perceived visually (Damasio, Bellugi, Damasio, Polzner, and Van Gilder,

1986; Marshall, 1986). One could summarize these latter Ladings by saying

that where there is conflict between characterizing the 'representational

domain' for which a hemisphere is specialized and the modality in which the

domain is expressed, then the representational domain takes (biological)

precedence.

vfiba

With respect to the specialization of the right hemisphere, Jackson's

conjecture has received impressive confirmation for some tasks. There are a

variety of visuo-spatial skills, including spatial orientation, learning and

memory that seem to be preferentially impaired by unilateral right lesions.

These include the ability to mentally rotate shapes (Ratcliff, 1979); the

learning of routes through a visually-guided maze (Ratcliff and Newroabe,

1973); and memory for topographical locales and routes, when these cannot be

verbally mediated (Whitty and Newcombe, 1973; Whiteley and Warrington, 1978;

Hecaen, Tzortzis and Rondot, 1980; Landis, Cummings, Benson and Palmer,

1986).

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27

There 1« also evidence t Che fine discrimination of differences

between visually-similar forms is maximally impaired by right hemisphere

lesion (Warrington and James, 1967; Orgass, Poeck, Kerschenstelner and

Hartje, 1972). Very substantial deficits in visuo-perceptual tasks that

require gestalt Integration, as in so-clled 'closure' tests, are also found

after right- but not left-sided injury (Ke.schensteiner, Hartje, Orgass, and

Poeck, 1972; Wasserstein, Zappulla, Rosen and Cerstman, 1984; Newcombe,

Ratcliff and Damasio, 1986).

The problem, however, is that whilst the generalizations 'language is a

left-hemisphere function' and 'visuo-spatial cognition is a right-hemisphere

function' are good summaries they are far from perfect in encapsulating the

entire range rf lateralized deficits. A few examples will suffice to

indicate the failures.

Some language skills are preferentially impaired after right-hemisphere

damage. The expression and comprehension of prosody, both in the service of

grammatical and affective functions (Weintraub, Mesulam and Kramer, 1981;

Roberts, Kinsella and Wales, 1981; Ross, 1983) is perhaps the most striking

example. This suggests a relationship between (some aspects of) language

and music. Thus singing can be rflatively well-preserved in cases of severe

Broca's aphasia (Yamadori, Osuml, Masuhara and Okubo, 1977; see also Gordon

and Bogen, 1974). There is also well-known evidence that the right temporal

lobe is preferentially involved in the discrimination and recognition of

timbre and melodic patterning (Milner, 1962; Zatorre, 1985). Musical

abilities can be retained at a high level despite severe aphasia consequent

upon left-hemisphere damage (Assal, 1973; Luria, Tsvetkova and Futer, 1965).

By contrast, severe disorders of muslcel execution are found after

unilateral right-hemisphere damage (Damasio and Damasio, 1977; McFarland

and Fortln, 1982).

Many disorders of arithmetic knowledge and skill, disorders that are

not secondary to either visuo-spatlal impairment or aphasia, are

preferentially associated with left posterior damage (Grafman, Passafiume,

Faglioni and Boiler, 1982; Warrington, 1982; see also McCloskey, Caramazra

and Basill, 1985).

Some disorders of visuo-perceptual functioning, detecting the hidden

figure, for example, in Gottschaldt's Embedded Figures Test have been found,

contrary to expectation, only in left-hemisphere patients with aphasia

(Orgass, Poeck, Kerschensteiner and Hartje, 1972). The capacity to

generate and utilize visual imagery is usually thought of as a righthemisphere skill. Yet recent reviews and studies provide little support for

this position (Ehrlichman and Barrett, 1983). It rather seems to be the

case that the generation of mental images at least is dependent upon the

integrity of left posterior cortex (Farah, 1984).

: :• :•:

- .

Other visuo-perceptual and visuo-spatial disorders are seen only with

bilateral damage. Examples include the visual agnosias (Davidoff and

Wilson, 1985) and locomotor map-following deficit (Ratcliff and Newcombe,

1973). Frank clinical prosopagnosia is usually dependent upon bl1ateral

lesions (Damasio, Damasio and Van Hoesen, 1982), although there Is some

recent evidence that the condition may be provoked by unilateral right

posterior damage (Landis, Cummlngs, Christen, Bogen and Imhof, 1986; De

Renzi, 1986).

Kurt Schwitters meets Le Corbusier

What price, then, hemispheric specialization? it is not in dispute

that unilateral lesions of one hemisphere often provoke cognitive

impairments that are qualitatively distinct from those provoked by lesion of

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28

the other hemisphere. But ... the notion of complementary hemispheric

specializaton qua over-riding dichott uy surely Implies that there Is a

unitary characterization of the left hemisphere's intrinsic competence such

that all the superficially different i anifestations of that coapetenca fall

under a deeper theoretical generalization. And likewise for the surface

manifestations of right hemisphere competence. In short, the hypothesis is

that the (anatomically) dual brain was designed (by Le Corbasier?) as an

organized biological structure wherein cognitive functions could rationally

co-habit: Similar functions should inhabit adjacent territory; mechanisms

whose operations call upon the output of other mechanisms should llkewi ,e be

neighbours. By contrast, radically different functions should be

geographically quite separate, independent mechanisms likewise. And the

great divide, the Danube separating the (quasi-) independent cites of Buda

and Pest is the corpus callosum. Lashley's exposition of the problem is

still classic:

5iS8

MM

w

"...separate localization of functions is determined by

the existence of diverse kinds of integrative mechanism

which cannot function in the same nerve field without

interference. (...) If temporal order is determined by

space factors in the nervous system, the fields in which

this type of organization is dominant cannot also serve

other space systems. There is thus some reason to believe

that the utilization of the spatial arrangement of

excitations in the timing functions determines an

additional group of isolated cerebral areas"

(Lashley, 1937).

- jnCil

But what do we actually find? The left hemisphere seems to be

preferentially specialized for: 'Core' language functions; sxilled praxis;

some aspects of arithmetic and calculation; some aspects of visual

detection, face and object recognition, route-finding, spatial attention and

visual imagery; and some aspects of autobiographical memory. The right

seems preferentially specialized for 'core' components of topographical

learning and memory; some aspects of spatial attention and computation, face

and object recognition; prosodic aspects of speech perception and

production; (many) aspects of music; and some aspects of autobiographical

memory! What then is the generalization that would make one recognize the

validity of hemispheric specialization over and above the unquestioned facts

of focal specialization between and within hemispheres?

The 'design' looks as if it were put together by Kurt Schwitters. Or

Rube Goldberg, as Gould (1977) suggests: "... the structures evolved ... are

Jerry-built out of available parts used by ancestors for other purposes".

During the course of the last thirty years or so, many theoreticians

dissatisfied with the language/visuo-spatial skills dichotomy have attempted

to unify each hemisphere under a variety of more 'abstract' labels. These

'new' dichotomies (which have the flavour of their nineteenth century greatgrandparents) include: Analytic/Holistic; Serial/Parallel; Focal/Diffuse;

Temporal/Spatial; High (spatial) frequency/Low frequency. Yet there is as

little evidence that these categories will suffice as there was for the

generalization of Soranus (see Marshall, 1981). Their primary vice, as

currently stated, is vagueness: their application to data-bases thus permits

unconstrained, post-hoc, 'strategic' fudges that allow almost any pattern of

results to fall under whatever label the theoretician chooses.

. • . • ,-

CONCLUSIONS ttv

To repeat: I am not denying that there are (important) differences

between the functions of the hemispheres. Neither am I denying that the

human brain/mind manifests at least duality (Bogen, 1985b). As Bogen notes,

»..-. ^. ••. ^

v •

'!•".-.•

• ••--.• .z, • . <. Oi

V. -•'--V V '•' '• V
ivwonmi.• J*v* L^V^,

the evidence from hemlspherectomy and coDmlssurotomy shows that one

I

hemisphere can function with minimal dependence upon (cortical areas of) the

other. My point is solely that the number two may well be too small.

Franz-Joseph Gall postulated forty-eight (quasi-) Independent cortical

organs that serve human cognition; each organ In his theoretical account

dealt with a different representational domain and drew upon Its own

resources of memory, attention, and volition (Marshall, 198A). And within

the human population. Gall asserted, there are substantial Individual

differences in the functional efficiency and correlated (anatomical) size of

these organs. I hold no brief for the claim that bigger means better, nor

for the number forty-eight. I do, however, suspect that forty-eight is

closer to the truth than is two.

Acknowledgement

".V

I thank Drs. Freda Newcombe and Joseph Bogen for many discussions of

these issues; neither friend should be held responsible for my continued

failures of understanding.

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ir.-SfS-N-'v >: ££iii£££rS^: 'Ov'VV •

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V

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Young, R,M. (1970). Mind, Brain and Adaptation in the Nineteenth Century.

Oxford: Clarendon Press.

Zatorre, R.J. (1985). Discrimination and recognition of tonal melodies

after unilateral cerebral lesions. Neuropsychologla, 23, 31-41.

' 'J* ." VJ

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12

IMPLICATIONS OF THE RIGHT SHIFT THEORY OF HANDEDNESS FOR INDIVIDUAL

DIFFERENCES IN HEMISPHERE SPECIALISATION

Marian Annetc

?.

Department of Applied Social Studies,

Coventry (Lanchester) Polytechnic,

Coventry, UK

Two main approaches to problems of individual differences In hemisphere

specialisat ion «re to be found In the literature. The first is avoidance:

subjects are restricted to fully right-handed males, with no known lefthanded relatives. It Is assumed that such subjects are likely to be

homogeneous for the typical pattern of cerebral specialisation. The second

approach Is to compare subjects for personal hand preference, or for Lhe

presence of left-handed relatives, usually taking care to treat the sexes

separately. In the expectation that these variables will be associated with

differing patterns of cerebral specialisation. The right shift (RS) theory

of handedness (Annett, 1972) suggests that the homogeneity of subjects In

the first approach, and the discriminating power of variables In the second

approach, are overestimated. Some of the challenges of the RS theory were

evident from Its Initial formulation, and others have been discovered In

subsequent explorations of Its Implications. A brief review of the

development of the theory was given by Annett (1981) and a full review by

Annett (1985). This paper summarises implications of the theory for

individual differences, giving first an o-ervlew, and then a selective

review of evidence for the m\in assumptions.

Overview of implications of the right shift theory for Individual

differences

The RS theory grew from an analysis of hand preference and hand skill,

but It led to a new way of thinking about hemisphere specialisation. The

theory suggests that individual differences in brain specialisation depend

first on chance anu, secondly, on the presence or absence of a gene (rs+),

and whether the gene is carried in single or double dose (rs—, rs+-t and

rs-H- genotypes). The gene is hypothesised to give to the left cerebral

hemisphere in early life a relative advantage that promotes the development

of speech control from hat side. The human species bias to right hand

preference is a by-product of the gene promoting left hemisphere speech.

In the rs—, there are no systematic biases to either side, but only

chance biases for hemisphere laterallsatijn and also for handedness, and

these chances are Independent of each other. About 50* of the rs— have

right hemisphere speech and about 502 left hemisphere speech; some small

unknown proportion may be classifiable as bilateral speakers. On obj< Ive

measures of hand skill bOX of the rs— are expected to be faster with the

left hand and 50Z faster with the right hand, but in many cases, the

• - • .^

•"^.
33

difference between Che hands Is so trivial that either hand could easily

acquire the ability to perform skilled actions. Cultural pressurer ensure

that the «ajority of rs— are right-handed. This leads to the t ..plication

that the «ajority of right brained apeaker« are right-hanued.

In the rr»— and rs-H-, the presence of the gene is sufficient, in normal

development, to ensure that speech will be controlled from the left side of

the brain. Anything that slows or distorts the normal developmental pattern

nay hinder the expression of the gene, and lateral biases for hand and brain

•re expected to diminish, reverting toward chance levels. The relative

advantage Imparted to the left hemisphere by the gene is sufficient to

Increase the probability of right-handedness, but it does not determine

dextrality. Some rs-*— and rs-H- genotypes are likely to develop left

handedness. Mixed handedness may develop In all genotypes. These

relationships imply that there can be no strong associations between

asymmetries of hand and brain; there can only be changes in relative •/vjvyi

probabilities. The chances of right brainedness for speech are certainly !w•''.'--.']

higher in left-handers than right-handers, but never higher than the

theoretical maximum of 30Z; the level of right brainedness predicted in

left- and right-handers varies with criteria of hand preference, so there

are no specific values that are true of all studies. £<.

Sex and twinning influence the expression of the rff+ gene. The JKMSS

incidence of right-handedness is higher and the rate of speech acquisition ^VJV^N^

faster in females than males and in the singleborn than in twins. These ^farv'V/

variables are also correlated with relative maturity at birth. This ÄBW«1

suggests that the gene works by modulating the relative growth of the left

and right cerebral hemispheres in late fetal life. Left hemisphere

specialisation for speech is likely to be stronger in early than late

maturers, at least in the neonatal period, and possibly later (Netley and

Rovet, 1983. Waber, 1976). '.V*

jf^ZsZi

In addition to leading to a re-evaluation of the role of variables well

established in the laterality literature, the RS theory leads to new fields

of exploration in individual differences. It suggests that variability at

the dextral side of the laterality continuum may be at least as important as

at the sinistral side. There is considerable evidence that the rs+ gene has

disadvantages as well as advantages, and that the genotype frequencies are • N

stable in the population in relationships that can be described as a

balanced polymorphism with heterozygote advantage. If the rs+- genotype is

the most favoured, it is very probable that undergraduates in higher

education are not representative of the general population for cerebral

laterality. This would imply that studies based on undergraduates are

sampling a restricted range of individual differences in hemisphere

specialisation. w^v^vi

Why right shift 7

The right shift analysis depended on a coordination of three sets of

data, hand preference in humans, hand and paw preferences in non-humans and

the distribution of left minus right (L-R) hand skill. During the 1960s

data were collected on hand preferences, r by observation and by ' ' * '^ w

j* - ^^i

questionnaire, from several large samples of college students, vvvv

•. .W^ schoolchildren and service recruits, who took part in class groups where £v!i>i'

there was little scope for volunteer effects. These samples were highly

consistent when subjects were classified as pure left-, mixed- and pure •

right- handers. v'Pure' means no preference for the other hand for any of

12 items, and 'mixed' means a definite preference for the other hand for at

least one item. Reports of 'either' hand preference were not counted as

evidence of non-dextrallty;. Percentages in 7 large samples wer» about A, '/jl,

30, 66Z, (ranges 2-5, 2V37, 58-71Z) left-, mixed- and right-handers O

MMn^ttK
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34

respectively (Annett, 1967).

Studies of hand and paw usage in other species suggested that if nonhumans mammals, Including primates, were classified on the criteria used

above for humans, the corresponding percentages would be about 25, 50, 257..

The proportions for both humans and for non-humans posed a special puzzle

because they fitted certain expectations of my first theory of the genetics

of handedness (Annett, 196A) but other evidence showed that the first theory

was wrong (Annett, 1967).

Measurements were made, also during the 1960s, of the skill of each

hand on a peg moving task In schoolchildren and undergraduates. When L-R

differences were plotted for large samples, It was evident that the

distribution is continuous and takes a form approximating a normal curve.

That there is a systematic relationship between degrees of hand preference

and degrees of L-R skill was also clear for several years, (Annett, 1970a;

1970b; 1976).

The RS solution was discovered when I asked what areas, under the

normal curve of L-R differences, would be required to represent the

frequencies of L, M, and R handedness observed. In Figure 1, each L, M and

R represents one per cent under the normal curve. The curve to the left

gives the proportions expected for non-humans; the mean Is at 0, or no

difference between the hands in skill. Close to the mean on either side, LR differences are small enough for the animal to develop mixed paw

preferences. At some critical value or threshold (about .67 SD) along the

continuum, the L-R difference will favour one hand or paw strongly enough

for the animal to d.velop a consistent preference for that side. Herce,

beyond the threshold .o each side, all animals are represented as L or R.

0.

>

::

u

re

E

o

c

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L L

L L

/

r

M M M V R R R

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/

M

\

R R R

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M M

1

1

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\

R R

"\

M M

/

M M R X R R R R

\

M

/

M M M R R

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7

I M M M R R R

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R R\

{ M M M M M R R R R

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M M M M M R R R R R R V««^RR \v

-.67 .67 SD

Lett minus right hand time

Fig.l The proportions of left-(L), mixed- (M), and right- (R) banders

expected if hand preference depends on differences in L-R skill.

Each letter represents IS under the normal curve. The thresholds

for consistent L or R handedness are about 0.67 SD from 0. The

curve with mean at 0 represents the distribution expected in nonhuman mammals; the curve with mean to the right of 0 represents the

hunan distribution.

IWTUTM '

•-• -A
i

7*r-frr \n r; vrfwjr:-vvyrnr'VrvT\.'^rKr'*Kir*- • b'wi.irL'^^"«vn^-,^wn^r ^r ^rv^ *n ^rnw«n H TT» i.

^

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The key discovery , en which the RS theory is based depends on what

happens when the normal curve is moved slightly to the right, while all

other relationships remain constant. The proportion of consistent lefthanders falls, and also the proportion of mixed-handers, but in

relationships that are mutually concordant for areas under the normal curve.

The distribution for non-humans becomes the distribution for humans, given a

shift of the curve to the right, and no other change. This implies that the

thresholds required to represent the proportion of mixed-handed humans and

of mixed-handed non-humans are identical. We can say that there is no

substantial difference between the distributions of humans and non-humans

except that the human curve is shifted such that the mean is to the right of

0, while the mean for non-humans is at 0.

This consistency has been demonstrated again in dyslexic children

(Annett and Kilshaw, 1984). The proportions of pure left-handers and of

mixed-handers were elevated in comparison with controls, but they were

raiced to the mutually consistent extents expected if a normal curve were

shifted not quite so far to the right.

Figure 2 shows the observed L-R distributions for 617 males and 863

females. Both distributiorj ?.re mo-e peaked and negatively skewed than

expected of a true normal rurvc liuth are consistent with expectations for

the sum of 2 or 3 normal sabrtisfT tions, which might correspond to the

genotypes hypothesised to make up -lie total population (Annett and Kilshaw,

1983).

The female distribution is farther to the right than that of males, at

almost all points to the right of 0. A stronger dextral bias in females

than males has been found in all my samples, whether or not incidences of

left hand preference were higher in males. It is especially worth noting

that at the left side of the L-R continuum there are no sex differences.

Whatever causes sex differences affects the right, but not the left, side of

the distribution. This is Just as expected if whatever causes the RS is

expressed more effectively in females than males, but in the absence of RS

NC^i

Stf*

vV

w

Fig.2 Observed L-R times on a peg moving cask of 617 males (solid line) and

863 females (hatched line), showing the proportions of subjects at

intervals of 2/10 s (from Annett and Kilshaw, 1983).

SK

."..vj

. .>.v

.VV
36

there are no sex differences for laterallty. This interpretation is

strengthened by the absence of sex differences in the children of two lefthanded parents (Annett, 1983).

The RS analysis requires only one systematic influence on laterallty,

something which shifts the distribution to the right. There is nothing to

suggest a factor that gives a systematic bias to the left, nor is there

evidence for such a factor in the laterallty literature. All claims to find

atypical biases depend on very small numbers of cases where small biases to

one side or the other could be due to chance. However, the laterallty

literature continues to search for the elusive essence of left-handedness.

McManus (1985) claimed to discover a left biased subgroup in my samples, as

represented in Figure 2. The claim applied to males only and seems to

depend on the little dip in the curve at -Is. An 'eyeball' test is

sufficient to suggest that this is trivial.

•"VvS «3

s<v

Since making this analysis in the early 1970s, I have been exploring

its implications for puzzles about laterallty. If there is only one

systematic influence on human handedness, an Influence that is not present

in our closest primate cousins, the most probable source of influence is

whatever biases the human left heminphere to serve speech. The RS theory

suggests that left hemisphere specialisation is the only specific factor

involved. All the rest can depend on chance.

The right shift as due to a bias to left hemisphere speech t*

The longstanding puzzles about the relations between left and right

hemisphere speech laterallty and right- and left-handedness can be regarded

as substantially solved, if the RS analysis is accepted (Annett, 1975,

1985). Independent support for the main assumptions has been given in data

of Ratcliff, Dila, Taylor and Milner (1980). Patients identified by the

Uada technique as left, right, or bilateral speakers were examined for the

distribution of structural brain asymmetry, as shown in the angle of the

posterior branches of the middle cerebral artery, visualised on carotid

angiograms. In patients with left hemisphere speech the distribution of

differences between the hemispheres was approximately normal and biased to

smaller angles on the left side. In patients with bilateral or right sided

speech, differences were also approximately normally distributed, but

clearly centred at L - R; 45Z were recorded as left-handed.

The idea that among right hemisphere speakers, the majority should be

right-handed, not left-handed, follows from the very reasonable assumption

that among people without strong biases to either side for skill, the

majority will be persuaded by cultural pressures to use the right hand. The

Idea looks paradoxical in the context of the usual approach to atypical

brsinedness, but analyses of data for dysphasics in large consecutive series

demonstrate that the expectation is fulfilled.

The widely held belief that left-handers are typically bilateral for

cerebral speech representation is without secure foundation. In some of the

major consecutive series of dysphasics compared for lesion laterallty and

handedness (Cloning and Quatember, 1966; Hecaen and Ajuriaguerra, 1964;

Hecaen and Piercy, 1956) incidences of lef t-handedness for the total sample

were comparable with expectation for the left threshold in Figure 1; for

dysphasics incidences were closer to expectation for the right threshold.

That is, the belief that right hemisphere speech is unlikely t-j be found in

right-handers led to a shift of criterion of non-right handedness. The main

evidence for bilateral bralnedness in left-handers has arisen from an

inflation of left-handers among dysphasics; there is no significant excess

of dysphasics among the left-handed, as the bilaterality argument demanded.

VJV.V

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tf

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mTMrrmfrmj 9Jrmfrmlrw*rw^v^rwm^mrl^v ^w^mvw^v^^wvwvw\rw^Im^lw^Jw\rw^mvw\m^Jwvwv^^ -. ~< -.,-..

37

The key question chat needs to be asked, from the viewpoint of the RS

theory, Is not how many right brained speakers there are in left-handers, or

how many in right-handers, but how many right brained speakers there are in

the total population. Irrespective of handedness. Using the combined data

of 4 aeries Annett (1973) estimated that 9.27Z of the population are wholly

or partially right brained. Two checks on this estimate from other sources

confirm that this is about correct (Annett, 1983). This implies that about

1 in 11 of the population have right or bilateral speech representation, and

the majority of these individuals (perhaps 60-70Z) are right-handed writers.

If this is correct, Che extent of individual variation of hemisphere

specialisation has been greatly underestimated in the general population and

in right-handers.

Why a genetic basis for the right shift?

The first support for the idea that the RS has a genetic basis came

from the absence of RS in families in which both parents are left-handed

(Annett, 1974). However, in families where parents reported significant

petsonal birth stress, or where parents showed abnormally slow right hand

peg moving times, (suggesting that the parental slnlstrality could be

pathological), the children were found to be strongly biased to the righthand. The importance of these observations was such as to make it worth

collecting a second sample, reported by Annett (1983). In the combined data

of two samples, there were 20 children in families where parental lefthandedness was Judged possibly pathological. The L-R times of this subgroup

showed a RS as strong as in general samples. In spite of being reared by LxL

parents. In the remaining 93 children, there was a normal distribution of

L-R times, with mean nonslgnificantly to the right of 0, a.> expected if the

rs+ gene were absent in the majority of children. A slmila- result was

obtained if families were differentiated, not on grounds of parental

pathology, but on the presence or absence of sinistral relatives of the

parents. These results complement the findings of an adoption study

(Carter-Saltzman, 1980) in showing that rearing by right- or left-handed

parents is not a major determinant of hand preference.

The second support for the genetic hypothesis came from the discovery

that the distribution for right- and left-handcdness In families could be

predicted, when parameters of the model were taken from data for dysphasla.

The frequency of the rs— genotype was inferred to be twice Che incidence of

right bralnedness as deduced in the consecutive series, mentioned above.

2(9.27) - 18.3A

The incidence of the rs— gene Is then Che square root of this figure (0.A3)

and the Incidence of the rs+ gene must be

1 - 0.43 - 0.57

:-«•:

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>:.

uci

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The other main parameter of the model required for genetic calculations

is Che extent of RS; ChaC Is, how far Is Che right-shifted distribution to

the right of the rs— distribution? Estimates have been derived from data

for dysphaslcs and also from distributions of L-R times in normal samples.

The best estimates currently available are that for males, the mean of the

rs-t- distribution is at 1 standard deviation, and the mean of Che ts-Mdistribution at 2 standard deviations to the right of the rs— mean (which

is 0 by definition). The shifts for females are expected to be slightly

larger than those for males. For twins of both sexes, shifts must be

smaller, to account for the slightly higher percentage of left banders among

twins than singletons, and for the distribution of RR, RL and LL pairs. The

same level of reduction is needed for monozygotic and for dizygotic pal'-s,

showing that the lesser bias is a function of twinning Itself, not zygosity.

*

^ratt^^^v:^^ .yv-.V
38

Given Chese assumptions, the theory predicts the distributions of handedness

observed In twins and In families, In all the major series of the

literature, published before and after the Initial discovery (Annett, 1978;

1979; 1985).

The details of genetic calculations depend on estimates of gene

frequency, extent of ahlft, and on the incidences of left- or mlxedhandedness recorded In any sample. Incidences vary as threshold criteria

are more strict or more generous, and expectations for genotypes In families

vary with changing thresholds. The distributions In Table 1 should be taken

as an example that depends on the particular Incidences reported by Ashton

(1982) and a particular set of assumptions as to parameters of the model as

discussed above. The example Is given to Illustrate the Implications of

familial slnlstrallty for individual differences In hemisphere

specialisation. Table 1A shows the distribution of the three genotypes In

the total population. Table IB shows the distribution of genotypes in each

of the 4 types of family classified for parental handedness, (distinguishing

sex of parent who is left handed). The distribution Is given for the whole

population (summing to 1). Table 1C gives the same analysis, expressed as

percentages within each family type.

Table I. Genotypes in Families

A. Total population

B. In families

R x R

L x R

R x L

L x L

C. As percentage within families

R x R 37

L x R 12

R x L 9

L x L 3

Genotype proportions

rs + + rs + -

.3242 .4904

rs - •

.1854

.3081 .4016 .1309

.0100 .0467 .0262

.0060 .0402 .0236

.0002 .0020 .0047

48

47

57

28

15

31

34

69

. i. \

\M\I

Calculations are based on assumptions of the RS model as described in the

text, and on parental incidences reported by Ashton (1982) for left +

ambidextrous fathers {8.97%) and mothers (7.642). In A the genotype

distribution is given as estimated for the total population. In B it is

given for each family type (father X mother) over the total population, and

In C as a percentage within each family type.

r>M^^'»^'^^

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39 N

IT the Individual differences In hemisphere specialisation of Interest

are taken to be right and bilateral speech, then on the RS theory these

occur as 50Z of rs— genotypes. Table IB shows that the majority of all Iv'v'«/''

rs— In the population (some 702) occur In the families of RxR parents (in ""iSSfl

the same way that the great majority of left-handers in the population occur

In this family type). Knowledge that one parent is left-handed raises the

probability of atypical hemisphere specialisation In the children, but this

Is still expected In not mors than about 1 in 6 cases. When both parents

are left handed, atypical cerebral speech is expected in about 1 in 3

children. . .

if individual differences in hemisphere specialisation are also to be y^^y

found in the rs-H-, as will be argued in the next section, It is worth noting #

in Table 1c that the presence to a left-handed parent is associated with a ••' ' !'''

marked decrese in the frequency of this genotype. It nay well be the case •l"*-'.-"v

that effects associated with familial sinlstrality, in the laterallty

literature, owe more to the fall in rs-H- than to the rise in rs— genotypes.

.v.

The rs+- genotype is the most frequent in the total population. It is

also the most frequent in RxR, LxR and RxL f?-!lies. In LxL families the

rs+- genotype is present in more than a quarter of children (given the UJj^ffiJffl

particular assumptions of these calculations). The main conclusion to be ." V.'AJ

drawn from Table 1 is that knowing that someone has a left-handed parent ""^"«I^'i

does not make much difference to the probability that the individual will

have right hemisphere speech. Similar considerations would apply to the 9

presence of a left-handed sibling also.

• •'«

•. -',

•:<

A Balanced polymorphism tor the rs->- gene fa&F'

The most exciting idea to be prompted by the genotype frequencies 9

(Table 1A) follows from the observation that the heterozygote, rr»—, is the ^•'.'J?

most frequent and about as high as possible (maximum 50%). This observation

suggests that the heterozygote is the most favourable genotype, and that the 'vw^i

rs— and the rs-H- both have disadvantages and advantages that are balanced '/vJvSI

over the total population. Balanced polymorphisms are very numerous in ""s's's"!

human genetics, and the majority are not fully understood, in the seise that 9

the costs and benefits of the genes involved are unknown. Since first J

deducing the genotype frequencies (Annett, 1978), I have looked for evidence

as to the costs and benefits of the rs+ gene, and some progress has been

made in understanding why the rs+ gene evolved but did not become universal

in the population.

The rs+ gene probably evolved in early hominids who were already

developing speech capacities. Speech is a human species universal; it

develops in all but grossly abnormal individuals, whether the rs+ gene is

present or absent. It is hypothesized that the function of the rs+ gene is

to expedite speech development by making speech production and speech

analysis occur on the same side of the brain. The Infant corpus callosum is

too immature to be an efficient channel for coordinating feedback from the yj^

mouth and the ear, if these two sorts of Information are being analysed in

different hemispheres. Some asymmetry in cerebral development was ] - /--!""• ""

Introduced by the gene to make one hemisphere, the left, more likely to MMIKS

control cpeech learning. The advantages of having speedy and clear speech,

in young, who are otherwise helpless and dependent on the goodwill of 9

adults, is sufficient to benefit those who carried the gene. V-s.'-'^ •>>.•.-.1

Although the gene mechanism is unknown, 1 believe that we can be fairly 'VS*1"/."'.'!

confident in the assumption that it works through cerebral maturation rates •"!''•".,'• S'"'

in late fetal life. Anything that affects maturation in that period affects

the expression of the gene. The fact that females are a little more mature
J-.V;

.V,

40

at birth than males Is sufficient to account for their greater shift to the

right. The fact that the growth of twins Is slowed to allow two fetuses to

be accommodated In the womb could explain why handedness in twin pairs can

be fully predicted by the RS model, provided the extent of shift is reduced v's''

in twins compared with the singleborn. Twins are well known to risk delayed

language growth in comparison with singletons (Mittler, 1971).

If the gene aids the development of speech, why is it not universal In *-.*V\

the population? In nature there are few benefits withcjt costs. An ''/•''\-'-l

analysis of the actual peg moving times of left-handers, mixed-handers and •< •-

consistent right-handers led Co the surprising hypothesis that the cost of

ensuring that speech control will develop in the left hemisphere is an

Impairment of the right hemisphere (Annett, 1980; Kilshaw and Annett, 1983).

In the rs+-, who have crly one dose of the gene's effects, the right

hemisphere Impairment Is relatively mild. In the rs-H-, there is a danger of

significant handicap to right hemisphere function. Further research is

planned to explore these possibilities.

What might this right hemisphere impairment by the rs-t- gene entail?

There is evidence, I believe, for three sorts of handicap. First, the left

hand is weak, slow and not very useful for skilled tasks (Kilshaw and Annett,

1983). Second, there Is Impaired capacity for visuo-spatial and X-/"-^

mathematical thinking (Annett and Kilshaw, 1982). The rs++ are not likely

to be found among high level thinkers in any field requiring non-verbal

intellectual skills. Evidence of poorer spatial ability In undergraduates who

are strongly right-handed than in others has been found for both sexes f .,...!

(Burnett, Lane and Dratt, 1982). Third, when one side of the brain is s$irC?!|

underfunctionlng, there is some finite loss of total intellectual capacity. '-/"vv**

The individual is likely to be less Intelligent, not only in visuo-spatial ^'s*'"'."?

directions, but in verbal ones also (Annett and Kilshaw, 198A). • j*->s"-i

^Af\4

Right hemisphere Impairment would give disadvantages in visuo-spatial vtf-,J

skills and in activities where close cooperation between two sides of the .. '/'

brain, and two sides of the body is required. Mathematicians use linguistic v'v'vS

symbols tc represent visuo-spatial relationships. In many sports, either or /W-J

both sides of the body must be able to react quickly. Surgeons must control

both hands very well, and must also envisage three-dimensional

relationships. Musical instruments may demand good control of both hands,

playing separately and together. The highest levels of human performance in

many skilled activities require freedom from the risks of the rrH- genotype. C^'v^

The slightly raised incidences of left- and mixed-handedness in Wv*

mathematicians, sportspeople, surgeons and musicians is probably due to the ^iViöQ

absence of the rs++ genotype (Annett and Kilshaw, 1982). A possible v % W

physical basis for the better coordination of the activities of the two

sides of the br?in in those not strongly biased to right-handedness has been

.-./.">

r_WL «

found by Witelson (1985; and this volume). •'VV'NI

It must be recognised that left-handedness, or a particular pattern of JjB

hemisphere specialisation, are not causes of superior performance in any of «V

the above activities. Rather, the rs+ gene limits the level of possible

achievement. This is why the gene has not become universal, and why some "• '•"/•

individuals must risk the problems of speech and language Development 'jS^v'*'

associated with its absence. With regard to the favourite subjects of the . \-;-. j

laterality literature, students in higher education, what has this analysis

to say? It seems probable that undergraduates selected for higher education

are more likely to be of rs-t— genotype than an unselected group of the

geneial population. Hence, the generalisation of results obtained for

undergraduates must be questioned.

With regard to sex differences, it was said above that the rs+ gene is

expressed more effectively in females than males. This is contrary to the

-•_'.*.•,.«_ *. v_ ^_ .•_ ^_ ^. .-- ^_ *_ v_ ^.-_ ^_ ^_ « _,.«•. *- f. ^- *- ^-V-V- ^^- ^- .-.•-.-.-.-...-.•- ^ -.. r. «•. • . ..«- .- ^ - . -..
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.11

hypothesis of cerebral bllaterallty In fenales. However, I believe Chat the

difficulties cncounted by psychologists trying to demonstrate laterallty

effects In females (usually undergraduates) may arise because females, even

when heterozygote, are more likely to have an underfunctionlng right

hemisphere than males. That Is, they try to solve all problems verbally, as

suggested by Sherman (1978). The critical difference is not so much between

a left-verbal and a right-nonverbal hemisphere, as between a better left and

relatively poorer right hemisphere in females. These relationships do not

occur only in females. They occur in rs-H- males also, but such males are

probably infrequent among right-handed undergraduates. The analysis of

Inglis et al. (1982) is especially important la showing that females tend to

rely on the left hemisphere for both verbal and nonverbal functions. This

is not a function of sex as such, but of the stronger expression of the rs-»-

gene in females. The present analysis suggests that females who are ro—,

or rrt- with relatively weak expression of the ra+ gene, might be as good in

visuo-spatial and mathematical thinking as men. Their main problem could be

that society does not expect them to be good, and opportunities for such

girls to develop in these directions are limited.

-•.V»

/•:

CONCLUSIONS

This chapter has summarised some key ideac about individual differences

in hemisphere specialisation, from the view point of the RS theory. The

theory offers a new perspective on questions of human lateral asymmetry,

provided the reader is prepared to accept the cognitive restructuring

required. Since the RS theory suggests that the main variable involved is

chance, and all systematic effects have to be detected against a random

background, the number of subjects required for adequate tests of hypotheses

must be substantially larger than have been used in the typical laterallty

experiment. The theory suggests that there is more intrinsic variability in

the typical right-hander than is usually recognised, and that the effect of

having sinistral tendencies in the subject or in relatives is smaller than

might be hoped. The most exciting impllcailois of the theory arise from the

idea that human cerebral specialisation for speech is a human evolutionary

adaptation which has costs as well as benefits. When relationships are

found between hand preferences and factors associated with hemisphere

specialisation (several chapters in this volume), the RS theory suggests

that the most useful interpretations will prove to be in terms of the costs

and benefits of the right shift gene.

REFERENCES

Annett, M. (1964). A model of the inheritance of handedness and cerebral

dominance. Nature. 204, 59-60.

Annett, M. (1967). The binomial distribution of right, mixed and left

handedness. Quarterly journal of Experimental Psychology.. 29, 327-

333.

Annett, M. (1970b). The growth of manual preference and speed. British

Journal of Psychology, 61. 545-558.

Annett, M. (1972). The distribution of manual asymmetry. British Journal

of Psychology. 63. 343-358.

Annett, M. (1974). Handedness in the children of two left handed parents.

British Journal of Psychology. 65. 129-131.

Annett, M. (1975). Hand preference and the laterallty of cerebral speech.

Cortex, 1_1^ 305-328.

Annett, M. (1976). A coordination of hand preference and skill replicated.

British Journal of Psychology, 67^, 587-592.

Annett, M. (1978). '"iTSingle Gen.; Explanation of Right and Left Handedness

and Brainedness". Lanchester Polytechnic, Coventry.

Annett, M. (1979). Family handedness in three generations predicted by the

right shift theory. Annals of Human Genetics, 42, 479-491.

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I

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• V V V

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'vi?j-..w.--.%^'-«.v..V • ^ ^^:^^^v:^s:^v^ •• .•.'..•
,> >»>

42

AnneCC, H. (1981). The right shift theory of handedness and developmental

language problems. Bulletin of the Orton Society, 31, 103-121.

Annett, M. (1983). Hard preferrnce and skill in 115 children of two left , v

handed parents. British Journal of Psychology, 74, 17-32. W'y

Annett, M. (1985). "Left, Right, Hand and Brain: The Right Shift Theory", ivSr

Lawrence Erlbaum, London.

Annett, M. and Kilshaw, D. (1982). Hathematical ability and lateral

asymmetry. Cortex. 18, 547-568.

Annett, M. and Kilshaw, D. (1984). Lateral preference and skill in ^SfvS

dyslexics: Implications of the right shift theory. Journal of Child •"%v'\'rV

Psychology and Psychiatry. 25, 357-377. '^SrS

Burnett, S.A., Lane, D.M., and Dratt, L.M. (1982). Spatial ability and

handedness. Intelligence, 6^ 57-68.

Carter-Saltzman, L. (1980). Biological and sociocultural effects on

handedness: Comparison between biological and adoptive families. '-'s*'^

Science. 209, 1263-1265. '>•;>

Cloning, K. and Quatember, R. (1966). Statistical evidence of •''< ''.

neuropsychological syndromes in left handed and ambidextrous patients. ''^- ^'

Cortex. 2. 484-488. ' IvV?'.*1

Hecaen, H. and AJuriaguerra, J. (1964). "Left handedness: Manual

Superiority and Cerebral Dominance". Grune and Stratton, New York.

Hecaen, H. and Piercy, M. (1956). Paroxysmal dysphasia and the problem of 's's^v

cerebral dominance. Journal of Neurology, Neurosurgery and Psychiatry ^"'vXr'"!

28, 194-201. ^ ^ ^

Inglis. J. Ruckman, M.S. Lawson, J.S. MacLean, A.V. and Mcnga, T.N. (1982).

Sex difference in the cognitive effects of unilateral brain damage. •

Cortex. IB_, 257-276. Ä'^

Kilshaw, D. and Annett, M. (1983). Right and left hand skill I: Effects ,-*s ••'<

of age, sex, and hand preference, showing superior skill in left 'NvH

banders. British Journal of Psychology, 74, 253-268. "'••!/V'

McManus, I.C. (1985). Right and left hand skill: Failure of the right 'y^V."]

shift model. British Journal of Psychology. 76. 1-16.

Netley. D. and Rovet, J. (1983). Relationships among brain organization.

maturation rate and the development of verbal and nonverbal ability.

In: "Language Functions and Brain Organization". S.J. Segalowitz. ^SÜSÖ

ed.. Academic Press. New York. 245-266.

Ratcliff, G. Dila. C. Taylor, L. and Milner, B. (1980). The morphological

asymmetry of the hemispheres and cerebral dominance for speech: A

possible relationship. Brain and Language. 11. 87-98. V

b'''',V

Sherman, J.A. (1978). "Sex-related Cognitive Differences: An Essay on viv'v

Theory and Evidence". Charles C. Thomas, Springfield, Illinois. ^''/•'/•J

Waber, D.P. (1976). Sex differences in cognition: A function of V'.v'.vlj

maturation rates. Science, 192, 572-574. 1*1'*'I

Witelson. S.F. (1985). The brain connection: The corpus callosum is i^

larger in left-handers. Science. 229, 665-668. v;Äv!i/

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43

IS CEREBRAL LATERAL1ZATI0N A GRADED OR A DISCRETE CHARACTERISTIC?

John C. Marshall

Neuropsychology Unit,

The Radcllffe Infirmary,

Oxford,

0X2 6HE, U.K.

SSssa

The human body Is replete with paired organs, buth externally (eyes and

ears, for example), and Internally (the kidneys). The anatomical similarity

between the members of such pairs leads us to expect that they will have

similar or even identical functions. This expectation Is born out in fact,

although some mechanisms of depth perception and sound localization demand

that both eyes and both ears are respectively operative. At the level of

gross anatomy, the human brain likewise shows every appearance of being a

double organ, and it is thus hardly suprising that, until the time of Broca

(1865), the two hemispheres were usually regarded as functional duplicates

of each other. Broca's discovery that a left unilateral lesion could

severely impair speech production (and the many later reports of cognitive

deficit subsequent upon either left or right unilateral damage) dealt the

duplicate model a blow from which it has never recovered. It was initially

replaced, however, by an equally simple dichotomous model. The notion of

complementary specialization was often taken to imply that, for many higher

functions, one hemisphere and one hemisphere alone possessed the relevant

underlying computational capacities, the other hemisphere being totally

inert within thai domain of processir;.

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But many scholars now regard the strict dichotomy model as too extreme,

not so much simple as simplistic. It is thus often argued that cerebral

laterallzation for many (all?) language and speech functions is a "graded

characteristic, varying in scope and completenebi from individual to

individual" (Zangwill, 1960). More generally, Bradshaw and Nettleton (1981)

have argued that for any of the 'Analytic Left, Holistic Right' kinds of

partitioning, the notion of a true dichotomy Is untenable. They claim that

there Is a "continuum of functions" such that the hemispheres should be

regarded as differing In degree rather than kind. Although the 'graded'

model of cerebral laterallzation Is currently the most acceptable vetslon of

brain specialization for most neurcpsychologlsts, I find myself In the

somewhat unfortunate position of having little (or no) idea of what the

claim Implies or even means (Marshall, 1973). The reason is that we have

not succeeded in specifying the metric over which degrees of laterallzation

should be computed.

Let us indulge ourselves tb«>n in a little numerology: Imagine that, in

principle, both hemispheres of the human brain can support all language

functions with a greater or lesser degree of proficiency. We now define

maximal proficiency for a single hemisphere as 100%, minimal proficiency for

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44

Interpret quantitative estimates of degree of recovery from aphasia in terms

of 'back-up' or relearning mechanisms in the non-dominant nemlsphere.

Likewise, It would teem to preclude «erious atudy of, say, the differential

effects of right- versus left-hemtspherectomy. Indeed, the absolutely basic

data of the field - the behavioral consequences of left- versus right-sided

lesion* - could become uninterpret ible.

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^

We thus appear to be committed to some form of numerology for the

lateralization of psychological functions, whether we like it or no. The

only concern is which numerology can be theoretically justified (Allen,

1983). One final point: The astute reader will have noticed that I have

Ignored (thus far) the, (possibly related) issue of degrees of anatomical

•symmetry. I have done to for the following reason: Bigger may or may not

turn out to be better, and it is only in the case that bigger is better that

psychologists have any reason to get excited. Should it turn out that there

Is any necessary (or even interesting) correlation between size and

proficiency, T hereby pledge my subscription for the erection of a statue to

Franz-Joseph Gall in Harvard Square.

* A cabbalistic method of interpreting the Hebrew Scriptures by

interchanging words whose letters have the same numerical value when

added. (The Shorter O.E.D.) - Ed.

Acknowledgement iN1^

1 am grateful to Dr. Patrick Hudson for many discussions on the Issues

raised here.

REFERENCES

^$11 v: « /

Allen, M. (1983). Models of hemispheric specialization. Psychological

Bulletin, 93. 73-104.

Bradshaw, J.L. and Nettleton, N.C. (1981). The nature of hemispheric

specialization in man. The Behavioral and Brain Sciences, A, 51-91.

Broca, P. (1985). Sur le facult^ du langage artlcuIT. Bulletin de la

Societe d'Anthropologie de Paris, 6^, 493-494.

Marshall, J.C. (1973). Some problems and paradoxes associated with recent

accounts of hemispheric specialization. Neuropsychologia, 11, 463-470.

Marshall, J.C. (1981a). Lateral and focal organization in the human brain.

In Y. Lebrun and 0. Zangwill (Eds.) Lateralization of Language in the

Child. Lisse: Swets and Zeitlinger.

Marshall, J.C. (1981b). Hemispheric specialization:

The Behavioral and Brain Sciences, 4, 72-73.

What, how and why.

Marshall, J.C, Caplan, D. and Holmes, J.M. (1975). The measure of

laterality. Neuropsychologia, 13, 315-321.

Zangwill, 0. (1960T Cerebral dominance and Its Relation to Psychological

Function. Edinburgh: Oliver and Boyd.

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INTRODUCTION

'»:

INDIVIDUAL DIFFERENCES IN THE ANATOMY OF THE CORPUS CALLOSUM:

SEX, HAND PREFERENCE, SCHIZOPHRENIA AND HEMISPHERE SPECIALIZATION

Sandra F. Witelson* and Debra L. Klgar"*"*" WSS

* Departments of Psychiatry, Psychology and Neurotclences, McMaster y^-"N'.'i

University, Hamilton, Ontario, Canada. '-/,V^J

Department of Psychiatry, McMaster University.

ABSTRACT {fjjj

Recent studies of the gross anatomy of the corpus callosuo show that

there is marked variation in its size and shape, but also considerable

consistency in these variations across very diverse studies. One study to *w

date has reported a larger callosum, particularly in the mid-and anterior .''v"/»,

regions, in mixed and left banders compared to consistent right banders. >S-'v*

Several reports have examined possible sex differences in callusal anatomy i

w!*.'!'>Jü'

and have produced apparently inconsistent results. The evidence clearly

does not support a larger posterior splenial region in absolute size in

females. However, a minority of the studies suggest that the posterior

region, proportional to the size of the total callosum, may be larger in

females than in males. Further clarification is needed- The early studies ^-'-!-'•]-'>

of callosal anatomy in schizophrenia suggested a thicker callosum in vVv

schizophrenics. Subsequent studies do not support this finding and may be .''v'^'

confoundeJ by variables such as chronological age, body size, brain size,

and type of control group. Any anatomical differences between schizophrenic *. % %

and normal individuals may involve some interaction of callosal region, sex 'iv'.'/*!

and hand preference. These results are discussed in relation to individual ^O'^jS

differences in hemisphere specialization and brain function.

.-

.•.•: The corpus callosum is clearly an essential structure in the

Integration of the functioning of Che two cerebral hemispheres (e.g..

Lepore, Ptito 4 Jasper, 1986). Neurosurgical section of the callosun. (by

cou.miFsurotomy or callosotomy) results in the dramatic isolation phenomenon

in which an individual behaves as if he were unaware of the incoming

Information and perceptions derived from one side of his sensory world, and

manifests two separate unintegrated streams of consciousness (Sperry, 1974). •/V's*'

The posterior segment of the callosum appears to be particularly important :':.:'\.

for the integration of sensory information and has been termed a sensory

window between the hemlspueres. The anterior regions of the callosum appear

to be involved in the interhemlspheric integration of higher level mental

processes such as the interaction between perceptual and mnemonic rather

than sensory information (Sidtis, Volpe, Holtzman, Wilson & Gazzanlga, WJ

1981). "<'.

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47

It has also been hypothesized that the corpus callosum plays a role In

the manifestation, and possibly In the maintenance, of the functional

specialization of the hemispheres (Wltelson, 1985b). The development of

hemisphere specialization is not Included in this hypothesis as there is

considerable evidence that hemisphere specialization - the differential

capacities that the hemispheres have in mediating cognition - does not '. '-.''-'/^

develop but is present from birth or very soon thereafter (e.g., Wltelson, >^'r/^

1985b; 1986b).

Within this framework, the study of the anatomy of the corpus callosum

is relevant to the study of the functional integration and specialization of

the hemispheres. A brief history of the early conceptualizations of the

functions of the corpus callosum and an overview of the types of anatomical

studies are presented elsewhere (Colonnler, 1986; Wltelson, 1986a). Any

variation in the anatomy of the corpus callosum found to be correlated with

aspects of functional brain organization would have theoretical significance

for understanding the brain as the substrate of cognition. It could also

serve as an anatomical marker in the clinical diagnosis of syndromes such as

dyslexia in which atypical hemisphere specialization may be a factor (e.g.,

Hynd & Cohen, 1983) or schizophrenia in which interhemispheric integration

may be relevant (e.g.. Cur, Skolnick, Cur, Caroff, Rieger, Obrist, Younkln &

Relvich, 1983), or in genetic studies of the heritabllity of hemisphere J

specialization. '

This paper will review the available studies of the gross anatomy of

the human corpus callosum. In some studies, particularly the older ones,

statistical analyses were not done, but the raw data were often presented in "'^

the original reports. Using these data, the present authors carried out

some simple statistical analyses relevant to the issues of this paper. The

picture that emerges is one of marked variation in the anatomy of the corpus kN^O

callosum, but also of considerable consistency in the variation, which was

observed in different laboratories, in studies done for very different

purposes, decades apart. In addition, even though the data are just

beginning to be accumulated, the variation appears to be correlated to some ^uyfi

extent with variables such as sex, hand preference and schizophrenia. ' .£<

Clinical and experimental neuropsychological studies have found some

correlation between individual differences in hemisphere specialization and

hand preference and sex (e.g., Bryden, 1982; De Vries, De Bruin, Uylings &

Corner, 198A). Thus the anatomical variation may be relevant to individual

differences in hemisphere specialization and cognition. 1

In recent studies of callosal anatomy, the variables of handedness and >o->S

ex have been investigated directly in relation to cerebral dominance. Some »"VTMEfl

of the earliest work considered sex as a variable, but only in relation to

possible group differences between the sexes or different races. The corpus

callosum has also received considerable attention in the anatomical

Investigation of the brains of schizophrenics as a result of the recent

interest in the neuroanatomical substrate of schizophrenia and the

possibility of abnormal inter', emispheric functioning (e.g., Cruzelier &

Flor-Henry, 1979). Thus, it seemed worthwhile to review this literature in * j

conjunction with the work on normal brains. «vv^S

ANATOMY OF THE CORPUS CALLOSUM IN NORMAL ADULTS -"vvv'

The earliest anatomical studies of the corpus callosum appeared at the ftWOnii

turn of the century. Spitzka (1902; 1904; 1907) and Bean (1906) were Arinterested in the callosum in relation to race, heredity, and intellectual - - ^

ability. Bean also looked at sex as a factor. Until the 1960's very little

further work appeared - only sporadic reports on the gross anatomy of the

callosum and the work of Tomasch (195A), which still remains some of the

only available histologlcal study of the human callosum. Then Raklc and
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48

Takovlev (1968) presented their detailed study of the gross morphcmetric

changes of the callosuo over development until maturity. In addition,

Takovlev and Lecours (1967) published their report of the myelogenetic

course of fibre tracts, Including the corpus callosum, over the life span,

and documented the fact that myelinatlon of the corpus callosum continues

until at least age 10 years. It was not until the 1980's, in the vake of

the extensive interest in neuropsychological research and its implications

for the functions of the corpus callosum, that attention was redirected to

the anatomy of the human corpus callosum. One of the first papers concerned

k case of conmissurotomy. It was noted that the Inconsistency of the

behavioral sequelae in apparently similar cases of commissurotomy could be,

in part, related to the variability of the shape of the posterior rounded

end of the callosum which is difficult to view during neurosurgery and,

therefore, to section completely (Greenblatt, Saunders, Culver &

Bogdanowicz, 1980). Lang and Ederer (1980), noting the need for an

extensive study of the size and shape of the human corpus callosum, measured

various aspects of the callosum in 100 postmortem brains. In the last few

years several studies have started to look in more detail at the size and

shape of the callosum and its subdivisions in relation to neuropsychological

and neuropsychiatrlc variables, not only in postmortem brains but in vivo,

by means of the new technology of magnetic resonance imaging (MRI) which

produces computerized Images of the living brain. The studies of

neuropsychiatrlc patients have provided information not only about clinical

populations, but also about control groups of normal individuals which can

be used as farther normative data.

The available studies deal with measurements of the maximal

anteroposterior length of the callosum, its total area, the areas and widths

of various subdivisions of the callosum along its mid-longitudinal or midsagittal axis, and widths of coronal sections of the callosum. All the

anatomical features, subdivisions and dimensions measured are shown in

Figures 1 and 2. Table 1 presents a summary of the main findings of the

gross anatomy of the corpus callosum in normal human adults.

Total Corpus Callosum

Maximal anteroposterior length and total area have been measured in

several studies. The results indicate a wide range of values, but much

consistency between studies. All studies reported mean maximal lengths

between 70-80 mm (see Table 1) with the exception of the study by Raklc and

Takovlev (1968) In which the value is about 15 percent less than in other

studies.

This raises the issue of the importance of considering the method of

tissue fixation when comparing values from different studies. All the

measurements in the Rakic and Yakovlev (1968) study are smaller tuan those of

other reports, due to the fact that their measurements were taken from

celloidin-embedded sections rather than from formalin-fixed brains.

Celloidin embedding results in considerable shrinkage (approximately 20

percent) whereas formalin-fixed tissue undergoes almost no shrinkage (van

Buren 4 Burke, 1972). Formalin fixation was used in all the other

postmortem studies reporting length. Tomasch (195^), who reported only area

measurements, used paraffin-embedded sections which also involve

considerable shrinkage and thus his values are also smaller than those

reported in other studies.

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Figu j ;. The corpus callosum of an adult human Is shown In mldsagittal

view. The various measures and subdivisions referenced In Tables 1, 2, and

3 are Indicated. Abbreviations: G, genu; B, body; S, splenlum; ACC and

FCC, ancerlornost and posterlormost points of the corpus callosum,

respectively, which form the line of maximal length used to obtain the

callosal subdivisions (the anterior and posterior halves, and the posterior

third, quartlle, and fifth). The midposterlor region (cross-hatched area),

labelled the parletotemporal region (p-t). Is defined as the posterior third

minus the posterior fifth region; GG., maximal width of the genu; SSj,

maximal dorsoventral wldrh of the splenlum; AA., a width of the anterior

part of the body of the callosutn; MM., midbody width; PPj, a width of the

posterior part of the body; LV; lateral ventricle; F, fornlx; IF,

Interventricular foramen; MI, massa intermedia; AC, anterior commissure; PC,

posterior commissure.

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Figure 2. Coronal (frontal) section of a normal adult brain at the level

of the Interventricular fora-nen. (a) Axis of coronal section Is shown. (b)

Coronal section. Abbreviations: LF, dorsal aspect of the longitudinal

(nidsagittal) fissure; SF, Sylvlan fissure; CC, corpus callosum; BBj,

nidbody width of the callosum (this mldbody width is taken in a plane

perpendicular to those in Figure 1); LV, lateral ventricle; F, fornix; IF,

interventricular foramen; IIIV, third ventricle.

' ^* ^ <" «w' K.'L'J' O •«" « " K" v" V s.*"» '«.""«.'i •

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A / ',.- V.V-.' ^y^. ...v. v.wa^aaa
• flogle hemisphere at OX. Without the Imposition of any further 51

constraints (1.«. assuming full Independence between hemispheres), this

would permit the relarlve efficiencies of total brains (I.e. left plus right

heolspheres) to vary from Ot to 2001 proficiency. Now assume a 'celling

effect' at 100t, auch that any capacity In excess of 100* Is 'spare'. Is

this the theoretical domain of 'brain-power' for language from which the

actually-occurring population of human brafns Is a statistically-biased

»ample? Within the above model we could find one Interpretation of the

notion that the non-dominant hemisphere for language (l.a. the hemisphere

for which Language.! < Language*!) is a 'back-up' device to be called into

service consequent upon injury to the dominant hemisphere. Within this

model, it follows that the greater the degree of bilateral representation

(in an individual aubject) the smaller the chance of any unilateral injury

resulting in (permanent) aphasic disorder (Marshall, 1981a).

•^ V N

If, on the other hand, we assume that there is additionally a 'final

common path' which is unique to the dominant hemisphere, then unilateral

injury to that hemisphere will result in impairment irrespective of the

degree of language proficiency or talent (OZ to 100%) of the non-dominant

hemisphere. Similarly, injury to the non-dominant hemisphere will result in

no impairment, again irrespective of its degree of 'Intrinsic' languagecapacity.

Consider now an alternative model where, again, the proficiency of each

hemisphere may vary between OX and 100Z, but subject to the constraint that

their sum may not exceed 100Z. This is to say that the hemispheres are no

longer regarded as independent devices. If we allow the hemispheres to

interact (communicate), then on this proposal injury to either hemisphere

will produce some impairment in all cases save for the two extremes of left

- 1002, right 02, and vice-versa. In other words, the model excludes any

'back-up' component; recovery from unilateral aphasia does not Involve

drawing upon 'uncommitted' tissue from the intact hemisphere. Is this the

theoretical framework which underlies the claim that lateralization is a

graded characteristic?

It might be objected at this point that the entire line of reasoning is

specious in that it involves the assumption that language is a unitary or

'global' function. The objection can be countered by running the argument

on any subfunction which contributes to the definition of language-abilities

(Marshall, 1981b). Indeed, the argument can be run on any unit of analysis

whatsoever (down at least to the level of an individual nerve cell, which

we presume must have a discrete, not a graded, spatial location).

Considerations of the aforementioned nature do, however, remind us of yet a

further qualitatively distinct interpretation of lateralization; the notion,

due in the first place to Hughlings Jackson, that aome language functions

may be more (and differently) lateralized than others. Such a concept would

allow control of speech production, for instance, to be firmly leftlateralized whilst another function (e.g. perception of emotive aspects of

prosody?) could be firmly right-lateralized. Likewise, comprehension of

apoken language might, as Jackson suggested, have a relatively bilateral

representation in the brain. If we insist upon capturing the notion 'degree

of lateralization' by a single number (Marshall, Caplan and Holmes, 1975),

should that number be the weighted product of a variety of differently

lateralized subfunctions of language ability? Would such a number have any

real meaning or value? Would a set of numbers be more appropriate?

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study of gematria*. Unfortunately, such a wholesale condemnation would seem

to deny any possibility of ever Interpreting the meaning of, say, dichotic

listening or split visual-field scores; it would make it difficult to

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59

Since the values in the Raklc and Takovlev paper are not true absolute

measures they are not appropriate baseline measures, although in the past

they have frequently been used as such, since for years the Rakic and

Takovlev report was the most recent extensive study. Their paper is unique

in presenting information about the relative aorphometric changes of the

total callosuB and its different subrcgions as it transforms in size and

shape from gestation to maturity.

At this point it is useful to note the relatively small discrepancies

between the mean maximal lengths obtained from formalin-fixed postmortem

material, such as 73-7 mm based on 100 cases (Lang & Ederer, 1980) and 72.4

mm based on 42 rases (Witclson, 1986a), and that of 78 mm obtained via MRI

scans (Nasrallah, Ardreasen, Coffman, Olson, Dunn, Ehrhardt 4 Chapman, 1986).

Midsagittal total corpus callosum area measurements vary across studies

with means ranging from about 560 tc 800 mm2(excluding the value of 325.1

mm2in the Raklc and Takovlev stu^y and the value of 532 mm2in the Tomasch

report). Individual values range from approximately 400 to 1000 mm . Area

measurements reflect the width and length of the callosum as well as the

variation in the width and shape of the genu, body and splenium. The

greater variation in the area measures of the callosum suggests that area

may be a better index of individual differences than measures of length.

vMvsJ

Spitzka's (1902; 1904; 1907) reports were concerned with anatomical

variation of the callosum in relation to heredity and intelligence. In one

paper (1904), he studied the brains of three brothers and found the length

of the callosum to be identical in each, in addition to similarities in

other anatomical aspects of the brains. In his 1907 report, he compared a

group of "scholars" and "ordinary" individuals. The conclusions Spitzka

drew from these data were not based on statistical analyses. However, the

inclusion of the raw data in Spitzka's papers allowed the present authors to

do some analyses which tended to support some of his statements. Both

callosal length and area (see Table 1) were found to be significantly larger

in the scholars group (t - 2.49, df - 17, p -<.02; t 3.46, df - 17,

p *<.003, respectively). However, callosal size and brain weight are

correlated. For example, as reported in Witelson (1985a), the correlation

between callosal area and brain weight is r - 0.51 (df - 40, p - <.001).

Mean brain weights tor the scholars and ordinary men were 1513 and 1443

grams, respectively, but analysis showed the difference to be nonsignificant

(t - 1.74, df "17, p .10). Thus, the callosal differences between the

scholars and ordinary men may not be completely accounted for by differences

In brain weight. Callosal area proportional to brain weight was 49Z for the

scholar group and 39* for the ordinary group. Nor does chronological age

and the associated decrease in brain weight appear to account for the

difference la callosal anatomy as the mean age at death for the scholars was

58 years, and for the ordinary men, with a smaller callosum, 33 years.

Spitzka (1907) also looked at the length of the corpus callosum

relative to the length of the hemispheres. Hemisphere length did not differ

between the two groups (172 mm for each group). Thus the brains of the

scholars not only had larger absolute callosa, but also larger collosa even

when hemisphere length, brain weight and age were taken into account. It

should be noted, however, that the group of ten ordinary men were prisoners

and it is not clear what this represents in terms of the intellectual

Mlity of the group. In addition, the cause of death was different for the

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group«. The •cholars died from Illnesses, the prisoners from electrocution.

Whether this factor affects brain structure at postmortem Is not clear.

Since callosal size correlates with brain weight (Vltelson, 1985a) and brain

weight correlates with body size and height (Holloway, 1980), it is

important to take into account the contribution to callosal size of these

and other variables such as nutritional history.

Bean (1906) studied total callosal size as part of an extensive

anatomical study of brains in different racial groups. Like Spltzka (1907),

Bean drew many conclusions from his data based solely on comparisons of the

relative value of mean scores without the precaution of statistical

analyses. Moreover, he made etrong statements regarding the correlation

between anatomical and cognitive differences between the races in the

absence of empirical evidence of either the existence of the cognitive

differences or of any correlation between the anatomical and cognitive

variables. Since Bjan also included the raw data, some statistical analyses

could be done by the present authors for those issues relevant to this

chapter. Some of the anatomical differences proved to be statistically

significant The total callosal area was greater in the Caucasian than in

the Negro group within each sex (males: t - 2.63, df - 103, p -<.01;

females: t 2.06, df - 40, p <.05, see Table 1). However, comparison of

absolute callosal size is questionable in this study since the mean brain

weight of the groups differed significantly, st least for males. Using all

the data available, the mean brain weight for the Caucasian and Negro male

groups was 1304 and 1216 grams, respectively (t - 3.34, df 108, p -<.001);

for the females. 1103 and 1068, respectively (t - 0.98, df - 38, p -<.33).

As indicated above, brain weight and callosal area are correlated. If

callosal area is considered proportional to brain weight, the mean ratio

scores are very similar in the two racial groups. For the male Caucasians

and Negroes, the mean ratio scores are 53 and 52 percent, respectively; for

the females, 57 snd 54 percent. The callosal differences may be related to

the brain weight differences and the brain weight differences may be

affected by any number of factors such as age at death, sex, height, body

size, nutritional history, cause of death and brain removal and storage

procedures.

Subdivision« of the Corpus Callosum

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A few suthors have reported measurements for subdivisions of the

callosum, such as area of the anterior and posterior halves and width of

different parts of the trunk or body of the callosum (see Figure 1). The

two studies that have reported area measures for the anterior and posterior

halves are quite consistent. The mean area for the anterior half reported

for Caucasian «ales is 368 (Been, 1906) and 367 mm2(Witelson, 1985a); and

314 and 345 mm2for females, resoectively. The mean area for the posterior

half for males is 301 and 305 mm7, end for females 289 and 310 mm2in the

two studies, respectively. In Bean's study, the area of the anterior half,

like the results for total callosal area, was significantly greater in

Caucasians than in Negroes, but this time only for males (males: t - 3.56,

df -90, p - .0006; femalea: t - 1.16, df - 31, p - .26.) (The issue of

possible sex differences will be considered in a aubsequent section). No

such difference between the races was obtained for the posterior half region

(males: t • 1.36, df - 90. p - .18; females: t - 17, df - 31, p - .87; see

Table 1). One simple approach to controlling for the possible contribution

of different overall brain size to group difference« in size of callosal

subdivisions is to consider the relative size of one part to another, for

example, the anterior half to the posterior half. Such ratio scores might

reveal possible group difference«. What, if any, functional significance

such anatomical variation may have remains to be determined.

The values given in the three studies that measured the width of the

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A 61

I callosun) at the old point of the body or trunk (see Figure 1) were S.7 mo for

I 100 postmortem brains (Lang 4 Ederer, 1980), 6.6 an for 42 postmortem brains

(Witelson, 1986a), and 5.5 am for 31 MRI scans of normal volunteers

(Nasrallah ct •!., 1986). From data given in the reports of Lang and Edere-

(1980) and Nasrallah et al. (1986), the maximal body width was 6.7 and 6.1

m, respectively, and the minimal width was 4.5 mm in both studies.

Splenium

.-..N. The posterior region of the callosum forms an expanded bulbous area JSisfl

i relative to the body of the callosum and is referred to as the splenium. It ^•'O

• has no clear anatomical landmarks to separate It from the body and,

accordingly, it generally has been arbitrarily defined for measurement by

geometrical definitions, such as the posterior fifth of the callosum, based

I on a linear division of the maximal anteroposterlor length (see Figure 1).

The «plenium has received considerable attention, both with respect to

' function and anatomy (e.g., Lepor/, Ptlto & Jasper, 1986). The splenium has

* been demonstrated by various experimental techniques to house the

interhemispheric fibres from the occipital prestriate cortex and from aome

temporal visual regions in rhesus monkey (e.g., Pandya, Karol & Heilbronn,

1971; Rockland & Pandya, 1986) and in humans (de Lacoste, Kirkpatrick &

Ross, 1985).

The maximal width of the splenium (12-14 mm) appears to be very similar W

to that of the genu (the anterior knee-shaped region of the callosum) (Rakic

6 Yakovlev, 1968; Lang & Ederer, 1980; see Table 1). The splenium has been

found to show considerable variation in size and shape. The variation in y^V]

shape may explain some of the inconsistencies reported in the manifestation •"-' /" .

of deficits following commissurotomy (e.g., Hyers, 1984). Greenblatt et al. y'vv

(1980) reported a case in which interhemispheric transfer of visual and ^ •''V"^

auditory sensory stimulation remained intact following splenial 1> /%

commissurotomy and this was attributed to inadvertent partial, rather than

complete, sectioning of the splenium due to its variability in shape. In

consideration of this hypothesis, Greenblatt et al. examined the shape of

t the splenium in ten normal brains and found that it varied from being barely ^'vC^

| bulbous and having almost no curve on the ventral border to being distinctly f*****

curved and bulbous. This anatomical variability has been described by .'./>!

others as well (de Lacoste-Utamsing & Holloway, 1982; Demeter, Ringo & Doty, '.-••<

1985; Clarke, Kraftsik, Innocenti & van der Loos, 1986). J^/V']

The absolute area of the posterior fifth region has been reported in a wfijl

few studies (e.g., Bean, 1906; de Lacoste-Utamsing & Holloway, 1982: -•/•!" ;

Witelson, 1985a, see Table 1) and tends to range from 160 to 220 mm .

Several studies have looked at possible group differences. Since groups may

differ In total callosal area, it is important to consider the posterior

fifth region proportional to the total area. Such a ratio score helps to

assess any internal callosal variation in shape without the confounding

effects of different brain size, body size and height, chronological age,

and fixation methods. Such analyses lead to surprisingly consistent results

between most groups and studies. These results will be discussed in the

following sections.

SEX DIFFERENCES AND CALLOSAL ANATOMY

Total Callosum and Sex J wv

The size of the total callosum, measured by length and area, has been >'v""S

Investigated for possible sex differences. Since the male brain is

significsntly larger than the female brain by about 10 tc 15 percent

(Holloway, 1980), one might expect that different regions, such as the
62

Table 2. Absolut" «nd relative «Ire of the posterior fifth region of the

callosum in males «nd females In different studies.

» . ■■■■

S'OJDY POSTERIOR FIFTH REGION (mm2

)

ABSOLUTE AREA AREA PROPORTIONAL TO

TOTALCALLOSAL AREA

MALE

N X

FEMALE

N X

MALE FEMALE

BEAN, 1906*

Caucasian 53 173 14 164 .25 .26

Negro 52 186 25 173 .29 .30

DE LACOSTE-UTAMSING et al 15 __b 13 __ ...

1981

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DE LACOSTE-UTAMSING &

HOLLCWAY, 1982

186 218 .26 .31

WITELSON, 1985a

Consistent right banders 7

Mixed banders 5

181 20 172 .27 .26

202 10 178 .25 .26

f.

CLARKE ct al

1986

32 26 ,26 .28

Ratio scores are based on N's for which both total and posterior

fifth areas were available.

| |

••. • > .1

U^

-- No scores given.

callosum, sight also be isrger In Bales. Most researchers considering sex

differences did not make explicit vhat difference, whether absolute or

relative. Bight be expected.

The first study of the human corpus callosum to look st the sexes

separately was likely that of Bean (1906), and this was done within large

groups of Caucasian and Negro Individuals. In 1982, another study looked at

the acxes although this was done on small samples: 5 female and 9 male

brains (de Lacoste-Utamslng & Holloway, 1982). Subsequently, several other

studies have considered the possible effects of sex: Wltelson (198 5a" In a

study on hnnd preference snd the callosum; Nssrsllah et al. (1986) In a

study of schizophrenia; and a few studies specifically attempting to

evaluate sex differences In callosal anatomy (Demeter, Rlngo & Doty,

1985; Clarke et al., 1986). Several other studies are currently underway

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63

In different laboratories.

A few studies measured length. Although values for the sale brain tend

to be minimally larger, the sex difference is not significant. Nor has any

sex difference been observed for total area. Again, values for the male

brain are larger, but not significantly, neither In those studies that

reported statistical analyses nor in those for which some statistical

analyses were done in this chapter based on raw data included in the

original reports.

Only In the small sample of de Lacoste-Utamsing and Holloway (1982) did

the mean callosal area tend to be lirger in females, but again the

difference did not approach significance. However, de Lacoste-Utamsing and

Holloway concluded that the total corpu• callosum "was greater in females

relative to brain weight" (p.1432) on tho basis that brain weight differed

significantly as expected, but callosal area did not. No statistical

analysis of any ratio score was done. Since brain weight and callosal area

are not perfectly correlated, there is no reason to assume that the lack of

a difference in callosal area in conjunction with the presence of a

difference in brain weight indicate: a significant difference in the

relative size of the callosum.

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In Witelson's (1985a) study of the callosum, which included 12 male and

30 female brains, sex differences were evaluated both for absolute area

measures and for area in relation to cerebrum weight (weight of the

hemispheres with the hindbraln removed) using an analysis of covariance.

The absolute values of the males tended to be larger as in other studies,

but not significantly so. However, even with the effect of cerebrum weight

partialled out with an analysis of covariance, no significant difference in

favor of females emerged. The results of Demeter et al. (1985) and Clarice

et il. (1986) ere still in short abstract form, but neither reported any sex

difference in "otal callosal area.

••Vv-V

In the above studies, the brains examined were either specified as

Caucasian or race was not indicated. Bean's study looked at sex differences

within race. No sex difference it. total callosal size was observed for

Caucasians (t - 1.73, df - 65, p - .09); however, comparison of the male and

female Negro groups indicated that Negro females had a significantly smaller

total corpus callosum (t - 2.75, df 78, p - .008). However, brain weight

difference was particularly large between the Negro groups (1216 vs 1068 gm,

t 5.06, df - 83, p < .00001), and the callosal difference may be related

to the difference in brain size. Further statistical analyses to determine

the contribution of brain weight would be necessary.

Splenium and Sex

N V ". "J

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The absolute area of the posterior fifth region of the callosum has

been investigated in five studies (Dean, 1906; Clarke ct al., 1986; de

Lacoste-Utamsing & Holloway, 1982; Demeter et al., 1985; Witelson, 1985a).

In no study was a significant sex difference found. In the Bean and

Witelson studies, there was no statistical difference between the sexes in

absolute area, and the male groups tended to have larger values (for Bean,

Caucasians: t • 0.85, df 65, p • .60; Negroes: t - 1.61, df - 75, p - .11;

see Table 1). In the Clarke et al. and Demeter et al. studies, again no

sex difference was observed in absolute size of the posterior fifth region,

although mean scoies were not reported in these abstracts (see Tnble 1). In

the de Lacoste-Utamsing and Holloway (1982) study, the mean value for the

female group tended to be larger. The difference was at the 0.08 level of

probability and was reported as a significant finding. Maximal splenial

width was also measured and found to be significantly greater in the female

group. Demeter et al. also measured maximal splenial width but found no

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64

The results of the studies by de Lacoste-Utamslng and Holloway

and by Vltclson may superficially appear to be discrepant and

difficult to reconcile. However, there is no true discrepancy. The

reported sex difference by de Lacoste-Utamslng and Holloway was not a

statistically significant one, and the results of Bean, Vitelson

and Clarke et al. in larger samples, clearly Indicated

that females did not have a larger posterior fifth region compared to males.

Although no significant sex difference was found in the size of the

posterior fifth region In any of these studies, in only the de LacosteDtamslng and Holloway study did the female group tend to have a

larger absolute splenial region. It is difficult to account for the unique

direction of this variation. The female group of the de Lacoste-Utamslng

and Holloway study Is very small (n 5) and one possibility is that

for some unknown reason it is an atypical sample. Moreover, it is not clear

how the 14 cases included in the de Lacoste-Utamslng and Holloway (1982)

report were selected from the 28 cases of the earlier 1981 report (de

Lacoste-Utamslng, Holloway, Rirkpatrick t Ross, see Table 1). In the 1982

report, the posterior fifth region tended to be larger in females, but so

did the total corpus callosum. This is the only report in which the total

corpus callosum tended to be larger in the female than the male group.

Although the minimum and maximum values for splenial width in the female

groups were the sane in both the 1981 and 1982 de Lacoste-Utamslng et al.

reports, the mean total callosal area of 662 mm of the total group in the

1981 report is considerably less than that of either the male or female

group (70A and 708 mm2, respectively) in the 1982 report, and the values of

the earlier report are more comparable to those of other studies.

v«:

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Since callosal size is correlated with brain size, although

imperfectly, and brain size is different between the sexes, anatomical

comparisons between the sexes become a complex issue. There are several

statistical procedures that may help to remove the effect of variation in

callosal size due to brain size: a proportional score of callosum to brain

size or analysis of covariance, partialling out brain weight or possibly

brain volum*, raised to the two-thirds power, as an estimate of cortical

surface. In Vitelaon's (1983a) report a second analysis of posterior fifth

cores was done using an analysis of covariance for cerebrum weight. No sex

difference was observed even with this analysis.

One further approach, which is also useful in helping to rule out

differences due to different materials and methods in interstudy

comparisons, is the use of a ratio score of the size of a callosal region to

total callosum. As reported elsewhere (Vitelson, 1985a, footnote 26), the

ratio scores of the posterior fifth region to total callosal area were

almost identical for all sex subgroups of the three studies except for the

de Lacoste-Utamslng and Holloway (1982) female group. Table 2 presents a

comparison of the mean ratio score for the posterior fifth region for all

the studies which measured this region in the sexes separately.

/ The values in '.'able 2 reveal the consistently smaller absolute size of

the posterior fifth region in the female group compared to the male group in

all studies except the de Lacoste-Utamslng and Holloway (1982) report. In

addition, the absolute values are quite consistent within each sex across

studies, except for the female group of the de Lacoste-Utamslng and Holloway

report.

The ratio scores also show remarkable consistency for all subgroups in

all studies except for the de Lacoste-Utamslng and Holloway female group

(score of .31) and Bean'a Negro female group (score of .30). It should be

noted that no statistical analyses were done to determine if these ratio

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HAND PREFERENCE AND CALLOSAL ANATOMY

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• cores are tlgnlfleantly higher Chan those for the sale groups. However, "!^^

the result of Bean's study say be relevant for soae of the apparently

dlscrepsnt sex difference findings in the different studies. It is noted

that the de Lacoste-Utaaning and Holloway paper did not apecify the racial . ^

origin of the groups, but did indicate that the bralna were obtained from '^v'"'<

the Dallas Forenaic Institute, Dallas, Texas. If callosal aorphology should 'A'-/-;

prove to be different in Caucasians and Negroes, one possible explanation of j^ *

the discrepant results «ay be that the de Lacoste-Utaasing and Holloway %

sample of 5 female brains included a high proportion of Negro women, " !'•!'•'

resulting in the proportionately larger splenial region.

On balance, the evidence does not support an absolutely larger splenial

region in the female compared to the male brain. However, there may be some frV^y

difference between the sexes in the morphology or relative proportions of *

different regions of the callosum. In Bean's study, within each racial .v

group, females had a significantly smaller area compared to males for the "vS/OSi

anterior half of the callosum (Caucasians: t - 2.14, df - 44, p - .04; -v'.v^

Negroes: t 2.50, df • 77, p - (.02; see Table I). In contrast, there was rV.-^s'

no difference between the sexes for the absolute or relative posterior fifth

region as indicated above, or for the posterior half in the Caucasian group

(t - 0.52, df • 44, p > .60), but in the Negro group the posterior half was

smaller in the females (t - 2.36, df - 77, p - (.02; see Table 1). In

Wltelson's study, no sex difference was found for absolute area or for area

corrected for brain size for the anterior half, posterior half or for the

splenial region. However, for the area of the posterior half, the

interaction between the factors of aex and hand preference, with cerebrum 9

weight as a covariant almost reached statistical significance (p • .08). vlMS

The analysis Indicated that for the posterior half of the callosum, males KVIJM

had a proportionately larger region relative to brain weighr than did /" "JvjH

vwysHM females among mixed banders, but not among right banders. In contrast, k •'.- -'■■'.-'

Clarke et al. reported that the anterior half region proportional to the

total callosum was not different between the sexes, although the splenial

region proportional to the total callosum was. Nasrallah et al. in an MRI

atudy of schizophrenics with normal volunteers as controls, reported that

for the normal adults the area of the posterior quartile of the callosum

; relative to the total callosum was larger In females than males. Thus some

> evidence is accumulating to suggest that the posterior region in some

respects maybe proportionately larger in females.

.V

«W:

Hand preference has been found to be correlated with direction and

degree of hemisphere lateralizatlon of function, both on the basis of -•."-.•

clinical studies of brain-damaged patients and experimental . Q

neuropsychological studies. The correlation is not perfect. Like right -'/v'-j^

banders, the majority of left banders appear to have language functions "C-/.^

primarily mediated by the left hemisphere, although a larger proportion of vv^

left than right banders have language functions mediated primarily by the yö^'i

right hemisphere. Moreover, left banders, regardless of direction of ^v^

hemisphere lateralizatlon, appear to have less strong lateralizatlon or ^

v

greater bihemispheric representation of function than do right banders JBP*^

(Bryden, 1982). If the callosum plays some role in individual differences QvW

in brain organization, it might be expected that the greater bihemispheric /

N

Vv

representation in left banders might be associated with a larger corpus /-'A'^y

callosum. This could allow for greater interhemlspherlc communication, .Cv.'v'.v

whether excitatory or inhibitory, at the physiological level.

In support of this hypothesis, Vitelson (1985a) found that in a group

of 42 brain specimens studied at postmortem, the area of the total callosum •!" ! ••!

was 11 percent larger in a group of 15 individuals with mixed hand

preference than in a group of 27 individuals with consistent right-hand •'ö'o'""''
v ^"v v*rm.- nrvH.iVnrVWVVVK'K'VWWWVKIvmr.WVW

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prtftrtnct. lUndcdncsi was cUsslfied on the basis of a 12-lCta hand

praftrtnct test adapted from Annctt (1967). Consistent right-handedness was

defined as 100 percent right hand preference; all others were classified as

Ixed (or non conslstent-rlght-handed), regardless of writing hand. No

individuals with consistent left handedness, defined as 100 percent left

-hand preference, were present In the aaaple. Such hand preference occurs In

only about 4 percent of the population. (See Wltelaon, 1985a, for further

detail.) The areas of the anterior and posterior halves were also larger In

the aixed hand group. These differences were also obtained when sex and

brain weight were controlled for.

Splenlua and Hand Preference

The aplenlum (posteilor fifth area) Is unique in that, in const rast to

the rest of the calloaua, it did not differ in size between the two

handedness groups. It «ay be noteworthy that the aplenlum is also

unique in other respects. The aore posterior regions of the callosua aay

have a different function than the anterior regions in interhealspherlc

transfer of inforaation. They appear to transmit mainly aensory

inforaatlon, rather than aore highly processed perceptual inforaation

(Sidtis et al., 1981). Based on experlaental work with monkeys, it has been

suggested that the presence of the splenlua is associated with unilateral

cngraas, whereas the anterior commissure is associated with bilateral traces

(Doty, Overman & Negrao, 1979). Consistent with these results are the

findings of Macko and Hishkin (1983) based on aetabolic aapplng of the

visual areas by the deoxyglucose aethod. They found functional differences

in different parts of the coaaissural systea and suggested that the callosal

input to the prestrlate visual cortex, which is known to course through the

splenlua, has suppressive rather than the facilitative clectrophysiological

influence that the anterior commissure appears to have.

wv.

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In addition, the neural developaental course is different for the

splenial region. After birth, the splenlua undergoes the greatest relative

growth in overall size compared to the rest of the callosua, tripling its

width compared to its size at birth (Rakic & Yakovlev, 1968). It is also

the first region to begin myelinatlon (at about the fourth postnatal month),

with callosal myelination spreading anteriorly from the splenlua (Yakovlev &

Lecours, 1967). Such anatomical differences may suggest some difference in

the course of neural regressive events in the splenium compared to the rest

of the callosua.

PARIETOTEMPORAL CALLOSAL REGION AND HEMISPHERE SPECIALIZATION

In a subsequent study (Witelson, 1986a), further callosal subdivisions

were examined. It was found that the posterior region of the body cf the

callosum, referred to as the parietotemporal region (ace Figure 1), «'as

markedly larger in the mixed than right handed group (by 19 percent). This

result is of particular interest for brain iateralization of function as

this region has been found to house the fibres that cross from the

parietotemporal regions of the two hemispheres, based on anatomical studies

In monkeys (Caminiti & Sbriccoli. 1985; Cipolloni & Pandya, 1985; Pandya et

al.t 1971; Seltzer t Pandya, 1983) and in humans (de Lacoste et al., 1985).

In humans, these cortical regions are crucial for language, praxis and

visuospatial functions, functions which are typically lateralized and may be

less lateralized in mixed and left banders. The larger parietotemporal

region in the mixed banders may be related to greater bihemlspheric

representation of functions.

Hand Preference as a Dichotomy

Hand preference has been defined in different studies in different

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ways: for example, by the hand used specifically for writing or the hand

used for the aajorlty of unlaanual tasks. Some researchers have suggested

that consistent or 100 percent right-hand preference may bt different than

even predominantly or «oderate right-hand preference (e.g., Annett, 1972).

In the callosal studies related to hand preference reviewed above,

handedness was classified as a dichotomy as In Annett's (1972) model of hand

preference: consistent right handers versus all others.

Callosal size was found to vary with the side of hand preference:

conslstent-rlght-preference versus non consistent-rlght-preterence. Further

analyses were done to determine whether the callosum varied with degree or

magnitude of hand preference (scores could vary from +12 to -12). Since the

27 consistent right handers had almost identical scores, the correlations

were calculated for only the 15 mixed handers which included members of each

•ex. The partial correlation (to rule out differing brain size between the

sexes) for total callosal area and hand score, which reflects both degree

and direction of hand preference, was r - -0.03 (df - 12, p - .92). The

partial correlation for absolute hand score, which reflects only degree of

hand Ttftrtnce, was r - 0.26 (di - 12, p - .40). Therefore, no evidence

was obtained that callosal size is associated with degree of hand preference

(see Wltelsoo, 1985a; 1986a). These anatomical findings support the

biological validity of a simple functional dichotomy of hand preference:

consistent right handedness versus mixed handers.

To ensuie that the difference was not merely between consistent versus

non-r nsl'-tent-hand-preference, HRI scans of the midsagittal view of the

callosum were obtained for two normal male volunteers having consistent left

hand preference, as no such individuals were available in the 42 cases

available for study at postmortem. For both men, total callosal area

measured from HRI scans appeared to be greater by about three standard

deviations than the mean based on postmortem messures for the group of

consistent right handed males. Thus, consistent left handers do not appear

to have as small a callosum as consistent right handers, but seem closer in

size to mixed handers (Witelaon, 1983a; 1966a). These results further

support a dichotomy between right and nonrlght in the classification of hand

preference.

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Only one other atudy has reported data on callosal size in right and

left handed men. This is an MR1 investigation of schizophrenics which

examined normal volunteers as controls (Nasrallah et al., 1986; see Table

1). In this study the left handers tended to have a smaller total callosal

area than the right handers. However, statistical analyses were not

presented comparing the normal subgroups nor were the raw data given, so

that no statistical analyses could be done by the present authors. No data

were given to indicate whether the groups were comparable in chronological

age. Total midsagittal cerebral area for each group could be calculated

from the information given in their Tables 2 and 3; and the right handers

showed a larger total midsagittal area which might account for any group

differences in callosal size. Finally, the definition of right and left

handed was not specified and right handed likely involved the typical

liberal definition of right handedness, which would include some mixed

handers.

5§sä S-:v.v;

Role of Experience

If hand preference varies with callosal anatomy, the question arises

whether one is an antecedent factor of the other. The hypothesis could be

raised that the experience of bimanual hand usage affects brain development

such that a larger callosum results. Several findings argue against this

suggestion. A further statistical analysis was done with respect to this

issue (Ultelson, 1986a). The mixed handers were subdivided according to

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68

vrltlog hand. The alxed haniets who wrote with their right hand were very

similar in aanual preference to the consistent right handers in that both

groups wrote with their right hsnd and the alxed group preferred their right

hand for alaott all tasks. The alxed handers who wrote with their left hand

were auch aore biaanual. If the experience of biaanual practice has any

to the elucidation of soae psychologicsl functions (Witelson, 1983).

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effect on the callosua, it aight be predicted thst the left-writing alxed '•'%■■%■■• •'

group, being aore blmanual, would have a larger callosua than the right- ^'•C'\t

writing alxed group. Analysis showed thst the two aixed groups were almost

identlcsl in csllosal size and both aixed groups differed from the

consistent right handers. Such results suggest that callosal size is not

related to the experience of biaanual hand usage.

Proa another field of reaearch, recent findings in developaentsl £^wC>>!

neurobiology suggest that few, if any, additional callosal fibres cross the

aidline sfter birth. In fact, cxperiaental evidence in different apecies

auggest that within days after birth there is a period of intense loss of

callosal fibres, snd that this period of axonal elimination, part of the

•arly regressive events in neursl developaent, appears to end with the onset "V'-'S1

of callosal ayellnation and rapid synaptogenesis. An cstiaate of the period |v'

of axonal elimination in the callosua in huasns is froa age one to four

postnatal aonths (Innocenti, 1986). This phenraenon of neural developaent

auggests that the number of fibres in the callosua is set by early infancy. A

If the larger callosum of aixed and left handers is a reflection of aore ..'r":

fibres and not aerely thicker fibres or soae other histological feature, ;';>; -.

thicker ayelin shesths, for exsaple, then the anatoaical difference is not -NCv^

likely the result of differential experience associated with different hand

preference. The question then is not what biological factor results in the •''vwj

Isrger callosum of alxed and left handers, but what prevents them from not /'^V-'

having a smaller callosum, comparable in size to right hsnders. As srgued 's^''*'-

previously (Witelson, 1985a; 1986a), there may be aome mechanism, possibly •

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genetically based, which results in less sxonal elimination, a larger 'Vs*'-!'

callosua, snd the behavioural manifestation of non-consistent-right- '#'

handedness. ^ .^*:i

few

These results, indicative of possible correlations between callosal V **>"

• anatomy and hand preference and sex, suggest that the individual differences •'!.'!/!-

4 in patterns of hemisphere specialization which have been found to be related V vSfc

to handedness and a-x aay have an anatoaical substrate. Given that regions ^ '

of the callosum show differential differences between the sexes snd between

hand groups, snd given the recent neuroblological documentation of early

neural development, these snstomical findings asy have implications for the

nature and origin of differences in healsphere specialization. The finding

that callossl size asy vsry in accordance with s dichotoaous classificstion

of hand preference suggests thst such a aodel of hand preference aay have

biological validity and aay be useful in other neuropsychologicsl rssesreh.

Such work Illustrates the wsy in which oeurosnatoaical analysis aay be a key OyfK

:'-\<>

Needless to say, the results to date are just the beginning and further

research is needed. Bistologicsl anslysis of the corpus callosua in

different individuals in relstion to psychological vsriables is essential.

Further neuropsychologicsl work is needed, for exsaple, in evaluating the

role of faailial handedness in callosal size, tnd studying callosal size in

relation to indices of healsphere specialization, auch as dichotic listening

and electrophysiological measures, and in relation to level of performance

on various cognitive tests. The issue of possible differences in fibre

number of in fibre size may be of considerable functional importance. If

the larger callosal size in aome individuals is a reflection of aore fibres, ''-/ •V-V

then this might result in aore communication between the hemispheres and, s^.\\-'\-

accordingly, in better performance in 4ome tasks re.ulring interhemispherlc

integration, such as biaanual aotorlc and sensory tasks, or in different

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69

cognitive profiles In «oine respect (tee Wltelson, 1986a). If the Increase

In callosal size is a reflection of a thicker diameter of individual fibres

or of a greater proportion of ayelinated fibres, then such factors may

result in sore rapid transmission along the axons and faster

interhemispheric conduction time as suggested by Green, Class and

O'Callaghan (1979).

SCHIZOPHRENIA AND CALLOSAL ANATOMY

In a series of studies done independently of those on normal adults,

the sallosum has been examined in the brains of schizophrenics. The initial

impetus for this work was a postmortem anatomical investigation of the

brains of schizophrenics by Rosenthal and Bigelow (1972), which indicated

that the width of the middle of the callosum was thicker in a small group of

schizophrenics than in a group of nonschizophrenic psychiatric patients.

This anatomical finding coupled with a growing body of neuropsychologlcal

findings suggesting atypical interhemispheric transfer in schizophrenics

(e.g., Gruzelier 4 Flor-Henry, 1979) resulted in further studies. Other

postmortem studies followed, involving various techniques and groups and

producing varying results. Some used postmortem coronal sections (Bigelow,

Nasrallah i Rauscher, 1983; Brown, Colter, Corsellis, Crow, Frith, Jagoe,

Johnstone ( Marsh, 1986) and others the postmortem midsagittal surface

(Machiyama, Vatanabe « Machiyama. 1985; Nasrallah, McCallcy-Uhitters,

Bigelow & Rauscher, 1983). Some of the recent studies have measured in vivo

midsagittal or coronal scans by means of magnetic resonance imaging (MR1)

(Mathew, Partaln, Prakash, Kulkorni, Logan 4 Wilson, 1985; Nasrallah,

Andrcasen, Olson, Coffman, Coffman, Dunn 4 Ehrhardt, 1985; Nasrallah et al.,

1986). Most of this work has focussed on the width of the callosum measured

at different points along its body. A few of the more recent studies also

considered the variables of sex and hand preference. Table 3 presents a

aummary of the studies and their results.

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Initially Rosenthal and Bigelow, and subsequently Bigelow et al. (1983)

reported that the body of the callosum was wider in schizophrenic than in

nonschizophrenic individuals (other psychiatric and neurological patients),

particularly in the mid-region of the callosal body along its longitudinal

axis. This difference in the callosum was the only one found in the ten

measures examined in the Rosenthal and Bigelow study. In the subsequent

study (Bigelow et al., 1983), only one subgroup of schizophrenics — those

having an early onset of the disease — was found to have a wider callosum

than the nonschizophrenic patients aad this ««". in the anterior and mid

regions of the callosal body. Machiyama et al. also reported that a small

group of schizophrenics had a significantly wider corpus callosum compared

to a group of nonpsychiatric patients, this time only in the anterior body,

although no measurements were given in this abstract.

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In the Bigelow ct al. report, early-onset versus late-onset

schizophrenics were compared. As stated above, the early-onset group was

reported to have a wider callosum in the midbody region compered to the

Iste-onsst group. However, the late-onset group hsd s signlficsntly lower

mean brsin weight then Che early-onset group snd thsn either control group

and this fsctor was not controlled for. In snother study (Nasrallah, et

ml., 1983), only the midbody was measured and no significant difference was

found between schizophrenics of csrly versus late onset (t * 1.97, df • 16,

p - .07, analysis by present authors). None of the other studies indicated

this disgnostic variable in their groups of schizophrenics.

In contrast to the above studies, the remaining reports found that

schizophrenics in general had either thinner callosal bodies or callosa of

equal width compared to control groups. In the' study by Nasrallah et al.

each of three psychiatric subgroups, early- and late-onset schizophrenics

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and • group of anlc-dcprcsslvcs, was found to have • significantly thinner

Idbody width than the group of aedlcal/aurglcal controls (t - 5.9, df - 20,

p < .0001; t - 6.0, df - 16, p < .0001; t - 7.0, df - 16, p < .0001,

respectively; analyses by present authors). However, the mean callosal

width of 9.2 mm for the medical/surgical control group la inexplicably high

compared to all other values for this sieaaure in normal brains.

A aubsequent study reported in abstract form was the first report to

study a group of achlzophrenics homogeneous for sex (Nasrallah et al.

198A}. In this study male achlzophrenics were found to be similar to

normals. This work may be part of the subsequent report by Nasrallah et al.

(1986) in which the total schizophrenic group was found to have a wider

callosum than the normal group, but an analysis by gender indicated that

this was true only for the femalea. Brown et al. studied a group of male

schizophrenics compared to three other paychiatric and neurological male

patient groups - affective diaordera, Huntingtons Chorea and Alzheimer's

Disease. The width of the callosa . midbody of the achlzophrenics did not

differ from any of the other clinical groups. However, the brain weight of

the Huntingtons group was aigoificantly less than the other groups. No

normal control group was included in the report.

A possible sex difference in callosal anatomy among achlzophrenics was

suggested in the Nasrallah et al. (1986) report. The study included

schizophrenic subgroups of each sex. The female achizophrenica were found

to have a wider callosal body than normal females in the middle and

anterior, but not posterior regions. However, these results may be

confounded with brain size as the schizophrenic females had a larger mean

cerebrum area, determined from the MRI scans, but this was not controlled

for statistically. Moreover, the results may also be confounded with hand

preference. The incidence of left handedness has boen suggested to be

relatively high in female achlzophrenics (e.g., Häuser, Pollock, Flnkelberg,

McCrall, Volneskos & Seeman, 1985) and the definition of right handedness

in this study was broad enough to include mixed banders who wrote with their

right hand which may have resulted in the female schizophrenic group being a

leas homogeneous right-handed group.

In sum, these studies provide very inconsistent results concerning the

width of the callosum in schizophrenic individuals compared to normals:

In different studies the schizophrenics were found to have either larger,

equal, or smaller callosa. Before considering the differences between and

within these studies, the values for callosal width of the schizophrenics

were compared to those available from the studies of normal individuals

summarised in Table 1. The compariaon revealed that the groups of

schizophrenics had midbody widths of 6.1, 5.1, 4.4, 6.1, 5.1, 6.1 and 4.5 mm

(see Table 3) which do not appear different from the midbody values for

normal brains (see Table 1) such as 5.7 mm based on 100 caaes (Lang 6

Ederer, 1980), 6.5 mm based on 42 caaes (Witelson, 1986a), and 6.0, 5.2 and

5.1 mm based on MRIs from normal volunteers (Nasrallah et al., 1986).

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If there is any consistent finding in these studies, it may be that

oat of the control groups used in the studies of schizophrenia Included

other neuropsychiatric patients and these groups may have a thinner roldcalloaal region than do achizophrenica or normals. Furtuer scrutiny of

these groups used as controls reveals that in almost all cases in which a

group had e thin corpus calioaum (taken arbitrarily as 5 mm or less based on

the results for normal individuals from Table 1), the mean age of the group

tended to be close to or greater than 70 years, aomewhat older than the

chizophrenic groups which had wider callosa, and considerably older than

the normal groups listed in Table 1. Thus, chronological age, a variable

which was not accounted for in most studies may be an important factor in

the callosal differences reported between groups. The callosum may shrink

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with advancing age, and neither total brain aize nor total callosum aize

were available in most of these studies to use as possible baseline values.

One study of schizophrenics which did use younger patients and a groap of

normal controls well aatched for age, did find callosal aeasures for both

groups that were very comparable to those of other groups of normal

individuals. In this study, a greater callosal width was found only for

female schizophrenics compared to female controls (Nasrallah et al., 1986). ÄCi

Only two studies of schizophrenics measured the total callosum. Mathev

ct al., in an MRI study, found no difference in callosal area

between a group of schizophrenics, including both sexes, and, a group of normal

controls. Schizophrenics were found to have a greater callosal length, with

no baseline difference in total brain mldsaglttal area. Unfortunately,

callosal widths were not reported to complete the anatomical picture.

Nasrallah et al. (1986) studied schizophrenic and normal individuals of

comparable age to the subjects in the Mat hew ct al., study. They

found no difference in area except for a small group of left handed male

schizophrenics who had a smaller callosum compared to matched controls, but

this difference disappeared when total brain mldsaglttal area was taken into

account. In contrast to Mathew ct al., Nasrallah ct al. found

no difference in length between the total group of schizophrenics and

normals, but did find the right-handed male schizophrenics to have a shorter

callosum than matched controls.

Possible sex differences emerged. Female schizophrenics showed a

greater callosal width in the anterior and mid-regions than normal females;

no such difference was observed for the male schizophrenics (Nasrallah ct

al. 1986). In the posterior region — specifically the posterior quartile

area (see Figure 1) — a smaller region was found in female schizophrenics

compared to normals; not in males (Nasrallah ct al., 1985). Right-handed

male schizophrenics showed smaller values for total callosal length than

matched normals; no such difference was observed for females (Nasrallah

ct al., 1986).

In sum, the possibility exists that the morphology of the callosum nay

be different in schizophrenics than in normals, but if so, it is clearly not

as simple a difference as a thicker or thinner callosum. Much current

research incorrectly assumes that the corpus callosum is enlarged in

schizophrenics compared to normals (e.g., Schwartz, Vinstead & Walker,

198A). If there is a difference between schizophrenics and normals, the

difference may lie in the relative proportion of anterior to posterior

regions, and this may differ between the sexes. Schizophrenic females may

have thicker anterior, but proportionately smaller posterior callosal

regions, compared to normal females. Male schizophrenics may be more equal

to normal males. In other words, there may be a complex interactlo

involving region of the callosum, sex and possibly hand preference. Before

any conclusions may be drawn about callosal anatomy in schizophrenia,

further studies are needed which consider the many relevant variables

unconfounded with each other: chronological age, body size, brain weight,

sex, hand preference and possibly other disease-related variables such as

age of onset of illness and symptomatology.

The recent studies implicating abnormalities in interhemispheric

transfer of information in schizophrenia (e.g., Gruzelier & Fior-Henry,

1979), left hemisphere dysfunction or overactivation (e.g., Cur et al.,

1983), and atypical activity in the frontal lobes (e.g.. Cur et al., 1983;

Weinberger, Berman 4 Zee, 1986) make both gross and microscopic

investigations in different regions of the corpus callosum particularly

interesting. Any atypical callosal anatomy documented in schizophrenia may

be part of a neuroanatomical substrate of the disease. Such work is of

particular interest for the etiology of schizophrenia in that given the

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current knowledge of neuroanatonical development, anatomical variation that

ay be found In schizophrenics may help point to the mechanisms and time

course of the neurobiological aspects of the disorder.

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Acknowledgements

Preparation of t'iis paper was supported in part by U.S. N1H-NINCDS

Contract N01-NS-6-2344 and NINCDS Grant R01-NS-18954 awarded to S.F.W.

The authors thank Toni Newman for library searches, Cheryl McCormick

for helping with the statistical analyses of the raw data reported in other

papers, Diane Clews for expert typing of the manuscript and tables, and

Janice Swallow for Invaluable editorial assistance.

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HEMISPHERIC SPECIALIZATION AND REGIONAL CEREBRAL BLOOD FLOW

Ruben C. Gur and Raquel E. Gur *

Brain Behavior Laboratory, **

Departments of Psychiatry and Neurology,

University of Pennsylvania,

U.S.A.

'/.'/.'

•

ABSTRACT

Many studies have demonstrated that the two hemispheres are

specialized, in the majority of individuals, so that the left hemisphere

regulates verbal-analytic cognitive abilities while the right hemisphere

predominates in spatial-synthesis functions. The studies also suggested

individual differences in the direction and degree of this hemispheric

specialization. Thus, not all individuals have the same organization of

cognitive processing in the two hemispheres. Our research program has

examined these variations both in brain damaged patients and in normals. We

have used the tachlstoscopic and dichotic listening techniques, as well as

paper-and-pencil tests, in the study of left-handed and right-handed males

and females. These studies have helped identify reliable behavioural

measures of hemispheric functioning. We also made initial steps toward

applying the new techniques for measuring regional brain activity Co the

study of human cognitive functioning. Our studies with the i33-Xenon

inhalation technique for measuring regional cerebral blood flow (rCBF)

showed laterallzed changes in rCBF for verbal and spatial tasks, and

the effects were influenced by handedness and sex. We also performed a

sfudy of local cerebral glucose metabolism using Positron Emission

Tomography (PET), which also found laterallzed changes for the

standardized cognitive tasks. A second line of research examined

hemispheric specialization for «motional processing. Clinical case reports

and tachlstoscopic studies suggested right hemispheric superiority for

emotional processing. Some evidence also suggested hemispheric asymmetry in

emotional valence, with the left hemisphere showing a "bias" toward positive

affect. These factors are yet to be examined with rCBF.

'A'.'

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A..- INTRODUCTION

Most of our knowledge on how behaviour is regulated by the brain in

humans has come from observations on the effects of brain lesions and brain

surgery and from studies of normal subjects using tachlstoscopic and

dichotic listening techniques (see Harnad et al., 1977, for reviews).

* Supported by NiMH Grant MH 30456, NIH Grant NS 19039, and The Spencer

Foundation.

** Correspondence to: 205 Piersol Building/Gl, Hospital of the University

of Pennsylvania, Philadelphia, Pennsylvania, 19104, U.S.A.

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A congruent finding fron this research Is that In the majority of humans,

the left and right cerebral hemispheres are specialized, respectively, for

verbal-analytic and spatial-holistic functions. However, there are

substantial Individual differences in the direction and degree of

hemispheric «peclallzatlon, and these differences have been linked to

variability in cognitive functioning (see Herron, 1978, for reviews).

* S J

Recent developments In Isotoplc clearance techniques enable the

measurement of regional brain activity as It Is reflected In regional

cerebral blood flow and metabolism. These techniques make It possible to

apply experimental manipulations of behaviour and examine their effect on

regional brain activity (see Gur, 1983, for review). Potentially, this will

vastly enhance the rate of acquisition of knowledge on brain behaviour

relationships and will add experimental rigor and direct measurement of

variables pertinent to functional brain mapping. During the past decade,

our laboratory and a number of other laboratories here and abroad have

demonstrated the sensitivity of Isotoplc clearance techniques to changes in

regional brain activity induced by cognitive activity. Thus, rCBF was found

to increase during cognitive activity, and to show greater increase to the

left hemisphere for verbal tasks and to the right hemisphere for spatial

tasks. Furthermore, variability in the direction and degree of these

changes was associated with handedness and sex.

The missing link in this research is a systematic evaluation of

individual differences in behaviour in relation to individual differences In

the pattern of rCBF changes during cognitive activity. This is the

objective of our ongoing research. In this chapter we will present briefly

our procedures foi obtaining measurements of rCBF and then summarize some of

our findings to date in the area of hemispheric specialization for cognitive

and emotional factors.

B. THE RESEARCH PARADIGM

1. The rCBF measurement

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Upon arrival in the rCBF laboratory, subjects are first accomodated and

acclimated to the laboratory environment. During this phase, subjects are

shown the cerebrograph, placed on the bed, and administered a "dry" rCBF

procedure. This is helpful in reducing anxiety and improving subjects'

comfort. Effort is spent in creating a friendly atmosphere. This aspect of

the procedure, by its nature, cannot be entirely standardized. The

personnel of the rCBF laboratory have been trained in fostering open

exchange cf information with subjects while maintaining a professional

attitude.

Following the accomodatlon period, aubjects are explained the tasks and

trained to uae the response lever. The response lever is connected to a

point light projector with which the subject can indicate his response to

the stimuli. The rCBF Is currently measured with a Novo Cerebrograph, a 32

detectors system which uses the 133-Xenon technique developed by Christ and

colleagues (Christ, Thompson, Vang and others, 1975; Christ and Ullkinson,

1979; Rlsberg et al., 1975). The technique provides a means of determining

regional cerebral blood flow by the use of a trace amount of 133-Xenon in

air (for inhalation) or in saline solution (for venous injection). A sample

of v*nous blood is removed to obtain hemoglobin level. For the inhalation

procedure, 5-7 mCl of 133-Xenon per liter is Inhaled through a mouthpiece

for one minute. The uptake and clearance of the Isotope from the brain Is

monitored for 14 minutes by colllmated Nal crystal detectors placed over the

scalp. Cerebral blood flow is computed from the clearance rates as

described by Christ et al. (1975). All rCBF studies are evaluated for

integrity of the blood flow measurements, which Includes absence of gross

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85

artifact In the recorded curves, good count rates and curve fits, and

adequate estimation of end-tidal C02. Less than 5 per cent of the flow

curves are typically rejected.

Our standard procedure is to examine in detail two flow Indices: IS

(Obrist's initial tlope - a noncompartmental index of grey matter flow) and

CBF-15 (a noncompartmental index of mean flow of grey and white matter). IS

is the initial tlope (at time zero) of the mathematically equivalent

Instantaneous bolus injection. CBF-15 represents the mean flow of all

tissues seen by the detector, including a snail cxtracerebral (scalp)

component. It Is mathematically equivalent to the height-over-area method

where the Integration is carried out to IS minutes. The latter time is

preferred over infinity, since it reduces the contribution of slow

cxtracerebral components (see Obrist and Wilkinson, 1979). Finally, a

useful index is the relative size of the fast compartment, Wl, which in

normals predominately represents the percentage of the grey matter

compartment (see Obrist ct al.t 1975; Obrist and Wilkinson, 1979). The CBF

values are corrected for C02, based on correction factors obtained in normal

control volunteers (3.0 percent/mmHg of change in PC02 for IS and 3.5

percent/mmHg of change in PC02 for CBF-15).

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All CBF data and the computed blood flow data are stored by the

computer on disks. The raw clearance curves can be displayed on the

Televldeo terminal. The final results are displayed in a table as well as

on a topographical outline of the tiain (See Figure 1).

Alternative methods are available for isotope delivery and monitoring

of isotope removal from the lungs. One method of particular interest to

studies involving psychological manipulations, particularly when it is

desired that the subjects talk during the study, is the monitoring of

Isotope concentration from a lung curve. Lung monitoring enables evaluation

of end-tidal expired air without having to use a mouthpiece or facemask

(Jaggi and Obrist, 1983).

2. The standard cognitive activation procedures during rCBF measurement.

Each task begins 5 min prior to isotope administration and continues

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for 20 nln. There is a 10 mln rest between conditions. This period permits

return of background radiation to baseline. The tasks are:

a. Verbal. The verbal task consists of analogies adapted from the

Miller Analogies Test, the Scholastic Aptitude Tests, and the Educational

Testing Service's Kit of Factor Referenced Cognitive Tests. The subject Is

presented with an analogy (e.g. Bird relates to Eagle as Car relates to a.

Engine; b. Wheel; c. Cadillac; d. Gasoline), and his task is to point to the

letter corresponding to the correct answer. Ther* are 5 practice trials

before presentation of test trials. Subjects proceed at their own pace and

the response activates presentation of the next trial.

b. Spatial. The spatial task consists of an adaptation of Beaton's

Line Orientation Test. The subject is presented with two lines and his task

Is to point to the digit adjacent to the lines on an array corresponding in

orientation to the stimulus lines. The procedure is otherwise Identical to

Task a.

C. HEMISPHERIC SPECIALIZATION FCR COGNITIVE FUNCTIONS

The effects of cognitive tasks on regional brain activity have been

measured by the 133-Xenon technique for measuring rCBF and by positron

emission tomography (PET) for measuring glucose aetsbolism. The effects of

handedness and sex on hemispheric activation has been specifically examined.

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Gur and Reivich (1980) reported the effects of cognitive activity

on rCBF in a sample of 36 right-handed undergraduate males. They found

reliable effects of increased rCBF during cognitive activity. The verbal

analogies task produced greater left hemispheric increase. The spatial task

In that study was the Gestalt Completion Test. It produced no lateralized

Increase. However, the 17 subjects who showed greater right hemispheric

Increase performed better.

Gur et al. (1982) reported the effects of handedness and sex on

hemispheric rCBF changes during cognitive activity. The sample consisted of

62 young, healthy undergraduate volunteers (15 right-handed males, 15 righthanded females, 15 left-handed males, 17 left-handed females). The main

findings were: 1. The rCBF increased during cognitive activity compared to

resting baseline. 2. The increase was higher to the left hemisphere for the

verbal (analogies) task, and higher to the right hemisphere for the spatial

(line-orientation) task. 3. The laterallty effects were moderated by

handedness; right-handers showed the effects while left-handers, as a group,

did not. A. Females had higher flows, both during rest and during cognitive

activity. 5. Females showed more lateralized changes during the performance

of the verbal and spatial tasks. 6. Females had a higher percent of fastclearing tissue (wl) presumably grey-matter. 6. Left-handers have a higher

wl than right-handers (Figures 2 and 3).

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The second study (Gur, Gur, Rosen et al., 1963) reported the effects

of the same verbal analogies and spatial line orientation tasks on local

cerebral glucose metabolism measured with PET. The study demonstrated

lateralized differences in areas corresponding to Wernicke's region for the

verbal task, and in homotopic right hemispheric region for the spatial task.

In addition, lateralized effects occurred in the ares of the frontal eye

fields, which control orientation. This finding was interpreted as

supporting Trevarthen's (1972) hypothesized network linking cognitive

activity to motor orientation (Figure 4).

D. HEMISPHERIC SPECIALIZATION FOR EMOTIONAL PROCESSING

This work has progressed from the assessment of lateral differences in

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Fig. 2. Initial slope (IS) index of blood flow to the left ( ) and

right ( ) hemispheres for the total sample and for right- and

left-handed females (0) and right- and left-handed males ( )

during resting (R), verbal (V), and spatial task performances

(S).

the intensity of emotional expression (Sackeim, Gur and Saucy, 1978; Sackeim

and Gur, 1978) to literature review of clinical case reports (Sackeim et al.,

1982) and experimental studies involving the tachistoscoplc technique (Natale,

Gur and Gur, 1983). We are currently investigating the effects of emotional

processing on rCBF.

Sackeim, Gur and Saucy (1978) obtained ratings of emotional Intensity

for faces expressing six emotions. The faces were presented in the original

and in composites consisting of the left or the right side of the face. The

left-left composites were judged more intense and hence it was concluded

that emotions are expressed more Intensely on the left side of the face.

Sackeim and Gur (1978) examined the specificity of this effect and found

tfat the significant difference in this direction was for the "negative"

emotions of sadness, anger, disgust and fear, whereas for the "positive"

emotions of happiness and surprise the trend was in the opposite direction.

Sackeim tt al. (1982) examined all published reports of:- 1. Outbursts of

pathological crying or laughing following destructive lesions; 2. Laughing

or crying occurring during epileptic seizures; 3. Mood changes following

surgical removal of a cerebral hemisphere. The main findings were that

crying outbursts occur with destructive lesions to the right hemisphere,

while laughing outbursts occur following right hemispheric lesions.

Correspondingly, left hemispheric activation during epileptic seizures was

associated with letal laughter, whereas four or the five reported cases of

ictal crying had right hemispheric foci. Finally, right hemispherectomy

resulted in postoperative Increase in euphoric mood.

Natale, Gur and Gur (1983) performed three experiments using the

tachistoscoplc technique with emotional stimuli. Experiment 1 found a right

visual field superiority for discriminating the emotional valence of faces

expressing a range of emotions. This effect was moderated by handedness ar.v.

writing posture; it was weaker for left-handers as a group and did not exist

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for left-handers who use the nonlnverted writing posture. Experiment 2

replicated the left visual field superiority effect for longer exposure

durations and specifically for discrimination of happy from sad faces. In

Experiment 3 chimeric faces composed of happy and sad expressions were

presented. The subject was required to decide whether the mood expressed

was positive or negative. Right visual field presentations produced a bias

toward positive judgments, whereas left visual field presentations produced

no bias (Figures 5 and 6). The paradigm of studying activation effects on

rCBF has not yet been applied to investigation of emotion.

E. CONCLUSIONS

• •• - 'J

The introduction of neuroimaging techniques to the study of brain

behavior relation pro 'ides new opportunities for a systematic research on

individual differences In cerebral organization. The research paradigm

presented here can yield data on the relationship between direct In vivo

measures of regional brain activity and major behavioral factors related to

cognition and affect. At present we are still in the very initial phase of

this research. We have determined the sensitivity and reliability of the

rCBF measures obtained with the 133-Xenon inhalation technique and found

that they show consistent effects of activation with cognitive tasks. These

Initial studies are encouraging and open the way for expanding the range of

factors to be examined. Such factors Include emotion. The sensitivity of

the technique to individual differences In brain organization such as are

associated with sex and handedness suggests that the technique could bt used

in further examination of individual differences. We are currently studying

"cognitive specialists", individuals with exceptional abilities in areas

such as mathematics and art.

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Laterality scores of ICNRgl for the seven ROIs in the :wo

groups of subjects (Verbal «nd Spatial). Error bars reflect

standard error of the mean and are drawn in the direction

allowing the necessary between-group comparisons.

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REFERENCES

Intensity ratings of chimeric emotional faces for males and

females in the two visual fields (Experiment II).

'.- .

Gur, R.C. (1983). Measurement and imaging of regional brain function:

Implications for neuropsychiatry. In P. Flor-Henry, and J. Gruzelier,

Laterality and Psychopathology. Amsterdam: Elsevier.

Cur, R.C., Gur, R.E., Obrist, W.D., and others. (1982). Sex and

handedness differences in cerebral blood flow durin' rest and cognitive

activity. Science, 217, 659-661.

Gur, R.C., Gur, R.E., Rosen, A.D., and others. (1983). A cognitive

motor network demonstrated by positive emission tomography.

Neuropsychologia, 21, 601-606.

Gyr, R.C. and Reivich, M. Cognitive task effects on hemispheric blood flow

in humans. Brain and Language, 9^ 78-93, 1980.

Harnad, S. and others. 1976. (Eds.) Lateralization in the nervous

system. New York: Academic Press.

Herron, J. 1979. (Ed.) The Neuropsychology of Left-handedness. New

York: Academic Press.

Jaggi, J.L. and Obrist, W.D. (1983). External monitoring of the lung

as a substitute for end-tidal Xenon-133 sampling in noninvasive CBF

studies. Journal of Cerebral Blood Flow and Metabolism, 2

(supplement).

Natale, M., Gur, R.E., and Gur, R.C. (1983). Hemispheric asymmetries

in processing emotional expressions. Neuropsychologia, 21, 555-565.

Obrist, W.D., Thompson, H.K., Wang, H.S., and others. ( 1975).

Regional cerebral blood flow estimated by 133 Xenon inhalation.

Stroke, 6, 245-256.

Christ, W.D. and Wilkinson, W.E. (1979). The non-invasive Xe-133 method:

evaluation of CBF indices. In A. Bes and G. Geraud (Eds.) Cerebral

Circulation. Amsterdam: Elsevier.

Risberg, J., Ali, Z., Wilson, E.M., et al. (1975) Regional cerebral blood

flow by 133 Xenon inhalation - preliminary evaluation of an initial

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91

si ^e index in patients with unstable flow compartaients. Stroke, 6,

142-148.

Rubin, D.A. and Rubin, R.T. (1980). Differences in asymmetry of facial

expression between left and right handed children. Neuropsychologia,

j8_, 373-377.

Sackeim, H.A., Greenoerg, M.S., Weiman, A.L., and others. (1982).

Hemispheric asymmetry in the expression of positive and negative

emotions: neurological evidence. Archives of Neurology, 39, 210-218.

Sackeim, H.A., Cur, R.C., and Saucy, M.C. (1978). Emotions are expressed

more intensely on the left side of the face. Science, 202, 434-436.

Sackeim, H.A., and Gur, R.C. (1978). Lateral asymmetry in intensity of

emotional expression. Neuropsychologia, 16, 473-481.

Trevarthen, C. (1972). Brain bisymmetry and the role of the corpus callosum

in behavior and conscious experience. In J. Cernacvec and F.

Podivinsky (Eds.) Cerebral Hemispheric Relations. Bratislava: The

Publishing House of the Slovak Academy of Sciences.

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INDIVIDUAL DIFFERENCtS IN THE ASYMMETRY OF ALPHA ACTIVATION

Stuart Butler and Alan Glass,

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Department of Anatomy,

The Medical School ,

Birmingham,

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Asymmetry in the distribution of the alpha rhythm first received

attention during the early seventies (Morgan, McDonald and MacDonald, 1971;

Calin and Ornstein, 1972a & b; Class and Butler, 1973; Butler and Class,

1974). The effect was attributed to the activation of lateralised

mechanisms serving language and 'visucspatial' functions and was therefore

perceived as a non-invasive method of investigating hemispheric

specialisation. It has recently become clear that alpha asymmetry varies

systematically as a function of gender and handedness. In this chapter we

shall consider the significance of this variation In terms of individual

differences in the structural and dynamic aspects of hemisphericspecialisation.

STRUCTURAL AND DYNAMIC ASPECTS OF HEMISPHERIC SPECIALISATION

Evidence for some form of variation in hemispheric specialisation is

provided by several sources:

(a) Gender differences exist in functions whose neural mechanisms are

normally lateralised. Certain verbal skills are acquired earlier and to a

higher level by females (Herzberg and Lepkin, 1954; Gates, 1961; Hutt, 1972;

Bryden, 1979), some aspects of hand preference are more strongly expressed

in females (Hicks and Kinsbourne, 1976); Annett, 1982;1985) whereas spatial

abilities are generally higher in males (Harris, 1978; Kimura and Harshman,

1984).

(b) Dichotic listening and split-field tachlstoscopy reveal significant

.left field superiority for the perception of non-verbal Information and

superiority of the right field for the detection of verbal material. They

clearly reflect the advantage of direct access to lateralised verbal and

spatial mechanisms. The effects are subject to significant variation as a

function of handedness and gender (McKcever and Van Deventer, 1977; Annett,

1982; Fairweather, 1982).

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(c) The incidence of aphasia after unilateral lesions is more common in

males than in females (for example: Landsell, 1962; McGlone, 1980; Inglis,

Ruckman, Lawson, MacLean and Monga, 1981; Basso, Capitani and Marascini,

1982; Sundet, 1986) and more common in left banders than in right banders

(Warrington and Pratt, 1973).
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Observations such as these have been Interpreted to mean that the

pattern on which cognitive mechanisms are lateralised is subject to

Individual variation, that lateralisation is more complete in males than in

females, and that reversal of the classical pattern of hemispheric dominance

is more common among left banders than right banders. These imply that

group differences can be accounted for by variation at the structural level,

Chat is to say, in the anatomical distribution of the neural mechanisms

responsible for cognitive processes. An early hypothesis of this type was

put forward by Levy (1969). This holds that the superiority of females in

verbal but not spatial skills is due to the recruitment of cortex of the

right hemisphere for linguistic processes (i.e. language is bilateral). Th»?

Involvement of the right side in language occurs at the expense of its

commitment to spatial skills.

There is no doubt that the anatomical location of mechanisms serving

verbal and spatial skills varies within the population. There are several.

Independent sources of evidence. Firstly, the system is remarkably

resistant to uiI lateral brain damage in the early years of life (Basser,

1962; Rasmussen, 196A; Rasmussen and Milner, 1977). Extensive left

hemisphere damage may be sustained without clinically detectable language

abnormality in adulthood. The inference is that areas of cortex of the

undamaged right hemisphere take on the function. Secondly, amytal studies

have shown language to be dependent on the right hemisphere in a significant

number of patients especially females and left banders (Uada and Rasmussen,

1960; Strauss and Wada, 1983). Similarly, aphasia is present in a

significant proportion of patients presenting with disorders of the right

hemisphere (Bryden, Hecaen and De Agostini, 1983; Basso, Capitani, Laracona

and Zanobio, 1985). Finally, there Is evidence for sex differences in the

intrahemispheric organisation of the speech areas. Kimura (1983b) finds a

dissociation between the aphasic disorders of males and females with lesions

confined to anterior or posterior cortical territories.

The existence of such cases has encouraged the view that variation in

the lateralisation of language and spatial functions may be fairly common in

the population as a whole. However, recent evidence suggests the contrary.

When patients with early brain damage and slowly progressive disorders such

as tumours are excluded there is very little evidence for right hemisphere

language in the population, Kimura (1983a) reports the effects of

unilateral lesions in a large group of patients, the majority of whom had

late-onset brain damage (strokes). Off 244 patients with left sided

lesions, 100 were aphasic. Lesions believed to be confined to the right

hemisphere were accompanied by aphasia in only two cases out of 179. Among

the 40 left banders, five were aphasic and all these had left sided

lesions. Similarly in a study by Strauss and Wada (1983) the proportion of

patients with right sided language was largely, if not entirely,due Co

Chose wich brain damage in childhood.

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Further investigation of verbal and spatial abilities following stroke

and head Injury is required to confirm the picture emerging from these

recent studies. If their findings are supported, then variation in the

structural aspects of hemispheric specialisation Is unlikely to account for

group differences in verbal and spatial skills, hand preference, and the

recovery of cognitive functions after brain damage because variation on the

standard pattern is much less common than was formerly believed.

As long ago as 1972, Bogen and his colleagues introduced another

dimension to this questior. with the concept of 'hemlsphericity' (Bogen,

DeZure, Tenhouten and Marsh, 1972). This referred to the tendency of

different individuals to make use of alternative cognitive strategies in

processing the same material. The activation of left or right hemisphere

mechanisms vzs no longer seen to be determined solely by external events, by

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the nature of the stimuli or the type of output required, but by the

individual's preference for particular cognitive strategies. Many types of

problem may be solved either by symbolic logic (verbal or mathematical) or

alternatively by imagery of spatio-temporal relationships. A trade-off will

exist between the approprit eness of the strategy adopted and the

individual's proficiency with it. Moreover, the role of one hemisphere in

any given task will depend of the individual's preference for verbal or

spatial modes of thinking, and the f. ility with which he or she interposes

and integrates these complementary modes. The form that such variation in

cognirive dynamics might take has been analysed by Cohen (1982).

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The significance of 'hemisphericity' in the present context is that

there «iay be systematic differences in cognitive style as a function of

gender, hand preference and even ethnic background (Bogen et al., 1972;

Bryden, 1978; Wolff, Hurwitz, Imamura and Lee, 1983). In other words the

group differences with which we are concerned may exist in the dynamics of

mental activity rather than in the neural hardware.

CROUP DIFFERENCES IN ALPHA ASYMMETRY

Evidence for a connection between EEC asymmetry and hemispheric

specialisation is provided by the observation that, averaged over a

sufficient number of subjects, the alpha rhythm suppresses to a greater

extent over the left hemisphere than the right during the performance of

verbal and mathematical tasks (Butler and Class, 1974; Butler and Class,

1976; Donchin, Kutas and McCarthy, 1977, for review of the earlier findings).

More recently it has been confirmed that alpha asymmetry is associated with

cognitive processes and is not due to any asymmetry in the load on sensory

or motor systems (Butler and Class, 1985).

•.•:•- ;

TASK

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handed subjects on tasks designed to engage the cognitive mechanisms

of left or right hemispheres. See text for details. Recordings

from 01,02 with respect to mastoids in average common reference.

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It is unlikely that alpha asymmetry provides a direct measure of

stru.-tural lateralisation in the sense that the intracarotid amytal test

identifies the hemisphere responsible for language (Branch, Milner and

Rasmussen, 1964; Rasmussen and Milner, 1977). Primarily, the amplitude of

the alpha rhythm is related to levels of activation and it cannot be assumed

that the distribution of cortical activity is determined simply by the type

of Information or material which a subject has been asked to process. As we

have seen, cognitive strategies may be adopted which are inappropriate to

the type of information to be processed. Indeed, many investigators have

been unable to detect alpha asymmetry during the petformance of tasks which

It was thought would engage only one hemisphere (inter alia: Provins and

Cunliffe, 1972*; Beaumont, Mayes and Rugg, 1978; Gevins, Zeitlin, Doyle,

Schaffer, Callaway and Yeager, 1979; Rugg and Dickens, 1982; John Shaw,

personal communication).

t

In particular, tasks which might be expected to rely on the cognitive

specialisation of the right hemisphere seem to be accompanied by small and

less consistent EEC asymmetries than those which accompany mental

arithmetic. For example. Figure 1 shows asymmetry in the suppression of

occipital alpha rhythm averaged over ten right handed subjects for a number

of different tasks. This work was carried out in our laboratory some years

ago by Peter Nava (Nava, Butler and Glass, 1975). The tasks included

serial subtraction and speech comprehension, intended to engage the left

hemisphere and a variety of visuospatial, stereognostic and musical tasks

designed to engage the right hemisphere, including pitch and tone

discrimination, listening to music, face recognition, a visual tracking task

and somaesthetic shape recognition. The EEC was recorded from 01 and 02

referred to average common reference electrodes on the mastoids. The

r.m.s. amplitude in the alpha band was computed from the amplitude spectrum

for each channel for each task and while subjects relaxed with eyes open

and closed. Asymmetry in alpha suppression was calculated using the

following formula which measures the asymmetry during the task against a

resting baseline:

(Left - Right) (Left - Right)

Rest TasW

A positive value thus signifies that the alpha rhythm declined more over the

left hemisphere than the right during the task. In Figure 1 the greater

suppression of alpha rhythm over the left hemisphere during mental

arithmetic with eyes closed is significant (P<0.04). Of the non-verbal

tasks only one, face recognition with eyes open Is consistently accompanied

by greater suppression over the right hemisphere (F<O.0A). Recordings were

also made from parietal and central regions. The only 'right hemisphere'

task which included statistically significant asymmetry over these areas was

visual tracking, and only in parietal regions. Similar findings for the

weakness of right hemisphere effects have been reported by others. Failure

to control the natural human tendency to adopt verbal strategies and to

Interpose verbal trains of thought even while required to tackle

visuospatial problems could well be sufficient to account for such failure

to observe right hemisphere suppression.

:•-.-.

V.V.

Further evidence that alpha asymmetry is not a simple index of

structural lateralisation is provided by the pattern of its variation among

* However, these authors presented evidence that total EEC power from

symmetrical posterior parietal electrodes was suppressed more over the left

cerebral hemisphere than the right during silent reading in right handed

not left handed subjects. All their EEC asymmetries (including alpha

asymmetries) were rejected from further statistical analysis because of

their apparent intertrial unreliability.

MM

C^i^•^ ^
HmrwKivvwivvwwmrvw

3B -,

20 -

10 -

97

RIGHTHANDERS PARIETAL. ELECTRODES

N • IBS

<8.e > BE

>e.e > wa

n n n

<-.5 -.W -.3 -.2 -.1 B.0 +.1 -».2 +.3 .!» -».5

ftsymmetry Index

vv

30

20 -

10 -

RIGHTHANDERS OCCIPITAL ELECTRODES

N 1W5

<0.0 - 90

>e.0 - 55

\=--F^

.5 -.V -.2 -.1 B.0 -».1 -».2

^symmetry Index

•».3 .V -».5

^ • -" •

Fig. 2. Asymmetry in the suppression of alpha rhythm during the performance

of mencal arithmetic by right handed subjects. Recordings from

electrodes 01,02,P3 and P4 with respect to mastoids in common reference.

Individuals. We have studied this most extensively in subjects performing

mental arithmetic. Mental arithmetic appears to be dependent upon

mechanisms resident in the left hemisphere (Grewel, 1952; 1969; Levin,

1979). It is not clear whether this is because the task is verbally

mediated or because it represents an additional mode of symbolic operation

for which the left hemisphere is specialised. In any event, we find that

this taste is more consistently associated with left hemisphere suppression

than overtly verbal tasks such as a speech comprehension test (Figure 1).

Perhaps this is because speech more potently evokes parallel imagery in the

right hemisphere.

'>:

^ta^rt^^^
OR

v?"

Fig. 2 enables us to examine the variation In alpha suppression during

mental arithmetic tasks in a large group of right handed subjects. The

histograms plot a measure derived by the following expression:

(Right - Left) (Right - Left)

Asymmetry Index - Rest - Task •

(Right + Left) (Right Left)

The numerators represent the difference in alpha power over opposite

hemispheres measured at rest and during the task. The denominators serve to

normalise for overall change in alpha power between the rest condition and

the task. As before, the use of a resting baseline controls for asymmetries

introduced by factors such as local variation in skull thickness since the

latter may have large effects on EEC power (Fisher, Butler and Class, 1986). • v'\''-

The calculation of the index is such that negative values signify greater

suppression of the alpha over the left hemisphere during the task than at

rest. /yTy

Fig. 2 shows that suppression is greater over the left hemisphere in 9

the majority of these right handed subjects over both occipital and parietal v'v'"''S

regions during mental arithmetic. However the features of particular l-'^,'",y'J

interest here are that the values are apparently normally distributed (even v'"v'vv

in spite of the fact that the values of the index must vary between limits

of -fl and -1), and that suppression is greater over the right hemisphere in

a third of the subjects. As we have seen, this is not what would be

expected on the basis of the clinical findings in patients without early '

r

"v','^'"<

brain damage. There is no indication from those studies of any graded •Gvivt

effect in the lateralisation of symbolic processes. Even in studies which vN->'

do not exclude patients with early onset lesions, there is no indication v^'-'v

that the right hemisphere plays the major role in symbolic processing in

such a high proportion of individuals (Bryden, Hecaen and Agostini, 1983).

Moreover, on our curve a large number of subjects have asymmetry indices Jj^JS^

close to zero indicating almost equal suppression of alpha activity over Vv'

left and right sides, yet the clinical lesion studies show that a bilateral

representation of language is the least common variant of hemispheric

specialisation.

A similar mismatch between the distribution of alpha asymmetry and

lateral dominance is to be found in left handed males. Estimates of the

right dominance for language in this group varies between 18X (Bryden, ^VNC-"*'',S

hecaen and DeAgostini, 1983) and virtually nil (Kimura, 1983a), and MfiX

depending on whether patients with long standing brain damage are excluded.

We should therefore expect a large majority Oi normal left handed

subjects to be left cerebral dominant for symbolic processes. In Figure 3,

the alpha asymmetry indices for this group are almost equally divided

between left and right hemisphere suppression during mental arithmetic.

Given that left hemisphere suppression during overtly verbal tasks is , jiV«^.

even weaker than that observed during mental arithmetic, the crucial role of 9

the left hemisphere in these symbolic processes is clearly not reflected in KSQ5!

the alpha asymmetry. If, as we have suggested, cl; ha asymmetry reflects the VÄJöfl

dynamics of cortical activation rather than simply an underlying structural W.'-'J.^''j

asymmetry, it reveals group differences in cognitive style and not üSJöSä

hemispheric specialisation. Indeed the difference between the alpha ''^"'i'Sil

asymmetry distributions for left and right handed subjects accords well with

laterality effects in divided field techniques (Annett, 1982, for review) ^yfy

which must similarly be subject to the effects of cognitive strategy. •

v

'

%

'**'r"

In view of the several lines of evidence for sex differences in

laterality, we may expect to see similar group differences in EF.G

activation. In fact, the evidence for sex differences in alpha asymmetry

is not consistent. The studies by Tucker (1976), Davidson, Schwartz, BSSH

KKW*

."-V V

v.v.v;
w^^^>%»^^>\y^»^.w^jtwT^T^ny*v«yptf"\r»v^viv^\T^^

'»n Äc&

LE:FTH^NDERS P*RlET*i- ELECTRODES

N « 32

<0.B - 1W

>e.0 « IB

20 -

10 -

r i

i i n h-H-J 1—| n-r^=h

<-.5 -A -.3 -.2 -.1 0.0 .! ».a -»^ .!» +.5

Asymmetry Index

LEFTHANDERS OCCIPIT(öIL ELECTRODES

3H

20-

1BJ

N • 6V

<0.0 = 32

>0.0 * 32

<-.5-.»» -.3 -.2 -.1 e.u •*.! *.2 -».3 .!» -».B

^symmetry Index

>:>

Üb

5^

v.

* . * ta '

^

.V-V.

Fig. 3. Asymmetry in the suppression of alpha rhythm in left handed male

subjects. Other details In Figure 2.

Pugash and Bromfield (1976), Ehrlichman and Wiener (1980), Rebert and

Wahoney (1973), Haynes (1980), Haynes and Moore, (1981a and b), Ornstein,

Johnstone, Herron and Swencionis (1980) and Galin, Ornstein, Herron and

Johnstone (1982) all failed to find any simple relationship between gender

and alpha asymmetry in any task.. Others using somewhat different

procedures or different metnods for quantifying the asymm^ry have found

that the suppression of alphj activity over the left hemisphere is greater

in males (Glass, Butler and Allen, 1975; Ray, Morrell, Frediani and Tucker,

197b; Trotman and Hammond, 1979; Ray, Newcombe, Semon and Cole, 1981, see

Ray, this volume). A collation of our own recent studies also reveals no

simple difference in the distribution of alpha asymmetry during mental

arithmetic between males and females. The data in Figure 2 refer to a

£4

•» ». ". i «* V i
PARIETr0

!!- ELECTRODES - M^LES

38 -,

28 -

18 -

<-.5 -.W -.3

r X

.2 -.1 8.8 -».1 -».2

^symmetry Index

N > 68

<B.B - "»a

>a.8 - 28

-R-H100

».3 -»A ^.5

ftn>>"

OCCIPITAL ELECTRODES - MALES

38 _

28 J

lo -

N = 91

<8.B ' 53

>8.B » 38

^=f T> [HH

<-.5 -.W -.3 .2 -.1 8.8 •».! -».2 -».3 •».! .S

Asymmetry Index

Fig. 4. Alpha asymmetry in right handed males, a subset of the data in

Fig. 2. "

mixed but predominantly male group of subjects. Although the number of

females is small (and records of gender unfortunately do not survive for

some of the early participants) there is nothing in the separate

distributions for males and females (Figures 4 and 5) to suggest that the

groups differ In alpha asymmetry during mental arithmetic. Assessed by

parietal electrodes, 672 of the males showed greater suppression over the

left hemisphere during mental arithmetic and, occipitally, 582 of the males

showed greater left alpha suppression. The incidences in the females were

almost exactly similar. Parietally, 562 of the females suppressed more

over the left hemisphere whereas occipitally 672 showed greater left

hemisphere suppression.

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j-ll-*- « -«-< t^i- <- '- < .n . <-' . ^. - . -.. - .. -. .. ... .'. W. V, . -.•-.V .-. .- W . .- V-.'V-'

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vwv^v^^»vY^'yjvvy\.'iii^wi^i.Ritfi^iwtf^i.'»niniwtf^iitv'.f>jf"jMWMnjinji

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PARIETAL ELECTRODES - FEMALES

101

3a -,

26 -

IB -

N > 36

<8.0 * 28

>0.B » 16

^

I

=l—F xi 1 1 1 1 1 t+^f 1 1 1 r

<-.5 -A -.3 -.2 -.1 e.0 •».! -».2 4.3 .«» .5

ftsyttifnetry Index

tt

OCCIPITAL ELECTRODES - FEMALES

30 -,

20 -

10 -

N « 36

<0.0 - 2

l

t

>0.0 * 12

^A ^

<-.S -.W

"I \ r~

-.2 -.1 B.0 ».! -».2 -».3 -».W *.5

ftsymmetry Index

I

Fig. 5. Alpha asymmecry in right handed females, a subset of the data in

Figure 2.

However, a somewhat surprising finding emerges if we look at alpha

asymmetry during additional tasks. We studied alpha asymmetry in 24 males

and 2A females during the performance of two tasks: mental arithmetic and

.oo^reC

^

0gniti0n, carried out uith the ^es open (Glass. Butler and Carter,

«8«}. Figure 6 shows the asymmetry of alpha sup;, ession over parietal

reg ons during these tasks. This figure uses the same measure of asymmetry

as In Figure I. It can be seen that both males and females show left

hemisphere suppression on the maths task and, as in Figure 4 and 5, there

is little difterence between the means for the two groups. But the females

also show left hemisphere suppression on the face recognition task whereas

this is accompanied by right hemisphere suppression in the males.

^ J* v-

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102

At first this appears to confirm the com-lusions of many investigators,

namely that lateral asymmetry is more marked in males than in females

(McClone, 1977; 197Ö; 1980).

Further examination of the data leads to a somewhat different

conclusion. The two groups of 2** subjects were each divided into two

subgroups; one comprised subjects with no left handed parents or siblings

(by convention referred to as Familial Sinistral Negative, FS-), in the

other subjects had at least one left hander among their close relatives

(FS+). The patterns of alpha suppression ir tnese subgroups have been

analysed in detail by Glass et al. (1984) and here we shall only summarise

the main finding. Figure 7 s

v

.ows the direction of alpha asymmetry in each

subgroup on each task. Where the hemispheres are shaded black and white,

there was a significant difference In the suppression of parietal alpha,

greater over the side shaded black (p<.03j, or less). Where the hemispheres

are shown stippled, there was no significant difference in suppression over

the two sides.

A complex pattern of individual differences emeges. First, it appears

that the tendency toward left hemisphere activation is Increased if the task

is mathematical, if the subject has no left handed relatives (FS-) and if

she is female. Right hemisphere activation is shown only by the group which

is male, has left handed relatives (FS+) and then only on the face

recognition task. A ^imilar interaction between gender and handedness

(overt not familial, however) has been reported by Galin et al. (1982)

though simple effects of gender were not obtained in that tudy. While it

is true that our males show a greater change in asymmetry from the maths

task to the faces task than tie females, no group shows a reversal of

hemispheric activation as would be predicted by models of lateralisation

which assume complementarity of hemispheric specialisation. This should not

be taken as evidence, one way or the other, on the question of

complementarity (bryoer ec al., 1983). It could equally well be the result

r.m.s. Le^'ovolts

6.5

e 25

-•.2ff

0.5

| I tlaths

Facts

P<.05

Females

n.s.

•v>:v^

QKWM

•'OK

Fig. 6. Asymmetry of suppression of alpha activity in parietal regions (PJ,

P^,referred to mastoids in common reference) in 24 males and 24

females during mental arithmetic and a face recognition task.

Negative values signify that the suppression was greater over the

right hemisphere during the task.

aaamttMa^MaMaaaa^^
iwn.'wwiiwvwiT^'wvwT.'vwv^rvrwwvwwk

103

3WVW

of the Intrusion of verbal strateg.es into all forms of human cognitive

activity to an extent which varies with gender and other factors.

>/<</

THE DYNAMICS OF HEMISPHERIC ACTIVATION

We have seen that Individual and group differences in alpha asymmetry

do not correspond to what is known of individual differences in the

structural features of laterallsation. We have seen that they would he

more readily accounted for by supposing that they reflect the dynamics of

cortical activation, i.e. ditferences in cognitive style. Such an

interpretation would make more sense in terms of physiological first

principles, in so far as we understand the significance of alpha rhythm at

this level. We shall now consider evidence that alpha asymmetry is inJeed

sensitive to cognitive dynamics.

Effect of Cognitive Set

Early searches for the effects of cognitive style on alpha asymmetry

were Inconclusive (Robbins and McAdam, 197A, Doktor and Bloom, 1977). More

recently ic has been shown that task related asymmetry is revealed most

powerfully if carry-over effects from the previous task are controlled for

(Grabow, Aronson, Greene and Offord, 1979) suggesting that alpha asymmetry

is sensitive to factors such as cognitive set.

We have confirmation of this in a retrospective analysis of data

obtained in our laboratory (Stern, Glass & Butler, 1981). Figure 8 shows

the order of tasks undertaken by 16 subjects in an experiment in which the

EEC was recorded from left and right occipital regions (0., O,). The order

in which the first three tasks (drawing with the eyes closed, writing a

letter with the eyes closed, and watching a cartoon film) were presented

was balanced across subjects. Menta1arithmetic was included as a fi.ial

task for all subjects, chiefly as a itmus" to check that the system

replicated earlier findings. Figurt > shows that the alpha asymmetry

averaged over all subjects (histograms labelled A) reached significant

proportions only for the drawing task. However, the magnitude of these

effects was influenced by some form of carry-over from preceding tasks.

Writing was immediately preceded by orawing (intended to engage the right

hemisphere) for eight subjects; similarly maths was preceded by drawing for

four subjects, and drawing was preceded by writing (intended to engage the

left hemisphere) in eight subjects. If we exclude from the analysis those

subjects doing a 'left hemisphere' task after drawing (histograms labelled

B) and those doing the rifht hemisphere task Immediately after writing (the

r

.«

w

J". *. '.

> V V '4

&

.VV

yzn

FS- FS+

FEHftLES flftLES FEPIftLES HALES

,0

0\

031

03

03 3!

flflTHS

FACES

v..

•> v vV

••:-•. , .', '

Fig. 7. The pattern of parietal alpha asymmetry in 48

of task, gender and familial h.indedness. See

of shading.

try in A8 subjects as a function

text for explanation

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104

histogram labelled C) Chen the mean alpha asymmetries all increase and the

probability of the effects being due to chance decreases in spite of the

reduced values of n (number of subjects).

v;

N TASK CRDER

V CARTOONS WHITING DRAWING MATHS

if CPiRTOONS DRAWING WRITING MATHS

If DRAWING WRITING CARTOONS MATHS

w WRITING DRAWING CARTOONS MATHS |

WAS

-»M

Fig. 8. Task order which revealed carry-over effects in alpha activation

see text for details and Figure 9.

Several mechanisms may be responsible for the sensitivity of alpha

asymmetry to such carry-over. The use of the cognitive strategies of one

hemisphere may increase the probability of their use In a subsequent task.

Alternatively, subjects may simply interpose thoughts about the previous

task during the early performance of a new one. Both amount to a

preservation of mental set, and both would reduce alpha asymmeCry.

."• A .1

A •-

•-.

Fig. 9.

Suppresjion

UM

Brettr on

Right N P

A

1

IE

1

ns

(.R

WRITING l1

i1

1

IS

12 <.»25

MATHS 1

1

\

IE

8

DRAWING A

\

c i1

1

-.1

1

.1

Sssa

r>\> m*

Asymmetry; Index

Effect of set on alpha asymmetry. Alpha asymmetry is reduced when

a task is preceded by one which calls for the engagement of a

different hemisphere. The tasks are those listed In Fig. 8.

Histograms labelled A represent alpha asymmetry averaged over all

subjects; those labelled B or C show the effects of removing this
105 >&'S

Effect of a potential conversant

Further evidence for the effects of mental set tomes from an unexpected

direction. In an earlier review of task specific alpha asymmetries (Butler

and Glass, 1976), we suggested that the failure of some investigators to

replicate the effects might be due to the conditions of social interaction

under which the recordings were made. We suggested that the common factor

in failures to replicate was that the subject was in the same room as the

experimenter, or was In some other way primed for verbal communication. The

set to process verbal information that this would engender would reveal

itself as unreactive alpha power over the left hemisphere, irrespective of

the given task.

We have recently investigated this prediction directly (Butler, Glass

and Fisher, 1966) in an experiment in which the EEG was recorded from left

and right parietal and occipital regions in 18 subjects under two

conditions. In one, they sat in a sound isolated chamber having been asked

simply to relax with their eyes open, after being assured that they would

not be disturbed for several minutes. In the second condition, they sat in

the same chamber, also with their eyes open with instructios to relax, but

in this case the door of the chamber had been left open after the

experimenter entered on the pretext of checking a troublesome electrode. In

this condition the experimenter remained in the view of the subject and

would have been heard had he spoken. The two conditions were randomised

across subjects. Figure 10 shows the mean power in the alpha band (in

arbitrary units) in each channel for the two conditions. The alpha rhytnm

is present with approximately equal power over left and right hemispheres

when the subject is isolated, but is suppressed over the left hemisphere in

both parietal and occipital regions while the door is open. Figure 11 shows

the change in asymmetry between conditions and the high levels of

statistical significance attached to this effect. Set clearly influences

EEG asymmetry whether It is induced by carry over from previous activity or

by preparation to respond with a certain strategy. The effect has important

implications for the interpretation of individual differences in alpha asynrnetry

ParLetaL

Left RLght

OccLpLtaL

Left RiaM

Left RlfiM

IsoLatIon

Left light

Open door

Fig. 10. Effect of social facilitation on EEC asymmetry (Eyes open, relaxed).

Alpha power over left atid right hemispheres (01 ,02 ,P3 ,P4, with

respect of mastoids in common reference) while a subject relaxes,

isolated in a sound proof chamber or in view of the experimenter.

»a

St

a

V

»

38* TO:.

Vsm

<C •_"

J- • •"

yv:
I ^X^TT*"*^W wK' Tl "Ti ^Ti WT( "Tj w^

106

Firstly, it shows that alpha asymmetry is not simply material specific.

This alone is sufficient to account for the finding that the relationship

between EEG asymmetry and structural lateralisation is a statistical,

stochastic one; the effect cannot be used to determine the localisation of

particular functions with confidence in a given individual. Secondly, it

may provide an explanation for the differences we have described in alpha

asymmetry as a function of gender, handedness and familial handedness. We

have seen that the data do nor correspond with individual differences in

structural lateralisation believed to exist in these groups. Instead the

effects may be due to group differences in cognitive style. In other words

the inclination (or set) to use particular cognitive strategies may differ

between males and females, and between left and right banders. Because the

alpha rhythm reflects levels of cortical activation, asymmetry in its

distribution reflects group differences in the usage of available cognitive

mechanisms (the strategies of left and right hemispheres). These are

effectively superimposed upon asymmetries of a purely structural nature.

CONCLUSION

In reviewing this data we have tried to show that the behaviour of the

alpha rhythm during mental activity reflects the dynamics of cortical

processing. Its distribution reveals a statistically significant asymmetry

which reflects bias in the cognitive sequence due to the underlying

structural asymmetry. Our data do not enable us, as yet, to say anything

about the fine structure of that cognitive flow. In particular we are

unable to address the issues raised by Cohen (1982) in her analysis of the

forms of Interaction between structural asymmetry and cognitive processing

because our experiments have had more limited objectives, and because the

technology has not existed. With the advent of compressed spectral arrays

we should now be able to follow the rapid time course of patterns of

cortical activation and so characterise individual differences in cognitive

style.

I

P

8

POUES (LEFT-RIGHT)

I

N » IB

(LEFT-RIGHT)

SF

Occ'tpi-tal: p < .80^

p«ri«t«L: p < .eae

A .•• .

£*1

Parietal Occipital

Fig. 11. EEC asymmetry: isolation versus social f ac i. i i tat ion . The data

of Figure 10 expressed as the differences in asymmetry, showing

the effect of social facilitation in bringing about suppression of

the alpha rhythm over the left hemisphere.

(I Isolated; SF • Socially Facilitated)

>
I

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107

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578.

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'WitWi rivfw^wvwv rVT\'T"..^n ^^rv i

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111

AGE AND SEX RELATED EEG CONFIGURATIONS IN NORMAL SUBJECTS

P. Flor-Henry,* Z.J. Koles+ and J.R. Reddon*

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* Alberta Hospital

Edmonton, Box 307

Edmonton,

Alberta, T6G 2G3

Canada

+ University of Alberta

Department of Applied Sciences in Medicine,

Edmonton,

T5J 2J7

Canada

:v^

INTRODUCTION

In an earlier study of the EEG characteristics of normal subjects with

a 4-electrode montage (Flor-Henry and Koles, 1982) we reported that women

had more EEG power than men, increased EEG coherence and a pattern of

relatively greater left hemispheric activation, men showing relatively

greater right hemispheric activation. These effects were independent of

handedness. In the present investigation, in order to examine further the

influence of age and sex or. the EEG, we analysed the EEG of a new sample of

normal subjects with an 8-electrode montage during various cognitive

conditions. The samples consist entirely of dextrals. A future study will

evaluate the influence of handedness on the EEG.

The general characteristics of the population are shown in Table 1:

Table 1.

Dextral Males

Dextral Females

N

57

56

Age

32.9

32.3

S.D.

10.7

9.6

Range

18-58

18-59

KvWS

vN«^

(Mean age differences between males and females was not statistically

significant, ? > .05).

METHODS

The EEG was recorded from 57 normal male subjects and ^6 normal female

subjects at locations P^, P3, T^, Tj, Fg, F7, T6, and T^ referred to Cz

(International 10-20 system) for two minutes during the following mental

conditions: at rest with eyes open, at rest with eyes closed, a vocabulary

exercise, a word fluency exercise and a block, design exercise. Two of the

three exercises described were subtests of the Wechsler Adult Intelligence

Scale (WAIS-R). The recordings from each scalp location were converted to

digital form directly during the sessions using 12 bit conversions at the

rate of 120 per second. A ninth channel recorded with the EEG was used to

indicate operator-flagged artifacts. A hand-held button was used to create

wwNt

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112

EEG FACTORS: (1-3). (4-7). (S-ISUSO^O)^

NORMALS

(Phase "A")

-O-

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.'.

Fig. 1

a rejection signal and this was recorded to Indicate that the accompanying

E£G should be excluded from the analysis because of excessive movement or

eye-blink artifacts. Digitized recordings were stored on a disk and

transferred later to a VAX 11/750 computer for subsequent analysis. The

analysis consisted of dividing the recordings from each location into epochs

of 128 consecutive samples, tapering these with a Manning data window to

&3

EEG FACTORS: (1-3). (4-7). (8-13). (2O-40)Hz

NORMALS

(Phase -B')

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Fig. 2

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113

m

EEG FACTORS: (1-3). (4-7), (8-13), (20-40)Hi

NORMALS

(Phaw'C)

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restrict spectral leakage and Fourier transformation. The coefficients of

each transformed epoch were grouped into the frequency bands of interest

namely, coefficients 3 and A for 1 to 3 cycles/sec, 6, 7 and 8 for A to 7

cycles/sec, 10 to 14 for 8 to 13 cycles/sec and 23 to 43 for 20 to 40

cycles/sec and the remaining coefficients discarded. For each of the

retained coefficients an 8 x 8 spectral matrix was formed using the relation

'xy - XY^*

where X is a particular Fourier coefficient fron scalp location X and Y is

the same numbered coefficient from location Y. The astarisk Indicates that

the complex conjugate of Y should be used (both X and Y are complex numbers

consisting of in-phase and in-quadrature components). In general, the

elements on the diagonal of the spectral matrix are the variances of the

potentials obtained from each scalp location in the frequency band related

to the particular Fourier coefficient. Off-diagonal elements are the

covariances between the scalp locations in the same frequency band. Unlike

the diagonal elements, the off-diagonal elements of the spectral matrix are

complex numbers.

The spectral matrices constructed as described for the retained Fourier

coefficients were combined to form a single matrix for each of the four

frequency bands of interest. This was done by averaging the respective

elements in the spectral matrices of all the Fourier coefficients in the

band. Specifically, for the 1 to 3 cycle/sec band the spectral matrices of

coefficients 3 and 4 were added element by element and the result divided by

2. For the 4 to 7 cycle/sec band spectral matrices of coefficients 6, 7 and

8 were added and divided by 3. This process was repeated for the 8 to 13

«nd the 20 to 40 cycle/sec bands as well, with the division being by 5 and 21,

respectively. In summary, then, coincidental 128 sample epochs fron the 8

scalp locations were Fourier transformed and reduced to a single 8x8

spectral matrix for each of 4 frequency bands. The diagonal elements of a

particular matrix are measures of the power (variance) in the electrical

activity recorded from the brain during the epoch a«; each of the 8 scalp

-*- *
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114

locations in one frequency band. The off-diagonal elements are measures of

the cross-power (covariance) in the electrical activity between locations In

the same frequency band.

An entire 2 minute recording of the EEC was processed as described in

128 sample epochs. Processing progressed from the beginning to the end of

the recording using overlapped epochs shifted from one another by 8 samples

(120 samples overlapped). Epochs containing samples which occurred with the

reject signal on were discarded. The 4 spectral matrices resulting from all

of the accepted epochs in a recording were then averaged together (element

by element) to produce 4 composite matrices each describing the covariance

structure of the recording in a particular frequency band. In addition, the

diagonal elements from the spectral matrices of each epoch were individually

stored to enable an analysis of temporal variations in right-left power

sym-jetry through a recording. Overlapping of epochs as described enabled a

measurement of the power in each of the A frequency bands every 8 sample

points or 120/8 - 15 times each second.

The composite matrices were used to obtatn estimates of the coherence

and phase between the scalp locations as described before (Koles and FlorHenry, 1981). Using the formula given by Welch (1967) with a Manning data

window and an 8 point epoch shift, estimates of coherence and phase obtained

in this way contained over A00 degrees of freedom and therefore were

essentially unbiased (Benignus, 1969). Rejection of half of a 2 minute

recording due to the presence of artifacts would leave the estimates with

200 degrees of freedom still more than adequate to all but eliminate bias.

Irrespective of this, no recording was utilized which contained artifacts

lasting more than 20 seconds. •

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RESULTS

In order to derive a measurement model for the EEC montage and the

resulting measures, a principal components decomposition was performed in

the sample of normal controls consisting of 57 males and 56 females. The

analysis was performed separately in each of the frequency bands on

variables that had been separately standardized to zero mean and unit

variance. A 13-dlmensional components solution replicated reasonably well

across the four bands in the varimax orientation and manifested good simple

structure. Consequently the same model was chosen to represent all four

bands.

kl*

'^y. r^.

The detailed structure of the fundamental EEC parameters emerging from

the components analysis were:

1. POWER a) frontal F7 Fg

b) parietal P^ P^l

posterior temporal Tc T^]

mid-temporal T^ T^)

Anterior

Posterior

2. COHERENCE General Ir.tra ]

Inter ] Hemispheric

3. PHASE:

a) (T5^T6); (P3^P4)

v-.-v-.-'Vv-. •- V-- •

TOW!
115

W

t: b) (F7^F8;; (T3^T4)

c) (T4^P4): (F8^T4); (F8^P4); (T^ P4); (F8^T6); (T4^T6)

d) (F7^-P3); (F7^T3); CT3^P3); (T5^P3); (F7^T5); (T^Tj)

e) (F7^P4); (F7^T4); (Tj^P^); (T5^P4); (Fy^Tj); (T^^)

d) (F8^P3); (T4^P3); (F8^T3); {T6^P3); (F8^T3); (T^T^

U. a) log. right/left FRONTAL POWER RATIO

b) log. right/left TEMPORAL-PARIETAL POWER RATIO

5. OSCILLATIONS* (9) r

a) Temporal-parietal

b) Frontal •

Figures 1 - 6 illustrate the patterns of phase relationships. It is

noteworthy that the right and left intrahemispheric, anterior^- posterior

and the interhemispheric phase leads are symmetrical, right and left whereas

the homologous left^-right interhemispheric phase relation is

unidirectional.

i

Age Effects

While the measures used in the present study are based on a unipolar

reference system, these measures are compared with an average reference

system (in Appendix I). With the exception of the phase measures, there was

a good deal of correspondence between the two reference systems. Phase,

however, is relatively meaningless in an average reference system.

Table 2 shows the overall age x factor (EEC) correlations for males and

females combined and across tasks in the four frequency bands. More

detailed results by sex and task separately are given in Appendix II. The

detailed results show task and sex interactions in the evolution of the EEC

with age. In general, with increasing age, power diminishes in the lower

but increases, in the fastest frequencies. Similarly there is a progressive

decrease in coherence with Increasing age in the lower frequency bands:

delta, theta and alpha. Further with age the left^-right, homologous

Interhemispheric phase lead is reduced in the theta and alpha. Further with

age the left right, homologous interhemispheric phase lead is reduced in

the theta range; a trend in the same direction is also seen in the delta

band. Interestingly the left hemisphere is again implicated in the

anterior^- posterior phase reduction (alpha range). As subjects get older

the log. of the right/left frontal power ratio becomes smaller In all the

frequency bands, except for delta. Finally, with age there is a slowing of

the right/left hemispheric energy oscillations in the delta, alpha and beta

bands.

Repeated measures analysis of variance was used to evaluate effects due

to sex, task, and task by sex interactions. The significant results are

summarized in Table 3. Cell means for each measure by task and sex are

given in Appendix III. Task effects in 1-3 Hz were significant for all EEC

measures but left»-right posterior phase. In the 4 - 7 Hz band the task

* a new EEC measure estimating the frequency of right/left hemispheric

energy shifts through time, calculated 15 times per second for every 2 "^'"J

minute epochs (see Flor-Henry et al., 198A). _*_J

m

r

f.

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u

" 116

Table 2. Aßc x Factor Correlation

EF.G FACTORS (1 - 3Hz) (6 7Hz) (K T 13 Hz) (20 - 4üHz)

V 1. Power

a) Frontal

b) Temporal-Parietal

2. Coherenie

3. Phase

a) Left>^«ight

Posterior

b) Left^^Right

Anterior

c) Right Intrahemispheric

d) Left Intrahemispheric

e) Lefa^Right Interhemispheric

f) Rights-Left Interhemispheric

A. Log. Right/Left Power Ratio

a) Frontal

b) Temporal-Parietal

5. Oscillations

a) Temporal-Parietal

b) Frontal

-0.21* -0.29* -0.18* 0.12*

-0.11* -0.30* -0.19* 0.06

-0.12* -0.32* -0.17* 0.07*

-0.06* -0.14* -0.01 -0.02

0.00 -0.09* 0.01 0.09*

0.06 -0.03

-r

-0.0* -0.04

0.00 0.00 -0.07* 0.01

0.02 -0.06 -0.03 -0.04

0.01 0.1*1* -0.04 -0.05

-0.05 -0.10* -0.07* -0.15*

0.07* 0.02 -0.03 0.02

-O.OA 0.01 -0.12* -0.20*

-0.07* 0.15" 0.03 -0.15*

•>:

Note: * denotes p < .05.

VlvSr*

effects for all EEC measures were significant. In 8; 13 Hz only left right

anterior phase and frontal log. of right/left power ratio did not demonstrate

significant task effects. In the 20 - 40 Hz band left right anterior

phase, left intrahemisphoric phase and frontal log. of right/left power ratio

were not associated with task effect. Main effects for sex appeared for

frontal power in all frequency bands except 20 - 40 Hz. In 4 - 7 Hz there

was also a main effect for sex for t e left»»-right posterior phase measure.

In 20 - 40 Hz there was also a main effect for sex for posterior power.

There was a task x sex interaction in 1 - 3 Hz and 4 - 7 Hz for frontal

power. In 4 - 7 Hz there was also a task x sex interaction for the

following phase measures: right intrahemispheric, left intrahemispheric and

right interhemispheric. In 20 - 40 Hz there was also a task x sex

interaction for left interhemispheric phase measure.

A univariate follow-up analysis of EEC measures by sex wlt'.in each

task, in the four frequency bands, was then carried out. (See Tables 4 - 8).

This showed that, in the eyes open condition, women had more EEC power than

men in the frontal region (delta, theta). Women had a systematically less

pronounced left»-right interhemispheric phase lead in the theta band, when

compared to men. Further, women exhibited faster frontal oscillations

(alpha). Similar findings occurred in the other conditions. In the eyesclosed situation women showed increased coherence (alpha), reduced

left »- right interhemispheric phase (beta) and a reduction in anterior sposterior phase relationships (delta) in t^e left hemisphere. In the

vocabulary task, frontal power was increased in all the frequency bands and

posterior power was increased in the beta range. Coherence was increased

(beta) and right s- left interhemispheric and left anterior posterior phase

was less pronounced (tnota). During Oral Word Fluency, frontal power was

increased (delta, alpha) and posterior power was increased in beta. Left

anterior »- posterior phase wore reduced (theta) but the left right

—<

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Table 3. Sur-mary of Significant Analysis of Variante Results

Measure I - 3 Hz 4 - 7 Hz 8 - 13 Hz

117

20 - Aü Hz

S T TxS S T TxS

Power

a) Frontal XX X X X

b) Tcnporal-Parietal X X

Coherenee X X

Phase

a) Left Right X X

posterior

b) Left Right »

Anterior X X

c) Right Intrahemispheric X X

d) Left Intrahemispheric x X

e) Left Interhemispheric X X

f) Right Interhemispheric x X

Log Right/left power ratio

a) Frontal >: X

b) Temporal-Parietal x X

Oscillations

a) Temporal-Parietal X X

b) Frontal X X

T TxS

x

x

X

Note: S Sex; T • Task.; TxS Task x Sex Interaction

x denotes results significant at p < .05

x

x

S T TxS

x

X X

X

X X

>:

x

i

$$

&&

EEG FACTORS: (1-3).(4-7), (8-13),(20-40)Hi

NORMALS

(Phaaa'D)

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118

EEG FACTORS: (1-3). (4-7), (8-13). (20-40)Hr

NORMALS

(Phase -r)

.-<>-

Fig. 5

t

posterior interhemispheric phase was redui-eL1 (delta, alpha) while the right

intraher.ispheric phase was reduced (theta). Lastly In the spatial

processing task. (Block-Design), frontal power was Increased (delta, theta

and alpha) as was posterior power (alpha). The left ^-right honologous

interhemisphcric phase was reduced (theta and alpha), as was the right

intraher.ispheric phase (alpha) and the posterior oscillations were increased

in delta.

EEG FACTORS (1-3). (4-7). (8-13), (20-40)H2

NORMALS

(Phaw'F-)

-OFig. 6

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Table U. Eyes Open Condition

Males VS. Females

EEC FACTOR HZ« 1-3 4-7 8-13

119

20-AO Male Female

1. Power

a) Fronlal

b) Temporal-parietal

2. Coherence

3- Phase

a) Left^Right

Posterior

Homologous

b) Lefo^Right

Anterior

Homologous

c) Left^-Right

Interhemispheric

5. Oscillations

b) Frontal

p<0.05 p<0.05

p<0.05

p<0.05

p<0.05

A

T

T

A

m wjw»v »".." v»vw'j

-i^-;

«saa

Table 5. Eyes Closed Condition. Males vs. Females

SHOW

EEC FACTOR H2> 1-3 4-7

2. Coherence

3. Phase

a) Left ^^Right

Posterior

Homologous

d) Left

Intrahemispheric

8-13

p<Ü.05

20-40 Male Female

p<0.05

p<0.05

A

T

y

soco

Table 6. Vocabulary Condition. Males vs. Females,

EEC FACTOR Hz- 1-3 4-7 8-13 20-40 Male Female

US$n

•.

>J

1. Power

a) Frontal

b) Temporal-parietal

2. Coherence

J. Phase

d) Left Intrahemipheric

f) Right »-Left

Interhemispheric

pOKOS p<0.05 p<0.05

p<0.05

p<0.05

p<u.

p<0.

p<().

0 5

05

A

A

A

T

y

MMI

v v niC

^ ->--.--.-Jt-.

•'/'.v.C-'.y.v.. A •/ .- y^Lw.v.v
'".'^.'"•V'JTV *vwjwjw\;wjwywvw\: »vw".Tr>rwv»%r»V"»v»v^j"»vwv•v»'.'»v»v »v»v»v»v » >w-»w-u'

1?0

Table 7. Oral Word Fluency Condition Males vs. Females

EEC FACTOR Hz- 1-3 4-7 8-13 20-^0 Male

1. Power

a) Frontal

b) Temporalparietal

3. Phase

c) Right Intrahemispheric

d) Left Intrahemispheric

e) Left»^Right

Interhemispheric

p<!).05 p<0.05

p<().05

p<0.C5

p<0.05

p<0.05

Table 8. Block Design Condition Males vs. Females

*

EEC FACTOR Hz- 1-3 4-7 8-13 20-40 Male

p<0.D5

1. Power

a) Frontal

b) Temporalparietal

3. Phase

a) Left Right

Posterior

Homologous

c) Right Intrahemispheric

5. Oscillations

a) Temporal-parietal p<Ü.05

DISCUSSION

p<0.05 p<0.05

p<0.05

p<().05 p<0.C5

p<0.05

p<0.09

Female

Ä

Ä

T

T

T

Female

i

i

T

i

The age dependent changes in EEC organization found in this

investigation are that, with increasing age, there is a progressive

reduction in slow activity and an increase in tue fast frequencies in the

20-40 Hz bands. This reduction in slow and increase in fast activity is

paralleled by a decrease in EEC coherence in the delta, theta and alpha

bands. Moreover with CNS maturation the phase lead of the left hemisphere,

left aright and left anterior ^ posterior becomes significantly less

pronounced while the log. of the right/left frontal power ratio becomes

smaller. This might suggest an Increasing preponderance of right

hemispheric processes as individuals become older. In this context it is

interesting that Duffy et al. (1984) in the study of age related differences

in the EEC of 63 healthy, dextral males ranging in age from 30 to 80 years

found, as in our material, a decrease in delta, theta (and to a lesser

extent in alpha) and in increase in beta activity as a function of age.

Furthermore, the age related EEC features were overwhelmingly right

hemispheric (n«33), a few were bilateral (n-9) and only 3 were predominantly

left-sided. These authors conclude that "the neurophysiological data

suggest that the ageing process affects the right hemisphere more than the

left" and wonder if this might not reflect compensatory changes for less

efficient left hemisphere functions. The majority of studies on the

influence of age and sex on the EEC are, in general, consistent with the

principal findings reported here. Creenblatt et al. (1944) studied the

problems related to the age factor In the interpretation of EEC

abnormalities in neuropsychiatric patients. There were 1593 acute

M'.SffA.^

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r

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121

neuropsyihiatric oatients and 24U normal concrols. The ages ranged from 25

to 55+. Althougn at a given age very different values held for the various

nouropsyihiatric disorders and normals and specific- abnormalities occurred

differentially in the various psychiatric disorders, there was underlying

all the groups, in«l iding the normals, an "age abnormality" curve

characterized by a sharp decline in slow activity (below 8-12Hz) to the age

of 35 and an increase in fast activity (over 8-12Hz) reaching its maximum

between the ages of 45 and 55. Matsuura et al. (19H4) review the major

subsequent studies on the age development of the EEC. Gibbs and Knott

(1949) find that delta and theta activity shows a general decline with age

and that beta increases with age. Corbin and Bickford (1955) concluded

that, in the evolution of the EEC in childhood, delta, theta and alpha bands

showed independent behavior. Matousek and Petersen (1973) reported that the

age development of various spectral parameters was linear in childhood and

logarithmic in older subjects. Ahn et al. (19805' in his nourometric

analysis of 2 large series in Sweden (n 561) and United States (n 750)

of normal subjects between the ages of 1 and 21 notes that relative power in

the delta and theta diminishes, while in the alpha and beta bands it

increases with age. In the examination of EEC power density in frequency

classes of 1 Hz width (frequency 1 to 15Hz) Colon et al. (1979) report a

general decrease in power with increasing age in 47 children age 8, 9 and 10

years. Matsuura et al. (1984) investigated a population of 1416 healthy

subjects between the ages of 6 and 39 and found that the age dependent

effects were more important than the sex related ones. With a technique of

quant it icat ion by a computerized wave form recognition method they found

that the average alpha amplitude decreased with age, reaching a minimum at

the ago of 21, the same being true for theta amplitudes. Average delta

amplitudes decreased with age until the age of J7. With respect to sex

differences they reported that after puberty occipital percentage alpha time

was higher in males but that the average alpha amplitude, in that region,

was higher in females after the ages of 18 - 21. After the age of 22, the

pfrcentage time of theta was higher in females although no sex differences

in theta amplitude were observed. Percentage beta time was higher in

females than in males at all ages and after the age of 21 the average beta

amplitude was also higher in the females. It should be noted that these

Japanese workers found a significantly higher alpha amplitude in females

than in mal^s in the occipital region, but no difference in alpha amplitude

in the other two cerebral sites in the left hemisphere which they monitored

(F 1 and C3), a result which cannot readily be attributed to the

differential skull thickness. These findings are very similar to our own,

except for the fact that, in several instances, in the Japanese material the

age dependent changes cease after the age of 21. This is probably due to

the composiLion of their population which, compared to ours, is heavily

skewed towards a much younger age: 88.2X are below the age of 25 and only

11.8% over that age. Duffy et al. (1984) in their "Brain Electrical

Activity Mapping" (BEAM) study of age related EEC effects, discussed

earlier, found that the largest change occurred between the ages of 30-40

and 50-59 years. Beaumont et al. (1978) studied the effects of task and sex

on alpha coherence and found that females showed higher coherence than males

overall, independent of task. In their small sample (n«16) the males showed

more power asymmetry than the females, once more a result not attributable

to skull dimensions. In both sexes the spatial task was associated with an

increase in right intrahemispheric coherence, but there was no corresponding

coherence change in the left hemisphere during the verbal task. However

Tucker et al. (1985) found in the intensive study of 2 subjects tested

weekly in a controlled laboratory, and examined for several months, that the

major change from resting state was an increase in left anterior coherence

during word fluency tasks. In this study, the analysis of variance showed

the presence of main effects for task and significant EEC measures x task

interactions in all four frequency bands. The EEC correlates of male-female

differences in verbally based and spatially based cognitive tasks have been

s*
^

,W'V>-^^TWvWT*'VFAr1VF^irvrTyr^m^nr^IHF^»n»^ irmrmr^v^ir«)rKirwrvin>ir«v«wir«wwrvww«ww«u> -

122

reported elsewhere (Koles and Flor-Henry, 1986, a,b). Briefly, taking

bipolar derivations of the EEC and using measurements of coherence to

evaluate synchrony between brain regions It was found that comparing resting

state (eyes open) with verbal and spatial states, that the spatial s.ate was

the most distinct. A stepwise discriminant fumtion analysis showed that a

left posterior ard right frontal component most strongly distinguished

between the verbal and spatial conditions and that while change in pattern

from resting state was stronger in men than in women for the spatial state

and stronger for women than men for the verbal state, the only significant

difference was in the spatial condition.

The analysis of variance across all bands (EEC measures x task x sex)

showed a significant main effect for task (theta, alpha and beta) and

significant task x measures Interactions in,all bands. However, analysing

the bands separately (males vs. females by task 6h the 13 EEC measures)

significant main effects for sex were found in 10 EEC measures. All the EEC,

measures x sex interactions were significantly different in men and women in

each of the four bands, although here the only significant main effect for

sex was in the beta range. Significant main effects for task were found in

all bands. It can be concluded that, although task related EEC effects are

stronger than sex related ones, there are nevertheless very systematic

changes in EEC organization that are gender dependent. These relate

principally to differences in power; right and left intrahemispherlc

anterior ^ posterior phase lead, and left right interhemispheric phase

relationships. Also EEC coherence was greater in women than in men.

Without exception, in women the phase relationships were less pronounced and

in particular, the lead of the left hemisphere rwer the right was reduced.

If we Ignore a few discordant findings In the bfta frequencies in which,

despite careful effort, there is always the ever present problem of possible

myogenic infiltration of the EEC signal, the directionality of these

differences in EEC organization by gender are remarkably constant in all the

four bands and across the five cognitive states. The overall Increase in

general coherence and the lesser degree of antero-posterior and left right

interhemispheric phase gradients suggest, in women a more synchronized and

less lateralized pattern of neuroelectric cerebral organization. This is in

keeping, of course, with the numerous cognitive studies which have shown,

statistically, that both verbal and spatial cognition engages more bilateral

brain systems in women than in men, who on the other hand show greater

lateralization for both verbal and spatial processing. The recent

demonstration by de Lacoste-Utamsing and Holloway, (1982) that women have more

abundant fibres in the posterior part of the corpus callosum than men

provides a possible neuroanatomical su^strat«» for the greater

bilateralization in female cognitive org.inization. It is noteworthy that

sinistrals compared to dextrals tend also to be more bilateral in their

cognitive processing and Witelson (1985) has observed a significantly larger

corpus callosum in sinistrals than in dextrals. The present study, as did

our previous investigation of male/female EEC differences, finds greater EEC

power in women. This was also found by Perris et al. (1981). A problem of

interpretation lies in the fact that the skull thickness of men is greater

than that of women and therefore this would attenuate the amplitude of the

EEC in men. However the brain mass in men is also greater, which might

compensate for the differential skull thickness. Furthermore the increase

in power is found in some conditions, in particular frequency bands - and not

in others - would suggest a neural, rather than an anatomico-physical causal

mechanism. In any event, the increased coherence cannot be attributed to

differential skull effects and, in a general sense power and coherence are

positively correlated. It seems probable that the increase in power in

women is related to the fact that women have a thicker cortical gray mantle,

and increased rate of cerebral circulation than men (Cur et al., 1982).

^'J^

mits

KT^

MOfltey::^^^
wwwnm'vww\w mvTJVT*rwvwm>wwwTw\i^ ^ ^ .. ^

123

CUNCLUS1ÜNS

Ku ti.ri.il ceihniques doinonstrate that the EtC of normal subjects

consists of 5 fundamental EEC parameters: power, coherence, phase factors:

anteroposterior and interhemispher ic, log. of ri>5ht/left power ratios and

oscillations. Analysed in terms of these parameters, the EEC organization

in men and women is different, women exhibiting more EEC power, a greater

decree of EEC coherence and a lesser degree of antero-posterior (bilateral)

and left^ right interhemispheric phase relationships. This configuration

is consistent with known neuroanatomical and cognitive differences in the

two genders. Ageing is accompanied by a reduction in the slow, and an

increase in the fast frequencies of the EEC power spectrum together with a

reduction in the degree with which the Irft hemisphere leads the right and

greater relative right frontal activation. Jt would appear therefore that,

in a certain sense, the ageing brain approximates the feciale pattern of

cerebral organization, in both sexes with increased right hemisphericpreponderance .

REFERENCES •

AAhn, H., Prichep, L., John, E.R., Trepetin, M., Brown, M.D., and Kaye, H.

(1980). Developmental equations for the electroencephalogram. Science,

210, 1255 - 125K.

Beaumont, J.G., Mayes, A.R. and Rugg, N.D. (1978). Asymmetry in EEC alpha

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Benignus, V.A. (1969). Estimation of the coherence spectrum and its

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Corbin, H.P.F. and Bickford, R.G. (1955). Studies of the

electroencephalogram of normal children: comparison of visual and

automatic frequency analysis. Elec roencephalography and Clinical

Neurophysiology, 4C), 113-131.

Colon, E.J., deWeerd, J.P.C., Notermans, S.L.H. and de Graaf, R. (1979).

EEC spectra in children aged 6, 9 and 10 years. Reference values.

Journal of Neurology, 221, 263-268.

Duffy, F.H., Albert, M.S., McAnulty, C. and Carvey, A.J. (198^). Agerelated differences in brain electrical activity of healthy subjects.

Annals of Neurology, 16, A33-«i38.

De Lacoste-L'tamsing, C. & Holloway, R.L. (1982). Sexual dimorphism in the

human corpus callosum. Science, 216, 1M31-1'<32.

Flor-Henry, P., Koles, Z.J. and Reddon, J. (1985). EEC studies of «ex

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S160.

Flor-Henry, P., Koles, Z.J. and Sussman, P.S. (19HA). Further observations

on right/left hemispheric energy oscillations in the endogenous

psychoses. Advances in Biological Psychiatry, 15, 1-11.

Flor-Henry, P. and Koles, Z.J. (1982). EEC characteristics in normal

subjects: a comparison of men and women and of dextrals and sinistrals.

Research Comrrunicat ions in Psychology, Psychiatry, and Behavior, 7^,

21-38.

Cibbs, F.A. and Knott, J.R. (19^9). Crowth of the electrical activity of

the cortex. Electroencephalography and Clinical Neurophysiology, ^,

223-229.

Greenblatt, M., Healey, U.M., & Jones, C.A. (1944). Age and

electroencephalographic abnorn. ility in neuropsychiatric patients.

American Journal of Psychiatry, 101 . 82-90.

Cur, R.C., Our, K.E., Ubrist, W.D. Hunger buh ler, J.P., Younkin, D.,

Rosen, A.D., Skolnick, B.E. and Rcivich, M. (1982). Sex «nd

handedness dlfrerences in cerebral blood flow during rest and cognitive

^>.

f VMSM

i

""^K***!

M

m

> .vIv'.V
rarrjn r^jrwjr-jr«

124

activity. S.icnce, 217, 659-661.

Koles, Z.J. and Flor-Hcnry, P. (1981). Mental artivlty and the EEC: task

and workload elated efteits. Medical and Biological Engineering and

Computing, ^9, Ih5-19A.

Koles, Z.J. and Flor-Henry, P. (19b6a). EEC correlates of male-feinale

differences in verbally and spatially-based cognitive tasks. Abstract

for the 12th C.M.B.E.C./lst Pan. Pacific Symposium, Vancouver, Canada.

Koles, Z.J. and Flor-l.-nry, P. (1986b). The effect of brain function on

coherence patterns In the bipolar EEC. Unpublished paper.

Lehmann, D. (1981). Spatial analysis of evoked and spontaneous EEC potential

fields. In N. Yamaguchi and K. Fujisawa (Eds.) Recent Advances in EEC

and EMC Data Processing. Amsterdam: Elsevier North Holland Biomedical

Pr7s~l 17-132.

Matousek, M. & Peterson, I. (1973). Automatik evaluation of EEC background

activity by means of age-dependent EEC quorients.

Electroencephalography and Clinical Neurophysiology. 35, 603-612.

Matsuura, M., Yamamoto, K., Fukuzawa, H., Okubo, Y., Uesugi, H., Moriiwa,

M., Kojima, T. & Shimazono, Y. (1985). Age development and sex

differences of various EEC elements in healthy children and adults -

quantification by a computerized wave form recognition method.

Electroencephalography and Clinical Neurophysiology, 60, 39^-^06.

Perris, C, von Knorring, L., Cunherpatch, J. and Marciano, F. (1981).

Further studies of depressed patients by means of computerized EEC.

Advances in Biological Psychiatry, b, M-A9. .

Tucker, D.M., Dawson, S.L., Roth, D.L. & Penland, J.C. (1985). Regional

changes in EEC power and coherence during cognition: intensive study of

two individuals. Behavioral Neuroscience, 99, 56^-577.

Witelson, S.F. (1985). The brain connection: the corpus callosum is larger

in left-handers. Science , 229, 665-668.

Welch, P.D. (1967). The use of the Fast Fourier Transform for the

estimation of power spectra: a method based on time averaging over

short, modified pcriodograms. IEEE Transactions Audio and

Electroacoustics, 15, 70-73.

•vvv Vvv

..•?^>:

wot t

APPtNDIX I

Dietrich Lehmann (I9H1) has persuasively argued that amplitude and

phase information in any given recording channel is ambiguous information

for depending on the chosen reference the value will differ. Avirage

reference is however "reference-free" since in such a system the EEC

potential fields are not determined by any particular montage. The

following two tables indicate the correspondence between the montage used in

the study and reconstructed average reference. It is seen that although the

global predictability of one system with respect to the other is modest, 15

- 202, the correiations for the EEC frequencies between the two systems arc

generally robust, except for the phase.

• vW>

f ■■:

J

^.%>.v.

Sec over/...

*^«i
1 .83 .77 .78 .87

.58 .65

.53 .54

.40 .46

.35 .38

.30 .32

.25 p <.05 .26

.25

.19

Pearson product moment correlations between measures

derived from unipolar and average references

Measure 1 - 3H2 4 - 7Hz 8 - 13Hz 20 - 40Hz

1. Power ffiffi

a) Frontal

b) Temporal-Parietal

2. Coherence

3. Phase

a) Left^-Right Posterior

b) Left^-Right Anterior

c) Right Intrahemispheric

d) Left Intrahemispheric

e) Left^Right Interhemispheric

f) Rights-Left Intrahemispheric

4. Log Right/Left Power Ratio

a) Frontal

b) Temporal-Parietal

5. Oscillations

a) Temporal-Parietal

b) Frontal

Canonical Redundancy Between Unipolar (UR) and Average (AR) Reference '".•^/ J

;-.-

Canonical Correlations

1 - 3 Hz 4 - 7 Hz 8 - 13 Hz 20 - 40 Hz

.801 .693 .642 .635

.360 .358 .744 .829

.366 .234 .665 .647

.056 .304 .264 .077

.226 .234 .122 .076

.054 .221 .274 .168

.094* .175 .211 .18;

.038 * .138 -.038 -.061

.097 .142 .039 .046

.367 .426 .341 .315

.323 .332 .327 .414

.515 .244 .625 .564

.356 .290 .515 .515

2 .58 .65 .72 .73 V>V:

3 .53 .54 .52 .58 'vV*^

4 .40 .46 .51 .52 yfr',

5 .35 .38 .43 .42

6 .30 .32 .41 .34

.v.v

» i

7 .25 p <.05 .26 .36 .31 V ' 8 .25 .28 .28 p< .05 I

9 .19 p < .05 .26

10 .19 p < .05 V

I

Canonical Redundancy

Percent UR AR UR AR UR AR UR AR

$P*

15.2 20.9 14.9 18.4 24.5 25.8 22.9 25.1 V

i.e. From Unipolar 20Z of Average Reference Predictable "rs'«/'«/

i.e. From Average 15^ of Unipolar Reference Predictable.

. »
. ».'A w.'^.FTWWtWWWHWWWWWWWlWfWWln. *. J

1

.r,\f'.'vevv?rrv.'v>-j'r*.'vr9.vsv'.-vrr.-rrs.--''.-r^r.-yr.'*'V7i*.-w.-y

126

Appendix II.

Males Age x Factor Correlations

Eyes Open

Frequency Bands (Hz)

Factor 1 - 3 4 - 7 8-13 20 - 40

1. Power

a) Frontal -0.25* -0.37* 0.04 0.14

b) Temporal-Parietal -0.26* -0.32* -0.05 -0.08

2. Coherence -0.20 -0.31* 0.00 -0.01

3. Phase

a) Left^Right Posterior -0.05 0.07 0.03 -0.14*

b) Left^-Right Anterior -0.02 OiflS 0.15 0.03

c) Right Intrahemispheric 0.22* 0.16 -0.16 -0.07

d) Left Intrahemispheric -0.05 0.11 -0.18 -0.03

e) Left Interhemispheric -0.12 0.25* -0.05 0.01

f) Right Interhemispheric 0.20 .0.21 -0.19 0.11

4. Average log Right/left

Power Ratio

a) Frontal -0.26* -0.27* -0.20 -0.22*

b) Temporal-Parietal 0.16 0.03 0.03 -0.13

5. Oscillations

a) Temporal-Parietal 0.13 -0.09 -0.22* 0.01

b) Frontal 0.16 0.16 -0.01 -0.06

JXW

Ä

Males Age x Factor Correlations

Eyes Closed

V

Frequency Bands (Hz)

Factor 1 - 3 4 - 7 8-13 20 - 40

1. Power

a) Frontal -0.31* -0.27* 0.05 0.13

b) Temporal-Parietal -0.24* -0.27* -0.18 -0.06

2. Coherence -0.31* -0.28* -0.13 0.01

3. Phase

• a) Left^-Right Posterior -0.07 -0.27* -0.04 -0.05

b Left»-Right Anterior 0.08 -0.38* -0.16 0.22*

c) Right Intrahemispheric 0.01 0.19 0.05 -0.21

d) Left Intrahemispheric -0.09 0.06 -0.04 -0.28*

e) Left Interhemispheric -0.18 -0.14 0.03 -0.03

f) Right Interhemispheric -0.13 0.34 -0.01 -0.19

4. Average log Right/left

Power Ratio

a) Frontal -0.27* -0.32* 0.09 -0.18

b) Temporal-Parietal 0.09 -0.15 -0.08 -0.01

5. Oscillations

a) Temporal-Parietal 0.04 0.26* -0.01 -0.16

b) Frontal 0.08 0.13 -0.24* -0.26*

J5W
if^w^"V>'v

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127

Males Age x Factor Correlations

Vocabulary

Frequency Bands (Hz)

Factor 1 - 3 4 - 7 8-13 20 - 40

1. Power

a) Frontal -0.29* -0.32* -0.14 0.03

b) Temporal-Parietal -0.09 -0.28* -0.13 -0.11

2. Coherence -0.10 ^ -0^26* -0.08 -0.03

3. Phase

a) Left^-Right Posterior 0.06 0.05 0.03 -0.10

b) Left^-Right Anterior 0.03 0.05 -0.01 0.22*

c) Right Intrahemispheric -0.01 0.08 -0.13 -0.12

d) Left Intrahemispheric 0.00 * 0.03 -0.14 0.05

e) Left Interhemispheric 0.13 0.01 -0.14 0.03

f) Right Interhemispheric -0.05 0.05 0.06 0.00

4. Average log Right/Left

Power Ratio

a) Frontal -0.13 -0.19 -0.08 -0.18

b) Temporal-Parietal 0.10 0.13 -0.14 -0.04

5. Oscillations

a) Temporal-Parietal 0.02 0.17 -0.02 -0.08

b) Frontal -0.03 0.03 -0.14 -0.13

&23

Factor

Males Age x Factor Correlations

Oral Word Fluency

Frequency Bands (Hz)

1-3 4-7 8-13 20-40

•',

1. Power

a) Frontal -0.025* -0.32* -0.13 0.21

•b) Temporal-Parietal -0.11 -0.32* 0.20 -0.17

2. Coherence -0.12 -0.32* -0.13 0.04

2. Phase

a) Left»-Right Posterior -0.11 -0.02 0.11 0.00

b) Left^-Right Anterior -0.02 -0.15 -0.10 0.18

c) Right Intrahemispheric 0.17 0.14 -0.16 -0.03

d) Left Intrahemispheric -0.03 -0.03 -0.22* 0.04

e) Left Interhemispheric 0.25* 0.03 -0.07 -0.02

f) Right Interhemispheric -0.01 0.35* -0.05 0.02

4. Average log Right/left

Power Ratio

a) Frontal -0.24* -0.23 -0.03 -0.12

b) Temporal-Parietal 0.12 0.08 -0.12 0.06

5. Oscillations

a) Temporal-Parietal -0.11 0.20 -0.04 -0.07

b) Frontal -0.16 0.03 -0.20 -0.23*

SrtS

w

•

••.-•,

rag
ü

M.es Age x Factor Correlations

sf

Block Design

Factor 1 - 3

Frequency Bands (Hz)

4-7 8-13 20 - AO

1. Power

a) Frontal -0.34* -0.41* -0.34* 0.12

b) Temporal-Parietal -0.10 -0.21 -0.22* 0.14

2. Coherence -0.10 -0.19 -0.18 -0.02

3. Phase 5

a) Left^-Right Posterior 0.20 -0/03 0.0C

0.00

b) Left^-Right Anterior 0.00 -0.32* -0.03 0.01

c) Right Intrahemispheric -0.07 -0.21* -0.14 0.28*

d) Left Intrahemispheric 0.08 -0.09 -0.03 -0.09

e) Left Interhemispheric -0.03 -0.31* -0.10 -0.08

f) Right Interhemispheric -0.22* -0.08 -0.17 -0.18

4. Average log Right/Left

Power Ratio

a) Frontal -0.01 -0.16 -0.22* -0.28*

b) Temporal-Parietal 0.07 0.03 0.01 0.03

5. Oscillations

a) Temporal-Parietal -0.08 -0.07 -0.02 -0.21

b) Frontal -0.07 -0.10 -0.02 -0.23*

m

Females Age x Factor Correlations

5

v

Eyes Open

Frequency Bands (Hz)

Factor 1 - 3 4-7 8-13 20 - 40

1. Power

a) Frontal -0.23* -0.40* -0.35* -0.20

b) Temporal-Parietal -0.31* -0.45* -0.36* 0.05

2. Coherence -0.19 -0.44* -0.40* -0.08

3. Phase

a) Left^-Right Posterior -0.16 -0.38* 0.04 0.08

b) Left^-Right Anterior -0.09 -0.24* 0.03 0.14

c) Right Intrahemispheric 0.03 -0.22* 0.09 0.05

d) Left Intrahemispheric -0.23* -0.35* 0.06 -0.02

e) Left Interhemispheric -0.06 -0.54* 0.12 0.04

f) Right Interhemispheric 0.20 0.08 -0.05 -0.16

4. Average log Right/Left

Power Ratio

a) Frontal -0.08 -0.13 -0.19 -0.19

b) Temporal-Parietal -0.11 -0.04 -0.20 0.15

5. Oscillations

a) Temporal-Pai xetal -0.37* 0.16 0.22* -0.42*

b) Frontal -0.07 -0.07 0.06 0.00

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129

Females Age x Factor CorrelaLJons

Eyes Closed

Factor 1 - 3

Frequency Bands (Hz)

A - 7 8-13 20-40

1. Power

a) Frontal -0.42* -0.54* -0.29* -0.06

b) Temporal -0.55* -0.52* -0.31* -0.02

2. Coherence -0.54* -0.54* -0.26* -0.03

3. Phase 5

a) Left^Right Posterior -0.40* -0.«7 0.13 -0.13

b) Left^-Right Anterior 0.00 -0.10 0.15 -0.03

c) Right Intrahemispheric -0.05 0.09 0.18 -0.11

d) Left Intrahemispheric 0.02 -0.05 0.14 -0.01

e) Left Interhemispheric -0.10 .0.02 0.29 -0.06

f) Right Interhemispheric -0.03 0.29* 0.00 -0.06

A. Average log Right/Left

Power Ratio

a) Frontal 0.04 -0.05 -0.05 -0.15

b) Temporal-Parietal -0.11 -0.11 0.03 -0.10

5. Oscillations

a) Temporal-Parietal -0.11 -0.13 0.13 -0.30*

b) Frontal -0.01 0.19 0.03 -0.15

MM

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Females Age x Factor Correlations

Factor

Vocabulary

1 - 3

Frequency Bands (Hz)

4-7 8-13 20-40

1. Power

a) Frontal -C.19

, b) Temporal-Parietal -0.18

2. Coherence -0.20

3. Phase

a) Left^-Right Posterior -0.16

b) Loftfc-Right Anterior -0.19

c) Right Intrahemispheric 0.22*

d) Left Intrahemispheric 0.05

e) Left Interhemispheric -0.07

f) Right Interhemispheric 0.25*

4. Average log Right/left

Power Ratio

a) Frontal 0.13

b) Temporal-Parietal 0.26*

5. Oscillations

a) Temporal-Parietal -0.18

b) Frontal -0.14

0.25* -0.26* 0.16

0.37* -0.34* 0.04

0.37* -0.31* 0.08

0.30* -0.13 0.27*

0.04 0.06 -0.10

0.15 -0.01 -0.23*

0.07 -0.16 0.08

0.07 -0.13 -0.11

0.10 -0.13 0.00

0.06 0.06 -0.03

0.22* 0.14 0.22*

0.19 0.18 -0.14

0.08 -0.07 -0.26*

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130

&

Females Age x Factor Correlations

Oral Word Fluency

Factor 1 - 3

Frequency Bands (Hz)

A - 7 8-13 20 .0

1. Power

a) Frontal -0.23* -0.31* -0.27* 0.24*

b) Temporal-Parietal -0.09 -0.37* -0.33* 0.12

2. Coherence -0.12 ,-0.38* -0.31* 0.28*

3. Phase 4

a) Left^-Right Posterior -0.22 -0.30* -0.23* -0.06

b) Left^-Right Anterior -0.07 -0.10 -0.15 -0.08

c) Right Intrahemispheric 0.04 -0.20 -0.10 -0.27*

d) Left Intrahemispheric 0.05 0.00 -0.16 -0.04

e) Left Interhemispheric -0.05 -0.01 -o to -C.09

f) Right Interhemispheric 0.11 0.16 0.13 -0.09

4. Average log Right/left

Power Ratio •

a) Frontal 0.14 0.07 -0.03 0.04

b) Temporal-Parietal 0.17 0.07 -0.03 0.12

5. Oscillations

a) Temporal-Parietal -0.36* 0.18 0.15 -0.18

b) Frontal -0.18 -0.04 -0.07 -0.38*

h

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Females Age x Factor Correlations

Block Design

Factor 1 - 3

Frequency Bands (Hz)

4-7 8-13 20-40

1. Power

a) Frontal -0.40* -0.44* -0.25* 0.26*

b) Temporal-Parietal -0.07 -0.16 0.04 0.30*

2. Coherence -0.32* -0.37* -0.22* 0.26*

3. Phase

a) Lefc^Right Posterior 0.01 -0.19 -0.17 -0.19

b) Left^-Right Anterior 0.19 0.09 0.12 0.25*

c) Right Intrahemispheric -0.09 -0.17 -0.25* 0.02

d) Left Intrahemispheric 0.05 0.17 0.11 0.13

e) Left Interhemispheric 0.16 0.10 -0.02 -0.05

f) Right Interhemispheric -0.06 0.01 -0.02 0.04

4. Average log Right/left

Power Ratio

a) Frontal 0.17 0.09 0.03 -0.12

b) Temporal-Parietal -0.01 -0.01 0.05 0.04

5. Oscillations

a) Temporal-Parietal 0.07 0.15 -0.29* -0.26*

b) Frontal -0.08 -0.12 -0.45* -0.34*

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131

Appendix 111.

CELL hEANS AND STANDARD DEVIATIONS (S.D.) BY TASK (1 - 3 Hz)

V ^.

¥

For Normal Males (n"57) and Normal Females (n«56 on "3 EEG Measures)

EEC Measure and Task

1. Power

a) Frontal

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

b) Temporal-Parietal

Eyes Open

Eyes Closed

Vocabulary

Oral VJ-C fluency

Block Design

2. Coherence

Eyes Open

Eyeu Closed

Vocabulary

Oral Word Fluency

Block Design

3. Phase

a) LefU^-Right

Posterior

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

b) Left»-Right

Anterior

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

c) Right Intrahemispheric

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

d) Left Intrahemispheric

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

e) Left Interhemispheric

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

Normal Males (n-57) Normal Females (n«56)

Standard Standard

Cell Meari Deviation Cell Mean Deviation

-0.577 0.439 -0.357 0.531

-0.782 0.174 -0.782 0.153

0.07A 0.688 0.720 1.243

0.035 0.783 0.437 1.118

0.233 0.928 0.911 1.210

-0.406 0.273 -0.355 0.221

-0.368 0.623 -0.460 0.198

0.249 1.075 0.300 0.767

0.302 1.348 0.297 0.876

0.170 1.968 0.224 0.786

-0.390 0 310 -0.311 0.294

-0.455 0.332 -0.465 0.183

0.116 0.667 0.340 0.835

0.204 1.138 0.260 0.795

0.325 2.344 0.341 0.772

-0.030 0.454 0.073 0.279

-0.014 0.442 -0.046 0.223

-0.049 0.966 0.002 0.469

-0.072 1.187 0.278 2.286

-0.080 0.604 -0.198 1.468

0.081 0.668 0.064 0.945

0.250 0.697 0.222 0.439

0.053 0.822 0.020 1.129

0.086 0.639 0.121 0.769

-0.418 1.531 -0.578 1.578

0.173 1.133 0.002 0.697

0.385 0.512 0.339 0.404

-0.360 1.146 -0.362 1.127

-0.127 1.323 -0.450 1.019

0.238 0.532 0.061 1.317

-0.161 1.022 -0.069 0.695

0.417 0.401 0.263 0.367

-0.059 1.334 -0.267 1.331

-0.105 1.289 -0.518 1.144

0.150 0.628 0.204 1.039

0.011 0.722 0.110 0.776

0.524 0.534 0.410 0.446

-0.077 0.964 -0.230 1.058

0.056 0.913 -0.116 1.004

-0.445 1.154 -0.512 1.570

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132

CELL MEANS AND STANDARD DEVIATIONS (S.D.) BY TASK (1 - 3 Hz)

For Normal Males (n=57) and Normal Females (n-56) on 13 EEC Measures

Normal Males (n-57)

Standard

EEC Measure and Task Cell Mean Deviation

Normal Females (n"56)

Standard

Cell Mean Deviation

f) Right Interhemispheric

Eyes Open 0.093 0.841 0.060 0.913

Eyes Closed 0.217 0.723 0.301 0.449

Vocabulary -0.224 0.970 -0.091 1.110

Oral Word Fluency -0.100 0.934 -0.254 0.680

Block Design 0.109 1.227 -0.018 1.752

4. Average log Right/left Power Ratio

a) Frontal

Eyes Open -0.119 1.041 -0.150 1.095

Eyes Closed 0.195 0.588 0.213 0.625

Vocabulary -0.103 1.203 -0.144 0.93b

Oral Word Fluency -Ü.205 1.152 -0.417 1.198

Block Design 0.336 1.110 0.205 0.875

b) Temporal-Parietal *

Eyes Open -0.180 0.691 -0.039 0.726

Eyes Closed -0.177 0.876 -0.119 0.804

Vocabulary 0.148 0.888 -0.131 1.021

Oral Word Fluency 0.020 0.953 -0.063 1.035

Block Design 0.281 1.357 0.197 1.512

5. Oscillations

a) Temporal-Parietal

Eyes Open 0.279 0.986 0.164 0.793

Eyes Closed 0.867 !.129 0.997 1.212

Vocabulary -0.263 0.926 -0.357 0.705

Oral Word Fluency -0.238 0.829 -0.231 0.725

Block Design -0.631 0.701 -0.397 0.485

b) Frontal

Eyes Open -0.020 1.054 -0.002 1.C26

Eyes Closed 0.765 1.090 0.712 0.921

Vocabulary -0.263 0.866 -0.198 0.971

• Oral Word Fluency -0.319 0.895 -0.546 0.917

Block Design -0.101 0.841 0.010 0.799

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133

CELL MEANS AND STAVDARD DEVIATIONS (S.D.) BY TASK (4-7 Hz)

For Normal Males (n-57) and Normal Females (n-56) on 13 EEC Measures

EEC Measure and Task

1. Power

a) Frontal

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

b) Temporal-Parietal

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

2. Coherence

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

3. Phase

a) Left^-Right Posterior

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

b) Left^-Sight Anterior

Eyas Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

c) Right Intrahemispheric

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

d) Left Intrahemispheric

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

BlocV Design

e) Left Interhemispheric

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Desien

Normal Mai es (n-57) Normal Females (n-56)

Standard Standard

Cell Mean Deviation Cell Mean Deviation

-0.600 0.453 -0.370 0.511

-0.652 n.591 -0.666 0.349

0.116 i.211 0.563 1.024

0.040 1.131 0.356 0.910

0.262 0.842 0.869 0.986

-0.444 0.557 -0.240 0.783

-0.064 1.285 -0.079 0.887

0.073 1.313 0.613 0.850

0.056 1.155 0.201 0.846

0.002 1.178 0.342 1.000

-0.382 0.563 -0.125 0.919

-0.088 1.136 -0.002 0.882

0.003 1.335 0.126 0.893

0.001 1.066 ' 0.147 0.835

0.125 1.494 0.203 0.817

0.199 0.792 -0.164 0.775

-0.068 1.420 -0.147 0.987

0.192 0.768 0.073 0.725

0.245 0.960 -0.049 1.429

0.015 0.605 -0.412 1.294

0.076 0.595 0.005 0.542

-0.003 0.738 0.054 0.175

-0.006 0.960 0.248 0.761

0.156 0.744 0.258 0.622

-0.338 1.700 -0.403 1.809

0.101 0.859 0.130 0.628

0.056 0.699 0.249 0.624

0.100 1.217 -0.048 0.925

0.229 1.323 -0.344 1.325

-0.299 0.721 -0.305 1.149

0.045 0.829 -0.072 0.810

-0.046 0.764 0.092 0.516

0.4-,! 1.161 -0.046 0.928

0.205 1.400 -0,352 1.278

-0.146 0.751 -0.192 1.200

0.264 0.662 -0.042 0.679

0.037 0.721 0.117 0.409

0.428 0.958 0.254 0.913

0.302 0.969 0.055 1.124

-0.680 1.477 -0.811 1.073

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134

CCrls

CELL MEANS AiND STANDARD DEVIATIONS (S.D.) BY TASK (4-7 Hz)

For Normal Males (n"57) and Normal Females (n-56) on 13 EEC Measures

v.vS'S-:

Normal Females (n"57) Normal Females (n«56)

EEC Measure and Task

f) Right Interhemispheric

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

A. Average log Right/left

a) Frontal

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

b) Temporal-Parietal

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

3. Oscillations

a) Temporal-Parietal

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

b) Frontal

Eyes Open

Eyes Closed

Vocabulary

Oral Word Fluency

Block Design

Standard Standard

Cell Mean Deviation Cell Mean Deviation

0.136 0.647 0.172 0.597

0.187 1.084 0.195 0.459

0.242 1.068 -0.187 0.936

0.149 1.004 -0.196 0.954

-0.471 1.191 -0.223 1.613

Power Rat io

-0.058 0.969 -0.186 1.092

0.255 0.431 0.171 0.475

-0.125 1.185 -0.150 1.000

-0.269 1.067 -0.366 1.434

0.217 1.067 0.243 0.881

-0.205 0.782 -0.226 0.781

-0.112 1.034 -0.057 0.968

0.118 0.859 -C.081 0.997

-0.011 0.936 0.068 1.029

0.227 1.207 0.199 1.339

-0.332 0.897 -0.401 0.925

-0.003 1.344 -0.162 1.111

0.231 1.058 0.312 0.741

0.434 1.094 0.273 0.896

-0.302 0.892 -0.213 0.605

-0.573 0.320 -0.491 1.109

0.310 1.270 0.215 0.912

-0.070 1.076 0.153 0.788

0.153 1.108 -0.012 0.853

0.117 0.778 0.071 0.814

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135

V

CELL MEANS AND STANDARD DEVIATIONS (S.D.) BY TASK (8 - 13 Hz)

For Normal Males (n«57) and Normal Females (n»56) on 13 EEG Measures

Normal Males (n«57) Normal Females (n=56)

if'

g

V.

Standard Standard

EEG Measures and Task Cell Mean Deviation Cell Mean Deviation

1. Power

a) Frontal

Eyes Open -0.456 0.755 -0.240 0.960

Eyes Closed 0.008 1.090 0.390 1.409

Vocabulary -0.259 0.687 0.310 1.249

Oral Word Fluency -0.258 0.716 0.161 1.209

Block Design -0.012 0.629 0.461 0.799

b) Temporal-Parietal

Eyes Open -0.281 0.580 -0.158 0.816

Eyes Closed 0.511 1.314 1.071 1.981

Vocabulary -0.258 0.545 -0.042 0.723

Oral Word Fluency -0.225 0.511 -0.032 0.718

Block Design -0.360 0.389 -0.186 0.468

2. Coherence , Eyes Open -0.243 0.565 -0.121 0.781

Eyes Closed 0.470 1.213 1.064 1.914

Vocabulary -0.254 0.610 -0.043 0.898

Oral Word Fluency -0.214 0.525 , 0.001 0.967

Block Design -0.304 0.564 -0.299 0.335

3. Phase

a) Left^-Right Posterior

Eyes Open 0.232 1.097 -0.085 1.019

Eyes Closed -0.185 1.039 -0.039 1.127

Vocabulary 0.229 1.034 0.086 0.896

Oral Word Fluency 0.231 0.906 0.048 1.005

Block Design -0.047 0.655 -0.478 1.312

b) Left^-Right Anterior

Eyes Open 0.174 0.512 0.105 0.471

Eyes Closed -0.063 0.435 -0.07n 0.358

Vocabulary 0.026 0.843 0.021 0.904

Oral Word Fluency 0.027 0.641 -0.000 0.721

Block Design -0.160 2.113 -0.085 1.626

c) Right Intrahemispheric

Eyes Open 0.171 0.895 0.150 0.873

Eyes Closed -0.264 1.245 -0.471 1.235

Vocabulary 0.108 0.960 0.106 1.273

Oral Word Fluency 0.055 0.984 0.081 1.274

Block Design -0.122 0.340 0.068 0.638

d) Left Intrahemispheric

Eyes Open 0.130 0.814 0.023 0.773

Eyes Closed -0.312 1.224 -0.254 1.280

Vocabulary 0.147 0.953 0.190 1.286

Oral Word Fluency 0.047 1.010 0.249 1.256

Block Design -0.211 0.452 -0.134 0.729

e) Left Interhemispheric

Eyes Open 0.400 0.887 0.253 0.892

Eyes Closed -0.320 0.853 -0.092 1.057

Vocabulary 0.147 1.200 0.051 0.963

Oral Word Fluency 0.033 0.983 0.180 0.923

Block Design -0.336 1.052 -0.441 1.103

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13fCELL MEANS AND STANDARD DEVIATIONS (S.D.) BY TASK (8 - 13 Hz)

For Normal Males (n-57) and Normal Females (n-56) on 13 EEC Measures

Normal Males (n-57) Normal Females (nm56)

Stf..ndard Standard

EEG Measure and Task Cell Mean Deviation Cell Mean Deviation

3. Phase .

f) Right Interhemispheric

Eyes Open -0.055 0.950 0.211 0.786

Eyes Closed -0.075 1.148 -0.107 1.082

Vocabulary -0.013 1.122 0.177 1.066

Oral Word Fluency 0.039 1.079 0.126 1.008

Block Design -0.275 1.026 -0.190 0.937

4. Average log Right/Lef t Power Rat io

a) Frontal

Eyes Open 0.168 0.767 -0.085 0.986

Eyes Closed 0.183 0.717 -0.015 0.739

Vocabulary -0.025 1.099 0.067 0.851

Oral Word Fluency -0.087 0.894 -0.206 1.094

Block Design -0.242 1.520 -0.013 1.026

b) Temporal-Parietal

Eyes Open 0.050 0.744 -0.128 0.817

Eyes Closed -0.008 1.159 C.168 1.249

Vocabulary 0.174 0.929 0.089 1.004

Oral Word fluency 0.143 1.093 0.186 1.048

Block Design -0.228 0.891 -0. 44 0.985

5. Oscillations

a) Temporal-Parietal

Eyes Open -0.280 0.939 -0.267 0.852

Eyes Closed -0.946 0.749 -1.143 0.826

Vocabulary 0.474 0.896 0.436 0.853

Oral Word Fluency 0.424 0.932 0.351 0.830

Block Design 0.429 0.612 0.305 0.487

b) Frontal

Eyes Open -0.477 0.887 -0.422 0.754

'Eyes Closed -0.375 1.281 -0.722 1.040

Vocabulary 0.594 0.787 0.678 0.817

Oral Word Fluency 0.353 0.791 0.529 0.808

Block Design -0.190 0.679 -0.087 0.831

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CELL MEANS AND STANDARD DEVIATIONS (S.D.) BY TASK (20 - 40 Hz)

Fc» Normal Males (n"57) and Normal Females (n"56) on 13 EEC Measures

Normal Males (nm57) Normal Females (n»56)

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Standard Standard

EEC Measure and Task Cell M, Deviation Cell Mean Deviation

1. Power

a) Frontal

Eyes Open -0.366 0.488 -0.357 0.275

Eyes Closed -0.A16 0.281 -0.379 0.262

Vocabulary -0.011 0.717 0.487 1.344

Oral Word Fluency 0.005 0.660 0.195 1.032

Block Design 0.226 1.084 0.693 1.986

b) Temporal-Parietal

Eyea Open -0.408 0.212 -0.341 0.180

Eyes Closed -0.339 0.359 -0.307 0.214

Vocabulary -0.158 0.421 0.230 0.744

Oral Word Fluency -0.107 0.429 0.204 0.837

Block Design 0.285 1.031 0.929 2.367

2. Coherence

Eyes Open -0.283 0.482 -0.238 0.335

Eyes Closed -0.157 0.673 -0.151 0.440

Vocabulary -0.132 0.614 0.214 0.994

Oral Word Fluency -0.129 0.519 0.080 0.757

Block Design 0.197 ..241 0.656 2.299

3. Phase

a) Left^-Right Posterior

Eyes Open 0.164 0.427 0.108 0.369

Eyes Closed 0.072 0.132 -0.074 0.4i4

Vocabulary -0.023 0.836 0.318 1.366

Oral Word Fluency 0.255 0.558 0.057 1.066

Block Design -0.177 1.572 -0.619 1.697

b) Left^-Right Anterior

Eyes Open 0.066 0.244 -0.077 0.553

Eyes Closed 0.024 0.462 -0.027 0.321

' Vocabulary -0.034 1.142 -0.071 0.912

Oral Word Fluency -0.055 1.350 0.143 0.898

Block Design 0.080 1.775 -0.108 1.420

c) Right Intrahemispheric

Eyes Open -0.026 0 .566 -0.022 0.308

Eyes Closed -0.021 0 .202 -0.145 0.501

Vocabulary -0.136 1 .071 0.050 1.140

Oral Word Fluency -0.210 1 .110 0.011 1.112

Block Design 0.261 1 .254 0.367 1.687

d) Left Intrahemispheric

Eyes Open -0.062 0 .458 -0.193 0.572

Eyes Closed -0.019 0 .340 -0.165 0.610

Vocabulary 0.070 0 .908 0.160 1.062

Oral Word Fluency 0.018 0 592 0.143 1.137

Block Design 0.042 1 .146 0.276 1.748

e) Left Interhemispheric

Eyes Open -0.053 0 263 -0.166 0.442

Eyes Closed -0.147 0 264 -0.250 0.309

Vocabulary 0.101 1 013 -0.111 1.029

Oral Word Fluency -0.400 1 133 0.102 1.067

Block Design 0.478 1 618 0.364 1.518

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138

CELL MEANS AND STANDARD DEVIATIONS (S.D.) BY TASK (20 - 40 Hz)

For Normal Males (n-57) and Normal Femalei (n-56) on 13 EEC Measures

Normal Males (n-57) Normal Females (n-56)

Standard Standard

EEC Measure and Task Cell Mean Deviation Cell Mean Deviation

3. Phase

f) Right Interhemispheric

Eyes Open -0.084 0.232 -0.165 0.504

Eyes Closed -0.190 0.334 -0.136 0.433

Vocabulary -0.151 0.875 -0.212 0.713

Oral Word Fluency 0.004 0.820 -0.034 0.*67

Block Design 0.402 1.739 0.620 1.566

4. Average log Right/Leift Power Ratio

a) Frontal

Eyes Open 0.223 1.360 0.097 0.784

Eyes Closed -0.133 0.963 -0.167 0.766

Vocabulary -0.084 1.159 0.105 0.808

Oral Word Fluency 0.058 1.109 0.042 1.093

Block Design -0.097 1.203 0.20C 0.589

b) Temporal-Parietal

Eyes Open -0.005 0.769 , -0.063 0.901

Eyes Closed -0.084 0.704 0.011 0.774

Vocabulary -0.063 1.062 -0.062 1.187

Oral Word F uency O.C43 1.105 0.143 1.044

Block Design 0.043 1.202 0.283 1.323

5. Oscillations

a) Temporal-Parietal

Eyes Open 0.328 0.811 0.194 0.717

Eyes Closed 0.745 0.905 0.611 0.881

Vocabulary -0.051 0.930 -0.262 1.100

Oral Word Fluency 0.071 0.921 -0.211 1.046

Block Design -0.732 0.829 -0.769 0.775

b) Frontal

Eyes Open -0.330 1.005 0.044 1.024

Eyes Closed 0.244 1.138 0.283 0.865

Vocabulary -0.164 1.037 0.082 1.087

Oral Word Fluency -0.072 0.659 0.187 1.015

Block Design -0.252 1.010 -0.012 1.056

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139

ATTENTIONAL FACTORS AND INDIVIDUAL DIFFERENCES REFLECTED IN THE EEC

William J. Ray

Penn State University

University Park,

Pa. 16802

USA

INTRODUCTION

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For the last few years the work in my laboratory has been directed

toward understanding how individual differences are reflected in

psychophysiological measures of cognitive and emotional processing. This

program has brought together two somewhat different approaches to research.

On the one hand we have sought to find the relationship between such

psychophysiological processes as EEC and the processing of cognitive and

emotional material (e.g., Ray & Cole, 1985). In this traditional approach

to experimental research, the relationship between the dependent and

independent variable is emphasized and individual differences minimized or

ignored. On the other hand we have also used the opposite research approach

which emphasizes individual differences. With this approach we seek to find

situations which allow us to demonstrate performance differences between

individuals or groups of individuals. These differences have been organized

in terms of sex, gender, anxiety, introversion/extraversion, or spatial

ability and are also present in behavioral measures and the EEC (cf., Ray,

Newcombe, Semon and Cole, 1981; Ray & Gesclowitz, 1985; Berfield, Ray &

Newcombe, 1986). In this chapter I will discuss research from each of these

parallel lines of inquiry. After a brief overview of the EEC hemispheric

activation literature, two recent studies from my laboratory examining the

role of basic a'tentional mechanisms will be presented. This will be

followed by presentation of work in progress showing how EEC measures may

aid in an understanding of individual differences. The emphasis throughout

the presentation will be on the limits of our present understanding of EEC

as well as potentially important new directions for research. The research

presented in this chapter benefited from the careful thought and hard work

of two graduate students. Work from the first tract was performed in

collaboration with Harry Cole and from the second with Lola Geselowitz.

The long term overall goal of combining these two different research

approaches is to define at what point or points in cognitive and emotional

processing do individual or personality differences play a role. It is

assumed that by examining the entire experimental session including periods

before informrtion is presented as well as periods in between formal tasks.

It will be possible to obtain a clearer picture of how personality and other

Individual differences play a role in the manner in which a given individual

approaches these tasks, in particular, and life in general.

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PREPARATORY PERCEPTUAL PROCESSING PRODUCTION

General What la Type of Response ^v^

State teen logic style

Fig. 1. Necessary aspects to consider when examining Individual

differences in Information processing.

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There exists a number of separate processes In which personality

differences may play a part. For organizational purposes I will use Figure

1 to represent some of the main potential areas In which personality and 0

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individual differences may play a role which in turn suggests specific vSxS

research questions to answer. V^'A'

First, one may ask if different personality groups approach a task

differently. This question asks if there is a particular set of preparation

which a particular individual, "high anxious", for example, brings to tht

experimental situation as opposed to another individual, such as a "low "•! '% ''

anxious" person. This could also include the general state of the organism '^"v'

as well as the meaning of the event for the person. Second, one may ask if Vv^

different individuals or personality groups perceive the situation or tasks

differently. This raises the possibility that personality differences may

be explained in terms of perceptual or cognitive structure differences. •''.•'•'/

That is to say, some individuals may focus on the emotional characteristics I-V^v

of a situation whereas others may pay more attention to particular details. "•'.'-'/

It is also the case that "experts" in a particular area (e.g., a '- ;••/•

professional) would have a more differentiated perception than a non-expert '.'•'.' ',

or novice. On another level, it is at this point that a metacontrol system

may bias the organism for a particular type of processing ranging from

orientating responses or defensive responses to hemispheric activation.

Third, one may ask if personality differences are the resultant of different "C'"^

ways of processing the information or task. In studying spatial abilities JvV^v'

for example, there is evidence to suggest that high spatial ability CN^W

individuals use a more synthetic approach whereas low spatial ability

individuals use a more analytic manner of process. It is at this point that

particular types of logic such a; analytic or synthetic processing would be

available for study. Fourth, one may ask if different personality groups £«y , produce or report their process!..g of cognitive, emotional, and motor tasks "' Ovl'i

differently. That is to say, it ray be that there exists individual •'." i-'I"^

differences in the ability to report responses (i.e., response styles) which

are separate from perceptual or processing differences. What remains

uncertain at this time is whether individual or personality differences may

be accounted for solely in terms of preparation, perception, processing or

production or some combination of these or whether individual or personality V'SJ1

differences pervade all the activity that a person engages in. Although V^V;

still in the early stages, it is our goal to apply this type of approach to

electrocortical measures oT cognitive and emotional processing with both WKf]

normal and psychopathological r

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Historical Views of EEC Activity

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The Initial reports by both Berger (reprinted 1969) and Adrian and "v">',

Matthews (1934) make for interesting reading. Berger in his original ^"'.-.'N'

reports suggested that EEC alpha activity (8-12 Hz) would offer insights 'v \

into the neural mechanisms of attention. This was related to his overall •C-'v'

desire to find physical measurements which represented the processing of the

^ mind. In his second report he stated: TZr?/'*

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"..I an nevertheless attracted by the view that the alpha waves

probably represent concomitant phenomena of those nervous

processes which have been termed psychophysical I.e., of those

material cortical processes which under certain circumstances

can also be associated with phenomena of consciousness. Among

the psychophysical processes one does not only include those

which in fact arc associated with conscious phenomena, but also

those which perform the so-called unconscious cortical activity.

Frequently only the results of the latter enter consciousness". (p.9l)

Later Berger suggested that alpha activity is to be found in all areas of

the cortex during periods in which one !s passively allowing thoughts and

Images Co arise spontaneously. When attention is actively focused, as In

the solving of a problem, alpha is arrested. This was seen to represent a

mechanism in which psychophysiological processes were localized, coupled

with a general inhibition in surtounding areas. The diffuse inhibitory

process is seen in the EEC as a blocking of alpha rhythm.

Adrian and Matthews agree with Berger and report that attention given

to a problem (e.g., mental arithmetic) even with the eyes closed will

abolish alpha "but the rhythm returns as soon as his attention wanders

(p.370)." Adrian and Matthews further note that "powerful muscular

contractions do not Interfere with the rhythm although the subject exerts

his full strength (p.371)." In the conclusion to their paper, Adrian and

Matthews present alpha activity as an Idling of the brain. In particular

they stated, "it was true that. In our view, the rhythm shows the negative

rather than the positive side of cerebral activity, It shows what happens In

an area of the cortex which has nothing to do, and It disappears as soon as

the areas resumes Its normal work (p.383)." Given these differences In

perspective. It Is surprising that more attention has not been paid to the

Implications of these underlying meta-assumptlons for EEG research. It Is

equally Interesting to n. -.e the similarity of the Adrian and Matthews

assumption that EEG alpha reflects "an area of the cortex which has nothing

to do" and the modern assumptions of the EEG hemispheric laterallzatlon

researchers that alpha activity In the one hemisphere suggests processing In

the opposite hemisphere.

V V V V 1

EEG Measures of Hemispheric Laterallzatlon

One basic conceptualization of the role of the central nervous system

has been derived from the work of Roger Sperry and his colleagues with split

brain patients (see Sperry, 1982 for an overview). This research has led to

the conclusion that the left hemisphere Is more Involved In the processing

of verbal/analytic material whereas the right hemisphere is more Involved In

the processing of vlsuospatlal/synthetlc material. Although Initially based

on research with epileptic patients, other research using a variety of

techniques Including dlchotlc listening, tachlstoscoplc presentation,

lateral eye movements, blood flow measures, evoked potentials as well as EEG

has given support to the original formulation (see Springer & Deutsch 1931;

Bryden, 1982; and Corballis, 1983; for general reviews of these areas).

In one of the first studies using EEG to reference hemispheric

processing, Morgan, McDonald & Macdonald (1971) reported proportionally less

alpha activity over the right occipital area (as compared to the left)

during spatial tasks (Imagining scenes) as compared to analytic ones (mental

arithmetic and word construction). Galln and Ornsteln (1972) using an

undlfferentlated EEG frequency band width ranging between 1 and 35 Hz

reported EEG hemispheric differences In the parietal and temporal areas

between spatial right hemispheric tasks (solving Kohl blocks and Minnesota

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142

Form Board) and verbal left hemispheric Casks (writing a letter atid mentally

composing a letter). A later study (Doyle, Ornsteln, & Galin, 1974)

reported that the task dependent asymmetries were strongest in the alpha

band and numerous researchers have limited their research to this band. In

general researchers have reported EEC results consistent with the

hemispheric lateralization hypothesis (see Donchin, Kutas, & McCarthy, 1977;

Davidson & Ehrlichman, 1980; Yingling, 198C for a presentation of these

studies).

Like other laboratories, in our early work we found differences in wide

band EEC between everyday tasks such as listening to music (right

hemispheric) and mental arithmetic (left hemispheric). However, we found

the expected asymmetry only for males and not for females (Ray, Morel 1,

Fredianl, & Tucker, 1976). While other studies have also reported sex

differences consistent with our results (e.g., Trotman & Hammond, 1979;

Wogan, Kaplan, Moore and Epro, 1979), others (e.g., Davidson, Schwartz,

Pugash and Bromfield, 1976) have suggested an opposite relationship with

laterallty and sex differences. In spite of much theoretical debate

concerning the broad question of sex differences and neurological

organization (cf. McClone, 1980; see also Butler, 1984), the sex differences

question especially in relation to EEC work remains an open one, although

recent work by Class, Butler and Carter (1984) suggest that familial

handedness may be one mediating variable.

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One of the interesting Individual differences measures we have

followed-up is the relationship between sex and spatial ability. It is well

known that males score higher on spatial ability tests than females and

there has been some speculation that this is related to neurological

organization and thus hemispheric differentiation (cf. McClone, 1980).

Based on some initial work by Fürst (1976) with EEC and Cur and Reivich

(1980) with blood flow, we (Ray, Newcombe, Semon and Cole, 1981) sought to

determine if differential EEC activity in high and low spatial ability males

and females was associated with successful solving of spatial problems. The

answer to this question was, "yes", but only for males. In addition, high

and low spatial ability males showed equal but opposite correlations with

performance. EEC ratios (right-left / right + left) with performances were

negative (-.77 during baseline and -.53 during tasks) for high spatial

ability males but positive (.77 and .56 respectively) for low spatial

ability males suggesting that different areas of the brain are associated

with successful performance in each group. This suggested to us that high

and low spatial ability males adopted opposite approaches to solving spatial

tasks, one a more right hemisphere (spatial/synthetic) and the other a more

left hemisphere (verbal/analytic). In addition, the higher baseline

correlations suggest the EEC may be a useful measure for examining the set

or preparation that an individual brings to a task. It would also be

Interesting to determine if these baseline diff - ances are related to the

slow wave potentials seen as a subject prepares for a task presentation (cf.

Birbaumer, Elbert, Rockstroh, Lutzenbeger and Schwartz, 1981).

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However, there are a number of methodological issues ranging from the

site of the reference electrode to the mode of analysis to the meaning of

the EEC itself that remain open issues at this time. Donchin, Kutas, &

McCarthy (1977) in their review of electrocortical measures of hemispheric

lateralization suggested that there existed a number of logical and

oethodologicil issues which made interpretation of the existing studies

difficult. Jevins, Zeltlin, Doyle, Yingling, Schaffer, Callaway & Yeager

(1979) su^g'.-sted that previously discovered lateralized differences in

electrocortical measures did not relate to cognitive processing but rather

reflected inconsistencies in stimulus properties, limb movements during

tasks, and/or performances factors such as subject'" ability or engagement

in a given task. This sort of methodological criticism suggested to us that

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143

simple EEC ratio Measures of alpha activity along a single verbal/spatial

continuum might not be presenting the entire story, and, partly motivated

the research discussed in the chapter. The positive side of the picture is

that whatever EEC is measuring, it is stable over time both in terms of task

related EEC asymmetries over sessions (Amochaev & Salamy, 1979; Ehrllchman &

Wiener, 1979) and in terms of a stable intraindividual trait (Gasser, Bacher

& Steinberg, 1983). Thus, there remains much research and conceptualization

to be done to answer such important questions as to what exactly EEC

activity is reflecting in the studies of hemispheric activation and to

delineare th».< manner in which individual differences play a role.

?--

HEMISPHERIC LATERALIZATION AND EMOTIONALITY

Not only have cognitive processes been associated with differential

hemispheric involvement, but also emotionality. Evidence has accumulated

from a variety of sources to support the idea that laterallzed central

nervous system activity and emotionality are functionally related (see

Tucker, 1981 fo* % review). In addition, recent evidence suggests that a

rostral/caudal dimension must also be considered. For example, Robinson,

Kubos, Starr, Rao and Price (1984) have reported differential

anterior/posterior as well as hemispheric involvement with mood disorders.

In an examination of stroke patient groups, Robinson et al. found that

patients with left frontal lesions reported significantly more severe

depression whereas less depression was noted in patients with lesions in the

posterior left hemisphere. A different pattern was seen in the right

hemisphere with depression being more pronounced in patients with lesions in

the right posterior areas while patients with anterior lesions were more

cheerful.

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Research with neurologically intact subjects has also suggested

differential hemispheric activity in terms of emotionality. Safer and

Leventhal (1977) employed a dichotic listening paradigm and reported greater

right hemispheric involvement with subjective/emotional information.

Sackheim, Cur & Saucy (1978) had subjects judge facial expression and

interpreted their results to suggest right hemisphere Involvement in the

recognition of emotions. Recording lateral eye movement, Schwartz,

Davidson, & Maer (1975) suggested that: greater right hemisphere involvement

was associated with the recall of facts about emotional experiences or the

differentiation of emotional words.

Electrocortlcal research has also suggested differential hemispheric

activation related to emotionality with both psychiatric (Jlor-Henry, 1979)

znd normal populations (Harman & Ray, 1977; Davidson, Schwartz, Saron,

Bennett and Goldman, 1979; Ehrllchman and Welner, 1980; Tucker, Stensile.

Roth & Shearer, 1981) using a variety of emotionally valenced tasks. The

particular emotional valence associated with each hemisphere has varied.

For example, in one of the first studies to examine EEC correlates of

emotional functioning, we (Harman and Ray, 1977) reported differential

hemispheric changes over time with the recall of positive and negative past

events. Left hemispheric temporal power (3-30 Hz ) increased during recall

of positive affect and decreased during recall of negative affect. Using

similar tasks and recording sites, Ehrllchman and Wiener (1980) also

reported greater right hemispheric activation during positive emotional

tasks.

Other research such as that requiring subjects to evaluate emotional

stimuli has also shown hemispheric differences. Davidson et al. (1978)

required subjects while watching a television show to subjectively rate,

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144

using a pressure sensitive device, how well they liked/disliked various

parts of the program. Bilateral frontal and parietal EEC activity In the

alpha range was compared during liked and disliked segments. The results

Indicated relatively greater right frontal alpha activity during liked

segments and relatively greater left frontal alpha activity during disliked

segments. No significant differences were reported for parietal activity.

Tucker et al. (1981) used a mood Induction procedure and then presented 'ÄPSflÄi

subjects with cognitive tasks. These results were interpreted as similar to v-S«^"'^

Davidson et al.'s, (1979) since negative mood was associated with greater ^•'S*'N^

left frontal EEC alpha activity. C^-frW

Methodological and Theoretical Questions in Relation to Emotionality

DIFFERENTIATION OF AROUSAL

General theoretical presentations have been made suggesting the

replacement of the unitary arousal model with a more dl ffprentlated one

distinguishing motor, perceptual, and cognitive Involvement (Kahneman,

1973). Posner (1975) suggests that the notion of arousal is related to a

general drive theory which is more compatible with stimulus response

psychology than to information processing formulations. Unlike the general

drive/arousal formulation, the information processing perspective suggests

that it is possible for a person to be in an optimal state for one type of

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Since the EEC studies examining emotion, mood, and preference have used

a variety of tasks and procedures involving different frequency bands and SJ^v^^

areas of the cortex, it remains unclear as to whether or not the different 'Äv>v

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EEC results may be attributed to variation in the EEC measures being

recorded (e.g. different frequency bands and/or data reduction), the manner

in which different areas of the cortex (e.g. frontal, parietal and temporal) s's"'«!''

are involved in the processing of emotional material, or the task •"vsI-S"'',

requirements themselves (e.g. the validity of the emotions produced). Part VS'^'Sj

of the problem is also one of definition since emotionality and arousal have "v's's"*^

been linked for years in the experimental literature. In fact, emotionality !.*.'.'.

as defined in many of the experimental studies dating back to the 1930s vv*-*

meant nothing more than activity on the part of an organism. Today, there Vov'^1'

is often little distinction between constructs such as emotionality, KSvVU

feelings and moods. Icftwivi

Theoretically, the most consistent view of EEC functioning in relation

to emotionality has been in terms of arousal. The traditional arousal model

has assumed a unitary continuum ranging from sleep to high activity which •I'v"^'"^

were thought to be indexed by any one of a number of psychophysiological «VVVX

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V-V. measures (cf., Duffy, 1962). With the discovery of the role of the ;\/VN -'

reticular activating system in desynchronization of EEG (cf., Moruzzi & v>S,*>',

Magoun, 1949), arousal seemed to have a firm theoretical basis on which to >V ^ ^ <

stand and a physiological mechanism by which to explain emotionality. EEG rvv

offered a convenient measure reflecting the activity of the reticular V

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activating system. In EEC research with awake subjects the common

assumption was that a'pha and beta activity reflected arousal. A separate '/v'vv"'

assumption was that alpha activity had an inverse relationship with beta and '.'r*/'/'S\

with mental processes. However, there are reasons to examin- these '"^ •'•''l

assumptions and to suggest that this simple view of EEG activity is limited

from both a theoretical and and empirical viewpoint. In particular the

arousal assumption places a much too important rule on EEG alpha and assumes

less specificity in the cortex than is usually assumed to be the case.

Indeed, although cognitive psychology has moved beyond a simple arousal

model, this transition has not been clearly reflected in EEG research.

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activity such as the processing of external signals and not for another such

as recall from long term memory. Some task-, such as sensory Intake and

motor outflow may even be antagonistic (Routtenberg, 1971). With the

transition to an Information processing perspective, Posner replaces the

concept of arousal with the general concept of attention. Attention Is

further described In terms of alertness, selection of Information, and

degree of effort. Posner uses the term alertness to refer to the reception

of external signals. Posner suggests that this Is manifested

physiologically by a decrease In EEG alpha activity and cardiac deceleration

as well as motor inhibition. However, Posner is uncertain how to describe

the attentional mechanisms related to internal processes as there exists

little research directed toward this topic. This of course offers an

important area for future research especially since many clinical processes

(hypochondriasis, for example) are related to either an over or

undersensitivlty to internal processes and their control.

Pribram and McGuinness (1975); McGuinness and Pribram (1980) have also

discussed the shortcoming of the unitary arousal conceptualization and

stressed the importance of differentiating arousal into at least three

components. The first component is that of a phasic response which they

refer to as arousal, and in many ways is similar to Sokolov's orientating

response (Sokolov, 1965) or Broadbent's notion of pre-attentlon (Broadbent,

1971). The second is a more tonic component referred to as activation. In

other formulations this is called attention (e.g. Broadbent). Activation is

a component which involves the voluntary direction of attention once the

organism has been physically aroused. The third component is an effort

component utilized to maintain the relationship between arousal and

activation. Pribram (1981) suggests that each of these aspects Involves

different brain processes.

Although the various models which differentiate arousal differ in

particular aspects. Tucker and Williamson (1984) have recently suggesced an

underlying similarity of processes reprerented in these models related to

hemispheric functioning. Although somewhat complex, their model does

suggest a rationale for the differentiation of emotional/feeling processes

from attentional factors, a distinction difficult to make within a unitary

conceptualization of arousal.

Direction of Attention

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Following Darrow (1929) and Lacey (1967) a distinction can be made

between two types of attentional tasks. The first type of task Lacey

referred to as "intake". These are tasks involving passive observation of

environmental stimuli. The second type of task Lacey called "rejection".

Rejection tasks are those such as mental arithmetic in which a person must

"reject" external input which might interfere with performing the task.

Different cardiovascular responses are associated with intake (heart rate

deceleration) and rejection tasks (heart rate acceleration) (Lacey, Kagan,

Lacey 6 Moss, 1963). At the physiological level, the Laceys (Lacey & Lacey,

1978; have suggested a link between autonomic arousal as represented by

cardlova^rular functioning and cortical arousal as represented by

electrocortlcal measures involving baroreceptor activity in the carotid

sinus althougt. this position is not without criticism (e.g., Carroll &

Anastaslades, 1978; Green, 1980). The complexity of the cardiovascularcortex interaction is further demonstrated by the recently discovered

medlational link related to hormones produced in the heart itself (e.g., the

strial natriuretic factor (Cantin and Genest, 1986). Whatever the exact

mechanism there does exist a two-way street between the heart and the brain.

For example. Walker and Sandman (1979) have Investigated changes in average

7

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146

evoked potentials (AEP) and heart rate and report that heart rate changes

are differentially reflected In the two hemispheres with lower heart rate

being associated with greater amplitude right hemispheric AEP's and higher

heart rate associated with larger amplitude left hemispheric AEP's. It

remains an open question whether these same type of relationships might be

seen also with EEG activity.

Empirical Studies of Cognitive and Emotional Processing

In order to better understand the role of attentional processes within

the hemispheric lateralization concept, we designed two studies. In the

first study performed (Ray & Cole, 1983), we examined cognitive processes

and in the second study (Cole & Ray, 1985) emotional ones. In the first

experiment, eighteen right-handed subjects (9 males, 9 females) of college

age were given 2 trials of 8 cognitive tasks on each of three days. The

second and third days differed from the first only in order of presentation

of the tasks and the specific items given. Presentations were

counterbalanced within sex. The tasks were of the type used in previous

hemispheric lateralization studies shown to reflect left and right

hemispheric processing and not requiring overt motor responses. The

verbal/analytic (left hemisphere) tasks and the spatial/synthetic (right

hemisphere) tasks were further divided into "intake" tasks requiring the use

of external environmental information and "reject" tasks which did not.

Thus, the hemispheric dimension was crossed with the Intake/rejection

attentional dimension in a 2 x 2 design. The particular tasks were as

follows:

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i

1. INTAKE TASKS (External Attention)

A. Verbal-Analytic (Left Hemisphere)

1. Task 1 — Count verbs in a passage.

2. Task 2 — Find the error in a maths problem.

B. Spatial-Synthetic (Right Hemisphere)

1. Task 3 — Paper-folding—choose the correct three

dimension representation of a geometric

design presented as a blueprint.

2. Task 4 — Mooney Faces—the subject determines the

location of a face In a high contrast

presentation of irregular shapes which initially

appear only as contours of light and dark

(Mooney, 1957). Right hemisphere damage

inhibits performance on this task

(Lansdell, 1967).

II REJECT TASKS (Internal attention)

A. Verbal Analytic

1. Task 5 — Mental Arithmetic.

2. Task 6 — Create sentences which begin with a certain

letter.

B. Spatial Synthetic

1. Task 7 — Mental Rotation of a geometric object.

2. Task 8 — Visualization.

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•vAll intake tasks were presented on a screen in front of the subject with the

tasks being matched for visual angle and relative brightness. During the

reject tasks subjects were instructed to keep their eyes open and to look at

the screen in front of them. In the first experiment, EEG was recorded for

25 sees, per trial from F3, F4, P3 and P4 referenced to linked ears. The

EEC was Fourier analysed and estimates of spectral power computed for 4Hz

frequency bands from .5-28 Hz. These data were analysed with analysis of

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Table 1. Mean Power Estimates for Intake ard Rejection Tasks

for Frequencies with Significant Attention by Hemisphere Interaction

Frequency

Experiment 1

8-12 Hz**

12-16 Hz**

16-20 Hz**

Experiment 2

8-15 Hz**

8-15 Hz**

INTAKE TASKS

LEFT RIGHT

Site

Parietal

540.5 649

196 256

97 126

Parietal

272.2

127

Temporal

Note: Power divided by 100000

** P<.01

319.6

188.6

REJECTION TASKS

LEFT RIGHT

Site

Parietal

1244.5 1791.5

.*-..

234

118

227.1

Temporal

327

165.5

Parietal

721.2 892.2

353.8

. -,

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In the second study, emotionally valenced material was presented to 40

right handed males of college age. They completed eight separate tasks (two

trials each) on each of two days. We used a 2 x 2 design in which

intake/rejection demands were "crossed" with positively and negatively

valenced tasks. The rejection tasks were based on those used in previous

research (Harman & Ray, 1977; Ehrllchraan & Wiener, 1980). These included

remembering a happy and sad event from one's past as well as imagining

future pleasant and unpleasant events. The intake tasks consisted of the

presentation of slides considered to evoke positive and negative affect

(Hare, Wood, Britian and Sholman, 1970; Ekman & Friesen, 1975; Safer, 1981).

These slides Included landscapes, happy faces, sad faces and accident

scenes. During all tasks subjects were instructed to keep their eyes open

and to focus on the screen in front of them. The duration of each trial was

30 seconds. In this second study, EEC activity from F3, F4, T3, T4, P3 and

P4 (referenced to linked earr.) was Fourier analysed and power estimates for

a low band including theta (2-7 Hz), a mid-range band Including alpha (8-15

K'- Hz ) and a higher band composed of beta (16-24 Hz ) computed. These bands

^ were chosen for computational ease since the first experiment suggested that

!/• little information would be lost by combining the bands in this way. These

;% data from the second experiment were analysed with a day, by attentional

V^ focus, by emotional valence, by hemisphere, analysis of variance and by a

» three mode factor analytic technique (PARAFAC) (see Harshman & Berenbaum

«.^ (1981) for a detailed description of this technique). Briefly, PARAFAC

R) described the different relative Involvement of EEG in relation to three

'.j separate modes: (1) left and right frontal, temporal and parietal sites;

•^ (2) the eight tasks on each of two days; and (3) the 40 subjects. The

r-\ subject node allowed us to determine if any given subject contributed

| differently from the others and thus represented an outlier. Mean heart

Tr rate during the tasks was also computed.

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148

Table 2. Mean Power in Parietal Areas on Verbal and Spatial Tasks

by Frequencies with Significant Task by Hemisphere Interaction

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FREQUENCY BETA

16-20 Hz*

20-24 Hz**

24-28 Hz*

Note: Power divided by 100000

* P< .05

**P< .01

SPATIAL TASKS VERBAL TASKS

Left Right Left Right

108.5 152 106.5 139.5

104 127 108 124

27.5 35.5 27 32.5

VMV

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From these two experiments we can report that attentlonal, cognitive,

and emotional factors are differentially represented in terms of EEC

frequency and site. In both studies, we found that the intake/rejection

dimension was reflected in parietal areas for the middle frequencies

including alpha. This finding is supported by a significant intake/reject

interaction with side (right/left hemisphere) in both experiments. The

ratio data also showed the same significant pattern. Consistently in both

studies there were higher levels of alpha during the rejection as compared

to the intake tasks in both hemispheres as well as an interaction showing

differentially more right hemispheric alpha during rejection tasks.

Specifically, this interaction was found in the first experiment for

parietal mid-frequencies (8-12 Hz, F(l,16)-11.657, p< .004; 12-16 Hz ,

F(l,16)-11.894; p< .003; 16-20 Hz , F(l, 16)-11.026, p< .004) and in the

second experiment for the mid-frequencies (8-15 Hz ) for both the parietal

(F(l,39)-10.891; p< .002) and temporal (F(l ,39)-10.068; p< .003) areas (see

Table 1). This interaction was not found in the frontal areas in either

experiment.

...,

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Whereas the attentional demands of the experiments were reflected in

the middle frequencies including alpha, the task demands (both cognitive and

emotional) were reflected in beta. In the first experiment this finding was

supported by a significant task (verbal/analytic vs. spatiaZ/synthetic) by

side (right/left hemisphere) interaction in the three upper beta bands (16-

20 Hz , F(l,16)-5.762, p< .029; 20-24 Hz , F(l ,16)-8.968, p< .009; 24-28 Hz ,

F(l,16)-6.335, p< .023) for the parietal areas (see Table 2). This same

pattern was reflected in the ratio and was also statistically significant.

These data show more beta activity in the right parietal area during spatial

as opposed to verbal tasks. In the second experiment there was a

significant main effect for emotional valence in the temporal (F(l ,39)-7.91;

p< .008) and parietal (F(l,39)-6.328; p< .016) areas with there being more

beta during positive as compared to negative tasks. Differential

hemispheric emotional involvement is clearly described by the PARAFAC

analysis with a factor being formed between the positively valenced tasks

and beta in the right temporal area (i.e., there was more beta in the right

temporal during positive than negative emotional tasks). These data are

presented in Table 3.

Consistent with previous cardiovascular research (see Molen, Somsen, &

Oriebeke, 1984 for a review), there was a significant difference using

analysis of covariance (F(l ,39)-39.14; p< .0001) in heart rate between the

intake and rejection tasks in the second experiment with the intake tasks

showing a lower hearc rate (x 72.17) than rejection tasks (x 73.79).

Intriguing findings were significant correlations between alpha EEC ratio

(R-L / R+L) activity in the temporal area and mean heart rate for each of

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Table 3. Parafac Analysis

Factors Involving Tasks Under Study

MEASURE ALPHA BETA

Site

F 3

F 4

.60

.59

.03

.16

3

4

.40

.68

.60

2.36

P

P

3

4

1.47

1.59

.09

.20

TASJC

Day 1

REJECT

Positive (past event) .97

Positive (future) .99

Negative (past) l.ll

Negative (future) 1.04

INTAKE

Positive (landscape) .35

Positive (face) .45

Negative (face) .43

Negative (accident) .34

Day 2

REJECT

Positive (past)

Positive (future)

Negative (past)

Negative (future)

INTAKE

Positive (landscape)

Positive (face)

Negative (face)

Negative (accident)

1.61

1.67

1.45

1.60

.44

.59

.60

.45

1.76

2.02

.60

.46

.92

1.24

.20

.70

1.38

1.06

.58

.17

.71

1.14

.01

.38

Note: These are the first factors extracted from two separate PARAFACs, one

with alpha and one with beta. Higher numbers suggest mure relative

involvement with that particular factor.

the four tasks (reject positive r-.484**; reject negative .--.394*; Intake

positive r-.446**; intake negative r-.462**; *-P>.05, *—i,>.01).

Since the intake/rejection difference appeared in both heart rate and

alpha activity in the present study, this raises the question of a possible

relationship between cardiovascular activity and hemispheric alpha. One

possibility lies in the report of Walker & Walker (1983) in which they

reported a relationship between EEC activity and carotid pressure. The

results of their study showed that readings from the carotid artery were

time locked to the rhythmic oscillations of the EEC especially in the alpha

band. This suggests that carotid activity may play a role in synchronizing

alpha. It m^ght also be speculated that it is through this mechanism that

cardiovascular activity has an inhibitory effect on cortical processing.

The particular candidate for such a mechanism would be the baroreceptor

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150 ysystem since research with animals has shown baroreceptor stimulation

produces cortical and behavioural Inhibition (Bonvallet, Dell 4 Hiebel,

195A; Bonvallet & Allen, 1963; Dworkin, Filewich, Miller, Craigrayle &

Pickering, 1979). The Dworkin et al. study leads one to the conclusion

that such disorders as hypertension may even function as a means of reducing

the experience of external stimulation in times of stress. With humans,

Lacey and others have speculated that a link exists between cardiovascular

changes In response to intake and rejection tasks and the baroreceptor

system. Thus, it is possible that increased alpha during rejection tasks in

this, present, study was associated with such a mechanism whose purpose was

to reduce unneeded external stimulation and allow for more efficient

internal processing (e.g. recall of past events).

In terms of emotionality the PARAFAC analysis suggested an unique

involvement of the right temporal areas in positive emotionally valenced

tasks. Examining the report of beta activity in Table 3 it is possible to

note that all positive tasks (in comparison to negative ones) had higher

loadings and that the brain area with similar loadings was the right

temporal lobe. This was true both across type of task (i.e., intake and

reject) and across days. This finding is particularly Interesting since

this study held the processing demands of the positive and negatively

valenced tasks constant. In other words, recalling a positive or negative

event from one's past should require similar cognitive processes and should

not require overt or differential motor responses. Likewise attending to a

face displaying positive or negative emotional expression should Involve

similar task requirements. Thus EEG activity in the present study may be

seen to reflect more than just motor task requirements as has been fiuggested

previously (Gevins et al., 1979). We also found similar results al^ng the

emotional dimension from both the Intake and rejection tasks in the present

study, which suggests both the perception of emotion in the intake tasks and

the emotional valence memory tasks in the rejection condition are reflecting

the same underlying process.

The contribution of the right temporal area to those processes

involving positive emotionality are intriguing, seen in the light of

research with temporal lobe epilepsy. Patients with right temporal lobe

epilepsy have described themselves as more elated than patients with left

temporal lobe epilepsy who described themselves as more angry, paranoid, and

dependent (Bear & Fedio, 1977). Thus in both the Bear and Fedio study and

in this one there is a suggestion that the subjective experience of negative

emotion of mood involves the left temporal areas whereas the subjective

experience of positive affect involves the right hemisphere. However, the

situation may be more complicated for in the Bear & Fedio study the

appearance of emotional behaviour produced a different relationship. The

same right temporal lobe patients who described themselves as more elated

were described by raters as being more emotional and displaying periods of

sadness. The left temporal lobe group on the other hand described

themselves as more negative yet were described by others as more ideational

and contemplative. Thus, there exists the possibility that subjective

emotion as experienced by the person and expressive emotion as observed by

another person may lead to differing and opposite conclusions concerning

differential hemispheric involvement in emotlorality. Since the observation

of emotional response was not considered in the present research, an

interesting possibility in a future study would be to allow for this

condition.

.•■■

^£i

Perhaps, there exist separate aspects of emotional processing

differently reflected in the brain. The first aspect would be a subjective

dimension in the emotional "flavor" of the task (e.g., remembering happy or

sad events) which is reflected in the temporal area. The second aspect

might be an evaluation factor (e.g., rate the pleasantness of a TV

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151

programme) reflected in the frontal areas. There may also exist the

possibility of a third factor which would reflect an expressive dimension of

emotion which would serve to communicate with others and which must on some

level involve the motor and language areas of the brain. To date, research

addressing this third area of emotional expression has used

electromyographic rather than electrocortical measurements. However, future

research combining both EMG and EEG approaches should prove fruitful.

Implications for Hemispheric Lateralization Research

In research using both emotional and cognitive tasks, we demonstrated

that EEG alpha activity reflected attentional factors although it Is not

possible at this time to suggest which aspects of attention (i.e.,

perceptual, motor preparation, etc.,) are represented by alpha activity. It

is also possible to suggest that the emotional valence of a task. Is seen in

more posterior beta activity. The exact mechanism involved again waits to

be described. However, in light of the results of these studies it becomes

important that we clarify the traditionally held view of EEG alpha as

reflecting arousal as well as attempting better conceptualiztion of our

constructs of arousal, attention, and emotionality.

«•TV. -• *m

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The EEG alpha differences in response to attentional demands and the

lack of any alpha differences in response to the cognitive or emotional

tasks further raises the possibility that previous hemispheric

lateralization research may have unknowingly confounded the external

(intake) and internal (rejection) attentional dimension with right and left

hemispheric processing dcaan4sa For example, a verbal/analytic (i.e., left

hemispheric) task that asks subjects to create sentences that begin with a

certain letter and a spatial/synthetic (i.e., right hemispheric) task in

which subjects were to solve a spatial problem presented on a table in front

of them would confound the task dimension (verbal/spatial) with the

attentional (intake/reject) demands of the task. The same possibility

exists for emotional situations and it is Important that especially with

children the positive and negative tasks have a similar attentional appeal.

Our experiments poin*- out the Importance of controlling for these

attentional factors ';n rhe lut^re.

In terms of previous criricism of EEG hemispheric lateralization

research (e.g., Gevins et al., 1979), we can lend support to the possibility

of potential problems in earlier studies which used alpha as a measure of

cognitive or emotional processing. Whereas Gevins pointed out differential

motor requirements in previously employed tasks, we point out differential

attentional demands as a potential confound. In the two experiments

reported in tMs paper we controlled for both attentional factors and for

motor requirements, with the resultant being no differences in alpha

activity in terms of the cognitive and emotional processes. However, EEG

alpha activity is important in its ability to reflect attentional processes.

In addition, even with the motor and attentional controls we were able to

report beta differences reflecting both cognitive and emotional dimensions

suggesting that EEG beta may be a potentially useful measure. Since EEG

beta activity has not received extension definitive research, an exact

interpretation of theso data await further interpretation.

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INDIVIDUAL DIFFERENCES

One of the intriguing aspects of EEG research has been the possibility
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Based on our own work In relation to EEG and attention, It seemed

reasonable • o record EEG while specific groups of subjects were either

actively engaged In a task or waiting between trials (Ray & Geselowltz,

1985). The between-trial sessions would show any differences In the

subject's more normal mode of processing. It would also offer the

beginnings of studies designed to determine whether certain personality

groups focused more Internally or externally. It seemed to us that Che

construct of introversion and extraversion might offer one logical place to

begin such a search since there existed a large amount of EEG work connected

•^a

V of understanding how personality or individual differences might be '%'"%J

manifested. Since both arousal and attentional mechanisms have been used as

a basis for personality theories, it is not surprising that EEG would be a

measure of choice for support of these theories. In my laboratory we have ^S^V

been asking if there are particular individuals who would be expected to

differ In the manner in which they would direct their attention and how the V^S

direction of attention might be used in a defensive or psychopathological Awfl

manner. This of course is not a new question. Uundt, for example,

suggested that some individuals turn inward in response to the outside world vV»'^

whereas others move toward the stimulus. Jung used a similar idea when he

suggestPfi that some Individuals are directed toward internal functioning

such as dreams, ideas, and so forth whereas other individuals are more r'"..^

concerned with the external functioning of the world. The former he

referred to as introverts and the latter extraverts (Jung, 1971, reprint).

Pavlov characterised the individual differences issue in terms of the

strength of the nervous system and borrows from the terminology of the

temperaments. Pavlov states, "We had good reason to distinguish four

different types of cerebral hemispheres: two extreme ones, the excitatory

and the Inhibitory; and two central, balanced ones, the calm and the

lively". (Teplov, 1964 p.21) In terms of the temperaments Pavlov described

the four types as follows: the choleric individual is passionate and

quickly irritated; the melancholic responds to events as inhibitory agents;

the phlegmatic is self-contained and quiet whereas the sanguine individual

is energetic and productive but only when the work is interesting. In terms

of th* extreme types, the choleric individual displays a predominance of

excitation whereas the melancholic displays inhibition. It was also

suggested that excitation types were easier to condition than inhibitory

types.

In his 1967 book, Biological Basis of Personality, H.J. Eysenck

developed an individual difference perspective based on excitability of the

nervous system utilizing the constructs of introversion and extraversion

(Eysenck, 1967). His system centered around the concept of arousal which was Jy

seen to be mediated by the brain stem reticular system. The reticular

systen, in turn, was seen to have an reciprocal relationship with the cortex Jf

which could be either inhibitory or excitatory. For Eysenck, extraverts VlM

were born with a lower level of arousal within the reticular system which in

turn resulted in their seeking stimulation to increase arousal. Introverts

on the other hand had a higher level of arousal and sought to reduce

stimulation. This formulation has led to a number of EEG studies asking the

question who is more aroused introverts or extraverts? Gale (1981) has ^;r\

extensively reviewed these studies and the methodological problems they ./^,,-

contain. For example, few, if any, of these studies utilized multiple . '/ ."

channels of EEG, making any type of hemispheric comparison impossible. •^"ViS

Likewise there was little attempt to manipulate the arousal level of the jSw?!

tasks presented. However, Gale does point to some testable implications of ä*JJ

Eysenck's theory if the arousal level were to be manipulated. For example, W

Gale (1981) suggests that, in low arousing conditions, extraverts will seek v'v'-

ways to stimulate themselves whereas in high arousing conditions introverts KvM

will withdraw attention in order to induce a state of calm. w« ÄV "

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153

wich this distinction. We had also been Interested In the construct of

locus of control as related to physiological funcf ^ing. From our

preliminary work we can report no EEG differences ./een locus of control

groups (i.e., internal/exi.ernal) either during tasks or during baseline

periods. However, the results with extraversion/introversion display a more

interesting picture which will be presented in this section.

In this study, we gave the subjects (6 male extraverts & 6 male ^'^yi

introverts) four visual tasks which allowed for various levels of

involvement. The tasks were all projected on a screen in front of the

subjects. In the first task the subjects were shown a slide of a single

color. At the end of each presentation the subject was asked to rate how

much he liked that color on a 1 to 9 scale. The second task was a

traditional paper folding problem in which the subject was shown a threedimensional figure presented in the form of a blueprint and asked to pick

out which of four alternatives represented the constructed figure. The "'■■y""'-^""

third task was a Rorschach-like task in which subjects were shown Inkblots #

and asked to say what they saw or what they looked like to them. The fourth vVW

task was a series of photographs chosen to Include an emotional component. /'v'-/V"

In between each series of tasks, as well as at the beginning and end of the vlvrvvl

experiment, a baseline was taken.

Huring the baselines and tasks, EEG activity was recorded from

bilateral frontal (F3 & F4) and parietal (P3 & P4) sites referenced to

linked ears. The duration of each trial was 25 sees divided into 5 sec

epochs. An online Fast Fourier program (FFT) was used to construct a J'',V

,'>'kVN

!

frequency spectrum consisting of the following frequencies: 1.5-4 Hz, 4-8 's'^-Zi

Hz, 8-12 Hz, 12-17 Hz, and 17-30 Hz. «SSfsC

In terms of the baseline data, performing a group vyj^PC

(extravert/introvert), by site (frontal/parietal), by trial (5 baselines), ^

%

-

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by hemisphere (left/right), analysis of variance for each frequency band "vX-'v"^

displayed significant group main effects in the bands below alpha.

Performing a similar ANOVA for the task data showed significant main effects

for group in all bands except beta (17-30 Hz). In each case the extraverts

show more power in the bands.

However, our interests in performing this study was not which group had

more power but to determine if there was a pattern to the EEG of the

subjects in each group. To answer this question we simply plotted the

means. Since alpha is the most commonly used frequency band in studies of

introversion/extraverslon, we began there. For simplicity, we limited our

discussion in terms of site and frequency. It Is Interesting to note the

left frontal arc baseline and tasks (Fig. 2). In this case the introverts

and extraverts showed very similar baseline means. However, the task means

for left frontal alpha dropped significantly for the introverts. What is

more interesting is the pattern. It is clear from both these figures that

for introverts, alpha drops during task presentation relative to baseline

whereas this is less the case for extraverts. This same pattern although

not as clear is present in other sites with alpha. In the right parietal '. V

area, for example, the extraverts also show a change between baseline and A/s"'«.''

tasks although not as great as the introverts. We can also note that the fcWjJiS

left frontal beta activity follows a pattern similia" to that of left

frontal alpha suggesting that the idea of an inverse relationship between

alpha and beta is clearly not supported in our data as well as in other data ^S^S^v'

(e.g., Daniel, 1965). 3TOMH

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154

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Fig. 2. Extravert and Introvert Left, Frontal (Fß)

It is important to understand that we see these data as preliminary and

at present are replicating the results. However, the patterns that are

present in thase data are suggestive, not only for understanding

extraversion and introversion but also for direction in designing future

studies in the area. In particular, the data suggests the importance of

Including both situations in which subjects are allowed to do nothing (i.e.,

display thei- personality) such as baseline periods as well as tasks varying

in degree of required involvement. From our own results, it is clear that

t'.e empirical presentation is more complicated than generally assumed.

However, to understand this complexity, researchers need to ask questions

more sophisticated than - who are more aroused, Introverts or extraverts?

They need to ask a complex series of questions on how each group uses his or

her mental processing in performing various tasks as well doing nothing

(i.e., baseline). As Gale has previously suggested (1983), it Is also

important to vary the difficulty and involvement of the subjects with the

task. It may also be useful to create situations which overload the

subjects as one might find with a difficult video game. Technically, new

studies must look at multiple sites, multiple frequencies, multiple measures

(both physiological and behavioral performance ones) as well as different

techniques of analysis (FFT, coherence, etc.,). We would suggest also that

since Individual differences are the topic of interest that future research

analyze the data in these terms. One possibility would be to examine the

data in two ways: first to analyze group data as one would normally do in

the experimental studies, and second, to examine the individuals in the

group as individuals and ask as with a case study approach how the

individual patterns coalesce to form the group pattern.

>>>:

CONCLUSION

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155

students and I have been concerned with over the past few years. In the

process I sought to point out some of the problems and promises of the area.

EEC is a seductive area in that it holds out the potential for understanding

mechanisms of cognitive and emotional processes not available in traditional

psychological studies. The question before us now is how to ask empirical

questions which are consistent with our theoretical understanding of

cognitive and emotional processes. From our perspective, attention appears

to be an important dimension which should be included in future studies.

EEG also offers the potential for mapping how different types of individuals

approach a specific task although it might be too simple an approach to

expect a direct one-to-one mapping of physiological responses to behavioral

measures. This particular study that was concerned with introverts and

extraverts suggests a more "ecological" approach that seeks to undertake

more than Just task differences between groups but looks instead for

patterns of EEG processing. We will have to await further research to

determine if this Is, Indeed, a fruitful approach to Individual differences.

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LONGITUDINAL AUDITORY EVOKED RESPONSES AND THE DEVELOPMENT OF LANGUAGE

Dennis L. Molfese and Victoria J. Molfese

Department of Psychology and School of Medicine,

Southern Illinois University,

Carbondale, IL 62901

INTRODUCTION

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Over the past 50 years, researchers have been Interested in problems

involving specific brain-language relationships. Issues pertaining to the

interrelationship of hemispheric specialization, cerebral lateralization and

language development have been explored by researchers utilizing a variety

of methodologies. One methodology that has produced promising results

Involves the use of auditory evoked response (AER) techniques. AERs refers

to the portion of the on-going electrical activity of the brain which is

time locked to the onset of some external auditory event. Using AER

techniques, researchers have been able to report evidence of specialization

and cerebral lateralization in human infants (Barnet, de Sotillo, and

Campos, 1

07

A: Crowell, Jones, Kapunial and Nakagawa, 1973; Molfese, 1972;

Molfese, 'iceman and Palermo, 1975; Molfese and Molfese, 1979a, 1979b, 1980;

Schucarc, Sr.hucard, Cummins and Campos, 1981). In recent years,

multivariate analyses of data obtained using AER techniques have yielded

information concerning the development of hemisphere differences. These

procedures have also enabled researchers to isolate and identify specific

components of the AER across hemispheres which appear to reflect responses

to specific language-relevant acoustic and phonetic cues.

•:•. :

This chapter has two parts. Section One contains a review of evoked

potential techniques as applied in brain-language investigations. In

Section Two the relationship between hemispheric responses to speech cues

recorded via auditory evoked response techniques early in development and

later language performance is described.

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I. EVOKED POTENTIAL TECHNIQUE

Evoked potential (EP) techniques attempt to establish strict temporal

relationships between the onset of some stimulus event and the onset of

changes in the various portions of the following EEG pattern. Because of

the small size of these electrical patterns (5 to 15 microvolts) relative to

other electrical noise sources, researchers must usually repeat the stimuli

a number of times in order to evoke further replications of the brain

potentials. The process of averaging, including the adding together of

evoked potentials, is used to extract the EP from the background noise of

non-replicable or non-redundant information in the brain activity. The

final quotient (the averaged evoked potential) is then expected to reflect
160

reliable brain activity elicited by some specific stimulus event. Once the

averaged evoked potentials are obtained, a variety of different analyses can

be utilized in order to determine whether changes in stimulus features might

produce corresponding changes in various proportions of the brain response. s-'I'j£X

In general, analyses focus on certain peaks in the waveforms that occur at •**>*>>''

certain time intervals or latencies following the onset of a stimulus event 1

(Picton & Stuss, 1980; Vaughan, 1969). Such analyses may be based on '.W.V

procedures as simple as direct time or amplitude measures between two peaks SiviVw

or Involve a complex factor analysis to reduce the complex waveform to a \vS'"V

sraller set of simpler components.

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There is a great deal of evidence that the averaged evoked potential

can reflect changes in the neural activity of the brain during sensory

processing (Regan, 1972, pages 31-116) and cognitive processing (Donchin,

Ritter and McCallum, 1978, pages 349-411). In the first case, EP components

associated with sensory processing appear to be rclstively "impervious to vSj-S^

variations of the psychological state of the observer" (Hillyard & Woods, v's^v-S

1979, p.346). These components (which for the most part occur prior to 100 5

msec following stimulus onset) seem to be very stable from one individual to y.%

the next and are not usually altered by subject state. Changes in some jjj

portion of these waveforms, whether in terms of the amplitude or latency of

waveform peaks or the absence of certain usually present waves, signal some

problem with a receptor, pathway, or brain area represented by that

component (Rockstroh, Elbert, Birbaumer & Lutzenberger, 1982, p.3). These

components have been referred to as "exogenous" components. On the other

hand, EP waveforms which are associated with cognitive or perceptual

processes of the brain are usually referred to as "endogenous components"

(Hillyard & Woods, 1979, p.346). In general, the portion of the waveform

which occurs after 100 msec will reflect endogenous activity. Here, the

various characteristics of the EP waveforms, although triggered by some

stimulus, are affected by the cognitive-perceptual processes Involved in

processing the stimulus. While the exogenous components are relatively

stable across different subject states and individuals, the endogenous '«W5vJS

components can show great inter-subject variability and may change across

different tasks and subject states. For the research to be outlined below

it would appear that the categorical-like effects elicit exogenous type of Ä

activity, given the consistent pattern noted across ages and tasks. r.v

In general, two different approaches have been used to study evoked v'v'vS

potentials: (1) "defining the neuronal substrates of EPs and their i'-l^'j

relationship to behavioral events" and (2) "...a purely empirical relation vI'^vS

of E

p

s and behaviour without recourse to neuronal mechanisms" (Purpura,

1978, p.83). While there are a number of excellent chapters documerting the

first approach described above which attempt to Identify discrete elements

within the brain that are responsible for generating the various components ''VCN^V"

of the EP (Goff, Allison & Vaughan, 1978; Klee & Rail, 1977), the exact • V

nature of these brain mechanisms remains in doubt and under discussion.

However, at a grosser level, topographic studies of human EPs do indicate

".hat major portions of the EPs originate in the primary and secondary ^, y-V

:ortical areas that are specific to the modality Involved in the detection -WV

of the stimuli presented (Vaughan, 1969; Simson, Vaughan & Ritter, 1977a). ^v*v%^

In this way, evoked potentials associated with auditory and visual

presentations appear to be generated in the secondary cortex of the auditory

and visual systems, respectively, as well as in the parietal association

cortex (Simson et al., 1977a, 1977b). At a grosser level, EP activity

recorded over the left side of the head originates for the most part in the S'S'.V

left hemisphere while EP activity recorded from over the right hemisphere

originates in the right hemisphere of the brain.

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Advantages of the Evoked Potential Technique

Evoked potential procedures offer a number of methodological

advantages. First, with the use of the EP techniques, there Is opportunity

to test children of different ages using one method that can be applied in a

consistent fashion across the different ages. Routinely, investigators in

the past have shown concern for possible "ceiling" and "floor" effects in

which one set of problems may appear very difficult for young children (and

consequently lead to a large number of errors) while these same problems may

be very simple for older children (who would then not generate many errors).

If analyses rely heavily on comparisons of error data, results from these

two groups of subjects could not be considered comparable since the level of

difficulty varies between groups. For example, one criticism of the

dichotic listening procedure when used with subjects ranging in age from

childhood to adulthood has been that it is difficult to control for stimulus

and response difficulty across ages (Bryden, 1982). The EP techniques,

however, can be applied in the same manner to all subject populations,

regardless of age. Second, these procedures can be used with a variety of

populations. Since they do not require an overt response, the investigator

is not limited by the usual dependency of age related measures such as

reaction time or language. Moreover, the procedures can be used as readily

with brain damaged populations (whose motor or verbal skills have been

impaired) as with normal intact populations. Third, with suitable controls

the investigator can collect the electrophysiological data while recording

other measures such as reaction time (which correlates well with components

of the evoked potential such as the P300), choice responses and errors. The

addition of this measure provides supplementary information which can be

used to evaluate the state and strategies of the organism. Fourth, for

those interested in hemisphere related effects, this procedure allows

Investigators not only to note possible differences in responding between

hemispheres but also differences within hemispheres as well.

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Concerns for Adequate Controls

There are a number of design factors that must be considered when

utilizing the evoked potential procedures if the results from such studies

are to be validly interpreted. While these concerns may cover a number of

Issues, three areas deserve special attention as they relate to the study of

hemisphere differences: task sensitivity, localization, and stimulus/s ibject

controls. In terms of task sensitivity. It is clear that the evoked

potential is Indeed sensitive to differences in task demands. The waveshape

of the evoked potential changes dramatically when the frequency of some

stimulus events are varied as in the case of the P300 component. Likewise,

both waveshape and amplitude of the evoked potential appear to change as a

function of the task demands (see Neville, 1980). This also appears to be

true for the magnitude of the hemisphere differences reported between

waveforms recorded from different hemispheres. As task demands increase,

laterality effects appear to Increase. In the Interpretation of results,

then, care must be taken to evaluate the possible contributions of task

related factors.

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There are severe limits on the use of the scalp recorded evoked

potential as a means of localizing the source of some process within the

brain. Although it appears that electrical activity recorded from locations

over the left hemisphere does originate from within that hemisphere

(similarly, the right hemisphere serves as a source for electrical activity

which can be detected with electrodes placed over the right side of the

head), scientists are unable at this time to localize the source of these

currents much beyond this superficial level. Consequently, discussions as

to the nature of the cortical structures involved in producing the EP and

their role in the task Involved in eliciting these responses must be

•^•^^^

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162

considered with great caution.

Finally, It has been known for some time that stimulus and subject

factors can also Influence the waveform of the evoked potential. For

example, there are a number of reports that the shape of the evoked

potential will change as a function of an Individual's hand preferences

(Hillyard & Woods, 1979; Molfese, 1978b; Molfese, Llnnvlllc, Wetzrl & f, ^ ^

Leicht, 1985). A variety of stimulus factors can also cause marked '^^'^•'

changes in the evoked potential. Factors surh as stimulus rise and decay /"vS"

time, duration and loudnes? can all differentially affect different segments

of the evoked potential (see Renau & Hnatlow, 1975, for a review of stimulus

effects known to affect the auditory evoked potential).

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2. EVOKED POTENTIAL RESPONSES AND LANGUAGE DEVELOPMENT

Our laboratory in the past 10 years has used evoked potential ^VV

techniques to study the importance of lateral iz ätlon and brain organization s

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for language development. In addition to investigating changes in the •.".%.-i

developmental patterns of lateralIzation across the life span, these studies

have attempted to isolate and identify the electrophysiological correlates

of various speech perception cues across a number of developmental periods. ' "•'v'H

One perceptual cue studied is PLACE OF ARTICULATION (PLACE). The PLACE cue

is Important for discriminating between consonants such as /b/ and /g/,

consonant sounds that are produced in different portions or places of the

vocal tract. The consonant /b/ is referred to as a "front" consonant

because it is produced at the very front of the vocal tract with two lips. v's^

The consonant /g/, on the other hand, is produce*, in the b^ck of the vocal SSJva

tract and is labelled a "back" consonant. When the following vowel sounds ^s^

are the same, the second formant transition (the rapid change in frequency ^>,

which occurs for the second concentrated band of acoustic energy) as

depicted in a sound spectrograph signals the place of articulation for the

consonant. In the case of the syllable, /ba/, the second formant transition

would be rising from its initial frequency to that of the steady state vowel

formant. This formant transition falls, however, for the Initial /g/ of the 'VN

syllable /ga/. In general, our studies note that patterns of electrical

activity recorded from different areas of the scalp change as a function of

Place of Articulation cues. Furthermore, these patterns of discrimination

do not appear to change to any great extent from early in infancy (Molfese &

Molfese, 1979b, 1980) into adulthood (Molfese, 1978, 1980b; Molfese & X\

Schmidt, 1983; Molfese, 1983). ••''/':

Studies with adults note that portions of the AER which occur 300 msec •".•*."

after stimulus onset and recorded from electrodes placed over the left —

hemisphere discriminate between consonants such as /b/ and /g/. That is, v^'*

the amplitude of this portion of the waveform as measured from the positive ','f\'

r

«

V.VJ peak occurring at 300 msec to the following negative peak at A00 msec is <..*>> "«

reliably larger for the AERs elicited by the /b/ initial syllables than for '"v^*."

the /g/ Initial syllables (Molfese, 1978a, 1980b, 1983; Molfese & Schmidt, JSSR

1983). In studies with adults in which electrodes are placed at multiple

Bites over the two hemispheres (Molfese, 1980b, 1983, 1984; Molfese &

Schmidt, 1983), an earlier occurring portion of the AER located at

approximately 100 msec following stimulus onset varies reliably when evoked

by a /b/ versus a /g/ initial syllable. This component behaves in a

similar fashion to the one oc «rring at 300 msec with the exception that it

occurs simultaneously over both hemispheres. In this way the AERs elicited

by speech syllables reliably produce changes in two portions of the waveform

in response to the /b/ and /g/ syllables. One area of waveform

discriminates between PLACE differences at one point In time only over the

left hemisphere electrode sites while a second portion of the AER changes

systematically over both hemispheres in response to PLACE changes.
WWWWWRrvvw v« r

\J^ rv rv< iPtrwBT

163

SUBJECT NO 9

LEFT

HEMISPHERE

NORMAL

4ERE I

LEFT

HEMISPHERE

SINEWAVE

RIGHT

HEMISPHERE bJ

SINEWAVE

b-'

RIGHT

HEMISPHERE

NORMAL

I I I I I I I I I I I I I

0 ms»c 700 0 m$»c

VvS

700

m

Flg. 1. The averaged AERs elicited shortly after birth from Subject #9, a

member of the HIGH MCVP group, in response to the speech and

nonspeech syllables beginning with the consonants /b/ and /g/. AER

deviation is 704 msec with positive deflection up. The calibration

marker is 10P V.

Building on this work with adults, st/eral recent papers have reported

comparable findings with newborn Infants. Molfese and Molfese (1979b) in a

report based on tests with 16 newborn infants, reported that the initial

large negative deflection or peak of the newborns' AERs which occurred

approximately 230 msec following stimulus onset (N230) was larger in size

when evoked by /b/ Initial syllables than by /g/ initial syllables. This

response difference occurred only over the left hemisphere electrode site.

As was the case with adults, however, a second portion of the AERs detected

at electrodes placed over both hemispheres were also noted to discriminate

between the /b/ and /g/ initial syllables. A later study with pretera

infants (Molfese & Molfese, 1980) reported comparable lateralized and

bilateral responses that discriminated PLACE cues. This pattern of

bilateral and lateralized discrimination of the PLACE cue as reflected in

different portions of the AERs occurs, then. In both young infants as well

as adults.

Auditory Evoked Responses as Predictors of Later Language Development

One major issue recently raised concerns the implications of these

lateralized and bilateral patterns of brain responses to speech sounds for

later language development (Molfese, 1983; Corballis, 1983). While data

have continued to accumulate in the past decade which support the general

view that lateralization of function is present in young infants, the

question concerning the relevance of such early patterns of lateralization

to later language acquisition has remained unanswered. Do these patterns of

responses have any implications for later language development or do they

reflect some basic patterns of auditory processing in the brain that have

little relation to language development?

This interest In the possibility of biological precursors of language

can be traced to a number of research findings published over the last two

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164

subserves language abilities. Evidence for such a view, he noted, could be

seen at a number of levels in humans. For example, even at the gross

morphological level of the vocal tract, humans (unlike other primates) are

structured in a certain way to produce a wide variety of speech sounds

(Lieberman, 1977). The pinna itself is structured to favor the perception

of sound frequencies that characterize tht majority of Importanr speech

cues. At the neurological level, Lenneberg argued that language acquisition

was linked to brain organization. For Lenneberg, lateralIzaron of brain

functions was a biological sign of language ability (Lenneberg, 1967, page

67). In this view, the presence of early laterallzed processes for language

could 'nfluence later language outcomes (Basser, 1962). Children who

demonstrated language skills early In development were thought to have

language already laterallzed to one hemisphere. If the Infant should then

suffer cerebral damage that affected the language hemisphere, the infant's

ability to recover language functions was thought to be more limited than a

child whose language system had not yet laterallzed. Although investigators

have challenged some of Lenneberg's specific hypotheses on lateralization

and language development (Molfese, 1972; Molfese, Freeman & Palermo, 1975),

his general view that there are specific biological underpinnings for

language that may facilitate language development continues to be supported

(Dennis & Whitaker, 1975; Molfese & Molfese, 1979a, 1979b, 1980; Segalowitz

& Gruber, 1977; Segalowitz, 1983). Given Lenneberg's (1967) notion that

lateralization is a "biological sign" of language, could such early patterns

of laterallzed and bilateral discrimination of speech sounds predict later

language outcomes? This was the major aim of a longitudinal study by

Molfese and Molfese (1985a, 1985b). This project attempted to establish the

predictive validity of demographic variables, behaviour scales and auditory

evoked potentials for identifying developmental deviations in language

abilities. The specific issue addressed concerned whether general

hemisphere effects per se or hemisphere differences that interacted with

specific stimulus characteristics would discriminate between children who

later differed in language skills.

In this longitudinal study, sixteen Infants were tested at birth. For

each subject the following information was obtained: sex, blrthweight,

length, gestatlonal age; the ages, income level, education and occupation of

both parents; scores on the Obstetric Complications Scale (Littman &

Parmelee, 1978); scores on the Brazelton Neonatal Assessment Scale (using

scores on each of four a priori dimensions [Als, Tronick, Lester and

Brazelton, 1977] and on the overall profile based on ratings for the 26

items of scale); mental subscale scores on the Bayley Scales of Infant

Developmental (Bayley, 1969); and scores on two language tes^s administered

at 36 months of age (the Peabody Picture Vocabulary Test, Dunn, 1965 and the

McCarthy Scales of Children's Abilities, McCarthy, 1972). Auditory evoked

responses were recorded at each testing period using recording electrodes

placed on the scalp over left and right temporal areas. Synthet.c speech

syllables varying in PLACE OF ARTICULATION cues were presented tc these

babies and children since these materials had been shown to generate both

bilateral and laterallzed stimulus related effects as well as the more

general hemisphere non-stimulus related effects (Molfese & Molfese, 1979a).

Eight related stimulus items were added in order to test the

generallzability of the findings for consonants across different vowel

sounds.

v.v

?:

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:

Predicting language performance at 3 years of age from AERs obtained at

birth

Analyses of the electrophysiologlcal data led to the identification of

the electrophysiologlcal response correlates of specific stimulus features

that appeared to predict later language performance from brain responses

recorded early in development and from behavioural responses. Several

S5K

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165

portions of the brain response systematically changed across hemispheres and

differentiated between specific speech and non-speech sounds.

x*

One component of the AER that occurred between 88 and 2^0 mse- reliably

discriminated between the High and Low Language Performance groups at

ceitain electrode (hemisphere) locations and under certain stimulus

conditions. Only the AER waveforms recorded from over the left hemisphere

of the High group systematically varied as a function of consonant sounds.

A right hemisphere effect was noted for this same group of subjects for

nonspeech stimuli.

The Individual averages for a High MCVP Infant (S#9) are depicted in

Figure 1. Here, the left hemisphere responses to the different stimuli are

presented at the top of the figure while the right nemisphere responses are

presented at the bottom. The region of the AER between 88 and 240 msec

changed systematically as a function of stimulus features. The peak

amplitudes as measured between points "a" and "b" were smaller for the /b/

initial syllables than for the /g/ syllables when the syllables were

composed of normally structured speech formants. This pattern was reversed

in the set of waveforms recorded from the right hemisphere in response to

the sinewave formant stimuli (depicted in the lower left of this figure).

No such amplitude variations are apparent In the two sets of waveforms

presented on the right side of the figure. No differences were noted for

the low group for these electrode sites or stimulus dimensions.

• • •»•• k/

'«AM

•-- V V

tt>.v.

."" v •' •

^TT:

/b/

LEFT

HEMISPHERE

NORMAL

/g/

/b/

RIGHT

HEMISPHERE

SINEWAVE

SUBJECT NO 7

LEFT

HEMISPHERE

SINEWAVE

RIGHT

HEMISPHERE

NORMAL

t I I I I I

0 msec 700 700

•: ••>:-

/•-■■.- -• i

1 .* J* .N .>

t

Fig. 2. The averaged AERs elicited shortly after birth from Subject^?, a

member of the LOW MCVP group, in response to the speech ar *

nonspeech syllables beginning with the consonants /b/ and /g/. AER

deviation is 704 msec with positive deflection up. Thp calibration

marker is 10 u V.

NVA,/. A

>.v.v/J

%- •* > •,

V'J-.V.VJ
tr

166

The Individual averages for Infant ft", a member of the Low MCVP group,

are depicted in Figure 2. No comparable /b/ versus /g/ differences can be

noted for this infant across the left hemisphere normal formant and right

hemisphere sinewave format conditions.

One other portion of the brain response that changed across hemispheres

approximately A50 msec after the sound began failed to discriminate between

the two language groups. No other group related effects were noted. Thus,

it appears that at birth there were hemisphere responses differentially

sensitive to specific stimulus characteristics which discriminated between

children at three years of age who appeared to have different levels of

language skills.

A second portion of the AER (as represented by Factor 7) with a late

peak latency of 664 msec also discriminated between the High and Low groups.

This component was recorded by electrodes placed over both sides of the head

and consequently reflected bilateral rather than only lateralized activity

that discriminated between the two consonant sounds. This component,

however, did not behave in the same manner as that first described in that

It was not affected by the speech-like quality of the stimuli. Furthermore,

the consonant discriminations were dependent on the following vowel sounds.

Thus, It appears that lateralized responses alone were not the sole

discriminators between children wlo later differed in language abilities.

These data suggest that the AERs are reflecting brain responsiveness to

specific language-relevant spaech cues rather than readiness of the brain to

respond to any general stimulus.

The findings of this last study of a left hemisphere response that

discriminates between the speech consonants /b/ and /g/ replicates an effect

reported earlier by Molfese and Molfese (1979a). Both studies note that

these left hemisphere lateralized responses are reflected in amplitude

changes for the first large negative deflection in the AER. Furthermore,

the bilateral effect that was noted in the present study (peak latency 664

msec) behaved in a similar fashion in terms of latency and response

characteristics to the bilateral response (peak latency 630 msec) reported

earlier in the Molfese and Molfese paper. Importantly, these replications

hold across changes in the stimulus set, thereby indicating the

generalizability of the findings across different vowel sounds.

Hemisphere effects were also noted that did not interact with stimulus

or subject variables. The presence of such Hemisphere effects, both

interacting with stimulus characteristics as well as independent of such

variables, suggests that hemisphere effects should be treated as a

multidimensional concept when applied to infants (Molfese & Molfese, 1985a

and b; Moscovltch, 1977).

One interpretation for the results of this study is that early

discrimination abilities uiay relate to later language development. The High

MCVP Infants in the present study not only discriminated between consonants

alone and consonants in different vowel environments, they also

discriminated between variants of the speech and nonspeech stimuli. This

pattern of responding could suggest that the High MCVP Infants were

advant aged in the process of language development because their nervous

systems were either more sensitive to or could make finer discriminations

between a variety of auditory events, that share some commonality with

speech perception events. Perhaps the earlier an infant can detect and

discriminate between patterns of sounds in their language environment, the

better able that infant will be to utilize such information as the extensive

process of language acquisition begins.

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An alternative interpretation of these data might suggest that the ,.

children who scored higher on the language test at three years of age were

generally brighter, more attentive, and more responsive infants at birth.

Such infants might respond in a mor^ consistent manner to the speech and SffiKSfil

nonspeech stimuli at birth, thereby presenting a pattern of more clearly r*".-VN

l/

>

defined auditory discriminations. Because of these factors, these infants t.sSe./..

could have been consistently more testable at every age. While this is a

viable explanation for these data we feel that it is not supported by the

results of the behavioural tests administered to these infants at birth. As

noted earlier, the Brazelton Neonatal Assessment Scale had been administered

to these infants at birth and the Bayley Scales of Infant Development at 6-

and 12-months of age. t-tests comparing the total scale scores on the

Brazelton show no differences between groups at birth nor were there

differences in developmental quotients on the Bayley for the High and Low ""v^C's'-s

groups at 6 or 12 months of age. The lack of differences on these '*v'^"'v''s

developmental tests at birth and during the first year of life suggests that

both groups of infants were equally responsive and achieved the same level

of performance in at lea^t these types of testing situations. It is, of

course, possible that differences in testability might have been missed

because the tests used were not sensitive to the relevant dimensions. ' ^•'^'^"''^

\ *. «. '

• . V" v

Behavioural Measures as Predictors of Language Development \'<.''V"

yvA]fl;

$58583

In other analyses, the contributions of behavioural measures to

predicting language performance at age three years have been determined. As

has been found in prior research by other investigators, the correlations

between the perinatal variables and the infant and child variables were low. y'.*/.'/.

In this case, few of the correlations reached significance. Significant

correlations were found between Brazelton Neonatal Assessment Scale scores

and 6-month (.41) and 12-month (.53) Bayley mental subscale scores.

Obstetric Complication Scale scores were significantly correlated with 6-

month Bayley mental subscale scores (.66) but not at other ages. The Bayley

mental subscale scores from age 18-months on showed stronger correlations "v'v,V

,''v

with the 3 year language measures. The 18-month, and 24-month Bayley mental v'-!'v''"s/

subscale scores significantly correlate (.71 and .58, respectively) with the IWVÖMJ

36-month Peabody score. The 18- and 24-month Bayley scores significantly

correlate (.63 and .73, respectively) with the 36-month McCarthy Scale

scores. The Peabody scores and the McCarthy Scale scores significantly '''^V'-^

correlate at .64. .-\-\-\«

Demographic characteristics were not significant correlates of infant ."VC'V

development and language performance scores. This may be due to the JWWnöfl

relatively homogenous nature of the families and infants involved in the

study and the small number of characteristics measured. The families were

middle class with average incomes of $20,000 to $25,000, and both parents "'C's-'v"'

had at least completed high school. V • •

Regression models were constructed to test hypotheses concerning the

usefulness of perinatal, demographic and infant development tests to predict

language performance at 36 months. The models showed that McCarthy scores

can be predicted from individual and combinations of the following

variables: birthwelght, length, gestational age, labor length, 18 and 24

month Bayley scores and Peabody scores (best full model is birthweight, V'vS'^i

length, gestational age, 18 month Bayley). Peabody scores can be predicted "uMnuflffl

from individual and combinations of the following variables: labor length, ,•,

Bayley at 18 and 24 months, McCarthy scales (best: models are Bayley-18 and

McCarthy, and Bayley-24 and McCarthy). When only birth scores (i.e., BNAS,

birthweight, gestational age, length, obstetrical events and complications) '*/'•'&,

were used to predict language scores at three years of age, the regression

models were not significant.

„s

>V.V//.'
If8

Regression models were also constructed to test hypotheses concerning

the usefulness of all the Independent variables (i.e., perinatal,

demographic, infant measures and AER factor scores) to predict the language

performance scores. The only regression model which was significant

involved predicting McCarthy Scale scores from Brazelton scores, Obstetric

Complication Scale scores and AER factor scores. This regression model

accounts for 3Z more of the variance using perinatal measures and AER factor

scores than was accounted for by using AER factor scores alone. Perinatal

measures alone were not significant predictors. Clearly, the addition of

non-brain related measares did little to Improve predictions of language

performance based on brain wave data alone.

A'

'I'SsA

'. /

t

Implications

From these data, it seems clear than brain activity measure at birth

can be used with a high degree of accuracy to predict performance on two

language tests at age three years. Children who later developed into better

performers on language tests produced brain responses to speech consonant

sounds at birth that were distinctly different from the responses produced

by children who did not perform as well. The predictive accuracy achieved

using the AER responses exceeds by far the predictive abilities of the other

perinatal and behavioural measures used in this study and in other studies

(Molfese & Molfese, 1985b).

It is our belief that hemispheric lateralizatIon when coupled with the

discriminating abilities for certain types of sounds would provide the best

predictors of later language development. While Lenneberg has suggested

that lateralization per se would provide a general Indicator of later

language development, our point in light of the data we have obtained is

that lateralization plus some specific discriminatory abilities are

necessary for proper language development. The High language performance

group did not simply differ from the Low group in their ability to

discriminate human from nonhuman sounds. Rather, the former group showed a

discrimination in the left hemisphere for language sounds (specifically,

place of articulation contrasts for stop consonants) and a right hemisphere

discrimination for nonlanguage sounds (rapid frequency transitions with

formant bandwidths not characteristic of speech) that were not shared by the

Low language group. The presence of certain early discrimination abilities,

then, are seen as facilitating the process of language acquisition. Infants

without those early abilities or who are slower in acquiring those abilities

would face more difficulty in acquiring language.

•.

#

. V'

:*

The data reported in the present study do not provide a sufficient base

on which to ground claims concerning a single cause for the variety of

language deficits which can occur throughout development. We are not

claiming that an infant's ability to discriminate between two stop

consonants Is a sufficient basis for identifying the potential for later

language disorders. The present study, however, does report data which show

a definite relationship between brain responses recorded shortly after birth

and relatively small differences in language performance three years later

between children who apparently followed a normal pattern of development and

who could clearly communicate with those around them. We have no data at

this time as to whether these procedures might discriminate between children

with language skills in the normal range and children who have clear

language deficits. A replication of this study with a much larger and

diverse population is now under way to address such issues.

&^>^:^^^ ^
169

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Segalowltz, S. & Gruber, F. (1977). Language development and neurological «

theory. New York: Academic Press. s-'V^?

Shucard, J.L., Shucard, D.W., Cummings, K.R. & Campos, J.J. (198i). ;VS£VNJ

Auditory evoked potentials and sex related differences in brain yfi2y«Si

development. Brain and Language. 13 91-102. N^V^'S'N"'

Slmson, R., Vaughan, H.O. Jr., & Ritter, W. (1977a). The scalp topography %i

v

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of potentials in auditory and visual discrimination tasks.

Electroencephalography and Clinical Neurophysiology, 42 528-535.

Slmson, R., Vaughan, H.G. Jr., & Ritter, W. (1977b). The scalp topography

of potentials in auditory and visual go/no go tasks.

Electro«ncephaplography and Clinical Neurophysiology. 43, 864-875. S£

Trehub, S. 4 Rablnovitch, S. (1972). Auditory-linguistic sensitivity in Vv •

early infancy. Developmental Psychology. 6^, 74-77. £ ^

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171

Vaughan, H.G. Jr. (1969). The analysis of brain activity to scalp

recordings of event-related potentials. In E. Donchin and D.B. Llndsley

(Eds.), Averaged evoked potentials; Methods, results, evaluations.

Washington, D.C.: NASA, pages 45-94.

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DIFFERENCES BETWEEN ANHEDONIC A>:D CONTROL SUBJECTS IN BRAIN HEMISPHERIC

SPECIALIZATION AS REVEALED BY BRAIN POTENTIALS*+

Brigitte Rockstroh and Werner Lutzenberger

Arbeitsbereich Klinische und Physiologische Psychologie

Gartenstr. 29, D-A700 Tubingen, F.R.Germany

^S

+ Research was supported by the Deutsche Forschungsgemeinschaft

INTRODUCTION

The purpose of the present paper is to discuss evidence for hemisphere

specific information processing in anhedonic subjects as revealed by event

related slow brain potentials. A hedonia refers to a profound deficit in

pleasure experience (see below) and is considered a risk factor for the

development of a psychiatric disorder. The investigation of humans supposed

to be at risk for a psychopathological development may offer insights into

(deviant) human Information processing. It may also uncover determining

factors or processes underlying the psychopathological disorders.

Evi&ence from many experimental and clinical studies has provided the

basis for the hypothesis, as stated by Flor-Henry, that psychopathological

disorders may be characterized by hemispheric-specific dysfunctions: this

hypothesis relates schizophrenia to left-hemispheric overarousal and

processing dysfunctions, while depression is considered a consequence of

right-hemispheric malfunctioning and overactivation Flor-Henry and Koles,

1980; Tucker, 1982; Kemali, Vacca, Nolfe, lorio & DeCarlo, 1980; a recent

critical overview is provided by Cevey, 1984). This relationship has been

strengthened by the finding of asymmetries in the EEG power spectra; for

example, Serafetinides (1972, 1973) reported more desynchronization over the

left hemisphere in schizophrenics (which was reduced under phenothiazine).

Flor-Henry (1976, 1979) found more left-temporal power in the 13-20 Hz range

In schizophrenic patients, while depressives demonstrated more righttemporal power in this range. As compared to normal control subjects,

manic-depressives showed a significant reduction in alpha power over the

right parietal area during verbal and visual-spatial tasks (see also

Goldstein, 1979; Shaw, 1979). On the other hand, Abrams and Taylor (1979)

found EEG-abnormalities only in 28Z of the patient sample. Those patients

showing lateralized abnormalities (8 out of 27 schizophrenics, 21 out of 132

affective psychotics) supported the hypothesis of a lateralized aberration

as proposed by Flor-Henry.

* Address correspondence to:

Dr. Brigitte Rockstroh,

Arbeitsbereich Klinische und Physiologische Psychologie,

Gartenstr. 29,

D-4700 Tubingen, F.R. Germany.

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SCHIZOPHR ANHEDON

173

high

low

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Fig. 1. Right-graph: Slow potential shift (CNV) during 2-sec interstimulus

Interval (S1-S2), as well as post-S2 CNV resolution in subjects

with high (solid line) and low (dotted line) scores on the

anhedonia scale. Left graph: SP in anticipation and following the

S2 under two-stimulus reaction time conditions recorded from a

schizophrenic patient. Notice the prolonged negativity (PINV).

From: Elbert, 1985, with permission.

(Iarthermore, the data of Ferris & Monakhov (1979) point to a more complex

relationship between symptoms in depression and hemisphere specific EEG

patterns.)

• »

The concept of anhedonia has a long history of association with

theories of schizophrenia, from the psychoanalytic (Rado, 1956) to the

biochemical (Stein & Wise, 1971). According to the concept of Meehl (1962),

anhedonia is one of the four crucial source traits that characterize the

schizotypic personality (together with cognitive slippage, ambivalence, and

interpersonal aversiveness). Anhedonia is defined as "a marked, widespread

and refractory defect in pleasure capacity" (Meehl, 1962, p.829) and is

considered one of the most consistent and dramatic behavioral signs of

schizophrenia. This personality trait is supposed to depict a potential

risk factor for the development of a psychotic disorder. Meehl assumes a

neural integrative defect as an underlying factor in schizophrenia, which

he calls schizotaxia. The imposition of a social learning history upon

schizotaxic individuals results in the personality organization of the

schizotype. Although Meehl stresses that only a subset of schizotypic

personalities decompensate into clln.cal schizophrenia, the investigation of

subjects at risk in this respect (such as anhedonlc Individuals) may

provide insight into characteristics of the schizophrenic disorder. This

similarity was not only supported by psychological tests (anhedonics showed

significant amounts of thought disorder on the Rorschach test (Edell &

Chapman, 1979; Baberman, Chapman, Numbers & McFall, 1979) but also by

psychophysiological responses (see Simons, 1981, 1982). With respect to

event-related brain potentials, schizophrenic patients very often show

smaller or altogther-lacking EP-components in the latency range between 50

and 350msec (F-'"K. 1977; for an overview of evoked potential results in

schizophrenics t»ee also Shagass, Ornitz, Sutton & Tueting, 1978; Shagass,

1979); this finding was also obtained in anhedonic subjects (see Simons,

1982; Miller, Simons & Lang, 1984).

Evidence for aberrant electrophysiological responses in anhedonic

individuals was furthermore achieved in studies or. slow brain potentials

(SPs): whenever two stimuli are associated or contingent, in that a f^rst

or warning stimulus signals that a (cognitive or motor) response will be

' ' uired by a subsequent imperative stimulus, then a slow negative DC-

(.ential shift is recorded from the scalp during this anticipation or

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preparatory Interval. This nost prominent slow potential (SP) Ua43jQ

representative, the Contingent Negative Variation (CNV), was first reported *» * *

by Walter, Cooper, Aldridge & McCallum (1964) and has been suggested to be a 's^^

sign of priming and preparation. Much of the work (for summary see

Rockstroh et al., 1982) suggests that negative SPs might be indicators of

the preparation or mobilization of cerebral resources for the anticipated t^VsP

cerebral performance and overt response. ^*-,J*

During or following the respective performance, the slow negative •»'•'^sjS

potentials usually decrease to baseline or to positive values. Under srv^s^

distinct conditions and in certain Ss, however, negativity is prolonged or ^JoWrSJ

even augmented. This prolonged negativity was originally observed in

psychotic patients (Dongier, Dubrovsky & Engelsmann, 1976, 1977; TimsitBerthier, Delaunoy & Rousseau, 1976) and has been called Postimperative

Negative Variation (PINV) (see Fig. 1).

While it was first assumed that a PINV represents the underlying VVdisorder, a PINV could also be induced in healthy Ss under conditions of '£''£•"'«

sudden contingency change, uncontrollability, or disappointed expectations " ^

of contingencies or reinforcement (Rockstroh, Elbert, Lutzenberger &

Birbaumer, 1979; Elbert, Rockstroh, Lutzenberger & Birbaumer, 1982;

Delaunoy, Timsit-Berthiei & Rousseau, 1975; Delaunoy, Gerono & Fousseau, 'vflXl

1978). This suggested to us to consider the PINV as a sign of prolonged

contingency evaluation or preparedness for further Information processing

requirements (Birbaumer, Elbert, Rockstroh & Lutzenberger, 1986).

9

Psychiatric patients (schizophrenics and psychotic depressives) vv^Jf

turned out to be more vulnerable to contingency change or contingency •-'" -'S'

ambiguity, since thty have already developed a PINV under conditions of less '"-'""-•'/

clearcut response-consequence contingencies, for example, if the response !-^"-''v

criterion was increased such that the imperative stimulus could be Ct*****"

terminated by the motor respnse only in a certain proportion of trials *

(Giedke et al., 1980, 1982). This susceptibility was also observed in

anhedonic Ss presumed to be at risk for the development of a psychotic

disorder (see Lutzenberger, Elbert, Rockstroh, Birbaumer & Stegagno, 1981): 'IV^.'C

Under conditions of sudden contingency change or loss of control over an

aversive stimulus, anhedonic subjects developed a larger PINV than lowscoring subjects. When a response-irrelevant stimulus was introduced into -,.-.

some trials which had to be discriminated from the respon e-relevant /".^w^

imperative stimulus occurring 2 sec later, anhedonics exhibited larger •'VCv/'

anticipatory negativity prior to the possible additional stimulus, as well '^'^••'.'J

as a PINV tendency following the Imperative stimulus (Lutzenberger,

Birbaumer, Rockstroh & Elbert, 1983). Miller, Simons & Lang, 1984) report

less anticipatory negativity (CNV) prior to hedonic stimuli (nude females)

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in anhedonic subjects as compared to controls which points at a reduced "'"v" "^j

sensitivity for hedonic stimuli.

SUBJECTS

On the basis of Meehl's concept, Chapman and colleagues (Chapman, £

Chapman & Raulln, 1976, 1978) have developed a self-report questionnaire for

the screening of subjects at high risk for schizophrenia. From a total of 'v-'c^v^

750 university students who filled in the questionnaire a sample of 40 male N>%>

Ss with extreme scores (high and low) on the scale was selected. The mean

anhedonia score was 11.3+/-7, Ss with scores higher than 15 on the scale

(that comprises 61 questions, i.e. 61 possible points)* were assigned to the

experimental group, while Ss wih a mean score below i.0 constituted the

*It has to be considered that subjects with low scores must not correspond >"V\V

to a control group in the sense of a normal distribution but may also v'^^j

Include hedonic subjects with a tendency for mania. •.^/•/»

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175

control group. The anhedonia score of this sample of AO subjects decreased

across time: across a time period of by now six years, the subjects

participated in several psychophysiological investigations and filled in the

questionnaire four times; the mean anhedonia score decreased from 21.8 in

1978, to 15.1 in 1983. [The anhedonia-score in hospitalized schizophrenics

exceed that of the present sample (15.9+/-8.7), although many schizophrenics

do not exhibit anhedonic tendencies at all. On the other hand, 19 out of 20

psychotic depressives gave a strong anhedonic self-report (mean 22.9+/-

6.9)).

In the present paper three studies are reported which investigate

hemisphere specific SP-shifts in anhedonic subjects to gain insights into

hemisphere specific functioning in Individuals supposed to be at risk for

the development of a psychotic disorder.

EXPERIMENT I

Method

In the first study, CNV and postimperative SPs were investigated in the

standard two-stimulus reaction time paradigm. A click (white noise of 65

dB SPL, 100 msec duration) was presented via earphones as warning stimulus

(SI). After an interstimulus interval of two seconds a light spot appeared

on a tv-screen in front of the Ss as imperative stimulus (S2). Ss were

requested to press a button as fast as possible in response to the S2

presentation. A total of 50 trials was given. Intertrial intervals

varied between 9 and 17 sec around a mean of 13 sec.

The EEC was recorded monopolarly from F3, F4 and C3, C4 according to

the International 10-20 system, with a time constant of 30 sec. Grass flat

silver disc electrodes, chlorided prior to each experimental session, were

used, Grass paste EC2 served as electrolyte. To achieve electrode Impedance

levels below 5 k Ohms, the skin below the electrodes was cleaned with

alcohol and the outer layers of the skin were removed by gently scraping

with a sterile scalpel. Reference electrodes were affixed to both earlobes

and were shunted via a 10 k Ohm resistor. Eye movements were monitored for

artifact control. Data were sampled at a rate of 100Hz and collapsed to 100

msec points by a digital filter without phase distortion for the slow

potential analysis.

DEC laboratory computers controlled the timing and presentation of the

experimental stimuli and stored the physiological data on magnetic rape.

Pressing the microswitch closed the Schmitt trigger in the digital computer

so that the response latency was stored to the nearest ms.

For data analysis, the digitized EEC and EOG data were averaged across

10 subjects and trials. Trials were rejected from further analysis,

whenever the mean EOG shift exceeded 50 V, or whenever the mean slow

potential (SP) shift during the stimulus interval exceeded 70 V relative to

the baseline value. The mean of the second sec during the interstimulus

Interval was taken as measure of the CNV; the mean of the third half-second

Interval following the S2 referred to the CNV amplitude represented the

postimperativs shift, PINV. Experimental effects were statistically

evaluated by an analysis of variance with the factors GROUPS (anhedonics vs

controls) and LATERALITY (left vs right hemispheric recording).

Furthermore, correlation coefficisnts determined the relationship between

anhedonia score and the hemisphere-specific PINV-amplitudes.

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176

ANHEOONICS

CONTROLS

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Fig. 2. CNV during the 2-sec anticipation interval and postimperative CNVresolution in anhedonic (solid lines) and control subjects (dashed

lines) recorded from the right (frontal: F4, precentral: CA) and

the left (F3, C3) hemisphere. Less CNV-resolution indicates more

pronounced postimperative negativity (PINV).

Results

Anhedonics demonstrate less postimperative negativity resolution

following the S2/button press response, thus, a more pronounced relative

PINV, than control Ss with low scores on the anhedonia scale. This is

documented by a main effect of GROUPS for the right-precentral PINVamplitude (F(l,39)- 4.1, p < 0.05), as well as for the left-precentral

PINV-score (F(l,39)- 6.7, p < 0.05). Closer inspection of the hemispherespecific SPs reveals the more pronounced postimperative negativity in

anhedonics over the left precentral area (see Fig. 2). The AN0VA documents

the group difference by an interaction of GROUP and LATERALITY with F(l,39)=

6.7, p < 0.05 for the PINV-amplitude. The group difference in hemispherespecific PINV is supported by significant correlation coefficients between

the anhedonia-score and the left-precentral PINV-amplitude, (r« .A0,

p < 0.05), as well as the left-right asymmetry (r- .42, p < 0.05).

This result suggests that increasing anhedonia-scores covary with more

pronounced PINV, and with more pronounced lateral asymmetry, i.e. a lefthemispheric dominance of the PINV. Anhedonics seem espescially to activate

the left hemisphere for their ongoing contingency evaluation.

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EXPERIMENT II

Method

In the second study with the two-stimulus reaction time paradigm,

the level of difficulty of the contingency evaluation was Increased In that

a response-irrelevant but similar stimulus had to be discriminated from the

response-relevant imperative stimulus in half of the trials. Ss heard again

a click (white noise of 80 db for 100 msec) as warning stimulus, which was

followed after 6 sec by a hissing noise (white noise of 80 db) that had to

be interrupted by an immediate button press. In half of the total of 50

trials, pseudorandomly interspersed, a hissing noise similar to the

imperative one was presented after A sec, but Ss were instructed not to

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177

c?

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TRIALS WITHOUT

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ANMEDON1C SUBJECTS CONTROL SUBJECTS £>?*

Fig. 3. SP-shifts during a A-sec interval preceding the possible

presentation of an additional stimulus (AS), recorded from the

vertex (Cz), the left (C3) and the right (CA) precentral cortex in

anhedonic (solid lines) and control subjects (dotted lines). Upper

graphs: trials in which an AS occurred at the end of the 4-sec

interval; lower graphs: trials without AS-presentation.

*&

WAS

respond to this additional stimulus (AS) but only to the IS. Since subjects

received delayed feedback about the adequacy of their discrimination only at

the end of the trial, the stimulus-response contingency was assumed to be

less clearcut or more difficult to evaluate.

The EEG was recorded along the midline (Fz, Cz, Pz), as well as from C3

and C4 according to the procedure described above. 38 Ss from the above

described sample participated in the study.

For data analysis the digitized physiological data were averaged over

trials separately for each subject x condition x recording cell. A

varimaxed Principal Component Analysis (PCA) based on covariances was

performed to decompose SP-waveforms. A weighted sum of principal components

was fitted to each individual waveform to obtain component scores. These

were submitted to an analysis of variance to evaluate statistical

differences.

Results

rVvTJ

In anhedonics, the negativ«« shift prior to an expected AS* is

significantly larger than in controls; this is supported by a main effect of

* If an AS is presented in 50*. of the trials the conditional probabilities

of two subsequent identical trials were 1 in 3, whereas the probabilities of

a change in type of trial were 2 in 3. Subjects obviously have established

subjective probabilities regarding the next trial on the basis of the

preceding one. Following a trial with AS, a subsequent trial without AS is

more likely to occur than another trial with AS, i.e. is expected.

Consequently, subjects developed a more pronounced negative shift prior to

the expected occurrence of an AS.

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178

GROUPS for the late SP-component In the 4 sec interval between SI and AS

(F(l,36) - 5.6, p < 0.05).

As is illustrated by Fig. 3, this preparatory negativity in anhedonics,

as well as the group difference, is most pronounced at C3, the left

hemisphere, especially, if an AS was expected and presented, (see footnote

on previous page).

Anhedonics also show less postimperative negativity resolution, thus, a

more pronounced PINV, than controls, especially if no AS was presented

during that trial (GROUP x AS: F(l,36)-8.3, p < 0.01, for an ANOVA of the

recordings along the midllne, Fz, Cz, Pz, and (Fl,36) 3.9, p < 0.05, for

an ANOVA comprising the recordings Cz, C3, 04). However, this PINV did not

show significant lateral asymmetry.

Furthermore, the N100 in the evoked potential turned out to be

significantly larger at the left-precentral location (as compared to CA) in

response to the AS (main effect of LATERALITY: F(l,36) - 13.8, p < 0.01) and

in response to the imperative stimulus (S2)(F(1,36) - 16.2, p < 0.01. The

S2-elicited P200, too, shows left-hemispheric predominance (F(l,36) - 9.3,

p < 0.05). This lateral asymmetry of the £2-elicited N100 is more

pronounced in anhedonics, giving rise to a significant inter ction between

GROUPS and LATERALITY with F(l,36) - A.9, p < 0.05).

Again, bcth results of this study, the larger preparatory negativity,

as well as the more pronounced N100 to the response-relevant stimulus over

the left hemisphere, indicated more pronounced left- than right-hemispheric

phasic activation in anhedonics. The tonic activation, however, could also

be lowered, which might give rise to higher phasic responses too. The N100

is mainly associated with selective attention (Hillyard, Hink, Schwent &

Picton, 1973), which seems to require more effort in anhedonics, when they

have to discriminate the S2 under the less clearcut contingency conditions

of the present study. We may speculate that this increased activation may

serve to compensate for left-hemispheric deficits, for example in the

discrimination between the AS and the IS. The PINV then indicates longer

lasting contingency evaluation in trials without AS, since following an AS

the presentation of the IS verifies the discrimination and the adequacy of

the response. Since the more pronounced PINV was observed in trials without

AS, it cannot be argued that anhedonics take longer to recover from the

distraction induced by the AS. Cj^..

EXPERIMENT I J.I

Finally, Ss participated in a SP-self-regulation training on the basis

of a biofeedback paradigm. The perception and reward of electrical brain

activity allows operant conditioning, ao that negativity can be increased or

reduced depending upon discriminative stimuli.

Method

The actual SP-shift is continuously fed back during Intervals of 6 sec

each by means of a little rocnet-ship (Fig. A), which moves across the tvscreen towards two goals. Ss are requested to direct the rocket into one of

the goals depending upon which of two discriminative stimuli (a high- or a

low-pitched tone) are presented simultaneously to the rocket's flight. The

height of the rocket during its flight is a linear function of the

Integrated S^-ahift at successive half-second averages, referred to the mean

of a A sec Vaseline. Reaching the required goal, thus producing the correct

SP-ahift, is rewarded by a point signalling the gain of l.-DM (A0 U.S.

Cents). Counterbalanced across Ss, one goal represents an SP-shift towards

Increased negativity, while reaching the other goal requires negativity
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score

Fig. A. The feedback display and the required changes in 5P negativity.

Dotted line and rocket-ship demonstrate that the more pronounced

negative shift corresponds to the higher position of the rocket on

the TV-screen as compared to less negativity (solid line and

rocket). From: Rockstroh et al., 1984, with permission.

r\rmvwvw\

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suppression. The EEC was recorded from Fz, Cz, Pz and from C3 and C4. The

feedback stimulus was determined by the average of C3 + C4. (Various

artifact control procedures prevent Ss from steering the rocket by eye

movements or muscle tension/relaxation; for a detailed description of the

feedback algorithm see Elbert, Rockstroh, Lutzenberger & Birbaumer, 1980;

Rockstroh, Elbert, Birbaumer & Lutzenberger, 1932).

Many studies based on this paradigm have demonstrated that human Ss are

able to achieve significant control, i.e., significant differentiation of

SPs In the required polarity directions within 100 to 200 training trials.

Control can also be maintained in transfer trials without feedback (see

Elbert et al.; 1980, Birbaumer, Elbert, Rockstroh & Lutzenberger, 1981;

Rockstroh, Elbert, Lutzenberger & Birbaumer, 1984).

KM*C,

ANHED0NICS

i9*dback

CONTROLS

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Fig. 5. SP-changes during the 6-sec feedback Interval in anhedonics (upper

graphs) and controls (lower graphs), averaged across trials with

required increased negativity (solid lines) and required negativity

suppression (dashed lines), and averaged separately for the right

(C4) and left (C3) precentral recording.

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180

Results

The SP-self-regulatlon ability in the control group of the present

sample does not differ from that described for other samples of student

volunteers, whereas anhedonics fail to achieve comparable SPdifferentlation. Fig. 5 illustrates SP-regularion in anhedonics as compared

to controls.

>*•} '•-<

While control Ss achieve the most pronounced adequate differentiation

especially at the left precentral recording, anhedonics fail to regulate

their slow brain potentials, especially over the left hemisphere. This

group difference is documented by a significant interaction of GROUPS x

POLARITY x LATERALITY with F(l,36) - 10.5, p < 0.01.

Similar deficits in SP-self-regulation (however, not in a hemispherespecific manner) have been observed in patients with bilateral lesions of

the frontal cortex and in children with attentional disorders (see

Rockstroh, Elbert, Lutzenberger & Birbaumer, I98A).

DISCUSSION

£

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Taken together, the present results suggest a left-hemispheric SPregulatlon deficit in anhedonics as compared to controls, which anhedonics

might try to compensate by a left-hemispheric overactivation: they show more

preparatory, more postimperative negativity, and an increased N100 amplitude

ov. r the left hemisphere. However, the present data do not allow a definite

conclusion, whether the observed left-hemispheric overactivation results

from overarousal or underarousal as the underlying deficit.

Do these results fit with findings as reported for schizophrenics (and

probably also depressives)?

1.) Left-hemispheric overarousal was reported for schizophrenics, and if we

consider anhedonics at risk for a schizophrenic career, then the present

data suggest that this left-hemispheric overactivation Is already evident in

a pre-psychotic state. Increased left-hemispheric activity in

schizophrenics is also supported by blood flow measurements, as described by

Gur (this volume).

2.) Furthermore, left-hemispheric proc .ssing deficits wer«» reported for

schizophrenics. We may speculate that processing deficits become evident in

the present sample in the impaired SP-self-regulation in the biofeedback

paradigm (which, for example, involves attention and the processing of Che

feedback and reinforcement stimuli); they may also become manifest in the

impaired or prolonged contingency processing as indicated by the

postimperative negativity. This processing deficits might well be the

consequence of a tonically underaroused state, which subjects try to

compensate by Increased effort, as indicated by increased (left-hemispheric)

electrocortical activity. These results support the continuity between

anhedonia and schizophrenia as proposed by Simons (1982).

3.) On the basis of EEG power spectra analyses, Flor- >nry and Roles (1980)

as well is Kemali, Vacca, Nolfe, lorio and Decario (1980) postulate less

lateral asymmetry In schizophrenics than in controls. Although the present

results are not based on power spectra analyses, they argue against a

reduced lateralization in anhedonics (as compared to controls), but

anhedonics certainly are not psychotic. We might speculate that a lasting

left-heminpheric overarousal could turn into habituation or exhaustion,

visible as reduced laterality in a later schizophrenic state.

On the one hand, it should be taken into account that anhedonia

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181

represents a disturbance of pleasure discrimination, which may characterize

several psychopathological disorders, also depression. Although anhedonia

Is considered a source trait of the schizotypic personality, which may

decompensate to a schizophrenic disorder, there is evidence that depressives

score high on the anhedonic scale, so that the present results, too, may

provide predictive evidence for a possible depressive development. The

primarily left-hemispheric regulation deficit In anhedonlcs could contribute

to their pleasure deficit, if we assume positive emotions to be represented

in the left hemisphere (see Sackeim, Gur and Saucy, 1982; Flor-Henry and

Koles, 1979; Tucker, Watson and Heilman, 1981). On the other hand, this

hypothesis would predict that activation of the left hemisphere should

induce positive emotions, which is not true for the present sample.

In the framework of our model about the behavioural meaning of slow

cortical negativity (Rockstroh, Elbert, Birbaumer and Lutzenberger, 1982),

the presently observed left-hemispheric activation might be interpreted as

sign of Increased effort to compensate for the (left-hemispheric) deficient

regulation of attention and preparatory resources. Because of this

regulation deficit, anhedonlcs and psychotic patients, see Giedke, Bolz,

Helmann and Straube, 1982) may be more susceptible to ambiguity of, or

changes in contingencies.

»

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184 .

HEMISPHERIC DIFFERENCES IN RELATION TO SMOKING

M

Thomas Elbert* & Niels Birbaumer

Department of Clinical and Physiological Psychology

University of Tubingen,

F.R.Germany

SUMMARY

The present investigations were designed to uncover differences in

hemispheric interactions between tobacco smokers, smoking cigarettes with

different nicotine concentrations, and non-smokers. In the first

experiment, sensorimotor tasks, associated with hemisphere-specific

processing, were presented either to the right hand (then stimuli had to be

counted) or to the left hand (matching of stimulus patterns). A lever

switch with the thumb of the stimulated hand was used to indicate the

correct solution of the task. A warning stimulus presented to the same hand

(6 sec prior to the task) primed these choice reaction time tasks.

Non-smoking subjects, all right banders, performed faster in the right hand

task. This difference, though more pronounced in sham-smoking subjects

(smoking cigarettes with zero nicotine content) than in non-smokers vanished

with increasing nicotine intake so that smokers responded faster in the

left-hand task. Similarly, a difference in error rate between the two types

of task was observed only in non-smokers or in smokers without recent

nicotine intake. After nicotine intake, heart rate in smokers was higher

for the left than for the right hand task and the task-dependent asymmetry

of the slow brain potentials also interacted with smoking intake. Results

may provide new evidence that nicotine ir. lower doses Improves interhemispheric coordination or activates the right hemisphere of the brain.

The second experiment tested the self-regulation of the hemispheric

asymmetry in slow brain potentials. Operant control was achieved by means

of a biofeedback paradigm in non-smokers and smokers as well. Though only

asymmetry over the central legions was required, smokers, unlike nonsmokers, demonstrated an extended change in SP-distribution. Sham-smokers

were less able to shift their slow negative brain potential to the left

hemisphere. The results Indicate that transmission of information between

brain hemispheres might be impaired in deprived smokers and that nicotine

helps to compensate for this regulation deficit. However, the finer tuning

within limited brain regions is achieved by non-smokers only.

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Dr. Thomas Elbert,

Department of Clinical & Physiological Psychology,

University of Tubingen, Gartenstr. 29, D-7400 Tubingen, West Germany,

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INTRODUCTION

Based on psychological considerations, we have suggested that nicotine

exerts its cortical actions priraarlly on the right hemisphere of the brain,

or that It alters information interchange between the hemispheres

(Birbaumer, 1981). On the one hand, smoking was found to reduce vigilance

decrement (Mangan, 1982) and to increase performance in signal detection

(Wesnes i Warburton, 1978; Williams, 1980), on the other hand it was

reported to reduce recall and categorisation of written words (Gonzales &

Harris, 1980). Such examples could Indicate that smoking enhances

performance for right rather than for left hemispheric tasks, although the

alerting effects oi nicotine generally confound this interpretation, and

controversial results have been explained on the basis of a dose-response

relationship and individual differences. (For a general review on smoking

see Ashton & Stepney, 1982).

Nicotine is known to influence cholinergic (ACh) pathways. While

facilitating synaptic transmission In low doses, it blocks the nicotine

receptors at higher concentrations. The structural similarity (in

electrical charge distribution) makes nicotine a perfect key to interact

with ACh-receptors. The resulting combination, however, is much more

enduring than the combination with ACh. ACh-receptors may still be occupied

by nicotine when a subsequent nerve impulse arrives at the synapse. In this

case, instead of being stimulated, the eventual response mediated at the

synapse will be inhibited or suppressed. This explains, why nicotine exerts

a biphasic effect on the arousal system (via the mesencephalic reticular

formation), which might increase or lower electrocortical arousal (depending

on dosage, deprivation time and actual arousal).

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In contrast, nicotine has a generally inhibitory effect on the

discharge of many cortical cells. While many cortical fibers are

cholinergic, no cholinergic fibers were seen ir the large tracts of the

white matter (including corpus callosum and anterior commissure; Bindman &

Lippold, 1980). By depressing cortico-cortical but not transcallosal

connections, nicotine, therefore, would facilitate hemispheric integration,

e.g. via presynaptic disinhibition of interhemispheric fibers. ACh is not

symmetrically distributed in the human cerebral cortex, as it is in animals

and this could also cause an asymmetrical action of nicotine. However,

there is some evidence that nicotine receptors are not limited to

cholinergic neurons (Abood et al., 1980), which makes predictions from

psychopharraacological considerations very difficult.

The present Investigations were designed to uncover differences in

hemispheric coordination between smokers and non-smokeis; during the

experiment smokers smoked cigarettes of different nicotine content.

Sensorimotor tasks with lateralized processing (Lutzenberger et al., 1985)

were chosen for the first experiment, since the rate of acetylcholine

release is greatest from the sensorimotor areas (Phillis, 1970). The

primary projection areas are not connected by transcallosal fibers.

METHOD

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Subject-sample. A total of A4 male right-handed students (as verified by

the Edinburgh inventory of Oldfield, 1971) were paid for their participation

in the two experiments. Age ranged from 18 to 32 years. 20 subjects were

non-smokers, 24 smokers were selected according to the following criteria:

at least 10 cigarettes per day with at least 0.8 mg nicotine per cigarette.

The average consumption was rated to be 15.3 cigarettes per day. Based on

the smoking pattern test (Taylor's version of Russell et al., 1974,

published in Ashton & Stepney, 1982) subjects attributed their smoking to

rhe categories INDULGENT (46+7-5*), SEDATIVE (38+/-7Z) and SENSORIMOTOR

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(A0+/-3Z) rather than STIMULATING (21 + /-7%) or PSYCHOS0CIA1, (18+/-4X).

Procedure. Subjects were Instructed not to smoke for two hourr before

the experiment would start. After electrode attachment, a clgarett? was

offered. Subjects were Informed that smoking might influence some ot thL

measurements to be taken and, therefore, were asked to smoke a standardized

cigarette type before each experiment. However, the smokers were assigned

to one of four groups, each receiving cigarettes with a different nicotine

content in a double blind setting. Concentrations were 0.0, 0.2, 0.4, 0.3

mg per cigarette.

Apparatus and Physiological Recordings. The E^G was recorded from C3-

C4, P3-P4 and from Fz, Cz, 03, P3 in reference to shunted earlobes. A

Heckman type R polygraph was modified to have a 30 sec time constant and

high frequency cut-off of 30 Hz. The monopolar EEGs from C4 and P4 were

obtained by off-line subtraction. Grass silver disc electrodes, chlorided

before each experimental session, were used with Grass EC2 paste as a

conducting agent. To keep electrode resistance below 5 k Ohms, the skin at

the electrode location was cleaned with alcohol and the ourer layers of the

skin were removed by gently scraping with a sterile scalpel.

For the recording of vertical and lateral eye movements, (VEOG and

LEOG), Beckman silver/silver chloride electrodes were attached 1 cm above

and below the left eye and as near as possible to the outer canthi,

respectively; Beckman electrode Jelly served as electrolyte.

Data were sampled at a rate of 100 Hz and collapsed to 5 points/sec for

slow potential analysis, using a phase-free digital filter.

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The EGG recorded from the lower r'b cage was fed into a

cardiotachometer coupler to detect R-waves, which Schraitt-triggered the

computer.

Timing and presentation of the experimental stimuli were enabled by

means of digital computers. Computer programs were used to reject trials

from averaging, when eye movements exceeded 70 yV, referred to prestimulus

baseline, or when a shift of more than 50yV/sec was detected in one of the

EEC channels.

Data analysis. Varinaxed principal component analyses (PGA) were used

to parameterize phasic physiological responses. The covariance matrices

were normalized so that the trace of the matrix equalled its dimension, and

two components were extracted to account for variances early and late in the

anticipatory interval (early and late CNV). A linear combination of

principal components was fitted to each individual physiological response.

The component scores, as well as behavioural response measures were

submitted to analyses of variance (ANOVAs). Separate ANOVAs were computed

for the non-smokers (Non-S.) and for the smokers (Sra.), the latter included

the between-subjects factor NICOTINE CONCENTRATION. Stars (*) indicate

p < 0.05 or (**), p < 0.01. (Only effects relevant in the present context

are reported.)

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EXPERIMENT I

Design

Ss placed index and middle finger of each hand on a small surface, from

which one to four solenoid driven pins would protrude for two sec. To

maximize lateralized processing, the right hand task was a decision to be

made according to the number of pins counted: either one or two pins, or

more than two. The direction in which a lever was moved with the right

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187

thumb Indicated the solution (see Fig. 1). The left hand task was to

compare patterns of pins between the two fingers and to decide, whether

those were equal or different (Fig. 1). In this case, a response with the

left thumb was required. The different solutions of both tasks had equal

probability. (The relationship between the direction of the levor switch

and the solution of the tasks was balanced across Ss.)

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The tactile task was preceded by a tactile warning stimulus SI (all

four pins protruded for one sec) on the hand t( which the task would be

given. For example, the perception of the pins at the right hand signalled

that the right hand task (to count the number of pins) would be presented

five sec after SI offset.

Subjects experienced 32 trials with the right hand task and 32 trials

with the left hand task in pseudorandom order. The total physical

stimulation was equal for both types of task. Ss were asked to switch the

lever as fast as possible to task presentation. If a wrong response or no

response within a four sec Interval following task onset was recorded, an

error was counted. The Intertrial Interval varied between 10 and 25 sec.

During the experiment ti.i subject sat in a reclining chair In a

soundproof and dimly lit room. After the preparation for the physiological

recordings, the subject read task instructions. Eight prac :ice trials,

supervised by the experimenter, introduced the task. Ss were advised to

fixate a cross in front of them and to prevent blinks and eye movements.

LEFT HAND

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right hand. Dots mark the number or configuration of protruded

pins (S2). Below each hand, the required response, i.e., the

correct direction of the lever switch is marked; dotted levers

indicate the start position.

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Fig. 2. Median of the reaction times (RT) for the left hand (1.) and right

(r.) hand task. N: Non-sraokers. Abscissa indicates nicotine

content of smoked cigarettes.

Results

Reaction time and error rate. Subjects press the button faster for

right-hand than for left-hand tasks (Non-S F(l,19)-22.3*^, Sra

F(l ,20)-45.1 **). For smokers, however, this difference vanishes with

increasing nicotine consumption (NICOTINE CONCENTRATION X TASK:

F(3,20)«A.2*), as shown by the medians of the reaction time in Fig. 2.

Error rates, too, document superior task performance of the right (11*)

as compared to the left hand (21%; Non-S F(l ,19)-38.3*A, Sm F(l,20)-6.5*).

Across trials the error rate of the left-hand task decreases in non-smokers

(TASK x SERIES, F(l, 19)-16.2**), as well as in sham-smokers, however,

accompanied by an Increase in the error rate for the right-hand task. With

increasing nicotine uptake smokers, however, are able to reduce error rates

for both tasks (NICOTINE x TASK x SZRIES: F(3,20)-4.1 *) (see Fig. 3). This

adaptive behaviour results in an overall improvement of performance under

nicotine (NICOTINE, F( 3,20)-3.8:»).

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The Heart Rate (HR). The HR increment due to nicotine uptake

(NICOTINE, F(3,20)-3.4*) is Illustrated in Fig. A.

The HR in trials with the left-hand task is higher than during righthand performance. This difference increases with nicotine uptake (NICOTINE

x TASK: F(3,20)-4.7*) (see Fig. 5).

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Fig. 3. Change in error rate from the first (1st) to the second (2nd)

series. Abscissa as in Fig. 2. • 1
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Fig. 4. Mean heart rate in beats per minute, averaged across the

experimental session.

Slow Brain Potentials. The SPs as illustrated in Fig. 6, show a taskdependent asymmetry. The asymmetry develops inraedlntely after SI and

Increases in amplitude during the task presentation.

The ANOVA results in significant Interactions for the early precentral

component (TASK x LATERALITY: non-S F(1,1 9)-21.2**; Sm F( 1 ,20)-22.6**).

Principal components are depicted in Fig. 7.

The asymmetry can be described by the difference in component scores:

C3-Ci (left hand) - C3-C4 (right hand). Fig. 8 shows these asymmetry scores

for early and late components.

Average asymmetry is lower In sham-smokers than in non-smokers but

increases with increasing nicotine inhalation to values comparable to the

non-smoker level (F(3,20)-4.2* for the early end F(3,20)-3.4* for the late

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values indicate a higher HR during left- than during right-hand

tasks.

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Fig. 6. Slow potentials averaged across groups in experinent I: Left

column: Bipolar SPs are averaged separately for trials with lefthand - right hemispheric tasks (dotted lines) and right hand tasks

(solid lines). Right column: Monopolar vertex potentials.

component). Thereby, the asymmetry develops earlier under nicotine. The

amplitude of the late component decreases in parallel (Fig. 9), especially

«t the fron:al recording site (F(3,20)-3.5*).

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Fig. 7. Loadings for the three varimaxed principal components from PCA of

the six sec anticipation intervals for experiment I (dotted lines)

and experiment II (solid lines).

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ASYMMETRY

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Fig. 9. Dependence of the late SP-component on nicotine intake.

Fig. 8. Asymnetry «cores for the early (dotted) and late (dashed)

component. The solid line Indicates the averaged SP-asymnetry.

Lateral and vertical eye movements are small and show no significant

effects.

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The EEC at the parietal sites was analyzed by means of a Fast Fourier

Transformation (using a Tuclcey-Hanning window) for 2.56 sec prior to SI- and

2.56 sec prior to S2- presentation (INTERVAL). During the anticipation

Interval a hemispheric asynraetry develops in a task-dependent manner for the

11-12 Hz frequency range: anticipation of the right-hand task reduces P3-

power more than the left-hand-task expectancy (TASK x LATERALITY: Non-S

F(l,19)-5.3*, Sn F(l ,20)«5.'i*). The desynchronisation in response to the SI

follows an U-shaped function with increasing nicotine intake, being lowest

in the group with 0.2 mg (see Fig. 10, NICOTINE x INTERVAL: F(3,20)-5.1**).

cwDiscussion

The present tattile stimulation associated with different types of

tasks for the left and right hand induces hemisphere-specific preparation

and processing. This is confirmed by brain potential analysis (see

Lutzenberger et al., 1985). The same physical stimulation was applied in

both tasks, but input 'contralateral hand), mode of processing

(counting/pattern matching), aid output (motor response with the

contralateral hand) activate primarily one hemisphere.

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Flg. 10 EEC power spectra recorded from parietal locations.

I (dotted lines) and experiment II (solid lines).

For experiment

«ÖS?

Obviously, the left- hand task (pattern matching), assumed to be

processed in the right hemisphere, was harder for non-smokers (slower

responses and more errors) than the presumed left-hemispheric task (stimulus

counting).

The different results for smokers can be explained by the hypothesis

that nicotine either interacts asymmetrically with the brain hemispheies

(arousing the right side?) or facilitates the interchange between

hemispheres. Smokers are better adapted to the presently required

continuous switching between hemispheres. They react faster with less

errors; their performance is more balanced between tasks and their brain

potentials are well regulated, i.e. the anticipatory negativity Is shifted

to the site of processing. A higher heart rate during left-hand tasks

also indicates a compensation for task difficulties. Smokers without

nicotine, on the other hand, perform worse than non-smokers. The depressant

action of nicotine on the cortex could result in a more extensive inhibition

exerted through commissural fibers on the brain hemisphere, which is not

processing the current task. Lower SP-amplitudes but Increased SPasymmetry, as presently observed, would be the consequence. Heart rate

becones generally higher with Increasing nicotine consumption, indicating

the well-known influence of nicotine on the autonomic nervous system and on

general arousal (see Ashton & Stepney, 1982). These unspecific actions,

however, cannut explain the reported specific effects. The second

experiment was scheduled to pursue this hypothesis oi an interaction between

smoking and hemispheric integration.

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EXPERIMENT II

Design

Regulation of CNV-like slow potentials (SPs) also may be achieved by

means of the biofeedback paradigm, in which human subjects are rewarded for

the generation of different S?-shifts. As shown previously also areaspecific SP-patterns can be brought under operant control (Elbert, 1985;

Rockstroh, 1986).

After a cigarette-break of 10 mfn the same subjects were tested for

their ability to regulate brain electrical activity differentially between

hemispheres. The bipolar C3-C4 S? difference was selected as the operant.

During Intervals of 6 sec each, the integral of C3-Ci EEC referred to preinterval baseline was continuously fed back within a game presented on a

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Fig. 11. Slew potentials recorded during biofeedback. Bipolar SPs are

averaged separately for trials with required larger left (C3) than right

(C4) precentral negativity referred to pre-feedback baseline (solid lines)

and vice versa (dotted lines). The averaged C3-C4 differences meet the

requirements of control.

video-screen. One of two discriminable visual stimuli (diffuse color light)

required more negative left-, than right-precentral SP-shift, while the

other color informed the subject that only SP-patterns which were less

negative at C3 relative to C4 would be rewarded by winning points (50 c per

point). A total of 80 trials (A0 trials of each condition) was scheduled in

two training blocks, each lasting about 20 min. Subjects smoked another

cigarette during a 3 mln break between the trial blocks. Simultaneous

lateral EOC-shlfts, which could have generated proportions of the recorded

C3-Ci shift, prevented successful trials, but could result in a loss of

points.

Results

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Results are illustrated in Fig. II. The data are averaged across

artifact-free trials separately for the groups and the two self-regulation

conditions. The significant C3-C4 differentiation of SPs documents that

subjects have learned hemisphere-specific S? regulation (p < O.001).

The essential similarities among SPs of both experiments are confirmed by

Principal Component Analysis (PCA). The separate PCAs disclosed in each

case two nearly identical components (plotted as a function of time in Fig.

7).

The SP-differentiation shifts towards earlier segments o- the 6 sec

feedback interval in smokers (N'ICOTINE x CONTROL P(3,20)-3.5*) for the early

component. The differentiation is more widespread in smokers than In nonsmokers (GROUPS x CONTROL x SCALP SITE, F(1,42)-4.7*).

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The EEC analysis reveals that asymmetry in desynchronisation covaries

with SP-as;/mmetry: the hemisphere with higher negativity shows less alpha

activiry (CONTROL x LATERALITY, Non-sm F(l ,19)-4.7*). Again, power in the

alpha-band follows an invertedly U-shaped function, being highest In the

group with 0.2 mg (NICOTINE: F(3,20)-4.5 *; see Fig. 10).

In contrast to non-smokers an asymmetry develops in smokers with less

right than left hemispheric synchronisation 'CROUPS x LATERALITY:

F(:,42)-7.4*)l but more beta-power (13-20 H2) over P4 than over P3 (GROUPS x

LATERALITY: F(l ,4:)-10.4**). This asymmetry, evident In all smokers,

becomes most pronounced after 0.4 mg nicotine cigarettes (NICOTINE x

LATERALITY: F(3,2Ü)-4.7*).

vJvfl

Discussion

The results replicate previous findings that operant control of S?-

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194

asymmetry can be achieved (Elbert, 1985; Rockstroh, 1986). Since EF.Gsynchronisation depends on SP-control, significant artifactual Influences

can be excluded.

In line with the results of experiment 1, the ability to regulate

hemisphere-specific activation seems to be Improved under nicotine, although

all smokers regardless of the actual amount of nicotine intake exhibit a

widespread SP-differentiation, which was not necessary to achieve reward.

Possibly smokers lack the finer tuning observed in non-snokers who restrict

SP-differentiation to the required brain regions.

We may even speculate that subjects with less efficient connections

between hemispheres may compensate for the regulation deficit between

hemispheres by taking advantage of the facilitating effect which nicotine

might have on callosal transmission. A genetic predisposition of righthandedness (RS+) has been suggested by Annett (this volume). These genes

might favour the developmental reduction in fibers crossing the corpus

callcsum (Witelson, this volume). This raises the question, whether

subjects with RS++ are more prone to smoking than those with other genetic

dispositions. Additionally, this would restrict the applicability of animal

models, since the right shift and hemispheric organisation in general seems

to be unique in humans (Annett, this volume).

Based on the assumption that cortical processing of emotions is

lateralized, the speculative action of nicotine might, furthermore,

contribute to an emotional balance (via the hemispheric balance) and control

emotional arousal, as has been reported for tobacco smoking. Selfregulation of SPs affects various behavioural responses (Rockstroh et al.,

1982). From these results we have concluded that SPs indicate the

allocation of attentional resources in the brain. The superior regulation

of the early SP-component suggests that nicotine can increase the

flexibility of resource allocation. This adds to the possibility to use

nicotine as an external regulator of various CN'S responses explaining

addictive behaviour.

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Acknowledgement

We acknowledge the support and advice of Dr. Gosswein and Dr. Meloh.

This paper is dedicated to Prof. Dr. Wolfgang Tunner on his 50th birthday.

REFERENCES

Abood, L., Reynolds, D., Bidlack, J. (1980). Stertospecific 3H-nlcotine

binding to intact and solubilized rat brain membranes and evidence for

Its noncholinergic nature. Life Sciences, 27, 1307-131A.

Annett, M. Implications of the right shift theory for Individual differences

in lateraliry. This volume.

Ashton, H. & Stepney, R. (1982). Smoking: Psychology and Pharmacology.

London, Tavistock Publ.

Birbaumer, N. (1981) Zur Psychologie des Rauchens. Forschungsbericht an der

Universität Tubingen, University of Tubingen,

bindman, L. & Lippold, 0. (1981). The Neurophysiology of the Cerebral

Cortex. London, U. Arnold.

Elbert, T. (1985). Externally and self-induced CNV-patrerns of the brain

hemispheres - a sign of task-specific preparation, Human Neurobiology

(in press).

Gonzales, M. & Harris, M. (1980). Effects of cigarette smoking on recall

and categorisation of written material. Perceptual and Motor Skills,

50, 407-410.

. -w .■■■ ->- -■■ -• —•■■'J
195

Lutzenberger, W., Elbert, T., Rorkstroh, B., BIrbaumcr, N. (1085).

Asymraetry of brain potentials related to sensorimotor tasks.

International Journal of Psychophysiology, 2, 28-29.

Mangan, G. (1982). The effects of cigarette smoking on vigilance

performance. Journal of General Psychology, IOC, 77-83.

Mangan, G. & Golding, J. (1973). An 'enhancement' model of smoking

maintenance? In: R.E. Thornton (Ed). Smoking Behaviour: Phypiologi:al

and Psychological Influences. Edinburgh, Churchill Livingstone, 131-

1A7.

Oldfield, R. (1971). The assessment and analysis of handedness: The

Edinburgh Inventory. Neuropsychologia, 9^, 97-113.

Phillis, J. (1970). The Pharmacology of Synapses. Oxford, Pergamon Press,

Rockstroh, B., Elbert, T., Birbauraer, N., Lutzenbergtr, W. (1982). Slow

Brain Potentials and Behaviour. Baltimore, Urban & Schwarzenherg.

Rockstroh, B. (1986). Operant control of slow brain potentials. In: J.

Hlngtgen, D. Hellharamer & G. Huppman (Eds.) Advanced Design Methods in

Psychobiology, Toronto, Hogrefe (in press).

Russell, M., Peto, J., Patel, U. (1974). The classification of smoking by a

factorial structure of motives. Journal of the Rcyal Statistical

Society, 137. 313-3A6.

Singh, M. M., Warburton, D.M., Lai, H. Central Cholinergic Mechanisms and

Adaptive Dysfunctions. New York, Plenum Press.

Wesnes, K. & Warburton, D. (1978). The effects of cigarette smoking and

nicotine tablets upon human attention. In: R.E. Thornton (Ed.) Smoking

Behaviour: Physiological and Psychological Influences. Edinburgh,

Churchill Livingstone, 1978, 131-147.

Williams, A. (1980). Effect of cigarette smoking on immediate memory and

performance in different kinds of smokers. British Journal of

Psychology, 71. 83-90.

Witelson, S. Individual differences in anatomical asymmetry. (This volume).

M

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196

INTERVAL HISTOGRAM ANALYSIS OF EEG HEMISPHERIC ACTIVITY IN SCHIZOPHRENIA

Antonio E. Puente and *Lelon J. Peacock

Department of Psychology

University of North Carolina

at Wilmington,

North Carolina, 28403, U.S.A.

•Department of Psychology

University of Georgia

Athens,

Georgia 30602, U.S.A.

While research into the psychophysiological correlates of maladaptlve

behavior has expanded during recent years, the Investigation of the

hemispheric processes related to psychopathology has experienced

unprecedented growth during the last f w years (e.g., Flor-Henry, 1979).

One particular branch of this type of hemlspherlcity research which has

received considerable attention and yielded results of heuristic value has

been the study of hemispheric activity In schizophrenics, see Flor-Henry,

Koles & Reddon (this volume); Flor-Henry & Koles (198A); Newlin, Carpenter

and Golden (1981) and Walker, Hoppes and Emory (1981) for comprehensive

reviews on this subject.

Within this general area we have developed a special Interest in the

electrophyslological (versus behavioral) asymmetries often observed In

schizophrenics. While the literature generally provides strong support for

left hemisphere abnormality, theories such as those exposed by Flor-Henry

(1979) and Gur (1979), numerous disparities between studies are apparent.

Most often, these disparities have been accounted for by the revision of

existing theories (e.g.. Walker & McGuire, 1982). Possibly a sounder

approach to accounting for these discrepancies would be to examine

methodological issues, rather than theoretical ones. Indeed, if

cethodologlca1problems would account for the varied results reported in the

literature, then the validity of existing theories would, in turn, be highly

questionable.

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While one could raise numerous methodological questions, one which has

largely been ignored has been the measurement of dependent variables. It is

not unusual for Investigators using electroencephalographic (EEG) measures

to use different electrode placements, filtering systems, and methods of

analyses. While spectral or frequency analysis has been the most widely

accepted method of EEG analysis, it is possible numerous statistical

assumptions are typically violated when using this approach. Central to the

assumptions underlying frequency methods of analysl': Is that the EEG wave is

a periodic, unchanging variable (Burch, 1959). This assumption becomes

especially critical since most Investigators (due to the large amount of

data obtained in EEG studies) tend to sample EEG for several seconds and

then generalize to the entire period from which the sample was taken

(usually minutes). In this study, we were Interested in examining the

hemispheric activation of schizophrenics using standard experimental

paradigms (e.g., Galln & Ornstein, 1972) but analyzing the ELG from a time

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Table 1. Mean Demographic Variables by Group

Group

Brain-damaged Non-Brain-Damaged Affective

Variable Schizophrenic Schizophrenic Disorders

Age ^»6.2 30.2 34.6

Year of Onset 31.5 21.4 29.3

Number of 1.7 5.0 2.3

Hospltallzatlons

Current Length 1163.1 113.7 57.5

of Hospltallzatlon

(In days)

rather than a frequency domain. Thus, the assumption of periodicity of the

EEC would not be violated, In this technique.

METHOD

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Subjects

From the In-patient population of a 1,200 bed state-supported

psychiatric hospital, 57 volunteers participated in this study. To be

included in the study patients had to be 18 years of age, have good

corrected or uncorrected vision, be right-handed by report and observation,

and had to read, comprehend, and sign an informed consent form. Additional

biographical information is contained in Table I.

From the pool of 57 subjects, three groups of 19 participants were

formed. The first group was composed of schizophrenics without brain damage

while a second group was composed of schizophrenics with brain damage.

Diagnosis of schizophrenics with brain damage was ascertained using a

standard diagnostic manual (DSM III) (American Psychiatric Association,

1980). Diagnoses were made independently by psychiatrists and psychologists

using the history as well as the results of a clinical interview, the Shearn

and Whitaker (1969) schizophrenic symptom checklist and the Whitaker Index

of Schizophrenic Thinking (1973). The results of the scores are shown in

Table 2. Brain lesions were determined by history of diffuse brain

pathology as documented by medical examination and laboratory tests (e.g.,

CAT Scan) as well as by the Luria-Nebraska Neuropsychological Battery

(Golden, himmeke & Purlsh, 1978). A third group of affective disorders was

included as a reference-control for the first two groups. Diagnoses were

determined in the same manner as schlzopurenia but using the criteria

outlined in the DSM-III for affective disorders.

Experimental Procedure

Each subject participated in psychological and electroencepiialographic

(EEG) testing. Odd numbered subjects (e.g., 1, 3, 5, . . .) participated in

the EEG part of the test in the morning and the psychological testing in the

afternoon. Even numbered subjects (e.g., 2, 4,6,.. .) did the reverse.

Morning testing began at 9:00 am and was completed by 11:00 am while

afternoon testing began at 1:00 pm and ended by 3:00 pm.

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Table 2.

Test

WIST;

LNNB;

Mean WIST and LNNB Scores by Gr oup

Group

Bra n-Oamaged Non--Brain-Damaged Affective

Scale Schizophrenic Schizophrenic Disorder

Similarities 5.9 8.5 2.A**

Word Fairs 2.7 3.A 1.3

New Inventions 3.1 3.1 3.4

Time 15.0 19.8 15.10

Index 26.7 34.8 22.2

14.2**

6.6*

8.9*

10.0

10.4*

15.2*

7.2*

6.5

8.4*

13.3*

30.0

15.7

5.4

6.3

* £ < .05

** 2 < .01

Variables Measured.

Neuroleptic dosages were converted to chlopromazine equivalents

according to the method suggested by Davis (1976). Dosages were altered

during the course of the study. These conversions are found in Table 3.

Motor 40.3

Rhythm 12.0

Tactile 13.5

Visual 15.1

Receptive Speech 18.0

Expressive Speech 26.3

Writing 12.2

Reading 9.3

Mathematics 17.8

Memory 18.4

Intellectual 38.5

Pathognomic 26.0

Left Hemisphere 11.8

Right Hemisphere 1A.8

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Table 3. Chlorproraazlne Equivalents (CPZE) by Groups •

CPZEmg ^M

Group Mean SD Range ""iviv

Brain-Damaged Schizophrenic

Non-prain-Damaged Schizophrenic

Affective Disorder

Mean SD Range

378.95 306.10 0-1200

1628.95 2091.00 0-7500

531.59 656.85 0-2250

t

The EEG was recorded from the 0. and Oj sites referenced to respective

ear-lobes (10-20 system) using a Grass Model 16 EEG. Signals were recorded

graphically (for visual inspection) and on magnetic tape via an Ampex FM

Recorder (for statistical analysis). Data from the tape was digitized using

a PDP 8 by an individual unaware of group composition using the period '

analysis technique of Sharp, Smith and Surwillo (1975). Data was then coded Js'^'s/

"blind" by another technician to disc via an Apple II Plus. "V.yi

'.WO The half-wave period was obtained using two manipulations. First,

noise was subtracted using averaging of a specific number of sample waves.

In addition, the peaks and troughs of a particular wave were selected

relative to its opposite using a combination of criterion amplitude •"."Vv'

(measured in V) and criterion duration (in msec). Once a half- -""'"v"

wave had been selected, it was dumped into one of 250 possible bins, each "NI'-'lj

having a duration of 1 msec. For the purposes of this study, 20 five msec

bins were constructed to cover the entire spectrum of duration extending :'- "'*

from 0 to 100 msec. A total of 50 half-wave were analyzed half way through

the testing period for each period of the EEG testing.

There were five separate Test periods (each three minute long and

with the subject sitting facing away from the polygraph operator and towards

a wall approximately six feet in front of the individual). During the

first Test period, the participant sat quietly with eyes open while a

resting baseline was obtained. A simple eye exercise involving fixating c

a black circle and on a black square as well as performing a series of

sequential eye movements followed. The next two Test periods were counterbalanced. For odd-numbered subjects, a visuo-spatial task involving the ^'-

solution of both "easy" and "hard" (as determined by a pilot study with

clinical subjects) problems from the Minnesota Paper Form Board Test

followed the eye exercise. For even-numbered subjects, a cask involving ' •!'-'/']

solving one «nd two digit (i.e., "easy" and "hard" as determined in a pilot

study) multiplication problems followed the eye exercise. During

presentation of the stimuli, the subjects were instructed to solve the

respective problems In their head and that, after presentation of all the

stimuli the subject would have the opportunity to provide the Experimenter

with the solutions. (Indeed after completion of all problems, the polygraph

was turned off and each stimulus was presented for five seconds once more

and the verbal responses were then recorded). After the verbal reports,

subjects were then presented with the alternate set of tasks; that is, for

odd numbered subjects, the multiplication problems and the even numbered

subjects, the geometric problems.

RESULTS ^

Two main sets of analyses were performed on the half-wave EEG data,

using the statistical package developed by Steinmetz, Romano and Patterson

(1981) on an Apple lie.
200 ÄW

The first set of analyses entailed examining within subject variables.

Histograms were constructed for each subject, across Test periods and ^•"^'^

hemispheres, and were grouped according to clinical diagnosis. The grouped 'Vv«/

histograms were analyzed by means of correlated t-tests from Test period to -'"^^

Test period as well as within Test periods with respect to laterality. ^V^'v

Thus, three sets of t-tests wert performed, one for each group. In order to .•.'->.

determine whether changes occurred in the last two Test periods relative to

the baseline Test period and whether hemispheric measures differed (within

Test periods). Regardless of the fact that a total of 30 t-tests were

performed, no significant differences were observed. The lack of

significance appears to be due to the wide dispersion of data within the

histograms.

The second set of analyses employed the dominant Interval recorded.

Vhus, instead of concentrating on the entire frequency distribution this set

of analyses focused only on the EEG period during which t'me most waves were

observed. An 3 x 2 analysis of variance, split-plot design was ased. The

design consisted of three between groups variables (clinical diagnosis) and

two within group variables (hemispheres). In total, three 3x2 ANOVAs were

performed, one from each major Test period of the experiment.

In Test period I, or "baseline", no significant Interaction or main VTJSJSI

effects for group was noted. However, a main effect for hemisphere was '"Ov'C^'

observed (F - 14.59; £ < .01). The means indicate that there is

preponderance of right hemisphere activity for slower EEG periods (mean

24. 31 msec) while faster intervals were observed in the left hemisphere

(mean 18.16 msec). For the geometric design Test period, a main effect of

hemispheres was noted (F 22.76; £ < .01). A highly similar pattern to

"baseline" was noted with regards to slow and fast activity across . "S"N

Hemispheres. The interaction indicated that this main effect appears to be

due to the relatively slow right hemisphere (especially in brain-damaged

schizophrrnics) activity with the relatively fast duration-periods for the

left noted for the two schizophrenic groups (especially the brain-damaged "v'"^'

sample). During the last Test period, or the multiplication problem task, yjy

only a main effect for Hemisphere was noted (F - 30.42;£ < .01). In

general, the same pattern of right versus left hemisphere activity seen in

the geometric Test period was observed with the largest left-rig'.it

. f.v:

v.v, difference being noted for the brain-damaged schizophrenic group. The means /v' '.v for each group across Test periods and Hemispheres are found in Table A. v\r"*.

DISCUSSION 1/X,*

The results indicate the hemispheric dysfunction in schizophrenia is a

complicated phenomenon tempered by numerous variables. As Flor-Henry (1983)

has suggested, hemispheric dysfunction is not a static but a dynamic

situation. '^v-'s

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Across the three Test periods, results indicate that faster EEG '»"'-a*"«^

activity was observed for all three groups in the left hemisphere. •

Conversely, slower activity was noted in the non-dominant hemisphere. 's'«,*//1

Baseline EEG indicated that largest hemispheric difference were found for KVMV

the Affective group. Indeed, the non-brain damaged Schizophrenic group

exhibited relatively similar activity for both hemispheres. Large leftright differences were observed in the geometric task Test period, this was

especially true for the Brain-damaged sample. While slowing of right

hemisphere activity was noted for the Brain-damaged Schizophrenic sample, .N'.NJSI^

slight increases in activity were noted for the two other groups. With IvvWS

regards to left hemisphere activation during this task, both Schizophrenic WW?

groups Increased activity (especially the Non-damaged sample). S"""^V-C

Interestingly, the relatively large hemispheric differences noted for the .C^A''-'!

affective disorders during the baseline Test period were eradicated during

Xc&^*tt&^&<*^ . j".

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Table A. Group

201

x Hemisphere x Group Interval (Half-wave) EEC Means

Group

Brain-Damaged Non-Brain-Damaged Affective

Test Hemisphere Schizophi

Period

Left 16.6

Baseline Right 22.1

"resting"

Difference 5.5

Left 15.5

Geometric Right 28.0

Difference 12.5

Left 16.4

Multi- Right 30.5

plication

Difference 14.1

21.4

25.3

3.9

16.7

2UU

9.7

15.8

24.9

9.1

16.4 18.1

25.6 24.3

9.2 6.2

18.3 16.8

21.3 23.6

3.0 6.8

15.9 16.0

24.6 26.7

9.0 10.7

äMw

PPM

the geometric Test period. During the final Test period, similar

hemispheric differences were noted between the non-brain-damaged

schizophrenic and affective groups. Nevertheless, relative to the baseline

Test period, the former group exhibited not only the fastest EEG activity

but had a large increase In the activity generally. While slowing of the

right hemisphere was not obser'^d in the Non-brain-damaged Schizophrenic and

Affective groups, significant decreases were noted for the Brain-damaged

Schizophrenic sample.

Several conclusions can be reached. Foremost, period analyses of

hemispheric EEG activity is a robust measure when considering group and task

comparison. While wide variability of the data complicated analysis of

frequency means, "dominant-wave" analysis provided a fruitful measure of EEG

activity. Secondly, the use of brain-damaged schizophrenics as well as

patients with affective disorders appear to be useful in defining the

boundaries for the limits of laterality abnormalities in putatively CNSintact schizophrenics. Indeed, the data derived from the subjects alone

provide useful information into the role of brain dysfunction in

schizophrenia as well as of affective pathology in hemlsphericity issues.

Finally, hemispheric differences in these groups appear to exist In response

to task demands and, to a lesser degree, at rest.

Superficially these findings support those of Gur (1979) as well as

interpretations of Newlin, Carpenter and Golden (1981), and Walker «nd

McGuire (1982). While dominant hemisphere overactivation was noted, the

data obtained indicate that sweeping generalizations about overactivation

must be tempered by numerous factors including baseline-task Test period

differences. Additionally, while changes were noted for left hemisphere

activation care should be taken in considering right hemisphere activation

(seen in the non-damaged schizophrenic group in response to geometric

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designs) and slowing (seen in the brain dauaged-schlrophrenlc group In 202

response to both tasks).

More definitive Interpretations await replications and consideration of

several limitations. Primarily, while dispersion of histogram data

complicated the analysis of means, that in itself may be worthwhile to

examine. As Surwillo (1978) indicatec, variability (rather than

central tendency) may be a more important factor in period analysis of the

EEC. Secondly, "change score" analysis may have resulted in mor. accurate

Interpretation of the data. Differences were noted during the baseline Test

period and while not significant, they do appear large enough potentially to

mask group differences observed during task activity.

Period analysis provides a less restrictive approach to EEC

interpretation of hemispheric activity. With further development, a more

comprehensive interpretation of psychopathology and laterality should emerge

as both frequency and time approaches to EEC analysis are considered.

»fi»^

REFERENCES

American Psychiatric Association (1980). Diagnostic and statistical manual

(3rd ed.). Washington, D.C.: American Psychiatric Association.

Burch, N. R. (1959). Automatic analysis of the electroencephalogram: A

review and classification of systems. Electroencephalography and

Clinical Neurophysiology, 11, 827-829.

Galin, D. & Ornstein, R. (1972). Lateral specialization of cognitive mode:

An EEC study. Psychophysiology, 9, 412-418.

Davis, J. (1976). Quantitative doses ano costs of anti-psychotic

medication. Archives of General Psychiatry, 33, 858-861.

Flor-Henry, P. (1979). Laterality, shifts of cerebral dominance,

sinistrallty and psychosis. In J. Gruzelier and P. Flor-Henry (Eds.)

Hemispheric Asymmetries of Function in Psychopathology. Amsterdam:

Elaevier/North Holland Biomedical Press, 3-19.

Flor-Henry, P. and Koles, Z.J. (198A). Statistical quantitative EEC studies

of depression, mania, schizophrenia and normals. Biological

Psychology, 19, 257-279.

Golden, C, Hammeke, T. & Purisch, A. (1978). Diagnostic validity of a

standardized battery derived from Luria's Neuropsychological test.

Journal of Consulting and Clinical Psychology, 46, 1258-1265.

Gur, R. E. (1979). Cognitive concomitants of hemispheric dysfunction in

schizophrenia. Archives of General Psychiatry, 36, 269-274.

Newlin, D., Carpenter, B. & Golden, C. (1981). Hemispheric asymmetries in

schizophrenia, Biological Psychiatry, 16, 561-582.

Sharp, F., Smith, G. & Surwillo, W. (1975). Period analysis of the

electroencephalograms of EEC half-wave durations. Psychophysiology, 12,

471-475.

Shearn, C. & Whitaker, C. (1969). Selecting subjects In studies of

schizophrenia. Schizophrenia, l_, 4-8.

Steinmetz, J., Romano, A. & Patterson, M. (1981). Statistical program for

the Apple II microcomputer. Behavior Research Methods £

Instrumentation, 13, 702.

Surwillo, W. (1978). Interval histogram analysis of period of the

electroencephalogram in relation to age during growth and development

of normal children. Psychophysiology, 12, 506-510.

Walker, E., Hoppes, E. & Emory, E. (1981). A reinterpret at ion of

hemispheric dysfunction in schizophrenia. The Journal of Nervous and

Mental Disease, 169, 378-380.

Walker, E., McGuire, A. (1982). Intra and Interhemispheric information

processing in schizophrenia. Psychological Bulletin, 92, 707-725.

Whitaker, L. (1973). The Whitaker Index of Schizophrenic Thinking.

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203

Los Angeles: Western Publishing Co.

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205

AGE AND SEX DIFFERENCES IN LATERAL ASYMMETRIES TO VISUAL AND TACTILE STIMULI

Andrew W. Young, Pamela J. Bion and Kathryn H. McWeeny

Psychology Department

Lancaster University

Lancaster, LAI AYF

England

INTRODUCTION

We have been studying the development of right hemisphere abilities in

normal children for a number of years. We began this research with the

strong expectation that right hemisphere superiorities would change across

age, and an equally strong distaste for the idea of sex differences in

cerebral organisation. Our findings have consistently tended to undermine

these preconceptions.

We will describe three series of experiments. The first series is

concerned with age and sex differences in recognising faces, the second

series with age and sex differences in lateral asymmetries obtained to

complex visual stimuli, and the third series with age and sex differences in

lateral asymmetries obtained to tactile stimuli. Most of the studies of

complex visual and tactile stimuli that we will describe involve the

enumeration of collections of dots.

Face recognition and dot enumeration are tasks which had already been

found to be associated with right ht»! ;?here superiority in both the normal

and the clinical literature when we ^«gan the research (De Renzi and

Spinnler, 1966; Kimura, 1966; Warrl-jtjn and James, 1967a, 1967b;

Rizzolatti, Umilta and Berlucchi, l97l; Billiard, 1973). We chose to

concentrate on them in order to look at abilities acquired at different

times during the first years of life. The abilities involved in face

recognition are present in early Infancy (Schaffer, 1971; Young, 1985) and

hence are well established in the age range most suitable for investigation

using the techniques we had developed (five years tj adult). In contrast,

although infants are now known to be sensitive to some aspects of number

(Starkey and Cooper, 1980), explicit enumeration is not learnt until an age

much closer to the boftom end of the range we could use (Klahr and Wallace,

1973: Schaeffer, Eggleston and Scott, 197A).

EXPERIMENTS

All of our experiments involved right-handed subjects. Children's

handedness was determined by a combination of hand used in writing,

teacher's report, and self report.

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The methods used in the experiments involve lateral presentation of

stimuli in the left or right visual hemifields (LVF or RVF), and to the left

and right hands. The basic principles involved in such studies have been

reviewed by Young (1982a) and Beaumont (1983), and their application to

developmental studies is discussed by Witelson (1977), Beaumont (1982), and

Young (1982b, 1983, 1985).

A. Face recognition

Experiment 1; Recognition of small sets of faces by children

(Young and Bion, 1980, Experiment 1) 1

Rationale: In this experiment, we studied differences in ability to

recognise the members oT small sets of faces of unfamiliar people presented

in the LVF or in the RVF. Both upright and inverted faces were used as

stimuli. Previous research (Leehey, Carey, Diamond and Cahn, 1978) had

shown that the LVF superiority for face recognition is reduced by inversion

of stimulus faces. This seemed a useful technique because it can eliminate

the possibility that any LVF superiority obtained only to upright faces

derives solely from the complexity of faces as visual stimuli, since faces

are equally complex whether upright or inverted.

Method: Faces were bilaterally presented (one in the LVF, one in the

RVF) for 150 ms; the task involved identifying the LVF face and the RVF face

from a display of four faces. The faces used were all of people who were

not known by the children studied. Each face subtended a horizontal visual

angle of 3

o

20', and the centres of the LVF and RVF faces were offset from

the midline of each stimulus card by 3

0

A8'. During the course of the

experiment only one set of four faces was used for each subject, but for

half the subjects these faces were easy to discriminate and for the other

half they were difficult to discriminate. The orientation of the presented

stimulus faces and response cards was upright for half the subjects and

inverted for the other half.

The presence of central fixation before each stimulus presentation was

determined by monitoring the subject's eyes with a video camera; this is a

simple and accurate technique (Young, 1982a). Order of report of the

bilateral faces was counterbalanced by cuing the face to be reported first.

Sixteen right-handed boys and sixteen right-handed girls of each of the

ages seven, ten and thirteen years acted as subjects. Data for each subject

consisted of LVF and RVF accuracy scores out of a possible maximum of 40

correct trials. Each subject was given practice trials with appropriate

stimuli before the experimental trials commenced.

Results: Proportions of upright and inverted faces correctly

identified from the LVF and RVF by children of each age are shown in Fig. 1.

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A five-factor analysis of variance of the accuracy scores was carried

out, to determine the effects of Age, Sex, Orientation (upright or inverted

stimuli). Difficulty (use of the easy or difficult to discriminate set of

faces), and Visual hemifield (repeated measure).

The principal findings were that faces were more accurately identified

from the LVF than from the RVF (Visual hemifield, F - 29.13, d.f.1,72,

p < 0.001), but this result held only for the upright stimuli (Orientation x

Visual hemifield, F-16.27, d.f.1,72, p < 0.001). There were also main

effects of Age (F-13.09, d.f.2,72, p < 0.001), Orientation

(F-26.18, d.f.1,72, p < 0.001), and Difficulty (F-34.67, d.f.1,72,

p < 0.001). No other statistically significant effects were found.

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FACE RECOGNITION:

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from the LVF and RVF by right-handed seven-, ten- and thirteenyear-old children in Experiment I.

The results of the experiment thus showed LVF superiority to upright

but not to inverted faces, with no change in the size of this LVF

superiority across age. The absence of visual hemifield differences in the

case of inverted faces shows that the LVF superiority to upright faces

derives from a right hemisphere superiority for face processing per se,

rather than for any complex visual stimulus. No evidence was found to

Indicate that this right hemisphere superiority changes in any way across

the age range studied. LVF superiority for upright faces was found for both

boy? and girls.

Experiment 2: Recognition of larger sets of faces by children

(Young and Bion, 1980, Experiment 2)

Rationale: In this experiment a larger pool of stimulus faces was used

than in Experiment 1. This gives subjects less opportunity to learn the

faces that can appear on each trial.

Method: The design and procedure were the same as for Experiment 1,

except that we increased the number of stimulus faces by changing the set of

four possible faces at regular intervals. This was done after blocks of

four trials throughovc the experiment, so that subjects now encountered a

total of forty different faces instead of the total of four faces seen by

each subject in Experiment 1. Sixteen right-handed boys and sixteen righthanded girls of each of the ages seven, ten and thirteen years acted as

subjects.

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Results: Proportions of upright and inverted faces correctly identified

from the LVF and RVF by boys and girls of each age are shown in Fig. 2.

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A four-factor analysis of variance of the accuracy scores was carried

out, to determine the effects of Age, Sex, Orientation (upright or

inverted), and Visual hemifield (repeated measure).

The principal findings were that faces were more accurately identified

from the LVF only by boys, with no visual hemifield difference in girls (Sex

x Visual hemifield, F-A.83, d.f.l,8A, p < 0.05); this was again only the

case for upright faces (Sex x Orientation x Visual hemifield, F-A.23,

d.f.1,84, p < 0.05). There was also a main effect of Age (F-29.95,

d.f.2,84, p < 0.001), and an Age x Orientation Interaction (F-18.98,

d.f.2,84, p < 0.001) In which only older children performed better to

upright than inverted faces. No other statistically significant effects

were found.

Results of Experiment 2 showed LVF superiority to upright faces for

boys only, with no change in the degree of LVF superiority across age. The

principal difference between these findings and those of Experiment 1 thus

lies in the absence of any LVF superiority for girls In Experiment 2. This

unexpected sex difference was stable across the range of ages studied.

FACE RECOGNITION;

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from the LVF and RVF by right-handed seven-, ten- and thirteenyear-old boys and girls in Experiment 2.

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Experiment 3; Effect of different stimuli to trials ratios on adults

(Young and Bion, 1983, Experiment 1)

Rationale: Experiment 2 of the pr«Lent series had shown that

increasing the number of faces used in the experiment can eliminate LVF

superiority for female subjects. We decided to explore the nature of this

sex difference by increasing the number of stimuli still further (to the

maximum possible), to see whether this would have any effect on the

performance of male subjects. The experiment was carried out with adult

subjects in order to check that the sex difference found for children in

Experiments 1 and 2 would also be found in adults.

Method: This experiment used adult subjects, and upright faces only.

The number of stimulus faces was systematically increased across the levels

used in Experiments 1 and 2 to a third level at which a new set of faces was

introduced on every experimental trial. Thus the ratio of stimuli to trials

was manipulated across three experimental conditions (low, medium or high

ratio of stimuli to trials); these conditions were given to subjects in a

counterbalanced order.

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Twenty-four right-handed male and twenty-four right-handed female

adults acted as subjects, with accuracy scores out of a possible maximum of

24 correct being recorded for LVF and for RVF performance in each

experimental condition. Other features of design and procedure followed

those used in Experiments 1 and 2.

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from the RVF by male and female subjects in each experimental condition are

shown in Fig. 3.

FACE RECOGNITION:

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A three-factor analysis of variance of the accuracy scores was carried

out, to determine the effects of Sex, Visual hemifleld (repeated measure),

and experimental Condition (repeated measure). There was an overall LVF

superiority (Visual hemifleld, F-32.12, d.f.1,46, p < 0.001), and a Visual

hemifield x Condition interaction (F-9.64, d.f.2,92, p < 0.001). The

principal finding, however, was the Sex x Visual hemifield x Condition

interaction (F-6.58, d.f.2,92, p < 0.01), in which LVF superiority was lost

for male subjects with the high ratio of stimuli to trials but for female

subjects with the medium and high ratios of stimuli to trials. No other

statistically significant effects were found.

Results thus showed LVF superiority for both males and females with

small numbers of stimulus faces (as in Experiment 1), LVF superiority for

males only with an increased number of stinulus faces (as In Experiment 2),

and no visual hemifield differences for male or female srbjects with the

large set of faces (high ratio of stimuli to trials). This demonstrates

that the finding of a sex difference made with children in Experiments 1 and

2 also holds in the adult range, and extends the finding by showing that sex

differences are only obtained at certain points along the continuum of

stimuli to trials ratios. Thus the S"x difference is clearly not due to

any absence of right hemisphere superiority in females, since right

hemisphere superiority can be either found or not found for both male and

female subjects according to the conditions used. It was also notable that

changes in the ratio of stimuli to trials affected LVF performance for both

male and female subjects, but had no effect on RVF performance.

B. Complex visual stimuli

Experiment 4; Enumeration of random dots by children

(Young and Bion, 1979)

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Rationale: The aim of this experiment was to explore visual hemifield

differences for dot enumeration in children with a technique approximating

to that used by Kimura (1966) and McGlone and Davidson (1973) with adult

subjects.

Method: Collections of 2-6 randomly arranged dots were presented in

the LVF or in the RVF to five, seven and eleven-year-old children, who were

asked to enumerate them as quickly and accurately as possible. Each

collection of dots fell within a circular area having a diameter subtending

a visual angle of 3

0

48', and the centres of the LVF and RVF collections were

offset by 5 4' from the midline of each stimulus card. Accuracy of LVF and

RVF performance out of a possible maximum of 20 correct trials per visual

hemifield and vocal reaction times (timed from stimulus onset) for correct

responses were recorded. Trials with central stimuli were also used to

control fixation on the argument that performance with central stimuli

should be equal to or better than both LVF and RVF performance if central

fixation Is occurring (Young and H. Ellis, 1976). Using this criterion,

groups of ten right-handed boys and ten right-handed girls at each of the

ages five, seven and eleven years were built up. Presentation times of

80 ms for each stimulus were used for seven and eleven-year-olds, and 100 ms

for five-year-olds. E^ch subject was given practice trials with appropriate

stimuli before the experimental trials commenced.

Results: Accuracies and vocal reaction times for correct responses by

boys and girls of each age are shown in Fig.4.

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A three-factor analysis of variance of the accuracy scores was carried

out, to determine the effects of Age, Sex and Visual hemifield (repeated

measure). A Sex x Visual hemifield interaction was found (F-7.45, d.f.1,54,

p < 0.01), with only boys showing greater LVF accuracy. There were also

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collections of randomly arranged dots by right-handed boys and

girls aged five, seven and eleven years in Experiment A.

main effects of Age (F-5.66, d.f.2,54, p < 0.05) and of visual hemifield

(F-5.30, d.f.l,5A, p < 0.05). No other statistically significant effects

were found.

A three-factor analysis of variance of the vocal reaction times to

correct responses was also carried out. The only statistically significant

effect involved the faster RT's to LVF stimuli (Visual hemifield,

F-5.63, d.f.1,54, p < 0.05).

In this experiment, then, LVF superiority for accuracy was found for

boys only. This finding of tn LVF accuracy superiority for right-handed

male subjects only Is consistent with a previous accuracy study using adult

subjects reported by McGlone and Davidson (1973). However, vocal reaction

times for correct responses in Experiment 4 were faster to LVF presentations

for both boys and girls. No changes were found in the size of visual

hemifield differences across age.

Experiment 5: Enumeration of random dots by adults

Rationale: Although the vocal reaction times recorded in Experiment 4

produced an interesting pattern of findings, they were collected in an

experiment that was primarily intended to examine accuracy. We decided to

look more carefully at vocal RT's in a study designed explicitly for this

purpose; this study used adult subjects.

Method: Collections of 1-4 randomly arranged dots were presented In

the LVF or in the RVF to adults, who were asked to enumerate them as quickly

and accurately as possible. Trials on which errors occurred were replaced

later In the series, until 20 correct LVF (5 with each size of collection)

and 20 correct RVF reaction times had been achieved. Thirty-six righthanded adults acted as subjects, with six males and six females being run at

each of the stimulus presentation times 40 ms, 80 ms and 150 ms. Central

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fixation before each trial was checked by monitoring the subject's eyes 212

using a video camera. Stimulus visual angles were as for Experiment 4.

Each subject was given practice trials with appropriate stimuli before the

experimental trials coraraenced.

Results; Vocal reaction times for enumeration of LVF and RVF dot

collations by male and female subjects are shown in Fig. 5.

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A three-factor analysis of variance of the vocal RT's was carried out,

to determine the effects of Sex, stimulus presentation Time (40 ms, 80 ms,

or 150 ms), and Visual hemifield (repeated measure). Although the number of

items to be enumerated is also plotted in Fig.5, this was not Included as a

factor in the analysis because of the small number of trials (5) in each

"ell of the design at this level. The only statistically significant effect

was the Sex x Visual hemifield interaction (F-8.84, d.f.1,30, p < 0.01),

with male subjects showing faster responses to RVF than LVF stimuli and

female subjects showing faster responses to LVF than RVF stimuli.

A three-factor analysis of variance of the number of trials that needed

to be repeated showed that more trials had to be repeated at the shorter

presentation times (Time, F-8.96, d.f.2,30, p < 0.01). With 40 ms

presentations 182 of trials had to be repeated, with 80ms presentations 152,

and with 150ms presentations 72. There was also a main effect of Visual

hemifield (F»5.74, d.f.1,30, p < 0.05), in which more RVF than LVF trials

needed to be repeated. The main finding, however, was a Sex x Visual

hemifield interaction (FM0.69, d.f.1,30, p < 0.01), which showed that only

male subjects needed more RVF than LVF trials to be repeated. No other

statistically significant effects were found.

Results of this experiment show faster vocal RT's for LVF stimuli in

females, but faster vocal RT's to RVF stimuli in males. However, in order

to achieve an equal number of correct RT's in each cell of the design more

RVF than LVF trials had to be repeated for male subjects. It Is thus clear

that despite the instruction to be both fast and accurate, male subjects

trade RVF accuracy against speed (though we do not mean to imply that they

do this consciously and deliberately). The need to repeat more RVF trials

for male subjects parallels the LVF accuracy superiority seen for males In

Experiment 5, but that experiment did not reveal the extent of the trade-off

of accuracy against speed.

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of randomly arranged dots by male and female right-handed adult

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Experiment 6; Enumeration of linear dots by children

Rationale: This experiment was Intended to explore the possibility

that the sex difference found in the accuracy data in Experiment 4 (LVF

accuracy superiority for boys only) was linked to the particular

quantification strategies adopted. Thus we arranged the dots in straight

lines; this makes it difficult to use strategies based on grouping the dots

into identifiable visual pattern configurations before enumerating them.

Method: The general design and procedure were the same as for

Experiment 4, but the collections of 2-6 dots were arranged along regularly

spaced horizontal or vertical straight lines. Presentation times of 15C ms

were used with seven- and eleven-year-olds, and 200 ms with five-year-olds.

Results; accuracies and vocal reaction times for correct enumerations

by right-handed five, seven and eleven-year-old children are shown in Fig.

6. ottS]

A three-factor analysis of variance of the accuracy scores was carried

out, to determine the effects of Age, Sex, and Visual hemifield (repeated

measure). Older children were found to be more accurate (Age,

F"A.93, d.f.2,5A, p < 0.05), and this was especially true for girls (Age x

Sex, F-4.37, d.f.2,54, p < 0.05). No other statistically significant

effects were found. The main effect of Visual hemifield did not reach

statistical significance (F-2.73, d.f.1,54, p > 0.1).

A three-factor analysis of variance of the vocal reaction times to

correct responses was also carried out. Vocal RT's were faster to LVF

stimuli (Visual hemifield, F-15.31, d.f.1,54, p < 0.001), and vocal RT's

were also faster for older children (Age, F-10.99, d.f.2,54, p < 0.01). No

other statistically significant effects were found.

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RVF linear collections of dots by right-handed five-, seven- and

eleven-year-olds in Experiment 6.

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The principal aim of this experiment was to study accuracy differences

in the enumeration of LVF and RVF stimuli. However, no visual hemifield

differences in accuracy were found, but the experiment did reveal faster

vocal reaction times for LVK stimuli. There were no age differences in this

LVF superiority in vocal reaction time.

*i

Experiment 7: Enumeration of linear dots by adults

Rationale: This experiment was intended to explore the fastrr vocal

reaction times to LVF presentations of linear collections of dots found in

Experiment 6, using a design explicitly suited to this purpose.

Method; Collections of 2-A dots in regularly spaced horizontal or

vertical straight line arrangements were presented for 150ms In the LVF or

in the RVF. Adult subjects were asked to enumerate them as quickly and as

accurately as possible; trials on which errors occurred were replaced later

in the series. Twelve right-handed male and twelve right-handed female

adults acted as subjects. Other features of design and procedure were as

for Experiment 5.

•.'/- -

Results; Vocal reaction times for enumeration of linear arrangements

of dots presented in the LVF and in the RVF are shown in Fig. 7.

A two-factor analysis of variance of the vocal reaction times was

carried out, to determine the effects of Sex and Visual hemifield (repeated

measure). Although the number of items to be enumerated is also plotted in

Figure 7, this was not included as a factor because oi the small number of

trials (3) in each cell of the design at this level. Reaction times were

found to be faster to stimuli presented in the LVF (Visual hemifield,

F-4.62, d.f.1,22, p < 0.05). No other statistically significant effects

were found.

A two-factor analysis of variance of the number of trials needing to be

repeated to obtain enough correct vocal RT's was also carried out. No

statistically significant effects were found, but a tendency for more RVF

trials to need to be repeated approached significance (Visual hemifield,

F-3.14, d.f.1,22, 0.1 > p > 0.05). For LVF trials U7. had to be repeated,

and for RVF trials 9Z.

:£

The findings of Experiment 7 thus show faster enumeration of stimuli

presented in the LVF by both male and female adult subjects. This shows

that the findings obtained from children in Experiment 6 also hold for

adults, and that they hold when an experimental design explicitly suited to

the investigation of vocal reaction times is used.

DOT ENUMERATION

LINEAR ARRANGEMENTS

aoo

tr

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O 700 *- u

a u

5 ? 600

/y

.RVF

LVF

Fig.

2 3 4

NUMBEP OF ITEMS

7. Vocal reaction times for enumeration of LVF «nd RVF linear

collections of dots by right-handed adult subjects in

Experiment 7.

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C. Complex tactile stimuli

Experiment 8: Tactile enumeration of random dots

Rationale; This experiment examined differences between the left and

right hands in the tactile enumeration of collections of randomly arranged

raised dots. Adults and seven-year-old children were studied. The

technique used was adapted from one found to produce left hand superiorities

in right-handed male and female adults by Young and A. Ellis (1979). The

principal aim of the present experiment was thus to see whetner this finding

would also hold for children.

&fc"

Method: Right-handed people aged seven years or adult felt

collections of 2-4 raised dots with the middle fingers of their left or

right hands. There were ten male and ten female subjects of each age. The

dots were approximately 1.5 mm in diameter, and raised by 1 mm. They were

formed by pressing heavily on the back of a piece of card with a ball-point

pen. Each of the raised dots was located at random in one of the nine

positions In a 1.5 cm x 1.5 cm grid. Subjects felt the raised dots with

their hands placed out of their own sight behind a vertical black cloth

screen; a circular wooden surround was used to define the area within which

the raised dots might be found. The subject's task was to enumerate the

dots as accurately as possible. Trials on which errors occurred were

replaced later in the series, until eighteen correct left hand trials (six

with each size of collection) and eighteen correct right hand trials had

been achieved. Reaction times for correct enumerations were recorded with a

stopwatch.

Left hand and right hand trials were separated into a number of blocks

given in counterbalanced order. During left hand trials a large felt-tip

pen was grasped in the right hand, and during right hand trials the same pen

was grasped in the left hand. This was done to provide some degree of

bilateral tactile input (see Witelson, 1974). Each subject was given

practice trials with appropriate stimuli before the experimental trials

commenced.

^

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^

I

Results: Reaction times for correct tactile enumeration of random

arrangements of dots by right-handed seven-year-olds and adults using their

left or right hands are shown in Fig. 8.

TACTILE ENUMERATION;

RANDOM ARRANGEMENTS

14

•

_ \

10 1^

o

z

o

*v \RIGHT

X^ \HAND

o

Ui 10 LEFfVN

V) HAND \

7 VR OLD ADULT

AGE

N . S .

MA'

Fig. 8. Reaction times for correct left and right hand tactile

enumeration of randomly arranged raised dots by right-handed

seven-year-olds and adults in Experiment 8.

W

**Stett&*X^^ l-V^.»..^^s
»"^ » II " M " 1 " p - "." ".r "«-v rv'rvn\rm:

216

A three-factor analysis of variance of the reaction tiraes was carried

out, to determine the effects of Age, Sex, and use of the left or right Hand

(repeated measure). This showed faster reaction tiraes for the left Hand

(F-13.58, d.f.1,36, p < 0.001) and faster reaction times by adult subjects

(Age, F-25.92, d.f.l,36, p < 0.001). No other statistically significant

effects were found.

tf

>:;

A three-factor analysis of variance of the number of trials that needed

to be repeated showed that more trials needed repeating for the seven-yearolds (Age, F-6.99, d.f.1,36, p < 0.05). For seven-year-olds 18Z of trials

had to be repeated, and for adults 6%. No other statistically significant

effects were found.

»»I

The results of the experiment thus show that right-handed people were

faster at enumerating the randomly arranged raised dots when using their

left hands. There were no sex differences, and no accuracy differences

between left and right hands. No change in the size of the left hand

superiority was found across age.

Experiment 9; Tactile enumeration of linear dots

'•/•.•V/v1!

ZA*

Rationale; Young and A. Ellis (1979) found that left hand

superiorities for tactile enumeration arose to randomly arranged dots but

were eliminated when the dots were placed along regularly spaced straight

lines (which makes their potential spatial locations much more predictable

during tactile exploration). The aim of the present experiment was to see

whether this finding would also hold for children.

Method: Design and procedure were as for Experiment 8, but the

collections of dots were arranged along regularly spaced straight lines. .>:

Results: Reaction times for correct tactile enumeration of linear

arrangements of raised dots by seven-year-olds and adults using their left

or right hands are shown in Fig. 9.

A three-factor analysis of variance of the reaction times was carried

out, to determine the effects of Age, Sex, and use of the left or right Hand

(repeated measure). The only statistically significant effect was the

tendency of adults to be faster (Age, F-25.48, d.f.1,36, p < 0.001). A

similar analysis of the number of trials that needed to be repeated also

showed only.

TACTILE ENUMERATION

LINEAR ARRANGEMENTS

1*

« 12

o

z

O

UJ

CD

7 YROLD ADULT

AGE

Fig. 9. Reaction tiraes for correct left and ri^ht hand tactile

enumeration of linear dots by right-handed seven-year-olds and

adults in Experiment 9.

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tr v -' '.^ ,« w % >-. ' _F rm " w ^ ^. "

217

that f« »'er trials needed to be repeated for adults (Age, F*=13.59, d.f.1,36,

p < ü.r i). For seven-year-olds 8% of trials had to be repeated, and for

adults 4«. Thus no hand differences in RT or accuracy were found at either

age or for either sex in Experiment 9.

AJCli'

Experiments 8 and 9 confirm the findings made by Young and A. Ellis

(1979), who used a similar method with adult subjects, and show that the

results also hold for seven-year-old children.

-

% Ä

3öQ

Experiment 10; Tactile form matching

Rationale: Unlike our studies using visually presented stimuli

(Experiments 1-7), Experiments 8 and 9 had not found any sex differences.

However, we doubted that the absence of sex differences was due to the

tactile modality of presentation, because sex differences in the tactile

modality had previously been reported (e.g. Witelson, 1976). Witelson's

(1976) study used a tactile form matching task, and found left hand

superiority for boys only in the age range six to thirteen years.

Experiment 10 was thus intended to examine hand differences in tactile form

recognition in adults and children.

Method: Subjects were required to decide whether or not pairs of

plastic shapes were the same as or different from each other. The plastic

shapes were all 0.5 cm thick and had a surface area of 6 cm . They were

mounted on 10 x 13cm pieces of card. All of the shapes used are shown in

Figure 10. On each trial the subject first felt one of the shapes for 5

seconds, using her or his left or right hand. A second shape was then

presented to the same hand, and the subject had to decide as quickly and as

accurately as possible whether or not it was the same as the original shape.

Reaction times were timed from the presentation of the second shape.

Six right-handed males and six right-handed females of each of the ages

six-years-old and adult acted as subjects. Incorrectly answered trials were

repeated later in the series. Other features of design and procedure were

as for Experiments 8 and 9.

. •

Results: Reaction times for correct tactile form matching by male and

female six-year-olds and adults using their left or right hands are shown In

Fig. 11.

A three-factor analysis of variance of the reaction times was carried

out, to determine the effects of Age, Sex and use of the left or right Hand

ft ^

•' • '

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L ^]

Fig. 10. Shapes used for tactile form ratching in Experiment 10,

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o

u

w 2

218

TACTILE FORM MATCHING

MALES

6YR OLD ADULT

6

FEMALES

6YROLD ADULT

fc >•. K

AGE

Fig. 11. Reaction times for correct left and right hand tactile form

matching by male and female right-handed six-year-olds and

adults in Experiment 10.

(repeated measure). A Sex x Hand interaction (F-4.63, d.f.l,20,p < 0.05)

showed that left hand RT's were faster for male subjects only. There were

also main effects of Age (F»52.87, d.f.1,20, p < 0.001) and Hand (F-6.65,

d.f.1,20, p < 0.05). No other statistically significant effects were

found.

Vsl

- *. *. % J

Thus the left hand was faster for male subjects only with the tactile

form matching task used in Experiment 10. There was no change across age in

the size of the left hand superiority.

SUMMARY OF FINDINGS

• J .- •* i

• . •. *.

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• v V .^

1

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A. Face recognition (Experiments 1-3)

The demonstration of LVF superiority for upright faces was affected by

how well subjects got to know the faces used. With a small set of faces

(that were in consequence often repeated) LVF superiority was found for both

male and female subjects; with a large set of faces (and hence little

oppor:unity to learn them) no visual hemifield differences were obtained.

Females switched from LVF superiority to no visual hemifield difference at

an earlier point along the continuum of decreasing stimulus familiarity than

did males. No developmental changes in LVF superiority were found.

W

vv

B. Complex visual stimuli (Experiments A-7)

These experiments produced the most complicated pattern of findings.

It was possible to show LVF superiority In both male and female subjects,

but this was related bc.h to the type of stimulus arrangement (random or

linear dot collections) and the measure of performance adopted (accuracy or

vocal RT); males sometimes produced consistently fast but inaccurate RVF

responses. No developmental changes in LVF superiority were found.

C. Complex tactile stimuli (Experiments 8-10)

Left hand superiorities were found for both male and female subjects

in the enumeration of random collections of raised dots, with no hand

differences for collections of raised dots arranged in straight lines.

These findings replicate those jade by Young and A. Ellis (1979) with adult

subjects, and extend them to seven-year old children. The use of a form

recognition task (Experiment 10) led to a finding of left hand superiority

for male subjects only. No developmental changes in left hand superiority

were found.

• > •>"^,

'•-•-•-•

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219

IMPLICATIONS

We have not found any evidence of developmental changes in the size of

lateral asymmetries. Thus it would seem that the underlying cerebral

functional asymmetries do not change in the age range studied (five years to

adult). This conclusion holds regardless of whether we have studied

abilities at ages relatively close to or distant from those at which they

are first acquired. Our findings are in line with Chose of other studies of

lateral asymmetries at different ages, but we will not review these here

because they have already been extensively examined elsewhere (e.g.

Witelson, 1977; Beaumont, 1982; De Renzi, 1982, (Chapter 2); Young, 1982b;

Bradshaw and Nettleton, 1983, (Chapter 12); Young, 1983, 1985).

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r\->J.-

We have, however, often (but by no means always) encountered sex

differences in lateral asymmetries. These Rex differences have always

proved to be stable across age in our experiments, and demand explanation.

Their stability across age is clearly inconsistent with theories (reviewed

by Harris, 1978) that try to link sex differences to a postulated

development of cerebral hemispheric lateralisation of abilities.

Other studies of lateral asymmetries in the processing of visual and

tactile stimuli have also produced findings of sex differences (see Harris,

1978; McGlone, 1980; for reviews). Two general types of explanation of

these sex differences in lateral asymmetries have been advanced. The first

type of explanation is in terms of sex differences in the degree of

functional asymmetry of the cerebral hemispheres, the second type is in

terms of sex differences in the cognitive processes used. To some extent

these explanations can be seen as existing at different levels, so that they

are not necessarily incompatible. Despite this, however, we think that

certain points can be made concerning the suitability of each type of

explanation for explaining the sex differences in lateral asymmetries found

in studies of normal subjects.

We do not think that an account in terms of a greater or lesser degree

of functional asymmetry in the male or female brain will alone prove

adequate in explaining sex differences in lateral asymmetries. We have

consistently found that sex differences can be produced or eliminated by

what at first sight appear to be relatively small procedural changes, and

that they can also depend on the measure used. The general trend of our

findings is in the direction of it being easier to demonstrate right

hemisphere superiority for male subjects, but there is no question that

right hemisphere superiority can be shown in females under appropriate

conditions and that it may occasionally be possible to reverse the usual sex

difference and find right hemisphere superiority in females but not males.

The key problem is thus to specify the conditions that do or do not allow

right hemisphere superiority to be demonstrated by male and female subjects.

%3

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:vrf

The second type of explanation, ir terms of sex differences In the

cognitive processes used, seems to us more likely to be of use (see also

Marshall, 1973; Bryden, 1979). In essence, the proposal is that males and

females may rely on lateralised or on non-laterallsed cognitive processes

under different conditions. However, it is important to distinguish two

variants of this type of explanation. The first variant sees the

differences in the cognitive processes used as reflecting strategy

differences, i.e., a voluntary choice from a repertoire of alternatives. We

were originally very attracted to this idea, and sought to tes.t its

prediction that findings of sex differences could be altered or even

reversed by instructing subjects to use different strategies. Unfortunately

we have never managed to produce any evidence for this from our own studies

(e.g. Young and Bion, 1983, Experiment 2). We have also found the strategy

explanation to be intellectually unsatisfying because a clear and

<&

. v^vlv:
220

independently -alidated'description of what the different strategies might

be is seldom offered by researchers using thus notion in attempting to

account for changes in laterality effects. However, advances In cognitive --.-.-v\

psychology may help to overcome this particular problem (e.g. Cooper, 1982). '-vV^y^yC

The second variant would see sex differences in cognitive processef as

reflecting factors that can be affected by task and procedural demands, but

over which the person has little voluntary control. Because of our lack of •

> 'J* *J* *> FJ

success in manipulating subject strategies by mere instruction ve are now '"v\-V^j

Inclined to favour this alternative. However, we are also only too well vCt^onS

aware that it still remains necessary to determine what these different -'V^w-VS

cognitive processes might be, and why males and females rely on them to /^'"N'S"

differing degrees under certain conditions. #>'.> .V A

Acknowledgement O'-N.-V/V

Most of this research was carried out with the support of SSRC Grant

HR5078. BSMM

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Divided Visual Field Studies of Cerebral Organisation. London:

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Beaumont, J.G. (1983). Methods for studying cerebral hemispheric •" i"-^'',j|

function. In A.W. Young (Ed). Functions of the Right Cerebral •NC'-^yN

Hemisphere London: Academic Press, 113-145. •

s

Vv%.^,J

Bradshaw, J.L. and Nettleton, N.C. (1983). Human Cerebral Asymmetry. '^' •"^ W

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Bryden, M.P. (1979). Evidence for sex differences in cerebral

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De Renzi, E. (1982). Disorders of Space Exploration and Cognition.

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De Renzi, E. and Spinnler H. (1966). Facial recognition in brain- 'v'v'v/'j

damaged patients. Neurology, 16, 145-152. s^Ä'«/"^

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McGlone, J. (1980). Sex differences in human brain asymmetry: a iVjSisNH

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Marshall, J.C. (1973). Some problems and paradoxes associated with recent

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Rizzolat t i, G., Umilta, C. and Berlucchi, G. (1971). Opposite

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Starkey, P.and Cooper, R. G.(1980). Numerosity perception in human

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Warrington, E.K. and James, M. (1967a). An experimental investigation of

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Witelson, S.F. (1974). Hemispheric specialization for linguistic and

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Witelson, S.F. (1976).Sex and the single hemisphere: specialization of

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/VVÜ

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222

ESTIMATING CEREBRAL ASYMMETRY AND INTERHEMISPHERIC TRANSMISSION TIME FROM

INDIVIDUAL DIFFERENCES IN BIMANUAL RESPONSE TO LATERALIZED STIMULI

fil

I

W. N. Schofleld

Department of Experimental Psychology,

University of Cambridge,

Downing Street,

Cambridge, England, CB2 3EB

ABSTRACT

This chapter is partly a critical review of selected divided visual

field studies of cerebral lateralisatlon using manual reaction time mostly

to simple stimuli such as dots or flashes of light, and of studies

purporting to estimate interhemispherlc transmission times from these

procedures. It is suggested that inconsistencies in the findings reviewed

rest on failure to take into account individual differences in processing

strategy, amongst other things, A method for overcoming these difficulties

is proposed, and support for this is found by re-analysis of right and left

hand RTs from an early study. The remainder of the chapter reports a simple

reaction time experiment in which blmanual response to bilateral stimulus

presentation is related to blmanual response to unilateral presentation. It

is shown that sex differences in lateralization following unilateral

presentation reduce to difference in between hand response speeds as

established for bilateral presentation, and it is suggested that this

represents individual hemispheric differences in processing strategy. An

influence from sighting dominance is shown both in initial analyses and in

multivarlate regression on factor scores. Estimates of interhemispherlc

transmission time are provided, but with suggestions for improved control.

It is argued that hand differences in reaction time will vary in relation

not to the hemisphere of initial projection of the visual stimulus but to

the hemisphere in which the response command is Issued, and that this could

well be a better indicator of processing hemisphere than visual field

differences.

INTRODUCTION

This paper reports an experiment in which the dependent variable was

reaction time (RT) to an Identical stimulus - a plain circular light source

on all trials, the only variation being that presentation was in the right

visual field, the left visual field, or the light source was duplicated and

appeared simultaneously in both visual fields. The presentation procedure

was thus similar to many other RT studies for which the example of

Poffenberger (1912) is often cited and which have been reviewed by Johnson

(1923), Woodworth (1938), Telchner (195A) and Swanson et al. (1978). In

the present experiment subject:, always made the same response, they raised

both hands no matter which stimulus condition was presented. These

presentation and response procedures vere employed in an endeavour to

Ova

Ssw
223

resolve conflicting findings reported for simple reaction time (SRT) studies

of lateralised hemispheric function, and also to resolve the very evident

confusion in the literature on using RT paradigms to estimate

interhemispheric transmission tise (IHTT). The design of the study was in

effect for two experiments run iimultaneously with the same subjects. Both

experiments involved biroanual response, but for one stimulus presentation

was always bilateral and for the other it was always unilateral. The

purpose of the bilateral presentation was to provide control information on

hypothesized individual differences in processing hemisphere relevant to

analysis and interpretation of the results for lateralised presentation.

The assumption of the study was that lateralisat Ion of function, if any,

would be consistent within individual subjects for a comparatively briefly

tested task, and Chat information on this from the bilateral procedure could

be tested in the unilateral data. The trials for the experiments were

Integrated and presented randomly in one block and the whole procedure can

be considered as one experiment with two conditions and will be reported in

those terms. Sex was controlled, and sex differences will be reported and

will be related to individual differences in bimanual response time.

Research on response to simple laterally presented visual stimuli has

Included what have been called cross education and dominance studies

(Herlitzka, 1908; Terashi, 1920; Metfessel and Warren, 1934; Cook, 193A;

Hellebrandt, 1931); it has included studies of stimulus-response

compatibility (Fitts and Seeger, 1953; Rabbit, 1967; Simon, 1968; Craft and

Simon, 1970; Wallace, 1971; Brebner et «1., 1972; Bertera et al., 1975;

Anzola et al., 1977; Berlucchi et al., 1977; Bowers and Heilman, 1980;

Cotton et al., 1980); and many studies of the lateralization of cerebral

function (Kimura, 1969; Jeeves, 1969; Jeeves and Dixon, 1970; Jeeves, 1972;

Umilta, et al., 1974; Pohl et al., 1972; Bryden, 1976; Allard and Bryden,

1979; Levy and Reid, 1978; McKeever and Huling, 1970; Berlucchi, 197A),

Including measurement of IHTT (Poffenberger, 1912; Jeeves, 1969; Bradshaw

and Perriment, 1970; Berlucchi et al., 1971; Rizzolatti et al., 1971;

Berlucchi et al., 1977; Anzola et al., 1977; Swanson et al., 1978; Harvey,

1978; Rizzolatti, 1979; McKeever and Hof, 1979; Di Stefano et al., 1980).

Basic to this work has been the assumption that nediational differences

(i.e. visual and/or motor pathway differences; hemispheric processing

differences; or associative Influence In cognitive processes) can be

inferred from differences in response related to the lateralization of input

and output.

v-VVV

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The present experiment parallels to some extent published work in all

of these areas but attention will be concentrated on studies of hemispheric

functional differences in dot detection or localisation and on the

estimation of IHTT from lateralized RT paradigms since the findings to be

reported have specific relevance in both areas.

Hemispheric Specialisation for Dot Localisation or Detection

Among straightforward studies of hemispheric functional differences

Klmura's (1969) early experiments on dot detection and localisation have

been Influential, but unfortunately are open to criticism on a number of

grounds, and it is not surprising that attempts to replicate have produced

both supportive and conflicting results (Pohl, Butters and Goodglass, 1972;

McKeever et al., 1975; Bryden, 1976; Allard and Bryden, 1979; Davldoff,

1977; Levy and Reid, 1978; Pitblado, 1979a & b). For dot localisation

Kimura (1969) reported what she called a "stronger" left visual field (LVF)

advantage for males than for females which was her interpretation of four

localisation experiments where in every case an LVF advantage was found for

the male subjects (P<C.02, P<0.10, P<0.01) but in only two instances was

significance reached, oi approached, for the females (P<0.10, P<0.01).

Kimura argued (from the lack of a finding) that for a task which could be

\^ v • • •

. S. S.S.'*

Kfl&^^^^ta:^^^

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224

performed by either right or left hemisphere males would employ right

hemisphere systems whereas females would be more likely to use a left

hemisphere (verbal) mechanism. It should be noted that none of Kimura's

loralifl»,-iüri experiments produced a left hemisphere right visual field,

(RVF) advantage, either for males or for females, and her proposals

apparently are based on inspection of unreported non-signlfleant effects.

For dot detection Kimura (1969) reported that in three threshold

experiments there were no significant RVF/LVF differences, neither overall

nor for males and females separately. The first experiment, however, was

grossly imprecise as measurement wis made In 10 millisecond bands, whereas

any difference was likely to be In the range of perhaps 2-4 msec. The second

was also imprecise since the celling for detection was approached by both

males and females for both visual fields (subjects were asked to respond

"yes" if they saw a 5 msec, dot) and possible Interaction from response

modality was not considered. In the third experiment, detection thresholds

were established by presenting a stimulus for 1 msec, and If both Its

occurrence and position (RVF or LVF) were not correctly reported

presentation time was Increased In 1 msec, steps to a maximum of 5 msec.

This Improved measurement to an appropriate Interval size and range, but

contaminated the detection task with a locallzatlor requirement.

Consequently the third experiment might be seen as a failure to replicate

the localization experiments when the localization task was simplified,

rather than as replication of the non-slgnlfleant findings for dot

detection.

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Apart from measurement, design and analysis problems the main defect In

Kimura's (1969) detection experiments Is the use of threshold differences to

operatlonallse functional differences In hemispheric processing, since these

might not register a difference wh^ch had effect subsequent to Initial

representation of the stimulus in the hemisphere tested. Although this

particular criticism does not apply to the findings for the localization

experiments It does apply to their Interpretation, since It cannot be

accepted that Kimura has succeeded In her Intention of ruling out functional

differences at the level of detecting occurrence of a stimulus.

Pohl et al. (1972), using adult male subjects, found no visual field

differences for dot localization when the array of dots appeared In a square

frame with Its centre marked by a cross. But when the frame and the cross

were omitted, a significant difference was found in the opposite direction

to that reported by Kimura for males. I.e., there was a significant left

hemisphere superiority. One defect in the Pohl et al., (1972) study was the

use after each error response of repeated testing with Increased stimulus

presentation times. Each subject made on average more than 160 errors in

the 65 trials; yet no information is given on the distribution of the

retestlng, nor is there Information on variability, or on Individual

results.

$&

Bryden (1973) also presented dots In the RVF and LVF but found no

visual field differences. Bryden (1976) conducted four experiments similar

to those of Pohl et al. (1972) and Kimura (1969) but with design

improvements, and in which the dependent variable was a count of correct

report for localization, cr for detection and localization separately.

These failed to resolve the conflicting findings of Kimura and Pohl et al.,

as there were no significant visual field differences in any of the

experiments.

Allard and Bryden (1979), using identical stimuli to Bryden (1976),

supported Kimura (1969) In so far as finding and LVF advantage, but this was

for detection where Kimura had found no difference. Further, Allard and

Bryden (1979) found no difference for localization, whereas for this Kimura

.-• :

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225

did report a significant difference. Worse, in Bryden a^d Allard's data the

LVF detection advantage in their control condition was significantly greater

for females than for males, again turning around Kimura's findings.

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m

One explanation of these inconsistent findings is the possibility that

when analysis is made of mean scores then visual half-field (VHF) differences

present at an individual level either cancel, or produce results in one

direction or another as an artifact of subgroup composition. Evidence

supporting this contention can be found in Bryden's 1976 experiments.

Certainly none of the studies reviewed has established that dot detection is

not lateralized, and the inconsistency in the reported findings would be

neatly explained if individual differences could be related to the reported

overall outcome of the experiments.

Using RT Paradigms to Estimate Interhemispheric Transmission Time

All three of Donders' (1868, tr. 1969) RT paradigms have been used in

VHF lateralization experiments to determine IHTTs The basic assumptions

have been that, at least for a simple reaction time (SRT) procedure, (I)

processing and response initiation take place equally well in either

hemisphere, and (2) the difference between conditions employing crossed and

uncrossed pathways is the time taken to cross the corpus callosum once.

Obviously the pathways actually involved in initiating and controlling a

manual response are more complicated than this (Rolls, 1983) but a further

assumption is that they will be balanced in the relevant comparisons.

Bashore (1981) has reviewed research designed to measure 1HTT. The widely

differing estimates of IHTTs ranging from about 2-3 msec. (Jeeves, 1969;

Berlucchi et al., 1971; Anzola et al., 1977; Berlucchi et al., 1977;

McKeever and Hof, 1979; Rizzolatti, 1979; Di Stefano et al., 1980) to values

of 16 msec, or much greater (Bradshaw and Perriment, 1970; Swanson et al.,

1978; Harvey, 1978; Filbey and Gazzaniga, 1969; Rizzolatti, 1979) have been

accounted for by the fact that the shorter times are from SRT studies,

whereas the greater times are from choice reaction time (CRT) studies

(Rizzolatti, 1979; Bashore, 1981; Bradshaw and Nettleton, 1983). Since the

shorter 2-3 msec, times approximate to what might be expected for

transmission over the neuropathways involved (but see Swadlow et al., 1979,

on variability in the speed of conduction of callosal axons) it has been

taken for granted (e.g. Rizzolatti, 1979; Bradshaw and Nettleton, 1983) that

these are the best estimates of 1HTT and that the larger figures are

inflated by processes necessary for the discriminative components of the CRT

task (including possibly stimulus-response contiguity effects). This

reasoning ignores the fact that both figures would be incorrect if

hemispheric differences were confounded in their measurement, and from the

findings which have just been reviewed this has not been ruled out.

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Rizzolatti et •!., (1979) have suggested that findings of hemispheric

differences in SRT experiments is a consequence of interference from a

concomitant task, however in an adequately controlled experiment such

effects, if present, should be unsystematic, i.e., they should be taken care

of by the randomisation of error variation assumed in the statistical models

applied. Presumably with grounds such as these in mind, in another paper,

Rizzolatti (1979) has argued that in SRT studies of IHTT the estimates

should reflect the conduction velocity of callosal fibres and should remain

constant irrespective of the absolute value of the responses. If all else

were balanced such constancy could be expected, but to assert (as he does)

that fairly constant small values confirm that IHTTs are being measured in

specious. Both the large and the small difference could be consistently

preserved if the difference at mean score level reflected a misbalance of

differences at individual subject level for classes of response differing

greatly, but consistently. In ra^an and dispersion. A systematic source of

uncontrolled error variation could be concealed equally well behind

,

^Afr^v:v^^ :
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226 .--S^ consistent small or consistent large differences. >',/. -^

• „

v- v.v.v;

Stimulus-response compatibility (or contiguity) effects (Fitts and

Seeger, 1953, Broadbent and Gregory, 1962, 1965) are a problem for IHTT and

other lateralization studies. Basically this work has shown that response ''

,V'.',

'K-"I

to a laterally presented visual stimulus is faster if the hand making the VyVS*

response is on the same body side as the stimulus, even if the hand is held

across the body to achieve this (Wallace, 1971; Brebner et al., 1972;

Brebner, 1973). Thus the right hand responds faster than the left hand to a Vs^'Wlflash of light in the RVF and left hand responds faster to a flash of light '^JSSrNI

in the LVF, but If the hands are held across the body midline so that the 'v^^C*"^"

right hand operates the response key on the left body side and the left hand -.V^W*'

operates the key on the right body side then these effects are reversed.

Response is fastest to the response position (not the hand in that position)

nearest to the stimulus position, irrespective of whether the contralateral \'J'/ .<7

or ipsilateral pathways are being tested. Clearly, if these findings are '',-!•'•'.'"%•

sound,, then the difference „ between —the uncrossed and crossed visual field /•y«/-.,^'. -. %'W

and response hand connections is not a measure of IHTT, but of the global W.>f''''.<f

time taken for cognitive requirements related to the stimulus-response •

, -"'"^"'^l'%,

configuration, or to a mixture of these and the pathway times. If correct, fl V, v. *, i

this not only destroys the rationale of manual RT studies of hemispheric VTV ^ .

transfer time, but points to a source of bias overlooked in many manual RT ^/"/^vS

studies of laterality. ^"JCs^VV

These findings have been challenged in recen* work comparing SRT and

CRT results. Rizzolati (1979) describes the work of his colleagues

Berlucchi et al. (1977) and Anzola et al. (1977). The former reported

that both for a SRT experiment and for a go-no/go design response speed was S^N'V"-!^

related to hand used rather than to the body side on which the hand was held '"•'"v"-!!-'v

during response. The latter confirmed the SRT finding and further reported 'N""V

/

S''"'/

that for a CRT task a strong S-R compatibility effect swamped any attempt to •*v'v'v;,

P.«

measure IHTT. Similar results have been reported previously by Callan et aV-w.V.y

al. (197A) for manual response to auditory stimuli, and by Bertera et al.,

(1975) for eye movement RTs. Taken at face value these appear to be

convenient findings for researchers working on transfer time, provided they 'v"^^^?

use SRT procedures, and this work will be reviewed as it is highly relevant -^r^vS^

to the present findings. '>'rv''rv'*vi

Berlucchi et al. (1971), using a SRT paradism and two separate groups *. .

of subjects, estimated IHTTs of 3.3 and 2.1 msec. They reasoned that the •••/'V

right hand would respond faster to stimuli in the R'^ (uncrossed reaction) • Ov|,

and thdt the contrary would be the case for the left hand (crossed reaction) >"'./v''!

because "the neural pathways serving crossed reactions should contain at

least one more synaptlc link than the pathways mediating uncrossed

reactions" (1971, p419). This follows Poffenberger (1912). Subsequent work

by these researchers, and others at the same laboratories in Pisa, Parma and \fSWr'vS

Bologna, has failed to provide unequivocal support for the contention that "/s"'«!'^"^

the time cost of one synaptlc link can be measured in the context of even a V'vNi"NJ

v

"simple" RT study, although the contrary is claimed (Rizzolatti, 1979; Di ä^Sffll

Stefano et al., 1980). For a start the procedure assumes that the .'.'•/. '

,.

hemispheres are equal in their ability to dtal with a SRT task (Rizzolatti, r ? .^v»!

et al., 1971). Surprisingly this was not the case even in Berlucchi et />

J

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al's. (1971) SRT experiment where a significant right hemisphere advantage ^'vS^v^

can be seen for one group of subjects. Consider the implications of this. ' *

%

Interhemispheric transmission time was found by subtracting "uncrossed" from 'yvp'OyAV^j

"crossed" RTs: uncrossed being when the visual stimulus is projected to the * BÖOflUfl

same hemisphere as would initiate the manual response, and crossed being ^J^,v '

when initial rrojection was to the hemisphere contralateral to that I*-"/-'^-'!"-"!

controlling the manual response. Thus for Berlucchi et al's. (1971) './.y.V?."

procedure the uncrossed responses were the average of the RVt-right hand

response ano the LVF-left hand response, and the crossed responses were the " •!"-"I'-*^

.

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227 AK'M

average of RVF-left hand and LVF-right hand. The claim was that this

procedure cancelled out unwanted differences In motor mechanism, and In

retinal hemifleld/vlsual half field effects (these were confounded as

•ubjects viewed solely with the right eye); and that for both components of

the crossed condition the manual response would require one additional

transcallosal cross, and, further, that although these would be In opposite

directions It was plausible to consider they would cost the same time. But

if stimulus detection/processing takes place In the right hemisphere (as was

found for one group of subjects, then LVF-L would require no

Interhemispherlc crosses; RVF-R would require two crosses, one for detection

and one for output; RVF-L would require one for detection, but none for

output, and finally LVF-R would require a cross solely for output. In this

complex situation, it is hard to say what the source of a significant

difference between uncrossed and crossed averages might be. There are, v'v/'^'v',s

however, clues. The authors reported that 9 of their 14 Ss responded faster s!r">'"w'

>

!?

with the left hand than with the right hand and presumably assumed that XyMWufl

these differences were balanced In the averaging. The validity of this v/Cv'

assumption depends on what the Individual differences represent. If, for

example, they reflect hemispheric processing differences then the supposed

estimates of IHTT would be nothing more than bias in an unbalanced mix of

confounded effects.

Rlzzolattl et al. (1971) extended this work to a CRT paradigm vVvV^

reasoning that this would Involve hemisp'ierlc functional asymmetry, and that *.'•'.'.',

the difference between response following stimulus presentation to the •

hemisphere preferred for the task and to the nonpreferred hemisphere would v^srVl

reflect IHTT. This experiment found a significant RVF advantage for a task •

s

''v*v*v

involving letter recognition (18.5 msec.) and a significant LVF advantage

for a human face recognition task (15.5 msec). The results were unusually

consistent for a laterallty study, with every subject except one for each

task having VHF differences in the same direction as the mean scores.

Surprisingly, this consistency was not maintained In between hand

comparisons where It might have been expected that the group showing a left

hemisphere preference would respond faster with the right hand, and that the

group showing a right hemisphere preference would respond faster with the

left hand. The mean scores, although not significant (F-2.02, Df"l,20,

P"0.171, calculated from the published values) went in the opposite

direction, and there was a high level of inconsistency for individual I^VVfr.'

subjects. Since this was an experiment where the authors predicted and ^J\y d

found a preferred hemisphere effect It Is Interesting to apply the same !'•'.•'%'.'

method as was used by Berlocchl et al. (1971) when they estimated IHTT In l''\'v'sw

an experiment where no preferred hemisphere effect was predicted, but where .'N/V-"*,'^

one was found (see above). From the published mean scores It was found that #

the difference between what In an SRT design would have been called the -. •'V

crossed and uncrossed pathways was 2.5 msec. The same difference calculated

for the face recognition ask was 7.5 msec. These differences are not

significant in the data given, but are similar In aize to those found In

Berlucchl et als. (1971) SRT study. The possibility remains in both cases

that something other than straightforward IHTT was represented.

• .«•.•.v.-j

Berlucchl (1974) reported that the findings of these experiments, vvvV

(Rizrolatti et al., 1971), held when the letter and face stimuli were "'v\r^v

presented In random sequence, and that a square patch of light Included In '«I's'"!-'^"

the same sequence produced n? VHF differences, but gives no further details. ^UTAUIIO

If substantiated, these further findings would be evidence against

attentional bias due to block administration of stimuli (Kinsbourne, 1970).

Berlucchl (1974) suggested further that a RVF superiority was found in the

first experiment because the letter stimuli were easily verbalised, but that

this would be more difficult when faces were discriminated.

In a further series of experiments a group including the same

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228

researchers (Umllta et al., 1974) trained right-handed Ss to discriminate

rectangles In varying orientations. In a go-no/go RT task Ss pressed a key

with right or left hand if there was a match In orientation. In the first

experiment RVF response was 12 msec, faster than LVF response (P<0.025) and

there were no other significant effects. In a second experiment requiring

ore difficult discrimination there were no significant effects, but In the

third and final experiment with even more difficult discriminations the

»ignlflcant advantage was for the LVF (p<0.01) with no other significant

effects or interactions. Response hand differences were not significant in

any of the experiments nor were there significant interactions between

response hand and visual field. The authors account for the significant RVF

effect In the first experiment by proposing left hemisphere mediation for a

task which they felt was more easily verbalised than that of the second and

third experiments. If Che reasoning of the earlier work is to be followed

then the difference ^etween tht RTs for the preferred and nonpreferred

hemisphere should estimate IHTT. By this method the estimate from the first

experiment would be 12 msec. As there was a left hemisphere advantage a

furthe.' estimate of IHTT should have been given by the difference between

right and left hand RT since the latter would require one extra callosal

cross, but the results were in the opposite direction and were not

significant. Once again the interesting point is unexplained individual

subject differences. The mean scores used in the analyses are based on: 6

subjects faster with the right hand 6 subjects faster with the left hand,

suggesting that the VHF and hand difference scores for these rubgroups might

usefully have been examined. There is similar disparity among subjects for

the third experiment. Clearly it would be inappropriate to estimate IHTT by

the crossed versus uncrossed pathway method in view of the hemispheric

difference in two of the three experiments. If it is done, however, then

the estimate would be 7.0 msec, for the first experiment and 4.0 msec, for

the »econd, both in the direction of the expected uncrossed pathway

advantage, showing that plausible results can be produced by invalid

comparisons. For the third experiment the difference is in the wrong

direction and the hypothetically longer pathway is 5 msec, faster than the

shorter pathway. Of the 12 Ss in this experiment 8 were fast with their

right hand and A with the left hand. If IHTT paradigm assump. tons are

correct then a normal distribution of left hand advantage differeace RTs

might have been expected with possibly a preferred hand practice advantage

applying a counter bias to shift the distribution without altering its

shape, but no information is provided on this in the published findings.

These experiments, also, did not take into account stimulus-response

compatibility effects.

• Berlucchi et al. (1977) repeated the work of Berlucchi et al., (1971)

but with binocular viewing and 5u'. of the trials given with hands and

response keys on the same body side as stimulus presentation and with 50*.

with hands crossed to operate keys on the opposite body side. This work was

planned as a rejoinder criticism from to Broadbent (1974) and to test S-R

compatibility effects (reference given earlier). In discussing their

findings the authors adhere to the belief that "the difference between

ipsilateral and contralateral responses in simple reaction time to

laterallzed stimuli is presumably a pure measure of interhemispheric

transmission time" (1977, p511), although their previous findings, and also

the findings they now report, include evidence against this assumption.

Firstly for one condition they report a significant LVF advantage, and from

a figure showing the mean scores (values are not reported) it can be seen

that for most conditions the VHF differences are consistent in direction

with this. Secondly, although the mean difference between the uncrossed and

the crossed pathways is significant (2.5 msec. P<0.0t) the results for 2b%

of subjects went in the opposite direction when keys ai.d hands were on the

same body side, and this increased to 312 when hands were crossed. No

information is given on the size of the differences for the reversed cases.

vVvV

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229

but the percentages are murh greater than would be expected it these were V^uOCk"

cases of reversed lateralization of function (Zangwlll, 1960), and even if

they were they would form a highly unwelcome subgroup, unless they could be

treated separately, considering the objectives of the research. Thirdly,

thrre were similar inconsistencies in response hand times. For example

almost one third of subjects were faster for the left hand for the stimulus

presented in the RVF, whereas both IHTT and S-R compatibility hypotheses

would predict that the right hand should have been faster. In some

circumstances the presence of error to this degree might be expected and

attention would only be given to estimates of central tendency and the

standard deviations from these. But in the present experiments subjects

lave undertaken many trials and the analyses are made on the means of

medians from these, and it is reasonable to expect consistent individual

results in the summary statistics. The size and distribution of the wayward

differences cannot be calculated from the results given, but if IHTT methods

are valid these should be in the tail of a uniroodal distribution, and any

suggestion of bimodality would cast doubt on validity. -

An important finding from this experiment was the complete lack of S-R &&j

compatibility effects. It would be helpful to know however, if there was

evidence of this effect in the data from the early test sessions and if this 'vVV*.

was lost in calculating the overall mean scores. Each subject had one !"\/V'

practice session followed by 8 test sessions on different days and a total N\V!I/"3

of 960 RTs was recorded per subject. Wallace's (1971) demonstration of

stimulus-response compatibility effect was based on Just one te t session

with 8 practice and 128 test trials. Brebner et al., (1972) used a large

number of test sessions and highly experienced subjects, and when their data

were re-examined Brebner (1973) found that the last trial of the main

experimental sessions gave an RT pattern which in the case of each subject "•S"^''^'^

differed from the overall pattern, and which suggested change with practice.

Brebner (1973) interpreted findings from 10 sessions for 10 subjects as

showing the gradual acquisition of a spatial frame of reference in which

Identification of the position of the hand in space becomes independent of

its normal body side. The figures published by Berlucchi et al. (1977) do

seem to suggest that individual comparisons might establish more differences '"-'%-\>^i

than those reported. Callan et al. (1974) also reported no S-R vi"v%>V

compatibility effect for a SRT design, but although there were 504 trials in

8 separate sessions no information is given on the possible effect of

practice.

In their second experiment, Berlucchi et al. (1977) further examined >VVV.

stimulus-response compatibility effects in a go-no/go design and, as in the ["''•"•V''.-

'first (SRT) experiment, found none. This finding rests on a significant .>V*.^"

interaction between response hand and VHF (P<0.005), together with a nonsignificant three-way interaction when response hand position (same or

opposite body side) was introduced (P<0.20). Once again, however, no

information is given on practice. The effect of this could have been

considerable as there were 1280 trials per subject, plus those of an initial

training session. The point of Interest is whether the three-way

interaction remained stable across these. Also of interest was the finding

that response with hands in the normal positions was faster to LVF than to >^"

RVF stimuli and *lso that for this condition response was faster with the {SOU

left hand than with the right. This implied right hemisphere mediation. '/A'AV'*!

Both visual field and hand effects were in the opposite direction for S'^Vyfl

response with hands held across the body, implying left hemisphere

mediation. These effects suggest to this reviewer a change in strategy for

the different conditions of the experiment. The possibility of changing

strategy is also supported by individual subject differences. For uncrossed

hands the finding in the mean scores of an LVF advantage rested on 11

subjects faster in that field, but 5 were faster in the RVF; and further, XBSJ&IM

only 9 were faster with thei' left hands than with their right hands. There e^CrVWH

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230

were similar individual differences for the crossed hands RVF advantage.

Undeterred by these inconsistencies the authors provided estimates of 1HTT

of 3.A msec, from the uncrossed hands condition and 2.7 msec, from the hands

crossed condition with a mean estimate of 3.0 msec. (P<0.01). An amazing

feature of these predictions of IHTT is that a large subgroup of subjects

were faster for the supposedly longer cerebral pathways than for the shorter

pathways (A4X for the hands across the body condition, 19% for the normal

condition). It is hard to accept Berlucchi et al's., conclusion that the

significant difference which remains when these individual differences are

averaged out are a valid estimate of IHTT. An alternative possibility is

that the mean value represents not IHTT, but lack of balance in strategy

preference and processing hemisphere.

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The 1971 study of Rlzzolatti et al. was repeated by Rizzolattl and

Buchtel (1977) using the same go-no/go design for face recognition, but with

both male and female subjects. The LVF advantage of the 1971 study was

confirmed for the males, but there were no significant VHF differences for

the females. The experiment was repeated with fresh groups of men and women

but with presentation time reduced from 100 msec, to 20 m&ec. It was found

that the LVF advantage for the males was greatly increased, and the finding

for females was unchanged. The significant finding in the analysis of

variance is largely because the men show a deficit when initial projection

is to the le.t hemisphere, however this is interpreted as showing that for

brief exposure and immediate judgment, "a laterallsed mechanism specialized

for faces can be activated only in males" (1974, p304). The published

report (Riz?olatti and Buchtel, 1977) has nothing to say on IHTT, but the

findings are relevant to earlier work by Rizzolattl and his colleagues. The

RVF advantage for the males was about 40 msec, when stimulus exposure was

100 msec, and 140 msec, when stimulus exposure was 20 msec. This can

be compared to the value of 13.5 msec, reported for the 1971 experiment.

Just why the more difficult discrimination should substantially increase a

supposed indicator or IHTT (and for men but not for women) and not simply

overall processing tine (as was the case for women) remains unanswered.

Anzola et al. (1977) followed similar objectives to Berlucchi et al.,

(1977) but with separate subgroups for the crossed and uncrossed conditions.

Again there were two experiments. The first was a SRT design and the second

a CRT design. Thus according to the logic of Rizzolattl (1979) and the

whole rationale of IHTT methods there should have been significant VHF

differences in the second experiment but not In the first. Unfortunately,

it was for the first experiment, the SRT design that an (unpredlcted) LVF

advantage was found; this once again undermines the s*nse of estimating IHTT

by subtracting uncrossed from crossed response times. The authors express

surprise at this finding but totally overlook its implication for their work

and report an overall "uncrossed pathway" advantage with a probability from

the analysis of variance of P<0.023. Clearly there is a systematic effect

from some source or another, but it cannot be what the authors claim.

-S

In the second, CRT, experiment reported by Anzola et al. (1977)

subjects responded with the hand on the same, or on the opposite, body side

as the stimulus; and had crossed, or uncrossed arms, for separate blocks of

trials. There was no main effect for VF, but a strong stimulus-response

compatibility effect (P<0.005) and main effects for hand (the right hand was

faster (P<0.025). In both experiments 450 trials were given across 9 test

sessions, i.e., about half the number of trial as in the go-no/go experiment

(Berlucchi et al., 1977) in which there was no effect in the overall means.

The difference between the ipsilateral and contralateral pathways was 10

msec, but this was not significant, and in any case was contaminated by the

significant VHF asymmetry. No information is given on individual data.

The experiments reviewed in the preceding paragraphs rest on the

rag
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231

assumption that more time will be required for a process whirh crosses the

corpus callosum than for a process which is identical in all other respects

except the need to cross. None of the work reviewed is satisfactory because

of the inability of the researchers to achieve balance of all factors other

than transcallosal-cross time, irrespective of whether a simple or CRT

design is used, and because of their failure to take into account

conflicting evidence visible even in their own data. Although S-R

compatibility effects remain a major problem, it appears to have been shown

that either they are not present in some SRT designs, or else that they

decline with practice and thus can be brought under control. The findings

of hemispheric asymmetry even In SRT tasks is a more fundamental difficulty

especially if this varies between or within subjects depending on strategy

used for performance. The firm stance on interhemispheric transfer times

adopted by Rizzolatti (1979) on the basis of this work (much of It authored

or co-authored by him) is without justification. His statements that "the

main factor determining which hand is faster in responding to a lateralized

stimulus is the basic organization of sensory and motor pathways" (1979,

p393), and that in a SRT experiments "both hemispheres are virtually equal

In their ability to analyze the stimulus (1979, p396) and that in "SRT

experiments since the 'transfer time' reflects the conduction velocity of

callosal fibres, it should remain constant regar^ess of the absolute value

of the responses" (1971, p396) are contradicted by findings evident in

papers published by himself or which he has co-authored. Wider acceptance

(Di Stefano, 1980; Biseach et al., 1982; Bradshaw and Nettleton, 1983) is

unfortunate.

t\WSA

THE PRESENT EXPERIMENT

The present experiment provided an opportunity to examine IHTTs in a

SRT procedure and at least to test some possible sources of uncontrolled

variation. It further provided the opportunity to test statistical

procedures which night increase control and »nsitivity in IHTT or

lateralization studies. The presentation of the identical stimulus in

either the RVF or LVF allowed comparison between these fields, but with

problems similar to some of those in the studies reviewed. The introduction

of a randomly presented condition in which the stimulus appeared

simultaneously in both visual fields provided control data to aid

interpretation of the results for unilateral presentation.

Further control was introduced by use of a method of response which

also was identical on all trials. Subjects had both hands resting on keys

and raised them both as quickly as possible thus making the same response no

matter what the stimulus presentation condition. The action trained was at

the wrist, and there was nothing to prevent additional movement either at

Che fingers or elbows. Thus there was the possibility that both distal and

proximal musculature was used to some extent. Di Stefano et al. (1980)

used key pressing and a lever-pulling task in a SRT design and reported that

the two methods produced similar results after unilateral presention of the

visual stimulus, but that ipsilateral-contralateral time differences were

reduced for bilateral key presses, and were completely removed for bilateral

lever pulling. Studies of bilateral movement time as reviewed by Kerr

(1978) are not directly relevant to the present experiment since the response

was simply to raise both hands, and this terminated the trial. I.e., there

is no requirement of subsequent movement to different targets, or to any

target at all It has been reported (Sulow, 1913;Jeeves, 1969; Jeeves and

Dixon, 1970; Nakamura and Salto, 197A) that bilateral responses are slightly

but systematically slower than unilateral responses.

O •* *J

Separate right and left hand response have been used in many manual RT

studies and comparisons between hands have also been made (Metf^ssel and

Warren 193A; Kerr et al., 1963). The published results have usually been

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232

reduced to differences between hands, or to the mean of left and right

hand, in an attempt to balance uncontrolled effects. For unimanual response

Anzola et al. (1977) reported an overall superiority for the right hand in

a CRT experiment. Berlucchi et al. (1977) reported no overall difference

between hands in a SRT experiment, as did Rizzolatti et al. (1971) for a

Donders' type C design and Umilta et al. (197A) for a line orientation

discrimination task. Bradshaw and Perriment (1970) also reported no overall

difference between hands. Poffenberger (1912) published data for 4 subjects

but only two were tested for all retinal conditions used. One of these was

right-handed, and one was left-handed and it is interesting to note that for

foveal presentation the left-handed subject invariably responded faster with

his left hand both for left and for right presentation. The right-handed

subject showed a less consistent advantage for the right hand.

Metfessel and Warren (1934) have published data giving separate results

for right and left hand for a bimanual SRT task in which subjects were

trained to press response keys simultaneously when a centrally positioned

light was briefly flashed. It seems likely that subjects responded

rhythmically to the expected flash, but even so the report of a clear left

hand advantage for the right-handers, and a clear right hand advantage for

the l^ft-handers is of interest. Groups of dextro-sinistrals and stutterers

(who were mostly right-handed) also had a left hand advantage. These

findings were consistent both for manual RTs and for action potentials taken

from the two forearms immediately prior to hand response - which was with

the first two fingers of each hand. Metfessel and Warren (1934) interpreted

these findings as due to over-compensation of the less used hand in an

attempt at simultaneous movement. However an alternative explanation could

be the intervention of hemispheric functional differences which, considering

the repetitive rhythmical nature of the task may have been consistently

maintained once established, but differentially between subjects.

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Fortunately these authors have published their raw data and from this

it can be seen that for a sample of right-handed subjects 17 vere faster

with the left hand at tiipes ranging from 1.2 to 18.3 msec, and 6 were faster

with the right hand at times ranging from 1.7 to 12.4 msec. It is at least

possible that these times identify separate groups, the former mediating

responses via a right hemisphere non-linguistic spatial strategy, and the

latter via a left hemisphere verbal strategy. Using Metfessel and Warren's

data it was calculated that the mean left minus the mean right hand RT for

the first group was 7.01 msec, with a standard error of only 1.22 and that

for the second group the mean was -5.68 msec, with a standard error of 2.07.

Thus when considered separately the two groups are clearly placed either

side of zero with the suggestion of a systematic source of variation

influencing the differences. Recalculation produced similar results for the

other samples. The left-handed sample had 11 subjects faster with the right

hand (mean 6.71 msec, standard error 1.53) and 10 faster with the left hand

(mean -6.98, standard error 1.57). A sample of dextro-sinistrals

(lefthanded writers who had been corrected in schooling to righthand writing

or righthanded writers who were lefthanded for most other purposes) had 16

faster with the left hand (mean 6.93, SE 1.22) and 5 with the right hand

(mean -4.94, SE 1.45). In a sample of 23 students (21 righthanded and 2

lefthanded), 19 were faster with the lefthand (mean 8.72, SE 1.18), one of

whom was left handed, and 4 were faster with the right hand (mean -6.20, SE

2.17). When data for all 89 subjects were pooled and the histogram for the

difference scores inspected there was a clear bimodal distribution both for

the action potentials and manual RTs. In the RT data the peaks were at 7.43

and -6.15 msec, and since the standard error was only 0.87 the separation

seamed decisive. The comparable figures for the action potential times were

8.95, -6.78 and 1.08 respectively on a sample reduced to 83. Thus in each

subset of separate hand data whether for the sample as a whole or the hand

preference/clinical subgroups, there is a suggestion not of

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233

overcompensation, i.e., bias in one population towards a particular tail,

but of separate distributions. In a footnote, Metfessel and Warren (193A)

mention results for a further group of A6 normal righthanded subjects.

Thirty of these were consistently faster with left hand; 12 with the right

hand, and A had no advantage one way or the other.

In his review of IHTT studies Bashore (1981) concluded that responses

made with one hand were faster than responses made with both hands

simultaneously. In support of this he cited Jeeves, 1969; Jeeves and Dixon

1970; and Di Stefano et al. 1980. Bashore (1981) further reported that

speed of onset of bilateral movements involving different muscles (measured

by latency to electromyograph activation following an imperative stimulus)

varied as a function of response side and handedness (Hongo et al., 1976).

That different cortical mechanisms mediate the production of unimanual and

bimanual finger movements is indicated by the fact that components of

movement related potentials measured at the scalp vary as a function of

which movement is being executed (Kristeva et al., 1979). In the present

study all responses are bimanual and the only variation is whether the

signal to respond is presented in the RVF, the LVF or in both visual fields

simultaneously. The possibility of an interaction between mixed use of both

unimanual and bimanual response within subjects is eliminated.

In the experiment to be reported stimulus presentation took place on

every trial, i.e., there were no blank, cards to detect anticipatory

responding (Bryden, 1976). The reason for this was that use of blank cards

would have transformed the procedure from that of a SRT to a go-no/go task.

Subjects viewed the dark interior of the tachistoscope fixating a low

illumination dot of light. The stimulus occurred after a random delay of

between to 3 sec. and this should have been a perfectly adequate method of

reducing c. iticipation to a few randomly distributed occurrences. But if

blank cards had been introduced subjects would have been set to expect one

of two stimuli: the flash of light from the blank card (or whatever), or the

dot of light, and would have to decide which had been presented before

responding. Bashore (1981) correctly describes this as introducing a gono/go component to the initial SRT procedure, but he is entirely incorrect

in his assumption that the former involves detection and that the latter

does not. He writes: "In an SRT task, stimulus detection is not actually

required because the subject knows that on every trial a stimulus will be

presented as soon as the fixation stimulus leaves the central visual field;

the subject need only prepare and execute the task" (p361). It would,

however, be a unfortunate defect in an SRT experiment if the fixation dot

disappeared at the onset of a laterally presented stimulus, since there

'would be no way of knowing whether the response followed the lateral or the

central Information. Since subjects are trained to maintain fixation in the

central position it seems highly probable that the information signalling

response would be found there.

Predictions

Predictions derived from the work reviewed included that there would be

an overall significant LVF (right hemisphere) advantage since despite

inconsistencies, and denial of what appear to be positive findings, these

have been previously found. Again, there have been inconsistent findings of

sex differences; even direction of prediction seemed uncertain, and the

safest prediction was that there would be none. Both the IHTT and S-R

compatibility research support a VHF and response hand interaction and it

was predicted that the right hand would be faster in the RVF and that the

left hand would be faster in the LVF at the level of mean scores. In

general these predictions follow the balance of reported findings, but

despite the volume of literature are certainly not strong in expectation.

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2 34

The study included original predictions aimed at accounting for the

Inconsistency in the research reviewed and at exploring the possibility that

current RT methods of measuring 1HTT are defective. These predictions were

tested in data from random presentation of unilateral and bilateral

identical stimuli (the dot of light in the RVF, LVF or both VFs) with

uniform bimanual response to all stimuli. This ensured that S-R

compatibility effects were balanced since response was always with a pair of

hands one of which was on the same body side as the stimulus and one of

which was not. The most important Innovation, however, was an attempt to

use the data from bimanual RT to bilateral stimuli as a control for

comparison with data from the bimanual RT to unilateral stimuli. If a

hemispheric preference were shown for the former (bimanual RT, bilateral

stimuli) then hypotheses could be tested in the latter (bimanual RT,

unilateral stimulus). It was reasoned that If there were hemirpheric

differences for the bilateral condition these would be revealed by faster

response for the hand on the opposite body side to one specific hemisphere

and that the other hand would be slower by a difference commensurate with

the need for one IHTT. Consequently the general research predictions were

that subjects faster in the both VF condition with the right hand would

respond on average faster in the RVF than in the LVF for unilateral

presentation, and that for these subjects response would be faster with the

right hand than with the left hand irrespective of visual field of initial

projection by a difference similar in extent to the RVF/LVF difference since

in both cases this would represent one cross of the corpus callosum. For

subjects faster in the both VF condition with the left hand it was predicted

that response would be faster in the LVF than RVF for the unilateral

condition; that the left hand would be faster than the right hand no matter

which VHF received the stimulus, and again that the RT difference between

hands would be similar in extent to the RVF/L'F difference.

The present experiment differs from most of thosv» reviewed in that the

subjects were 9 year old children rather than adults (usually students, or

the researchers themselves). This should in no way be a methodological

defect. If there were a lack of hemispheric specialisation for a SRT task

at 9 years of age then findings would follow those predicted for the IHTT

research reviewed, although the Innovative hypotheses would remain untested.

A further difference is the comparatively small amount of data collected

from each subject - only 120 RTs each, whereas 1000 or more is not unusual.

This was seen as a necessary condition for minimising possible changes in

response strategy (and processing hemisphere) within subjects and was

matched by an increase in sample size.

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'Method

Subjects. The subjects were 11 girls and 9 boys drawn at random from

two parallel mixed ability classes at an inner city school in the south of

England. In addition 3 boys and 3 girls were tested when the procedure was

being established, and the data from these pilot Ss were included in some of

the analyses made. Mean age (for 26 Ss) was 8.91 years (SD 0.16 years).

All subjects were London born; had normal vision in both eyes; and were

without physical or neurological handicap. Information on hand preference

and visual dominance was not collected until after the conclusion of the

experiment. None of the children had previously taken part in research of

any sort. Procedure and objectives were not discussed with children or

teachers.

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Stimuli. The stimuli were two circular sources ot light each with a

luminance of 8.6 cd/m appearing in a blackground of approximately 0.14

cd/m*. Each stimulus subtended approximately 1 degree of visual angle, as

established by tachistoscoplc presentation. They were arranged 2 degrees

either side of fixation and could be presented singly or simultaneously.

KXM tttf^^W^^
235

Stimulus duration was 60 msec, throughout the experiment. The fixation dot

subtended approximately 0.3 degrees of visual angle and had a luminance 4.3

cd/m in a black background of 0.14 cd/m .

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Equipment and Procedure. Stimuli were presented using two fields of a

three field tachistoscope (Electronic Developments Ltd), fitted with a long

viewing mask. A dull black 7cm x 12cm tachistoscope card with a 0.30cm

diameter hole at its centre was prepared from heavy mounting board. White

translucent cine leader film was mounted on the back of the card completely

covering this hole so that the appearance from the front was of a white

opaque dot at the centre of a black card.

M;

The card so prepared was sealed with adhesive to the internal black

iiask provided by the manufacturers within the tachistoscope approximately

8cm in front of the usual card presentation position. Thus the card was

located between the field lamps and the S's eye and the only light which

could pass was through the central hole. A plain grey filter, fitted within

the tachistoscope viewing mask, further reduced the amount of light which

could pass to the subject's eye. This field was on throughout the

experiment.

A similar card was mounted in the second field of the tachistoscope but

with two holes of 1 cm diameter centred on the horizontal midliwe of the

card but 2 cm to each side of the card centre. This card was also covered

on the rear side to give the same effect as for the fixation card. An

assembly was fastened to the rear surface of this card containing two covers

(one for each aperture) moveable in fixed horizontal tracks. These could be

operated from outside the tachistoscope. With either or both covers in the

open position light could pass through the apertures to the viewer's eye.

The covers were moved between every trial, whether necessary or not. The

plain grey filter at the viewing mask also reduced the amount of light

reaching the viewer's eye from this field.

After these internal alterations had been made the rear of the

tachistoscope was completely shielded from external light and the fidelity

of the arrangements were checked with both child and adult subjects not

involved in the experiment.

The effect to a viewer when both fields were off was of total darkness,

nothing was visible within the tachistoscope. When the first field was on

(and it remained on throughout the experiment) the viewer saw what appeared

to be a small light in the central position. What the viewer saw when the

'second field «as flashed depended on the position of the two covers: in

this experiment he saw either two lights evenly spaced either side of the

fixation light, or he saw one or other of these lights together with the

fixation light.

Subject's were individually trained and tested in one session. After

chair height had been adjusted S was seated at the tachistoscope and trained

to fixate and to raise both hands from the surface of the table whenever a

stimulus was presented. Micro switches linked to millisecond counters were

inset beneath switch covers level with the table top. The switch covers

were centred 75cm on either side of the 's midline. Table height was

adjusted so that S's forearm was parallel to the surface. The keys, wiring

and timers were alternated between hands for each subject. Calibration

checks confirmed that the difference between timers was less than one msec.

for measurement up to one sec. Timing began when a stimulus was presented

and ceased if a hand movement broke the circuit to the millisecond counter

associated with that hand. There were 6 practice trials (2 for each

condition) followed immediately by 60 trials (giving 120 RTs), 20 for each

condition (40 RTs) presented in a randomly dete-mined sequence. Ss were not

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236

told how fast they had responded. Less than 0.5Z of data was lost through

procedural error on the part of Ss.

When all Ss had been tested each was again seen separately, to obtain

data on hand preference and visual dominance, which In this report is taken

to mean sighting dominance (Crider, 1944; Porac and Coren, 1976) or

preference. A binocular rivalry task, tachlstoscopically presented, was

used to assess sensory dominance (Coren and Kaplan, 1973), but as this was

found to be unrelated to sighting dominance, and made no significant

contribution either as a main effect or as an interaction with other

variables, the data have not been used in the analyses reported. Subjects

were asked to write their names and the hand used was recorded. Ss stood

near a table and a rectangular card 7cm by 12cm with a single 0.3cm hole at

its centre was placed un the table at the S's midline. The S was asked to

pick the card up and to look through the hole at the experimenter. The eye

used was recorded. Eye used was similarly recorded for sighting a toy gun

and for looking into a kaleidoscope. During normal class activities all Ss

were observed writing, cutting with scissors and painting and it was found

that two Ss used their left hand for all three of these activities, whereas

eighteen always used the right hand.

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The design of the experiment end the available measures permitted a

series of multifactor analyses of variance Involving both between and with S

comparisons, and also the introduction of covariates. Factor analysis was

used to display relationships between within Ss variables. Multivariate

regression and canonical analyses were used to explore the possibility of

predicting visual field differences from the factors.

Results

The raw data were screened and examined in histograms and values

outside a range of 100 to 750 msec, were arbitrarily excluded. Winsorized

mean scores were then calculated and 95% confidence limits established for

each variable (Dixon, 1983). Less than 1% of the data were lost by these

procedures, and it was clear that outlying values were sparsely and randomly

distributed. The remaining data were logtransformed, to correct the typical

RT skew, and the mean scores were recalculated. Medians and other estimates

of central tendency were calculated, including Hampel's, Andrew's and

Tukey's estimates of location (Andrews et al., 1972). These followed a

similar pattern to the mean scores from the winsorized log transformed data

on which all analyses were made. Analysis was also made of RTs for

individual trials following logarithmic transformation wich no exclusions

other than values outside the 100 to 750 msec, range, and ?f means computed

'from this untrimmed data. These precautions were taker beeiuse the mean

scores were estimated from fewer observations than is cust' mary.

Preliminary analysis for fixation control. To establish that fixation

was maintained, a three-way analysis of variance was made in the form, sex

(male or female) x presentation position (right or left or both) x response

hand (right or left). The only significant main effect was for visual field

position (F-3.94, Df-2,32, P<0.028) and post-analysis of variance

comparisons established that the mean score for the Both condition was

significantly faster than for RVF and LVF presentation grouped (t-2.054,

Df-36, P<0.01), and It was concluded that Ss maintained fixation. The mean

RTs in msec, were 269.35, 266.43 and 261.31 for the RVF, LVF and Both

positions respectively. The 2.92 msec, difference between RVF and LVF was

not significant (t-0.952, Df-36).

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Analysis with visual pathway and contiguity effects balanced. To

establish which hand responded fastest when pathway and visual contiguity

effects were balanced, a two-way analysis of variance was made of data for

the bilateral VF condition in the form, sex (male or female) x hand (right

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237

or left) in which levels for the final factor were repeated measures.

Although in the overall mean scores for this analysis, the left hand was, as

predicted, significantly faster than the right hand (F-5.32, Df-1,18,

P<0.033) this finding was complicated by a significant Interaction with sex

(F-A.51, Df-1,18, P<0.05). For the males the left hand advantage of about 8

milliseconds, was highly significant (t-2.415, Df-18, P<0.01); but for the

females response times for the separate hands were almost identiral

(t-0.13A, Df-18). This effect is illustrated in Figure 1 where it can also

be seen that the males and females did not differ when comparison was made

between their left hands rt-0.178, Df-18), but they did differ significantly

when the comparison was between right hands (t-2.937, Df-lS, P<0.0001).

v.

The possibility that these results were artifacts of sighting dominance

was tested. Since most Ss achieved either maximum or minimum score on the

sighting dominance Indicators the scores were dichotomised at 1.5. This

gave 7 girls dominant in the right eye and 4 dominant in the left eye,

against 3 boys dominant in the right and 6 boys dominant in the left eyes

(Phi«0.302, corrected Chi-square-0.808, Df-1, NS).

The analysis (which was by a regression method) was repeated with

sighting dominance Introduced as a second grouping variable. Sighting

dominance was not significant either as a main effect (F-1.06, Df-16) or in

interaction with other variables.

For each subject RT for the left hand in the bilateral VF condition was

subtracted fron RT for the right hand in the same condition. A histogram of

mean scores for all 20 subjects on the variable thus created was distinctly

bimodal with peaks either side of zero, suggesting two separate groups of

observations (see Figure 2). From the statistics given below Figure 2 it

can be seen that the mean for each group shown is more than four times its

standard error from zero, and that only one observation is more than three

standard errors from its mean in the directic of the other group mean.

280

280

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Response Hand

Fig. 1. The highly significant interaction between sex and response hand for

the stimulus presented simultaneously in both visual fields (F-4.51, Df-18,

P<0.05.

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Histograms were also computed displaying the differenre scores for each

S individually and none of these were bimodal. In each case the

distribution of difference scores was centred on one side or the other of

zero, with mostly only a few tail values crossing to the other side. Data

for the 6 Ss tested during pilot work were similar.

Subjects were divided into two groups as shown in Figure 2. Males and

females were unevenly distributed within these groups. There were 6 females

but only 1 male in the group which was faster with the right hand, .is

against 5 females and 8 males in the other group (Phi-0.453, corrected Chisquare-2.428, Df-1, NS). To simplify presentation the two groups will be

referred to as the fasthand right and the fasthand left groups, which should

be understood to mean "the group of Ss individually faster with the right

hand than with the left hand in the bilateral condition" and "the group of

Ss individually faster with the left hand than with the right hand in the

bilateral condition", respectively.

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Group 1

(right hand faster)

Group 2

(left hand faster)

Milliseconds

32

28

24

20

16

12

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Statistics (with pilot Ss included given in brackets):

MEAN

S.E.

MAXIMUM

MINIMUM

N

5.853

1.231

•3.721

7.652

7

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( 1.09)

(-1.65)

(-16.2)

(11)

9.997 ( 9.91)

2.158 ( 1.88)

30.486 (30.49)

0.365 ( 0.31)

13 (15)

Fig. 2 Histograms of the bilateral difference RTs (right hand - left

hand) for the two groups. Ejch asterisk represents mean data for 60 trials

from one subject. Pilot Ss are indicated by the symbol 'V.

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239

Analysis of RT for RVF and LVF Presentation

A three-way analysis of variance was made comparing response tines

after RVF and LVF stimulus presentation. The factors in the analysis were

sex (male or fenale), visual field (RVF or LVF), and response hand (right or

left). The two final factors were repeated measures. There was a highly

significant two-way interaction between sex and visual field (F=3.28,

Df-1,18, P<0.01) and the three-way interaction between sex, visual field and

hand approached significance (F«3.0^, D>1,18, P<Ü.098). The two-way

interaction is illustrated In Figure 3. Although the hand x sex interaction

looked very similar to the significant effect reported for the both hand

condition It was not significant (F»2.7A, Df-1,18, P<0.115), and there were

no other significant effects in the analysis. Post-analysis of variance

comparisons established that the males responded significantly faster in the

LVF than In the RVF (t-2.912, Df-18, P<0.01) but that there was no

difference between visual fields for the females (t«1.062, Df«18). The

females were significantly faster than the males for RVF presentation

(t-3.519, Df-18, P<0.005), but not following LVF presentation (f0.544,

Df-18).

Taken at face value these findings would appear to suggest that:

(1) the males responded significantly fastp' whi.?n initial projection was to

the right hemisphere than when initial projection was to the left

hemisphere.

(2) although there was no RVF/LVF difference for the females, they were

significantly faster than the males when projection was to the left,

language dominant, hemisphere; but not when Initial projection was to

the right hemisphere.

260

275 —

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Fig. 3. Th-j significant interaction between sex and visual field (F«8.28,

Df-1,18, P<0.01).

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Further analysis took advantage of the findings for the bilateral condition

and established that these VHF by sex dlfferenrts could not be taken at fare

value.

Re-analysls taking Into account individual bl.lateral findings. The

analysis of the previous section v.as repeated with the Introduction of

fasthand (as explained previously) as a second grouping variable. The

factors In this analysis were sex (male or female); fasthand (right or

left); VHF (right or left); and response hand (right or left). The only

significant effect was an interaction between fasthand and response hand

(F-15.58, Df-1,16, P<0.0012), but as there was only one male in the right

fasthand group the analysis was remade with the daca for the 6 pilot

subjects included. Results were almost identical to those obtained for the

20 subjects. The only significant effect was the Interaction between

fasthand and response hand (FM6.61, Df-1,22, P<0.0005), and there were no

significant, or near significant, effects involving sex.

Taking into account difference in response hand speed from the

bilateral presentation condition removed all suggestion of sex differences

related to visual field of presentation and initial projection to

different hemispheres. The apparent VHF difference between males and

females reduced to the finding that in the augmented sample of 14 females 9

responded faster with their left hand, and 5 were faster with their right

hand; whereas of the 12 males only 2 were faster with their right hand,

against 10 who were faster with the left hand. This distribution of

frequencies was significant (Phi-0.A81, corrected chi-square»4.211, Df-1,

P<0.05).

As sex was not significant, and to improve the quality of the analysis

as affected by subgroup size, it was dropped from the design. The effect of

the fasthand grouping variable on VHF differences was tested in an analysis

of variance in which the factors were fasthand (right or left), VHF (right

or left) and response hand (right or left), and into which a covariate was

introduced representing overall reaction time. The purpose of the covariate

was to remove from the analysis individual differences in response speed

since a difference of say six msec, might represent different functional

magnitudes for relatively fast and relatively slow responding subjects. The

estimate of overall RT was obtained fro.n the bilateral condition data which

was not being otherwise used in the analysis except to provide the grouping

variable. The correlation between mean RT for the both visual fields

condition and the overall mean RT was 0.99. Slope for the covariate did not

differ significantly for the subgroups. In the event the covariate was

highly significant (F-86.82, Df-1,17, P<0.0001), but the main effect for

fasthand remained non-significant. There was a highly significant

Interaction between fasthand and response hand (F-BA^'-i, Df"l,18, P<0.0001),

which was an expected consequence of the design. In addition the

interaction between VHF, hand and fasthand closely approached significance

(F-A.Ol, Df-1,18, P<0.061).

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This interaction is illustrated in Figure 4 and is of considerable

Interest, despite the border-line probability level. Since both the visual

field and hand differences were predicted, straightforward post-analysis of

covariance comparisons remained appropriate. Only the comparisons relevant

to the predicted within group effects have been tested and are given in

Table 1. To provide real time information the comparisons are given for the

unadjusted mean scores, but significance levels were confirmed for adjusted

comparisons. It can be seen from Table 1 that for both fasthand groups the

differences between right and left hand were significant at P<0.001, both

for the RVF and for the LVF, and were in the expected direction. It can

further be seen that the VHF differences also all go in the predicted

directions. For the fasthand left group the VHF differences are significant

m
241

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280

275

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280

255

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Fig. A. The interaction between visual half field, response hand and

fasthand (F-A.01, Df-1,18, P<0.061).

w. * *, v.

at F<0.001, both for the right and left hands tested separately. But for

the smaller fasthand right group this reduced to P<0.02 for the left hand,

and the right hand VHF cooparison was not significant.

Two cells in Table 1 have larger differences than any other within

subject comparison. These compare right hand in the RVF to left hand in the

LVF, separately for each fasthand group. For both groups, the level of

significance is considerably greater than the value of P<0.0C1 tabled.

According to the assumptions of IHTT studies these comparisons should not be

significant because both involve uncrossed relationships, but according to

the predictions of the present experiment they should be larger than any

other within group comparison because they compare a mean from a condition

which requires no inter-hemispheric transfer to a condition which requires a

transfer for detection and a transfer back for manual response.

Aralyses including Sighting Dominance. The analyses of the preceding

section were repeated with the inclusion of sighting dominance as a grouping

v riable. Sighting dominance was not significant as a main effect but

approached significance in interaction with visual field (F-3.45, Df*l,16,

P<r» 082). A

11

the analyses reported were also made on untrimmed

Toi ransfo: 4 mean RTs and although this produced the same results as

eatxier, f £ «.his particular interaction there was an increase in

significance to P<C.039, and there was a mean LVF advantage attributable to

sighting dominance of 5.99 msec, for the group dominant with the left

eye, and a mean RVF advantage of 2.90 msec, for the group dominant with the

right eye. Also, when analysis was made of the logtransformed individual

RTs hare again the slshtin^ dominance x visual field interaction was

significant (P<0.04). Finally, for an analysis grouping by sex anJ sighting

do nance the interaction was significant (P<0.029) and also when the 6

piijt Ss were introduced (P<0.019).

Exploratory factor analysis. Further descriptive, rather than

hypothesis testing, analyses were mide aimed partly at parsimonious

description of the relationships already described, and partly at the

general issue of measurenent in lateralizuion studies (Marshall, Caplan and

Holmes, 1975; Repp, 1977; Bryden and Sprott, 1981; Richardson, 1976).

1 » •

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242

Table 1. Individual comparisons for the visual field (RVF or LVF) x

response hand (right or left) x response group (right or left hand faster in

the bilateral condition) interaction from the analysis of data for the

unilateral condition (F-A.01, Df-1,18, P<0.06).

FASTHAND RIGHT (N-7)

RVF LVF

FASTHAiND LEFT (N-13)

RVF LVF

MEAN

right

hand

left

hand

right

hand

left

hand

right

hand

left

hand

right

hand

left

hand

(1)

253.41

(2)

259.56

(3)

255.39

(4)

263.70

(i)

278.89

(6)

27A.31

(7)

274.37

(8)

266.45

-6.15**

-1.98 4.17*

-10.29** -4.15* -8.31**

4.58**

4.52** 0.06

12.44** 7.86** 7.92**

P<0.02; ** - P<0.001, one-tailed tests

The RT data for the three visual field positions (RVF, LVF and both VF)

for each hand; the difference between hand scores, and the three indicators

of sighting dominance were factor analysed. Sex and age were also included

in this analysis. Factor extraction by the principal components method

followed by orthogonal rotation produced four distinct factors together

accounting for 90.9% of the variance. Communalities were high for all

variables, confirming the relevance of the variables included to the

analysis made. Figure 5 illustrates the absolute values of the correlations

in sorted shaded form. From these the constitution and the distinctiveness

of the factors can be seen.

The first factor, which took up 502 of the variation loaded heavily on

the six RT variables, with negligible contribution from other variables.

This would appear to be a plain RT factor representing response speed. The

second factor (about 18.5'. of the variation) loaded heavily on the three

hand difference variables with a small contribution from sex, and more

Importantly, very little from the sighting dominance measures. It

represents the difference between right and left hand In response time, and

confirms that all three Image representation positions provide almost

completely the same Information for the hand difference measure. The third

factor (14.7J; variation) represents sighting dominance. In a preliminary

analysis hand preference also loaded well on this third factor, but a larger

sample with more left handed Ss would be needed for inclusion of this

variable to be meaningful. The fourth factor (8* variation) loaded heavily

on age and sex alone. The conjunction of these two variables would seem to

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243

Variables

5 LVFL

3 RVFL

4 LVFR III

2 RVFR 1 1 1 1

7 BOTHL

6 BOTHR 1

8 RVFDIF • • ""

10 BOTHDIF • • . 1 1

9 LVFDIF " • - I 1 I

28 EYEGUN . 1

25 EYEKAL • II

21 EYECARD • • • • III

16 AGE • " "

—

• • • " * •

17 SEX - + + - .

*s

The absolute values of the matrix entries have been shown above in

shaded form according to the following scheme:

less than or equal to 0.123

0.123 to and Including 0.246

0.246 to and including 0.369

f 0.369 to and including 0.492

X 0.492 to and including 0.615

I 0.738 to and including 0.861

I greater than 0.861

.v.v.v.

KEY: LVFL - left visual field, left-hand response, RVFR - right visual

field, right-hand response, etc. DIF - difference; EYEGUN, EYEKAL,

EYECARD eye used for aligning gun, or card, or for looking into

kaleidoscope.

Fig. 5. In this table the factor structure is illustrated by representing

the absolute values of the correlations between variables in

sorted and shaded form.

have been fortuitous, since although in a one-way analysis of variance the

males and females did not differ significantly on age, there were more

females than males at the upper end of the six months age range of the

sample. The interesting point was that sex could largely be separated into

a factor orthogonal to those representing RT and hand differences.

A similar analysis including the 6 pilot Ss produced the same 4 initial

factors, loading on the same variables, and accounting for 46%, 23X, 13% and

7X of the variance respectively - a total of 90X. There were similar

findings for a maximum likelihood factor analysis followed by both

orthogonal and oblique rotations, and for analysis using Kaiser's second

generation little jiffy (Kaiser, 1970) with orthoblique rotation. The

loadings from these methods differed in no important way from those of the

orthogonal methods. Mostly correlation was introduced between factor 4 a .d

the other factors, but also between factor 2 (hand differences) and factor 3

(sighting dominance) and between factors 1 (reaction speed) and 2 (hand

difference).

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244

Analysis of Factor Scores« Two-way analysis of varianre of the form

fasthand (right or left) x eye dominance (right or left) were made of the

factor scores. For the first factor there were no significant main effects

for either fasthand or sighting dominance and the Interaction was not

significant, which is consistent with the interpretation of this factor as

representing general speed of RT. For the second factor, representing

differences between left and right hand in response time, there was a highly

significant effect on fasthand (F-41.36, Df-1,16, P<0.0001). There was also

a significant interaction between this variable and sighting dominance

(F-4.85, Df-1,16, P<0.0A2), hinting at construct validity problems in the

sighting dominance measure connected possibly with hand preference. (It

seems likely that a kaleidoscope will be put Co the eye on the same body

side as the hand which picks it up). For the third factor, loading largely

on the sighting dominance Indicators, the only significant effect was for

sighting dominance (F-93.01, Df-1,16, P<0.0001); and for the fourth factor,

as would be expected, there were no significant effects.

The question of Interest was whether the factors gave a clearer

definition of visual differences than the initial unfactored variables, and

that was why the visual field differences were not Included in the set of

variables factor analysed. Canonical correlation established that there was

a high level of dependence between the 4 factors and the right and left hand

VHF differences considered jointly, and that about S9Z of the difference

score variation could be expressed by the first canonical variable extracted

(Chl-square-22.34, Df-6, P<0.0001). However this loaded more or less

equally on all three factors, and the second variable extracted, which

loaded mostly on the hand difference factor, did not provide significant

prediction.

In a multivariate regression analysis, the VF difference scores were

predicted from the first three factors. The results differed between hands.

For the left hand VF differences the RT speed factor approached significance

(t-1.91, Df-22, P<0.07), the hand difference factor predicted significantly

(t-2.62, Df-22, P<0.01), as did sighting dominance (t-3.1A, Df-22, P<0.005).

The results were In the same direction in the right hand data, but only the

contribution from sighting dominance was significant.

^

;

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The analyses presented in this report have been weakened by the

procedure of applying separate analyses of variance to the data studied in

piecemeal fashion. This, however, has allowed exploration of complex

effects more directly than would have been possible in one global analysis

'where the effects of interest would have appeared as complex interactions.

It is also in accord with the basic design of the work as two separate

experiments run in an Integrated framework. The analyses reported included

two subjects who were lefthanded. Each analysis was repeated with these

subjects excluded with no effect on the findings except to reduce the

degrees of freedom and thus to a small extent probabilities.

DISCUSSION

In the experiment reported, a plain circular light source subtending

approximately one degree of visual angle was used as a stimulus on all

trials, and on all trials Ss responded by raising both hands as quickly as

possible from micro-switches built into the table top. The treatment of the

experiment was that the light was randomly presented either to the RVF or to

the LVF. Randomly interspersed with this treatment was a further condition

in which the stimulus was duplicated and presented simultaneously in both

visual half fields. This bilateral presentation condition, in which

stimulus and response parameters were balanced, provided control information

to aid the analysis and Interpretation of results for the unilateral

condition.

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245

To place the experiment in the context of previous work using reaction

times in divided VF studies of cerebral lateralization the data were first

analysed without taking into account the information from the bilateral

presentation condition, except to establish that fixation had been

maintained.

'.>.>.

In these analyses the prediction that response would be faster when

initial projection of the stimulus vas to the right hemisphere failed in the

data overall, as did the prediction that response would be faster with the

left hand than the right hand. However this was due to a cancelling of

differences between male and female subjects. Both predictions held for

males, but in neither case was there a significant difference for females.

Female Ss were, however, significantly faster than males wh°n initial

projection was to the left, language dominant, hemisphere but were not

faster when initial projection was to the right hemisphere.

Tak' . at face value these results appear to be yet another addition to

the Inconsistent findings reviewed In the introduction. Thus there was a

VHF difference for detection, following Allard and Bryden (1979) but not.

Klmura (1969); and a right hemisphere advantage was shown by males but not

by females, a finding in the same direction to that of Klmura (1969) but

opposite ti Ulard and Bryden (1979). It now seems clear that the only

valid conclusion from studies such as these is that different results will

be produced on different occasions, and that replication with improved

procedures and analyses such as undertaken by Bryden and Allard will not In

Itself be sufficient to resolve Inconsistency. A possible reason for this

Is suggested by Bryden's 1976 report of no VHF difference for detection or

localisation In 4 replications of Kimura's experiments, yet in the

individual data 88% of subjects were faster in one VHF than in the other.

Of these 60% were faster in the LVF and 40X were fas>ter in the RVF. Bryden

Interpreted this as corroborating the finding from the analysis of variance

made on mean data of no significant differences between visual fields. But

a more plausible Interpretation would have been that the Individual

differences were evidence of an uncontrolled effect confounded in the mean

scores, and their distribution should have at least been Inspected. It is

unfortunate that Allard and Bryden also failed to provide information on the

individual distribution of error counts In their 1979 data.

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Jeeves and Dixon (1970) also mention, but do not describe or take into

account, individual differences inconsistent with the mean scores on which

their analyses were made. The point is that some inconsistent subjects

Cilgnt be expected as a consequence of measurement or experimental error, but

'overall the difference RTs should be normally distributed with the

in insistent subjects in the tail of a distribution which crosses zero

difference. The fact that these authors test their results with a

distribution-free test suggests that perhaps this was not the case. They

propose that the motor responding area in the left hemisphere is faster at

initiating a response than the corresponding area in the right hemisphere,

since In their mean scores LVF/left hand rejponse was slower than for

LVF/right hand, i.e., the condition held to require a callosal cross was

faster than the condition which did not. This interpretation overlooks the

possibility of confounded individual differences within the mean RTs.

Jeeves (1972) repeated this work with children; once again there was

Inconsistency in the Individual data, and on this occasion also in the mean

scores. No information is given on the distribution of the difference RTs

and the possibility that the Individual inconsistencies affect all the mean

scores Is not considered. It seems possible that the direction of the mean

scores was an artifact of group composition and would depend on the

Incomplete balancing of confounded individual difference and not on cerebral

processing or pathway differences.

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246

The bilateral presentation condition was introduced into the design in

an attempt to provide a method of predicting in which direction the results

would go. This method was suggested by previous work (in preparation); but

there also seemed to be evidence in the early SRT literature of unnoticed

hemispheric differences when response was bimanual. The use of simultaneous

response with both right and left hand has been common in RT studies, but

usually only tie average time for both hands has been analysed in the

mistaken belief that this provided control - which It did to some extent,

but at the cost if confounding central processing differences.

•»V •

As has been seen, one study which did separately report right and left

hand RTs was that of Metfessel and Warren (193A). Their finding was that

subjects responded on average faster with the non-preferred than with the

preferred hand, and they accounted for this by supposing that Ss asked to

respond as quickly as possible with both hands "overcompensated" with the

non-preferred hand in an attempt to produce simultaneous movement. However

re-analysis of their data (see Introduction) established that the hand

difference scores were distinctively bimodal in distribution. For example

the 21 lefthanded subjects were not all faster with their right hands, nor

was there a normal distribution of difference scores centered on one side

from zero, to represent an advantage on the part of one hand (the right)

with one tail crossing zero in the direction of a left hand advantage for

some subjects, as would be expected if "overcompensation" were biasing a

preferred-hand advantage. Rather II of the 21 lefthanded subjects were

faster with the right hand, but 10 were faster with the left hand, and the

difference scores were distributed as if from two separate normal

distributions either side of zero with means of 6.71 and -6.98 msec.

respectively with standard errors of less than 1.6 msec, in each case.

The prediction that the data for the bilateral component of the present

experiment would follow a similar bimodal distribution held. Distinct

separation of Ss into two groups can be seen in Figure 2. The mean

difference scores of 9.99 and -5.85 msec, are each separated by more than A

standard errors from zero in opposite directions, and are comparable in size

to those found in the data of Metfessel and Warren (1934).

It had been proposed that this effect, if found, would be consistent

with hemispheric processing differences; and it was predicted that if

subjects were separated into two groups, those faster with the right hand

and those faster with the left hand to bilaterally presented stimuli, then

the former group would respond faster in the LVF and the latter group in the

RVF to unilateral presentation of the same stimuli. In the event bb% of the

'sample were faster with the left hand and 35': with the right hand, and when

this classification was taken into account in the analysis of the unilateral

data the results were as predicted. The group which was faster in the

bilateral cor itlon with the right hand responded faster to LVF presentation

than to RVF } -sentation in the unilateral condition, whereas the group

which was faster in the bilateral condition with the left hand responded

faster to RVF presentation than to LVF presentation in the unilateral

condition. These findings applied equally to males and females.

The results for these important findings were presented in detail in

Table 1 and some comment on the significance levels is required. Firstly,

the overall effect in the analysis of variance reached only P<0.06, but this

need cause no reservation as the paired comparisons and their direction were

predicted (Winer, 1971). Twelve comparisons in Table 1 were relevant to the

predictions of the experiment, and although this increased the possibility

of a type 1 error this seemed preferable to an increase of risk in the

opposite direction, by use of a conservative post hoc method. The use of

Scheffe's method would have been indefensible considering the large number

of paired and grouped comparisons of no interest. Tukey's HSD method may

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247

have been a preferable alternative, but even so 16 of the possible paired

comparisons were not relevant. A cautious reader will not search for

alternative methods of testing comparisons; but might tentatively hold as

Interesting the effects which can be seen in Table 1, pending replication.

The VHF results as listed in Table 1 are all in the predicted direction

and for Ss who were faster with the left hand in the bilateral condition are

highly significant (P<0.001 or less), both for the right hand and for the

left hand. This is strong evidence for right hemisphere processing, and for

consistency between hand difference and VHF difference as measures of

functional cerebral asymmetry. The results are also in the expected

direction for Ss who were faster with the right hand in the bilateral

condition; but although the VHF difference for left hand response at 4.14

milliseconds was similar in size to the highly significant difference for

the other group, the greater variability for the smaller group reduced

significance to P<0.02; and for the right hand the VHF difference, although

in the predicted direction, was not significant.

otfraa

&&

The 4 cells in Table 1 where both VHF and hand are varied are of

special interest. These are RVF right hand compared to LVF left hand; and

RVF left hand compared to LVF right hand, separately for each of the two

response groups. If the assumptions quoted from Rizzolatti (1979) are

correct then there should have been no significant difference for any of

these 4 comparisons. This is because the first compares uncrossed pathways

via one visual field to uncrossed pathways via the other visual field, and

the second compares crossed pathways by one visual field to crossed pathways

by the other visual field, i.e.. In both cases both sides of the comparison

have the same advantages and disadvantages. But if the interpretation

offered for the present findings is correct, then in the case of the

fasthand right group the RVF right hand/LVF left hand comparison will have

one component requiring no crosses (the first) and one component requiring a

cross for detection plus a cross (or use of the less efficient ipsllateral

motor pathways) for response and accordingly the difference should be twice

the estimated IHTT for that group. From Table 1 it can be seen that the

difference of 10.29 msec, was indeed very close to twice t'.ie time estimated

as the mean for the other 4 conditions (5.15 msec). For the fasthand left

group the same comparison will also involve one conditim with no crosses

(LVF, left hand) and one with two crosses (RV/?, right hand) and here the

difference score (12.44 msec.) is precisely twice the IKTT as estimated by

the mean for the othtr 4 comparisons for the same group. The remaining two

cells for within response group comparisons in Table 1 are not predictable.

^or both components there is a single cross, but for one component this is

for detection whereas for the other it is for response. The outcome

consequently is uncertain, and in the event for the larger group there was

no difference, but for the smaller group the condition when the cross was

for detection was significantly faster than when the cross was for response.

The research reviewed in the introduction on estimating IHTT needs very

little further discussion. If the present findings are correct then the

assumptions on which this work is based are defective, and the times given

for example by Berlucchl et al. (1971, 1977), Rizzolatti et al. (1971,

1979) and Anzola et al. (1980) using the SRT paradigm are not estimates of

IHTT but are small residual differences left after the balancing of various

confounding effects. This In Itself requires no further discussion In the

present context since It Is a conclusion which can be drawn by anyone who

looks closely at these researchers own published findings.

V.v^s<«Jl

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The present findings do provide estimates of IHTT where at least

relevant process'"g differences *re not confounded, but have also shown that

sighting dominance should be taken into account, and group size was too

small for this to be usefully done. There Is, however, a fair measure of

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248

consistency, and IHTT estimates based on hand differences were 6.15, 8.31,

A.58 and 7.92 msec, giving a mean of 6.74 msec, which compares closely with

the results extracted by a similarly regrouped analysis of Metfessel and

Warren's (1934) data. Except for one non-significant value the estimate

based on VHF comparisons with response hand held constant, including the

non-significant value, are 1.98, 4.15, 4.52 and 7.86 msec. Thus the mean

for the estimates from the hand difference comparisons is 6.74, and the mean •

for the estimates from the VHF comparisons is 4.63. The overall mean from "^"V^JW

the estimates from both sources is 5.68, and if the weighted times for the -V^^^j

comparisons with two IHTT crosses are introduced then a mean rounding to -VVNS

5.68 msec, is produced as the best estimate of IHTT using the present data, fflfimffl

with the important qualification that this estimate is known to include

significant uncontrolled bias due »o sighting dominance and possibly also

from a preferred hand practice effect to be discussed later. Also, there is

no reason to suppose that results for 9-year-old children either will or

will not, match those for adult subjects.

Very little need be said about the additional analyses presented in the

results section. These tested alternate explanations for the findings, and

a certain amount of discussion has been necessary in their presentation.

Subjects were sampled randomly from their school year groups to avoid the /NVN

possibility of reactivity from sampling procedures or overt selection of any Q

sort apparent to teachers or children. This led to the testing of two left- .^%

handed children, but it was shown that inclusion or deletion of these Ss in

no way affected the findings. Since a method was being used to infer

processing hemisphere, any relationship of this with handedness might not

have seemed important. However, any practice advantage for the preferred

hand was not been controlled.

The inclusion of a sighting dominance measure was important. Although

sighting dominance was not significant as a main effect and did not • _J

influence the VHF interaction with response group and response hand, there "•/••/v-"/

were other grounds for concluding that visual dominance would need to be ^'v^SviT

taken into account in a more finely tuned experiment. The additional VVVW

analyses established that visual dominance was significant in interaction s,i

%

>'^>J

with other variables in a changing pattern of responses across the 120 RTs V^^Vjoy

for each subject. It was clearly separated from the hand difference

variables and from the indicators of overall RT in the factor analysis, and

when visual field difference wc-e regressed on the factor scores the

sighting dominance factor was the best predictor of these differences.

1 Kimura (1969) also tested sighting dominance, and reported a

significant bias on the part of right-handed females, but not right-handed •

males, (P<0.02, N-192) towards left eye sighting dominance. An effect such ^v""/^

as this might conceivably provide an alternative explanation of sex

differences in a lateralization study using a VHF method. But th« value of

Kimura's finding has to be balanced by :he fact that the relationship

accounted for only 2.7Z of the variation and also against the lack of ^JLÜÜ

significance in any of the 7 data sets pooled to give the sample of 192

(calculated from the published results). There were no sex differences by

sighting dominance in the overall analyses made of the present data, nor

were the frequencies by sex significant but sample size was small. About

58% of the sample were right eye dominant; 42% were left eye dominant, and

none were classified as mixed. These figures are within the range of values

for eleven studies reviewed by Porac and Coren (1976), but on average show a 0 i

lower incidence of right dominance contributed mostly by the male subjects. >-,0**-v'*sj

visual dominance effect was for faster response when presentation was to the V&'OSv

visual field on the samo body side as the dominant eye, i.e., when the image Sj>i>jSi

£*.**:

From the mean scores it could be seen that the general direction of the

1 dominance effect was for faster response when presentation wa

1 field on the samo body side as the dominant eye, i.e., when t

was presented to the nasal hemiretina of the dominant eye and to th(i

-«rafl
250

temporal hemiretina of the non-dominant eye. This observation is

speculative, and is based on inspection of mean scores and not on

significance testing, but it suggests that it would be wise to control both

sighting dominance and use of the crossed and uncrossed visual pathways if

IHTT is to be reliably estimated by a lateralization study. Young (198'

has remarked that although it was once customary to measure eye dominan 1

Ss in VHF studies, it was now accepted that this was of no use as an

indicator of cerebral organisation. However the importance of sighting

dominance in the present context is not whether it is a useful indicator of

cerebral lateralization, but whether or not it is confounded with the VHF

d.fferences used to operationalise predicted differences in cerebral

organisation. Bryden (1982) has suggested that the relationship between

sighting dominance and lateralization should be examined in a dichotic

listening task, since in such a task sighting dominance would not have a

peripheral sensory effect, and any relation observed would be a truer

assessment of the relation between sighting dominance and cerebral

specialisation. However, if no effect were found this would say nothing

about the influence, if any, of sighting dominance on the results cf VHF

studies. The only way to gain such information would be by careful VHF

experiments with sighting dominance, for one thing, controlled.

ASM

\\Kfi

'ZfZ*

It was notable that the introduction of the fasti and factor into the

analysis of variance removed the significant sex differtnces. This in

itself supports the interpretation of the hand difference measure as an

indicator of hemispheric differences, since it seems improbable to suppose

that males and females differ as to which side of the body produces the

fastest movement quite independently from central processing differences.

Put another way, one interpretation of the findings could be that some

people are faster with their right hands and others are faster with their

left hands for reasons which have nothing to do with VHF or hemispheric

differences, it is hard to see what these reasons could be other than hand

preference, which could not be applicable in the present case. It is even

harder to see what reasons could be given compatible with the finding of sex

differences, apart from stranegy/processing differences.

:-r.

The procedure followed removed the sex differences from the analysis of

variance and showed that if Ss were grouped in term", of a proposed indicator

of hemispheric asymmetry for the set task then it was this and not sex which

accounted for visual field differences. However this merely moved the sex

differences back one level. A substantial majority of the males was faster

with the left hand, suggesting right hemisphere processing, whereas the

females were more evenly balanced. Kimura's (1969) suggestion that females

'would be more likely to use a verbal, left hemisphere, procedure and males a

spatial, right hemisphere procedure (see also Witelson, 1976; McGlone, 1980)

rested on, as has been shown, very shaky ground but is supported by the

present findings. The apparent sex and VHF interactions in the initial

analyses are a consequence of this dl'lerence. Marshall (1973) on the basis

of a review concluded that many reports of sex differences in hemispheric

spec alisation could be accounted for as differences in strategy preference.

Segalowitz end Stewart (1979) have suggested that in a letter matching

paradigm sex differences might be accounted for as strategy differences,

males tending to use nonverbal strategies and females being more variable in

their use of either a verbal or nonverbal strategy. It is one thing to find

that males and females choose, possibly as set by unnoticed situational

influence, prior experience, or experimenter reactivity, different task

strategies, either linguistic or non-linguistic, and quite another to

propose that there are functional brain differences between males and

females. Further when group size is small a significant lack of balance on

an uncontrolled difference is not unlikely, and could go by chance in either

direction. Allard and Bryden (1979) provide one instance when a sex

difference for a comparable task is in the opposite direction to the present

;««

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• V ^

^täiW&W&tä :<<<..<''' >_VJ". . & - KV a _ m. ~ - » • - f
M———iwwm^wr.Ti^ "'^''•»' »'i^i^vTi-r^vm.'^LFTif^Ti/yywv^rwir^irwT^giumT^r-i

251

finding. It remains to be seen whether or not further use of the present

design and analyses will show that sex differences in response group

composition consistently go in one direction or not.

CONCLUSION

In conclusion, it has been shown that even in a SRT procedure in which

Ss made identical response on every trial to unilateral and bilateral

presentation of a dot of light, there are VHF differences which are

confounded, unless Ss are grouped by response strategy. It has been shown

that sex differences in VHF effects evaporate when response strategy is

taken into account; or rather that the VHF differences reduce to strategy

differences, which is something different as these seem more likely to have

an experimental rather than a structural origin. An approach for correcting

deficiencies in IHTT studies has been outlined, and it has been argued that

none of the previous work on IHTT is satisfactory. It is suggested that if

a SRT procedure is to be used for reasonably accurate estimations of IHTT

then not only hand preference, sighting dominance, and hemiretina of

stimulus presentation will need to be controlled, but also response strategy

- however difficult that may be. The alternative is that individual

hemispheric differences will be confounded, either to the extent of

cancelling all evidence of VHF differences, or to the extent of throwing VHF

differences in one direction or the other as an artifact of subgroup

composition. It also seems clear that the habit of collecting a large

amount of data from individual subjects may well provide narrower confidence

limits for the means estimated, but the question has to be asked, means of

what? Control of response strategy is more likely to be achieved in small

amounts of data from many subjects, since the likelihood of a change in

strategy on the part of individual Ss will be reduced. Finally the

experiment has suggested an Important method for the operatlonallsatlon of

predicted asymmetries In hemispheric function. This Involves the analysis

of hand difference RTs since the direction of these will vary In relation to

the hemisphere not of Initial projection of the visual stimulus but to the

hemisphere in which the response command Is Initiated, and this could well

be a better Indicator of processing hemisphere than VHF differences.

Certainly If this technique can be reliably developed many Interesting

possibilities for laterallzatlon experiments and their analysis will follow.

ni

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-VV"

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256

SELF-RtPORl OF NEUROPSYCHOLOGICAL DIMENSIONS OF SELF-CONTROL

ABSTRACT

•//:

Thomas R. O'Connell, *Don M. Tucker and Thomas B. Scott •>^>-i"«5

Counseling Department *P8ychology Department vv""^"''

University of North Dakota University of Oregon

• ,

S "- *w -J

A central notion in research on individual differences in hemispheric ^vvvi

specialization is that some people emphasize one hemisphere's cognitive .' '.' •:/?i

processes as a general mode of functioning. We begin this chapter by r';'/-. /'*

considering this construct of a laterallzed cognitive style, and the

methodological and theoretical problems it has raised. If the construct is

to be scientifically useful, it must be supported by empirical assessment of

cognitive performance - or at least cognitive strategy. For the

neuropsychological approach to contribute uniquely Co personality research,

it will be Important to relate the psychological traits to physiological

measures of brain activity. In •idltion, en important observational method

is self-report: given the appropriate ..tstionnaire, we argue that most

people can describe their cognitive and f motional functioning in ways that v

s

'

%i%j

are meaningful to neuropsychological constructs of personality. We present •y"y"'*'v'

preliminary data on the O'Connell Cognitive and Affective Style Scale SfV^JM

(OCASS), a self-report scale designed to assess cognitive and emotional ivVsW"

dimensions of self-control. '•/•."'''/v'

INTRODUCTION

The traditional neuropsychological study of brain lesions showed that

damage to certain areas may impair specific psychological functions. The

commissurotomy studies of the 1960s (Spurry, 1966; Sperry, Gazzanlga and

Bogen, 1969} provided the more dramatic demonstration that an isolated

hemisphere could perform the fundamental cognitive operations we consider ^"'^'^

necessary for an Intelligent mind. As the characteristics of each M?vö'

hemisphere were described, it became clear that a hemisphere'» SJÄSiö

specialization involved not just specific functions, but a general mode of

approach to problem solving; the left hemisphere seemed to analyze tasks

into parts, while the right hemisphere was better able to integrate parts

into wholes (Bogen and Bogen, 1969; Levy, 1969). It was not necessarily the v*v'v*v|

case that a hemisphere's involvement in a task would be appropriate to the •''.'•''SJv!!'

task requirements. Levy's (1977) studies suggested that activation of a v^'^V

hemisphere during a task may or may not be appropriate to the hemisphere's '"'S'S''.'-'

competence to perform the task. // wtfwöv

teMMM*^
v wv^v »v ^l>. ^. w^r. i^. PV^. y. ^.' ^ry. vwnjw. wj w. w:*•, w:w:i

"^" »»nr ^.-v'".wi

257

Thus, it has become apparent that hemispheric function during cognitive

activity is a dynamic process, and it Is insufficient to consider brain

laterality only in terms of a static localization of mental abilities. The

progression from being concerned with fixed abilities to considering dynamic

strategies is reminiscent of the development of Individual difference

approaches to intelligence. Whereas the issue at the beginning of the

century was differences among people in intellectual ability, by the middle

of the century the popular issue had become differences in strategy or

cognitive style (e.g., Witlcin, Dyk, Faterson, Goodenough and Karp, 1962).

For many readers of the hemispheric specialization studies, the

particular styles shown by the two hemisph^res seemed intuitively appealing

as descriptions of differences among people in cognitive style. The left

hemisphere's analytic, verbally-mediated cognition was contrasted with the

right hemisphere's more holistic, spatially-organized cognition; certainly

some people seemed to draw on one of these cognitive strategies more than

the other. The problem in researching how these hemispheric modes could be

related to normal cognitive style was one of measurement; how is

differential hemispheric function to be assessed In an intact brain?

A convenient method suggested itself in the form of eye movements to

the left or right during reflective thought. Teltlebaum (1954) had

suggested that a person is likely to move the eyes laterally while thinking

deeply about something. Day (1961; 1964) observed that an individual's

characteristic direction of movement was related to emotional and

personality characteristics. A right-looker was described as experiencing

anxiety from external causes, whereas a left-looker was described as

experiencing anxiety in a more internal, subjective fashion.

The important link to lateral brain function was made by Bakan (1969).

He proposed that a person's direction of eye movement during thought

Indicates use of the contralateral hemisphere; thus the more vivid imagery

reported by left- than right-lookers shows a greater use of the right

hemisphere by those subjects. Bakan (1969) reported that left-lookers were

more likely to choose college majors in humanistic, as opposed to scientific

or quantitative, lielwS. Similar results were found by Combs, Hoblick,

Czarnecki and Kam.'.er (1977). Bakan (1969) and Weiten and Etaugh (1974)

reported left-looVers to have lower quantitative SAT scores than rightlookers. Greater usage of right than left hemisphere processing by leftlookers would be compatible with the finding by Crouch (1976) that they are

more responsive to facial than verbal cues. Consistent with Day's original

findings, other studies found left-lookers to be more inner-attentive

(Meskin and Singer, 1974) and mure artistically diverse and creative

(Harnad, 1972; Hines and Martindale, 1974). On the Allport-Vernon-Lindzey

Scale of Values, left-lookers scored higher on aesthetic and social scales,

while right-movers scored higher on theoretical and economic scales (Weitan

and Etaugh, 1973).

Bakan (1969) found that left-lookers were more hypnotizable than rightlookers. Similar results were reported by Gur and Gur (1974) and Gur and

Reyher (1973). Day (1967) had reported higher amplitude, lower frequency

EEGs in left-lookers. Consistent with this suggestion of a lower level of

brain activation, Bakan (1969) found higher renting alpha in left- than

right-lookers. Bakan and Svorad (1969) replicated the finding of higher

alpha in left-lookers, and observed that higher hypnotizability was also

related to higher resting alpha.

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The general pattern of results in this research seemed encouraging for

a hemispheric model of cognitive style. Yet, as is often the cane with

personality measures, replicability has often been a problem ^Ehrlichman,

1977; Etaugh, 1972; Etaugh and Rose, 1973; Hartlage and ..»lison, 1979).

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258

Furthermore, the rationale for linking an eye-movement to engagement of the

opposite hemisphere has been shown to be less compelling than at first

thought (Ehrllchman and Weinberger, 1978). Efforts to validate lateral eye

movements with measures of ability in verbal and spatial cognition were

largely unsuccessful (Ehrllchman, 1977; Galln and Ornstein, 1974; Hiscock,

1977b).

There have been attempts to examine cognitive style with measures of

hemispheric activation other than lateral eye movements. Galln and Ornstein

(1972) evaluated the EEGs of lawyers and potters, exemplars of left and

right hemispheric cognitive styles, respectively. Because there may be

differences between left- and right-lookers in overall EEG activity (Bakan,

1969; Day, 1967), EEG studies must consider not only lateral asymmetries but

the problems of assessing characteristic overall activation levels that have

arisen in the introversion-extraversion literature (see Gale, 1973).

The validity of lateral eye movements as measures of Individual

differences in characteristic hemispheric estivation has received some

support from studies of event-related potentials (Shevrin, Smokier and Kool,

1980) and regional cerebral blood flow (Gur and Gur, 1980). Remarkably

little attention has been given the question of why activating a given

hemisphere would cause subjects to move their eyes in the opposite

direction. Bakan (1969) and K'nsbourne (1972) suggested that motor activity

in the more activated hemisphere would overflow into the frontal eye fields.

This ocular-motor synkinesia would not seem to be a particularly adaptive

way for the brain to work. Another interpretation considers the function of

eye movements while thinking: to avoid the visual distraction of the

questioner. The direction of the eye movements is selective; a right

movement, for example, shields the right visual half fields and left

hemisphere from the distraction facing the subject. Considered in this way,

lateral eye movement behaviour could reflect not only characteristic

hemispheric balance, but an individual's susceptibility to interfering

visual input (Yutrzenka, 198; Tucker, Yutrzenka and Heck, 198A).

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Just as the measurement of "hemispheric activation" has proved more

complex than initially thought, the theoretical aspects of this notion have

also become complex. Levy (1983) has emphasized the need to consider

hemispheric activation as a dynamic process in research with normal

subjects as well as with commisurotomy patients. Although people may vary

In their tendency to activate one hemisphere over the other

characteristically, the two hemispheres are variably activated according to

task demands, and this must be considered when assessing hemispheric

contributions to task performance. In their research with normals. Levy,

Heller, Banich and Burton (1983) assessed the tendency to activate a

preferred hemisphere by measuring each subject's visual field asymmetries on

a syllable-identification task. Those with a left hemisphere approach

(I.e., a right field advantage) showed poorer performance when tested on a

face recognition task, consistent with the proposal that these subjects show

less left and greater right hemisphere activation in a variety of

situations.

Caplan and Kinsbourne (1981) examined the preference of children for a

verbal rather than a visual style of problem-solving. Those preferring a

verbal approach were better readers, suggesting that cognitive style is

related to skill development. The preference for a verbal strategy also

showed a small but significant correlation with a right ear advantage, and

thus left hemisphere processing, on a dichotic listening task. Caplan and

Kinsbourne emphasized the importance of differentiating between brain

lateralization - the stable, anatomically-based functional differences

between the hemispheres - and cognitive style - the dynamic usage of the two

hemispheres in problem-solving.

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A similar dlsclnctlon has been drawn recently by Sackeira, Weiman and

Gregia (1984). They suggest that activation asymmetry, a person's tendency

to engage a given hemisphere preferentially, should not be assumed to be

identical with brain lateralization. They assessed LEM (Lateral Eye

Movement) measures of preferred hemispheric activation in groups known to

differ in brain lateralization - left banders, right-handers and those with

left-handers in the immediate family. Interestingly, significantly more

right LEMs were found in left-handers and those with left-handedness in the

family. However, there was no simple congruence between lateralization

group «nd LEMs, supporting Sackeira et al.'s contention that activation

asymmetry, which is analogous to lateralized cognitive style in the context

of the present discussion, should not be seen as identical with basic

functional lateralization.

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It is simple enough to think that people vary in their tendency to use

one hemisphere more than the other. It is more complex to consider a

hemispheric function in a dynamic sense. In addition, the evidence is

growing that not only cognitive but emotional factors influence hemispheric

functioning. In reviewing this evidence, Tucker (1981) concluded that in

both normals and psychiatric patients certain forms of emotio"«! arousal

have been associated with asymmetries of hemispheric activation. High

trait-anxious normals showed a right-ear auditory attentional bias and a

detail-oriented perceptual style suggefting left hemisphere activation

(Tucker, Antes, Stenslie and Barnhardt, 1978; Tyler and Tucker, 1982). For

both normal students and depressed patients, changes in mood level seemed to

Influence the right hemisphere's function particularly (Tucker, 1981;

Tucker, Stenslie, Roth and Shearer, 1981). The implication of these

observations for cognitive style is that emotional factors - either traits

or states - may be important determinants of asymmetric brain activation and

thus hemispheric contributions to cognitive function.

V.V.

Self-regulation Through Activation and Arousal

Perhaps the more important implication of these observations is that

the processes regulating emotional arousal in the brain seem to be

inherently asymmetric. To explore this implication, Tucker and Williamson

(1984) examined the literature on the control systems determining brain

activity. They drew on Pribram and McGuinness's (1973) distinction

between activation and arousal systems, then went on to formulate the

differential control properties of these systems by reviewing Che relevant

literature on the neurochemical substrates of activation and arousal in

animals. The activation system augments motor readiness. It produces a

conic Increase in brain activity, supporting vigilant attention. When

overactivated pharmacologically in animals or humans, this system produces

stereotyped, repetitive behaviour. Tucker and Williamson (1984) conclude

that this reflects the redundancy bias which is the elementary cybernetic

mode of the activation system. In contrast, the most elementar., attentional

control on the perceptual systems seems to operate in a different fashion,

with a phasic increment in brain activity in response to novel input. This

arousal system seems to operate under a habituation bias, a tendency not co

respond Co perceptual input unless it is novel.

As McGulnness and Pribram (1980) emphasized, these are fundamentally

motivational and emotional systems, yet they are essential to controlling

attention during higher cognitive processing. Tucker and Williamson (1984)

review evidence that the neurotransmitter substrates of activation and

arousal are asymmetric in the numan brain. This evidence could help explain

Che hemispheric asymmetries observed in the psychopathological disorders

chat are thought to be associated with neurotransmitter dysfunctions.

Furthermore, it is possible to formulate a theoretical model of how the

elementary controls of activation and arousal are differentially important

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in regulating the cognitive operations of the left and right hemispheres.

The redundancy bias of the activation system is important to focusing

k'.tention; this may be integral to the analytic cognitive operations of the

left hemisphere. Many features of higher motor control seem to depend on

left hemisphere processing. In contrast, the right hemisphere seems to show

an affinity for integrating the perceptual input processes of the posterior

brain. The cybernetics of the arousal system may facilitate this directly.

By selecting for novel input, the arousal system fills representational

capacity with a broad range of unique information. This may be the

attentional control underlying the right hemisphere's skill in holistic

perception.

The major division of the brain found when considering activation and

arousal is not right/left but anterior/posterior: arousal facilitates Input

while activation provides the sequential control for motor organization.

Tucker and Williamson theorized that the lateral specialization of the brain

occurred to capitalize "^ each of the cybernetic modes of activation and

arousal with n a hemisphere, the left hemisphere elaborating its cortical

organization around control by activation, the right hemisphere elaborating

an entire hemisphere around control by arousal.

Pribram (1981) emphasized the distinction between anterior and

posterior cortical systems in self-regulation. The posterior intrinsic

cortex facilitates representation of the external context, and thus tends to

make the organism context-sensitive. Pribram terms this the aesthetic mode.

The frontal cortex offers inhibitory control over this tendency, thus

allowing the organism »reater internal control over behaviour. This is the

ethical mode. Pribram points to early psychometric studies of brain lesions

suggesting that extraversion is increased by frontal lesions (Petrie, 1952).

Tucker and Williamson (1984) propose that the specific cybernetic effects of

activation and arousal can explain many of the differences between

introverts and extraverts. Whereas Eysenck (1967) formulated this

personality dimension around the notion of reticular activating system

function, this was a unidimensional concept of brain arousal; clearer

formulations of the self-control patterns of introversion and extraversion

are possible by considering the qualitatively-specific cybernetics of

activation and arousal. The redundancy bias of activation affords constancy

that facilitates internal control over behavior. In an extreme form, this

can produce pathological Introversion. Animals and humans whose activation

is pathologically augmented by dopaminergic agonist drugs show social

withdrawal (Ellinwood, 1967; Kukkinidis and Anlsman, 1980). The habituation

bias of the a'ousal system causes novel environmental events to gain control

over the extravert's behavior, leading to a responsive emotionality, a need

for novel excitement, and a limited attention span.

Although they will undoubtedly require modification and revision, these

formulations offer ways of thinking about neurocybernetics - how an

elementary neural control process can be important to higher-order

attentional control. In the current cognitive psychology literature, an

important distinction is that between "controlled" cognitive processes,

which require attention and volitional effort, and "automatic" processes,

which seem to organize themselves spontaneously (Neisser, 1967; Posner,

1978; Schneider and Shiffrin, 1977). The unique control properties of

redundancy and habituation biases would seem Integral to these different

kinds of cognitive control.

Thus there are specific predictions available for experimental test on

how alterations in motivational and emotional control systems in the brain

lead to changes in Information processing. Neuropsychology may allow a more

integrated approach to the study of personality, wherein emotional selfWS*M

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control and cognitive self-control are described within a single framework.

A Scale for Self-Report

If the neuropsychological approach is to provide more than theory, it

will be necessary to examine measures of brain activity and relate these to

the hypothesized processes of cognitive and emotional self-control.

Performance measures are required to find if there are at^entional effects

of the hypothesized control processes. These empirical assessments are

predicted directly by the neuropsychological constructs, and could provide

new experimental directions for the s'-udy of personality.

In addition, we suggest that there is an important place in this

research for self-report measures of cognitive style. Any laboratory

assessment of a person's cognitive approach or emotional responsiveness can

only cover a few representative situations at best. The subject has some

degree of awareness of the approach he or she takes to handling the tasks of

daily living in innumerable specific contexts. We propose that at least the

major dimensions of cognitiv* style are sufficiently available to everyday

introspection that, given the appropriate self-report questions, most

subjects will be able to describe where they fall on these dimensions.

In asserting the utility of self-report, we are aware of the evidence

that self-report abilities are remarkably limited, and have been

traditionally overrated. When asked to introspect on a variety of

processes, subjects often show little evidence of being able to access their

Internal psychological processes directly, but rather make up plausible

explanations for their behaviour post hoc (Nesbltt and Wilson, 1977; Bern,

1972). Furthermore, when considering a lateralized cognitive style, there

may be intrinsic biases in self-report depending on which hemisphere is most

Important Co the person's style. Bear and Fedio (1977) observed that lef*ttemporal-lobe epileptics, whose ir.tellectualized and ideational style

suggested an exaggeration of left hemisphere functioning, were more critical

of their own behaviour than wer<> observers. Right-temporal-lobe epileptics,

whose increased emotionality suggested an exaggerated right hemisphere

contribution, tended to deny problems and bias their self-report positively

In comparison to observers. In research with normal university students,

Swenson and Tucker (1983) found that those reporting a more right

hemispheric cognitive style on the Preference Questionnairf. (Zenhausern and

Gebhardt, 1979) not only reported less timidity and depression on the

Emotions Profile Inventory (Plutchik and Kelle.man, 1974) but also showed a

greater bias toward positive self-description than those with a left

hemispheric style.

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Thus, it must be considered an open question whether subjects are

sufficiently aware of their cognitive processes to describe their

characteristic styles accurately (assuming, of course, that these styles

exist), and whether there will be Intrinsic biases in self-report associated

with one style or the other. Our intention was to devise a scale that would

present a number of alternatives that exemplify major dimensions of

«motional and cognitive style, and allow the subjects to choose which style

seemed most characteristic of their behaviour.

The psychometric method of this study was thus a rational, rather than

empirical one. In developing psychological assessment instruments, there

has been a tradition of attempting to avoid problems of self-report by

ignoring the content of the questionnaire items and blindly selecting those

Items which relate empirically to some external criterion, such as a

diagnostic category. Recent psychometric thinking has questioned whether

this approach leads to meaningful assessment (Burisch, 1934; Jackson, 1976).

The recent trend st ms to be to accept the limits of self-report, and to K

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262

develop a questionnaire which targets well-defined psychological constructs,

with items that are clearly representative of those constructs (Goldberg,

1972; Jackson, 1976).

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The constructs targeted by the present scale were cognitive and

emotional self-control styles, as described by Tucker and Williamson

(1984). Although the theory proposes that cognitive and emotional selfcontrol are parallel manifestations of the same underlying neural systems,

our primary objective was to assess cognitive control as a separate

psychological dimension from emotional control. Thus, any correspondence

between the cognitive and emotional dimensions would occur empirically,

rather than being created artifactually by including these within the same

scale. This has been a cause of concern with the Preference Test of

hemispheric style, which Zenhausern and associates (Coleman and Zenhausern,

1979; Zenhausern and Gebhardt, 1979) developed from Torrance's "Your Style

of Thinking" test (Torrance, Reynolds, Ball and Riegel, 1978). Some of the

Items, such as those dealing with verbal versus nonverbal cognition, seem

clearly related to hemispheric function. Other items, such as one

questioning the subject's preference to read while sitting upright, are

related only to an intuitive notion of what comprises right and left

hemispheric styles. For the present self-report instrument, the intention

was to develop subscales for assessing cognitive and emotional control, each

of which was related explicitly to a major theoretical construct of the

Tucker and Williamson (1984) model, and each of which was comprised of

homogenous items rationally consistent with the construct targeted by that

subscal«.

Construction of the Scale

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O'Connell reviewed rhe Tucker and Williamson (1984) formulation tu

determine those aspects of cognitive and emotional self-control that were

central to the model and that would be reasonable targets for self-report.

In addition, he drew on Shapiro's (1965) characterization of neurotic

personality styles, which takes an ego psychology approach in describing

attentional processes as integral to a person's personality styl«. Tucker

and Williamson pointed to Shapiro's clinical descriptions in suggesting how

exaggerations of normal self-regulatory processes may produce the cognitive

dysfunctions of psychiatric patients.

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The emotional control dimension was termed "Control-Spontaneity", and

was characterized as follows (O'Connell, 1985):

"Controlled individuals show restraint when expressing emotions.

Interacting with others, and making decisions. Their emotional reactions

«re subdued and controlled. They come across to others as calm and

rational. They can be described as cautious, private, dependable,

disciplined, patient and serious. They can tolerate boredom, and they use

routines to structure «nd control their lives. They are goal-oriented, and

they use self-control to attain their goals. They base decisions on

rational considerations; they do not act on impulse. Because of their need

to think before «cting, they are sometimes slow to make decisions «nd to

«ct. In the extreme, control shades into Inhibition, where feelings and

impulses are rigorously guarded against; these highly controlled individuals

might be described as "obsessive-compulsive" personalities: they are hyperrational to the point of "isolating" themselves from their emotions.

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Spontaneous individuals are emotionally expressive and open. They tend

to make decisions on the basis of their immediate feelings and Impulses.

They have a low threshold for boredom and frustration, and they have a need

for excitement and emotional stimulation. They come across to others as

«motional, open, lively, playful, enthusiastic. They make decisions • j

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263

relatively quickly. Just as control shades into inhibition, spontaneity

shades into impulsivity. Lacking adequate self-control, highly spontaneousimnulsive people may act unpredictable and undependable; there is an element

of immediacy to their behaviour and decision-making which may get thera into

trouble".

The characterization of the primary cognitive control dimension, termed

"Deliberate-Impressionistic" is as follows (O'Connell, 1985):

"The deliberate cognitive mode may be described as reflective, rational

and logical. Individuals who rely on this tend to think in ways that are

practical, systematic and organized, and realistic. They are able to

narrowly focus their attention on their ideas or the task at hand; they are

able to concentrate intensely. Their style of thinking is suited for paying

attention to details. Sometimes their chinking is repetitive; they keep

processing the same ideas over and over in greater detail. They prefer

conversation and group discussions that are structured and do not wander off

from the main topic. Because they pay attention to details, their memory is

exact and precise; they also express their ideas with precision. Their

attention to details leads them to think in complex or complicated ways.

They like to use their minds for intense, focused and concentrated

thinking. To some extent, this style of cognition is similar to Freud's

concept of secondary process thinking.

The impressionistic cognitive mode involves the use of imagination,

fantasy and intuition. Individuals who rely on this cognitive mode like to

daydream, fantasize, engage in romantic thinking. Their thoughts are often

loosely organized, drifting. They do not impose organization and structure

on their i^eas and thoughts. They chink in a free-flowing, unstructured

way. They have difficulty focusing their attention, and their attention

span is short. They value original and "creative" Chinking, rather than

realistic and pragmatic chinking. They get "hunches" and act on them. They

do not require evidence before accepting aomethlng as true. Ideas tend to

race quickly and disconnectedly through their minds. Their mode of thinking

is suited for focusing on the "whole" or Che general picture; they lack Che

focused actentional mode i.eeded for attention to details. They lack an

interest in intellectual matters or other interests that require sustained

concen'.nation. Their lack of detailed, analytical thinking leads them to be

open to getting hunches, being surprised by things chat happen, and

remembering dreams. Decisions are formed quickly on Che basis of hunches

and impressions, and mey be changed Just as quickly. This cognitive mode

Incorporates Freud's notion of primary process thinking".

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In addition Co these primary subscales, two additional subscales were

developed. Because anxiety has been an integral issue in both clinical

(Shapiro, 1965) and neuropsychological (Tucker, 1981) thinking, an Anxiety

affective subscale was developed. As Implemented within ehe present scale

chis included ewe facets: a tendency Co be cense and worrisome:, rather Chan

relaxed and easy-going, and a tendency Co be self-critical, raCher Chan

confident and optimistic. A Verbal-Konverbal cognitive subscale was

developed, since chis aspect of cognitive preference is not necessarily

aligned with Che Deliberate-Impressionistic dimension, and is important Co

Che notion chat these cognitive styles are related to hemispheric function.

A verbal rao-'e invrlves a preference for dealing with words or numbers, such

as shown by writers or accountants. A nonverbal preference includes dealing

with physical-sensory data (colour, music, movement) and thinking with

mental pictures and images, and would be more characteristic of Che

activities of palmers, photographers or dancers.

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A pool of 70rsimple declarative statements was written by the first

author to exemplify these psychological dimensions. These were edited to

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377 Items chat were evaluated for clarity and content relevance by five

Judges with expertise in psychology and psychiatry. In addition, Tucker

reviewed the items for their reasonableness as exemplars of the Tucker and

Williamson formulation. At this point, 257 remaining items were

administered to 183 university students and evaluated for the students'

ratings of item clarity and for statistical evaluation of internal

consistency within each subscale. The Marlowe-Crowne Social Desirability

Scale (Crowne and Marlowe, 1960) was also administered to the first sample

to assess response bias; these results were used to assure that selected

items correlated more highly with their subscale on the OCASS than with the

Social Desirability Scale. A set of 129 Items was then selected and crossvalidated for internal consistency with a second sample of 99 students.

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One noteworthy feature of the item selection process was that items

relating to analytic, detail-oriented thinking did not show good internal

consistency within the cognitive control subscale, and thus tended not to be

included on further revisions. Apparently, the analytic/holistic aspect is

not integral to the Deliberate-Impressionistic dimension, or it is not as

accessible to self-report as the more central Issue of tight versus loose

cognitive control.

From the second administration, 99 items were selected to create a

preliminary version of the O'Connell Cognitive and Affective Style Scale (c.

Thomas R. O'Connell, 1984). Internal consistency indicated by coefficient

alpha for the subscales of the OCASS was: Emotional ControlSpontaneity, .86; Anxiety, .87; Deliberate-Impressionistic Cognition, .84;

Verbal-Nonverbal Cognition, .81. On each scale there was a sufficient range

of responses to differentiate among individuals, and the scores were

symmetrically distributed (the measures of central tendency were similar).

The only significant difference between males (0-53) and females (n-46) was

the higher score by females on the Anxiety subscale (p < .02). Handedness

and presence of slnistrality in first-degree relatives were assessed.

Although a significant effect of familial slnistrality on the Deliberate

Cognition dimension was observed (p < .04), with subjects who reported

familial slnistrality showing a more impressionistic cognitive mode, no

effect of subject handedness was found on this or any other subscale.

However, it is of interest that seven of the eight effects of familial

slnistrality on the four OCASS subscales differed in the same direction,

i.e., left handedness and familial slnistrality tended to be related Co

higher scores on dimensions of right hemisphere control. A complete

description of the psychometric issues and the procedures for test

construction and item selection will be provided elsewhere (O'Connell and

Scott, in preparation).

Subscale Intercorrelations and Concurrent Validity

An important theoretical question was whether or not the cognitive and

emotional control dimensions, assessed independently by the two sub-scales

would correlate as predicted. Table 1 presents the intecorrelations among

the OCASS subsctles, and the correlations of the subscales with the total

OCASS score. These data suggest that if there is a "core" subscale to the

OCASS, it is Emotional Control-Spontaneity; this was the most highly

correlated with the other subsc?les and with the total score. Consistent

with the theoretical model, greater emotional control was associated with

more deliberate cognition, with verbal cognition, and with higher anxiety.

The cognitive subscales (Deliberate and Verbal) were more highly correlated

with each other (.44) than with the emotional subscales, and the emotional

subscales (Control and Anxiety) were more highly correlated with each other

(.55) than with the cognitive subscales, suggesting that, although the

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Table 1. Correlations of the OCASS with Itself,

Trait Anxiety, the EPI, and the HPQ

OCASS Subscales

Emot. Control Anxiety

OCASS Total

Cog. Control Verbal

OCASS

Emot. Control

Anxiety

Cog. Control

Verbal

Trait Anxiety

.55**

.34**

.29**

.27**

EPI

Introversion .75**

Impulsivity -.53**

Sociability -.69**

Preference Test

Left hem. score .2A**

Right hem. score -.31**

.55**

.IT

.03

.63**

.A5**

-.21**

-.48**

.16

.20*

.34** .29** .81**

.11 .03 .65**

— .44** .68**

.44** — .61**

-.29** -.12 .20*

.41** .24** .69**

-.51** -.37** -.59**

-.17** -.04 -.50**

.57** .29** .45**

-.22* -.53** -.45**

•A.^

* p < .05 ** P < .01

emotional and cognitive control dimensions «re interrelated, they may be

considered as separate dimensions. Although it was correlated with

Emotional Control, the Anxiety subscale of the OCASS was not correlated with

the cognitive dimensions (Deliberate and Verbal) as was expected.

In order to assess the concurrent validity of the OCASS, several

theoretically relevant self-report scales were selected and administered

with the OCASS to the second sample of students. The correlations of these

scores with the OCASS are also presented in Table 1. The Speilberger (1968)

Trait Anxiety measure showed fairly strong correlation with the OCASS

Anxiety subscale (.63) and a positive correlation with Emotional Control

(.27). Consistent with the findings reported above, Speilberger Trait

Anxiety also falle 1 to correlate with the OCASS cognitive subscales as

predicted, and actually correlated with the Deliberate subscale (-.29) In

the direction opposite to the theoretical predictions.

The correlations of the OCASS with the Eysenck Personality Inventory

Introverslon-Extraversion (I-E) scale were In the predicted direction of

introverts reporting greater Emotional Control (.75), Anxiety (.45),

Deliberate Cognition (.41) and Verbal Cognition (.24). As with the internal

correlations for the OCASS, Emotional Control had the strongest correlations

with I-E and was most representative of the total OCASS score correlation

with I-E. The subdivisions of the I-E dimension, Impulsivity and

sociability, showed an interesting divergence in their relations to the

OCASS subscales. Impulsivity showed the expected negative correlation with

all 4 OCASS subscales, but sociability was more specific in Its relation to

the affective scales of the OCASS.

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Table 1 also shows the correlations of OCASS subscales with

Zenhausern's Preference Test. The items from this test were summed

separately to provide scores for both the right and left hemisphere style

dimensions. These data are generally consistent with the notion that both

these scales are related to similar cognitive styles (although the question

of actual hemispheric usage, of course, requires independent verification).

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266

There was a remarkable symmetry in the correlations of the Preference Test

Left Hemisphere and Right Hemisphere «cores with the OCASS total score. The

cognitive subscales of the OCASS showed the stronger relations to the

Preference Test, as might be expected, with a Left Hemisphere Ityl«. on the

Preference Test more strongly related to Deliberate Cognition on the OCASS

(.57) and a Right Hemisphere preference negatively related to OCASS Verbal

Cognition negatively (-.53). Again, the Emotional Control dimension of the

OCASS showed a relation to the cognitive dimensions of the Preference test

in the expected direction.

Scores on the Marlow-Crowne Social Desirability Scale were correlated

with the OCASS Anxiety subscale as would be expected (-.22), but did not

show significant correlations with other OCASS subscales.

DISCUSSION

The aim of this work was to create a self-report scale that would have

reasonable psychometric properties and that would accurately target the

constructs of emotional and cognitive self-control. The OCASS contains

items that the subjects found understandable and that the judges found

consistent with the appropriate constructs. The subscales showed high

internal consistency and enough variance to serve as a sensitive individual

difference measure with normal subjects. Furthermore, the pattern of

correlations among the subscales and between the OCASS subscales and other

relevant instruments was generally as expected, further indicating the

validity of the items as exemplars of the desired constructs.

In the scale construction process, the items written to indicate an

analytic, detail-oric.-.tated cognitive approach did not show high internal

consistency with other items on the Deliberate-Impressionistic Cognition

subscale. One possibility is that this aspect of cognitive structure -

analytic versus holistic - must be considered separately from the dimension

of cognitive control assessed by the Deliberate Cognition subscale.

Construction of a specific subscal» for this purpose could be an objective

for further research. Alternatively, it may be that subjects are

insufficiently familiar with notions of cognitive structure to be able to

recognize and report on their own preferred organizational tendencies. We

have observed individual differences in preference for local versus global

perceptual organization in laboratory tasks (Tyler and Tucker, 1982).

Actual performance measures, rather than self-report, were used in the

traditional assessment of analytic versus global cognitive styles (Ultkin et

al., 1962). Because the analytic/holistic dimension is so central Co

neuropsychological theory and to the question of cognitive style, further

examination of this issue is required.

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We expected chat higher scores on Che Anxiety scale would be associated

not only with greacer Emotional Control, but with higher scores on the

Deliberate and Verbal Cognition subscales. Instead, the OCASS Anxiety

subscale did not relate to the cognitive subscales, and the Speilberger

Trait Anxiety measure actually showed a small negative correlation with the

Deliberate Cognition scale.

Based on a number of previous findings (Tucker, 1981; Tucker, Antes,

Stenslle and Barnhardt, 1978; Tyler and Tucker, 1982) we expected that

greater anxiety would be associated with a more tightly controlled, verbal

cognitive style, consistent with greater left hemisphere activation. It

could be argued that anxious subjects often experience left hemisphere

overactivatlon, and thus a more dysfunctional Deliberate cognitive mode.

Anxious subjects do show deficits such as speech anxiety that suggest

Impaired function on verbal, focused attentional tasks. Yet this post-hoc

explanation is unsatisfactory: even if their cognitive performance is

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267

impaired In the Deliberate Cognition domain, it might be expected that

anxious subjects would still show a cognitive style with these qualities. •'..<

Further research is required to clarify the conditions under which _,>/•

activation or overactivation of controlled, left-hemispheric processing is ^ '3

found in high anxious subjects. A related issue is whether there may be

dissociations between self-report and cognitive performance in anxious

persons.

One problem in research on anxiety may be that this single construct is

used to mean too many things. It often refers to general emotionality or to

autonomic arousal, and these uay be quite different phenomena than the V^yi

hypervigilant attention and overly mutinized cognition and behaviour »^

characteristically observed In the chronic anxiety of obsessive-compulsive

or schizophrenic persons. It may be that better theoretical differentiation s'*'

of the construct of anxiety will be necessary for greater precision in 'yW

measurement. In the OCASS Anxiety subscale, two features were indicated by <yft3

the items in Che final version of the subscale: a tense, worrisome attitude .»yW

and a tendency Coward self-criticism. Although Che high Internal •.''.

consistency of the Anxiety subscale argues that these dimensions were

closely related, it might be important for theoretical purposes to assess

them separately.

Related to self-criticism is Che question of Che influence of social

desirability on Che OCASS. Because items were selected to minimize social

desirability, Che OCASS will not be helpful in evaluating what may be an

intrinsic relation between self-report bias and lateralized cognitive style '"s^

(Bear and Fedio, 1977; Swenson and Tucker, 1983). This should not be a V»;'.-.

major drawback; it Is probably not the best approach to relate self-report

bias Co a self-report measure of cognitive style. For example. It could be

argued that the Swenson and Tucker (1983) findings simply reflected a

positive bias coward Che right hemispheric Items written by Zenhaus^rn and

Torrance for Che Preference cest. Further research on self-report biases

might better examine cognitive performance or brain activity measures of

individual differences in neuropsychological function rather than a selfreport measure of cognitive and affective style. £v^

The major purpose of constructing the OCASS was to assess social and

emotional aspects of self-control separately from cognitive aspects of selfV control, then to allow the relatedness of these domains Co be assessed

^ empirically. The present results did indicate these dimensions to be

related. The Emotional Control-Spontaneity subscale was not only

significantly related to the Deliberate and the Verbal Cognition subscales,

but appeared Co be ehe core subscale of ehe OCASS. Furthermore, this

dimension showed Che predicted correlation with the Introversion- /^^

Extraversion measure that was high enough Co be wiehin Che range of Che ||s^

reliabilicy for many self-report tests. •''' '.

This rclacion is consistent with Tucker and Williamson's (198A) .^.•.v

formulation of the differential effects of self-regulation with activation

versus arousal systems on Che individual's degree of Internal versus Vy.'

external control. It Is also consistent wich Pribram's (1981) account jKwfl

of Che shift between Internal and external control provided by Che relative JMöj

balance between anterior and posterior cortical systems. Eysenck (1967)

proposed that it is differences in characteristic neural arousal chac leads

co ehe personality differences b'tween introverts and extraverts. By

considering hww the cybernetic effects of a redundancy bias differ

qualitatively from those of a habl'.uation bias. Tucker and Williamson (198A)

could explain how one form of neural control augments a tonic internal

control over behaviour, while an in rease in a different neural control

system augments a phasic responsiv.'• y to external Influences.

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268

Increasing our understanding of the self-regulation of neural systems,

thus provides new ways of theorizing about self-control in the personality

domain. Although the interest in neuropsychological models of individual

differences in recent years has centered around concepts of differential

hemispheric function, and these concepts remain important to the present

approach, it is important to recognize that the notions of activation and

arousal are more fundamentally related to the anterior/posterior than the

left/right dimension of brain organization. Thus we seem to be returning to

earlier neuropsychological concepts of personality, considered in terms of

frontal versus posterior systems (Petrie, 1952; see Pribram, 1981). This

emphasis could pose some interesting measurement problems for attempts to

relate psychological issues to neural function. The laterality approach has

been relatively easy to implement in research with normal persons because

the function of the two hemispheres is roughly parallel. Thus, stimulus

materials can be presented to one hemisphere or the other, or the EEG

responses of one hemisphere can be compared with those of the other during a

cognitive or emotional process. These fairly sensitive right/left

functional comparisons may not be as easy when attempting to assess the

degree to which individuals show a tendency to engage frontal versus

posterior brain systems as general cognitive mode. Certainly the left/right

dimension will continue to be important; it seems to be closely

interdependent with the anterior/posterior dimension (Tucker and Williamson,

1984). But considering this dimension presents new challenges to the

assessment of individual differences in a neuropsychological framework. It

will be important to meet these challenges if we are to move beyond selfreport scales of cognitive and emotional styles and show how these styles

are related to biain activity, emotional behaviour, and cognitive

performance.

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as a function of

Perceptual and

as related to

Perceptual and Motor

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272

HANDWRITING POSTURE AND CEREBRAL ORGANIZATION

#

A.M. Weber and *J.L. Bradshaw

Department of Psychology

University of Victoria

P.O. Box 1700

Victoria, B.C., Canada

V8W 2Y2D

* Department of Psychology

Monash University

Clayton, Vic, Australia 3168

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ABSTRACT

There seems little support for Levy's (1982) r "ised hypothesis that

writing hand/posture Indexes lateralization of selected aspects of verbal or

spatial functions. There is limited support from certain reading studies

and dichotic listening studies using speech sounds, but even this evidence

is at best equivocal. While there is some suggestion that motor control may

be more bilaterally organized in inverters, the evidence so far is

Inconclusive and requires further clarification. Moreover, the notion of

ipsilateral pyramidal control of writing movements in inverters is generally

contradicted by the available data. Finally, there is evidence that

callosal agenesis is not associated with inverted writing posture. In

conclusion, we do not regard the modifications offered by Levy (1982) as

adding substantially to her earlier position.

INTRODUCTION

Levy and Reld (1976, 1978) proposed that cerebral lateralization of

verbal and spatial functions could be predicted from a knowledge of the

subject's writing hand (left or right) and posture adopted in writing

(inverted or normal). Their hypothesis received only very limited support

from other empirical studies, and these findings together with Levy and

ueid's theoretical rationale were critically evaluated by Weber and Bradshaw

(1981). Levy (1982) responded to such criticism with a modification of her

original hypothesis; instead of assuming that verbal (or spatial) functions

are lateralized to one (or the other) hemisphere in left-handers, she now

(p. 592) proposes that in such subjects language (or spatial) functions may

be bilaterally represented with different aspects of a given function

occurring in separate hemispheres. Levy also contests Weber and Bradshaw's

interpretation of her earlier position and of the relevant empirical

literature. The present paper evaluates her new proposals and also offers

some clarification concerning the conflict between her interpretation and

our own.

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CONFLICT OF INTERPRETATION

To avoid burdening the reader at this stage with a detailed refutation

of Levy's criticisms of our 1981 paper, point by point, this refutation has

been relegated to the appendix. However, it might be helpful to outline

briefly the method by which we arrived at our interpretation of levy's

ideas. Her publications concerning writing hand/posture (Levy, 1972, 1974;

KStt:

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273 •'.. V*'<1

Levy and Reid, 1976, 1978), were carefully examined and interrelated

proposals were grouped together. Where inconsistencies or ambiguities

apparently arose in Levy's statements, these were evaluated in the context

of the overall trend and logic of related statements in order to establish

the predominant theme of such statements. The results of the analysis were

the four postulates presented and evaluated by Weber and Bradshaw (1981).

Such a clarificatory formulation of Levy's proposals was a necessary

prerequisite to their evaluation. We believe that if the interested reader

performs the same painstaking analysis, he or she will come to the same

conclusion. . . .

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LEVY'S MODIFIED HYPOTHESIS - PRELIMINARY COMMENTS S-*^

Levy (1982) stresses the non-unitary nature of functional cerebral \ xif

asymmetry in left-handers. Certainly, many research findings have supported JvVpVj

the notion that left-handers show less marked lateralization of verbal "^WJvi

function than do right-handers (see review by Bradshaw, 1980). There is

also considerable evidence of at least some bilateral representation of

certain aspects of language in right-harH-. _, (Gainotti, Caltagirone, Miceli,

& Masullo, 1981; Knopman, Rubens, Klassan & Meyer, 1982; Patterson, 1981;

''earlman, 1977; Urculoli, Klein & Day, 1981; Wapner, Hamby & Gardner, 1981;

Zaldel & Peters, 1981), Prediction of functional asymmetry must indeed take '•J*^

into account such bilateral representation and, as Levy (1982) points out, VS"C"!^

the exact nature of the associations and dissociations of hemispheric

representation of the different aspects of language (or spatial) functions

Is a matter for empirical investigation.

However, Levy's realization of the well-known "bilateralization" factor

is surely too general and speculative to constitute a substantial new

contribution to our theoretical understanding of cerebral asymmetry or to be

of practical use at a clinical or applied research level. Furthermore,

although Levy has modified her original hypothesis, much of her reply is

devoted to defending this earlier hypothesis. The resulting confusion and

vagueness may encourage people to continue referring to the original more

clearly delineated hypothesis. There is particular risk that busy •'^i^j

clinicians without the time for extensive review of the research literature 'v£"'^

will continue to accept the original hypothesis as a quick and simple index J*- ^'"^

of language lateralization as, for example, in the recommendation of

Eastwood and Stiasny (1978).

Before proceeding to evaluate the new Levy hypothesis, it seems

desirable to list briefly all recent empirical evidence not previously 'v"'v'-j

discussed by either Levy (1982) or Weber and Bradshaw (1981) and which HTNAI

pertains to the original hypothesis. Such findings will be dealt with in

more detail subsequently. Of the sixteen known studies, none give clear

support for the old hypothesis, eight give at best a little tenuous or

partial support (Dabbs & Choo, 1980; Miller, 1983; Natale, Gur & Gur, 1984;

Reuter-Lorenz, Givls, & Moscovitch, 1983; Searleman, 1980; Springer &

Searleman, 1980; Tapley & Bryden, 1983; Wellman & Allen, 1983), and eight

offer strongly contrary findings (AJersch & Milner, 1983; Bashore, Nydegger,

& Miller, 1982; Beaumont & McCarthy, 1981; Ellis & Miller, 1981; Jones,

1980; Strauss, Wada, & Kosaka, 1984; Volpe, Sidtis, & Gazzaniga, 1981;

Warrington & Pratt, 1981). These findings are consistent with those

previously reviewed (Weber & Bradshaw, 1981) in their rejection of the

notion that writing hand/posture is a reliable index of cerebral functional

asymmetry as formulated in the original hypothesis.

» _

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MODIFIED HYPOTHESIS

Levy (1982, p. 593'» modified the Levy and Reid conclusions regarding

the relationship of hand/posture to functional asymmetry by substituting

"reading of tachistoscopically presented nonsense syllables and location of

tachistoscopically presented dots" for the general terms "verbal*1 and \

f

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274

"spatial" functions. She argues (p. 598) that many research findings

support the notion that there is some difference in the asymmetry patterns

of left-inverted and left-normal subjects, and that left-inverted and rightnormal subjects are similar and both are different from left-normal

subjects. Later (p. 605), she concludes that "my interpretation of the

currently available data is that these (left-inverted and left-noimal

subjects) are neuropsychologically distinct populations, that the handposture dimension is an important correlate of neurological organization"

(parentheses added).

If writing posture does indeed distinguish two neurologically different

groups with respect to cerebral asymmetry, the crucial question is how.

Levy's evaluation of the literature is not a. all clear on this point.

Given that various aspects of language (or other) function may be

differentially lateralized, the following analysis seeks some pattern in the

current data.

Replication Studies

As Levy and Reid's (1976, 1978) results give strong support to the idea

that lateralized function is predictable given a knowledge of hand/posture,

the appropriate starting point would seem to be an examination ot similar

studies. Wellman and Allen (1983) administered the Levy and Reid

tachistoscopic tasks to 7-9 year old children but did not replicate the

hand/posture differentiation findings. Levy (1982, p. 593) mentions Smith

and Moscovitch (1979) as one such study and points out that they have

confirmed Levy and Reid's findings on their syllable task. On their dotlocation task, however, while right-normal and left-inverted subjects showed

the expected left visual field (LVF) advantage, left-normals showed no

significant asymmetry. Levy points out that the Smith and Moscovitch dotlocation task may not have indexed the same underlying function as that of

Levy and Reid because they used a wider visual angle of dot-presentation (up

to 7° lateral to fixation) than Levy and Reid (up to 2.7°). Levy refers to

Kimura (1969) as finding larger visual-field asymmetries for more medial

dots when compared with relatively more lateral dots. In fact, Kimura

states that the most marked field differences occurred along the middle

horizontal row and apparently found field asymmetries using a range of

visual angles similar in lateral extent to that of Smith and Moscovitch.

Thus, visual angle differences do not seem to explain the discrepant

findings of the two studies with respect to dot-location.

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A more recent study of dextral Inverters and normals by Tapley and

Bryden (1983) found a right visual field (RVF) superiority on the syllable

task and a LVF superiority on the dot-location task but no writing posture

effects. If, therefore, there is a neurological differentiation of

inverters from normals with respect to the two tasks. It would seem only to

apply to sinistrals and not to dextrals. If confirmed, such a neurological

phenomenon would require explanation.

Even if sinistrals were to show the task asymmetry differences

specified by Levy and Reid, and were to do so consistently, the question

would remain as to what functions were being measured. The response mode

together with the use of a fixation number (see below) may well introduce

possible contaminants, and render difficult any simple intepretation of the

findings in terms of phonological processing or spatial location of visually

presented material. Thus, Smith and Moscovltch's subjects were required to

respond in the dot-location task by calling out the identification number of

the judged location. Although Levy and Reid (1978) do not explicitly

specify this response mode, they do say (p. 127) that location was reported

from a card mounted below the tachistoscope. As Levy (1982) does not mention

response mode as a methodological difference between the Levy and Reid study

and that of Smith and Moscovitch, and as she and Reid made no mention of any

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275

counterbalancing of response hand In their methodology, it would seem

probable that Levy and Reid used a similar response mode to that of Smith

and Moscovitch. Such a response mode is perhaps rather surprising in view

of the fact that it was Levy, together with Trevarthen and Sperry (1972),

who demonstrated that response mode may influence hemispheric lateralization

of stimulus processing. An oral response in which subjects name the

Identification number of the dot positions is likely to invoke the

hemisphere dominant for speech. A counterbalanced left-right manual

response might have been more appropriate. Tapley and Bryden (1983) also

appear to ha^e used the number method of identifying dot positions.

In an attempt to ensure that subjects maintained central fixation

during the stimulus display, Levy and Reid (1976, 1978) used the McKeever

and Huling (1970) procedure of requiring subjects to report a central

fixation digit presented within the stimulus display. Smith and Moscovitch

(1979) and Tapley and Bryden (1983) also used this method. This procedure

can be criticized in that such digits may constitute a form of verbal

stimulus (Bryden, 1970; Gordon & Carmon, 1976; Klmura, 1961; Levy & Bowers,

1974; Satz, Achenbach, & Fennell, 1967; Zurif & Bryden, 1969). Thus the

central digit may enhance the verbal nature of the syllable task and add a

verbal element to the dot-location task. Findings concerning the possible

effects of the central stimulus upon the nature of the stimulus display are

currently equivocal. Kershner, Thoraae, and Callaway's (1977) study

demonstrated that the verbal or nonverbal nature of the central fixation

check influenced the direction of field superiorities for verbal lateral

stimuli. Similar conclusions were reached by Carter and Kinsbourne (1979),

Heilige and Cox (1976), and Mancuso, Lawrence, Hintze, and White (1979).

However, in othe- studies, Duda and Kirby (1980) and Hines (1978) found no

effect on field asymmetries from the nature of the central check. Indeed,

this procedure ma" not necessarily even guarantee fixation. If a subject

can fixate centrally and still see the lateral stimulus, there Is no reason

why Lne subject may not also look at the lateral area and still be able to

see the central digit. In any case, there is evidence (Geffen, Bradshaw, &

Nettleton, 1972; Harcum, 1978, p.U9; Jones & Santi, 1978) that such an

attempt to control fixation is unnecessary and that such deviations from

fixation as occur are either very rare or are likely to be evenly

distributed between the fields.

Weber (1980) omitted the central digit from the syllable and dotlocation tasks and also used a manual response mode (hands counterbalanced)

for the dot-location task. With such modifications in the interests of

Improved experimental controls, neither task was found to be associated with

hand/posture. An overall RVF advantage was found for males on both tasks

and females showed a RVF advantage on the syllable task and a LVF advantage

on dot-location.

Although each of the four studies have used very slightly differing

hand/posture criteria, they would appear to be generally similar and

deviatioi from Levy and Reid's criteria as such does not appear to account

for the extent to which the other studies do or do not support the original

finding.

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Other Studies

Other studies concerned with the hand/posture effect are now examined

to see whether there are any clues as to what aspects of cerebral

functioning might be associated with hand/posture.

Spatial and nonverbal material. Bradshaw, Nettleton, and Taylor (1980)

in a face discrimination task found no hand/posture effect. This finding is

in keeping with the face-processing data of Heller and Levy (1981, cited in

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276

Levy, 1982), Levy, Heller, Banich, and Burton, (manuscript, cited in Levy.

1982), Jones (1980), but not those of Natale, Gur and Gur (1983) who found

that left-inverters were lateralized at a level intermediate between

dextrals and left-normals, or Reuter-Lorenz, Givis, and Moscovitch (1983)

who found that left-normals and left-inverters were oppositely lateralized.

A person's own facial expression does not appear to be lateralized in such a

way as to discriminate between inverters and non-inverters (Campbell, 1979;

Moscovitch and Olds, 1982). Lawson (1978) did find the expected

hand/posture effect for males but the reverse pattern for females. Levy

(1982) raises the possibility of field dependence and independence effects

to explain Lawson's findings. It is not entirely clear why such a factor

should account for Lawson's data more than that of other studies. However,

the trend of findings at this stage indicates that there is no hand/posture

effect in relation to face-processing. Ellis and Miller (1981) found only

very weak evidence that there may be some difference between right-normals

and left-normals with respect to which side of an advertisement picture

subjects preferred the written message. In summary, there seems to be

little evidence of hand/posture effects In association with particular

facets of spatial or nonverbal functioning so far, and these negative

findings seem to apply across the various hand/posture criteria used by

different studies.

Verbal material. Examination of visual field studies does not reveal

any clear association between aspects of language function and hand/posture:

Bashore, Nydegger, and Miller (1982) using letter naming, Bradshaw,

Nettleton, and Taylor (1980) for lexical decisions, Bradshaw and Taylor

(1979) for reading words and nonwords, McKeever (]979) for word reading, and

McKeever and VanDeventer (1980) for letter masking. McKeever (1979) found

weak support for a hand/posture effect for color naming, left-normals

showing a weaker RVF advantage than left-inverters. Miller (1983) reported

a nonsignificant trend with respect to a hand/posture effect for word

recognition.

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Dichotic listening studies using speech sounds provide weak or no

evidence of hand/posture effects (Searlem&n, 1980; Smith & Moscovitch, 1979;

Tapley & Bryden, 1983; Volpe, Sidtis, & Gazzaniga, 1981). Studies using

digits show no hand/posture effects (Beaumont & McCarthy, 1981; McKeever &

VanDeventer, 1980; Warrington & Pratt, 1981). Other dichotic listening

studies whose material is unspecified were Thistle's (1976) study which

found no hand/posture effect, and Springer and Searleman's (1980) study

which found «ome hand/posture differences for dichotic listening in twins

but not in singletons.

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Other relevant studies include Allen and Vellman's (1980) finding that

the closer dextral children came to using normal pos*.ure, the better their

reading level. But Wellman and Allen (1983) found that this association of

writing posture and reading skill in dextral children was not so much

related to hemispheric lateralizatirn of verbal or spatial skills as to

maturational factors. They suggested that nonnormal posture indicates

maturational lag which is also associated with left-right directionality

problems which in turn lead to lower reading scores. Bryson and McDonald

(1984) found that among grade 5 sinislral children, it was boys who used

parallel posture (neither inverted nor normal) who showed poor reading.

Younger boys (grades 1 & 3) and all girls (grades 1, 3, & 5) showed no such

association between read.ng and posture. Gregory and Paul (1980) showed a

variety of cognitive deficits in invented adults relative to normals.

Perhaps these various reading and cognitive deficits are related to

maturational lag factors. Herron, Galin, Johnstone, and Ornstein (1979)

found evidence of more right occipital involvement in reading and writing

tasks for left-normals than for left-inverters or dextrals. Perhaps the

most substantial evidence against the argument that hand/posture can index

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277

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the lateral ization of speech processes comes from the recent unilateral ECT

and amytal-ablation studies. Thus Ajersch and Milner (1983), Strauss, Wada

and Kosaka (1984), and Volpe, Sidtis, and Gazzaniga (1981;, found that

Inverters could not be distinguished from normals wi:.h respect to speech

lateralization. Exactly similar findings were reported by Warrington and

Pratt (1981) on the basis of transient dysphasl^ following unilateral ECT in

non-neurological (depressive) patients.

Generally the findings with respect to verbal material offer no really

clear indications that lateralization of specific aspects of language

function are predictable on the basis of hand/posture. Although Herron et

al.'s findings suggest some link with reading, the exact nature of this

link is unclear and would seem to be a very specific one, pos&ibly related

to maturational lag factors, given the generally negative findings of the

visual field studies involving reading. Levy and Reid's (1976, 1978) and

Smith and Moscovitch's (1979) syllable task findings constitute the only

strong evidence, and it is difficult to see what their tasks and those of

Allen and Wellman and Herron et al. might have in common to distinguish them

from the other visual field tasks. Dichotic listening studies are hardly

more encouraging although there is some weak evidence for the hand/posture

hypothesis from studies of speech sound discrimination. Warrington and

Pratt V.J.981), using transient dysphasia after unilateral ECT as a measure of

speech lateralization, concluded that dichotic listening was not a reliable

index of speech lateralization. Chiarello (1980) also points out the

unreliability of dichotic listening in subjects over time, and that it has

never been shown that size of ear effect is proportionate to the degree of

hemispheric dominance for language. Halsey, Blauenstein, Wilson, and Wills

(1980) claim a relationship between lesion side, aphasia and hand/posture

but unfortunately give no details. These generally negative findings with

respect to verbal material occur across a variety of hand/posture criteria

and do not seem to be associated with such variations.

It is not feasible, either, to relate all these findings to the

question of a possible interaction of hand/posture with familial handedness

in predicting cerebral lateralization. However, the findings with respect

to a possible relation between familial handedness and functional «.jrebral

asymmetry are in any case equivocal. Some authors have claimed that right

hemisphere language is more prevalent in people with left-handed relatives

than in people without such relatives (Andrews, 1977; Hecaen & r,auguet,

1971; Zurlf & Bryden, 1969) while others have made the reverse claim

(Newcombe & Ratcllff, 1973; Warrington & Pratt, 1973).

Levy (1976, 1978) suggests that Bradshaw and colleague's negative

results with respect to hand/posture and cerebral lateralization differ from

those of American researchers. The above review of findings suggests that

In fact the Australian findings are closely similar to many American ones.

In considering Levy's reference (1982, p.599) to strong confirmation for

some form of relationship between hand/posture and cerebral asymmetry, the

reader should also note that Levy makes only brief reference (p. 598) to the

fact thrt "not all investigators have found a distinction between the two

hand-posture groups with respect to asymmetry." Any objective appraisal of

the status tf Levy's proposal must of course include such negative findings

as well as the positive ones. We believe that Levy (1982) rather neglects

to do this.

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However, in the above context of possible cultural differences. Levy

(1982) speculates that perhaps Australian school children are strongly

pressured to write with a normal posture, and that obviously "the handposture dimension cannot represent the same underlying factors in the two

continents". The guidelines for teacning writing specified by the Education

Department of Victoria (Australia), and the senior author's extensive

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278

«• ^••:

professional contact with children and teachers regarding educational

problems, together with anecdotal reports from some inverters about how they

changed to this posture In imitation of peers after some years of schooling,

all indicate that children are not typically pressured to use a normal

posture, or for that matter an inverted one. More Importantly, if

hand/posture is a cultural phenomenon as Levy (1982) suggests, then this

would detract from the probability of Its also being "an important correlate

of neurological organization" which is the major thrust of Levy's hypothesis

(and see 1982, p.605). The varying Incidences of inverted posture across

age groups suggest the involvement of some non-neurological factor, as

discussed by Weber and Bradshaw (1981, np.80-81) and as has also been

suggested by Shanon (1978), Peters (1983), and Guiard and Hillerat (1984).

Searleman, Porac, and Coren (1982) found some association between Inverted

posture and birth stress In left-handed males but not in females or righthanded males and the birth-stress factor did not unambiguously discriminate

Inverters from noninverters even among left-handed males (94* stressed and

41% no stre&s left-handed male subjects were inverters). Searleman, Porac,

and Coren (1984) also found that among left-handed males, unlike other

groups, inverted posture was associated with left-sided preference with

respect to hand, eye, foot, and ear. They suggest that left-handed male

inverters would be the most likely candidates to display leftward lateral

preferences owing to an excess of pathological left-sidedness. However,

although this association between hand/posture and lateral preference is

statistically significant, it Is far from reflecting a perfectly correlated

association. Porac, Coren, and Searleman (1983) report a relationship

between hand/posture in parents and offspring which could be indicative of a

genetic factor but not a simple, straight forward one and cultural

influences are not ruled out. Hence, although these data suggest the

possibility of a neurological basis for inverted posture, they are far from

conclusive in this respect. There is in fact some suggestion of a link

between writing hand/posture and possible brain damage or defect (Allen &

Wellman, 1980; Gregory & Paul, 1980; McKeever & Hoff, 1979; Strauss et al.,

1984; Wellman & Allen, 1983). The exact nature of such a link remains to be

defined.

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Motor function. Parlow's (1978) data Indicate some relation between

motor control and hand/posture, but also that the neural mechanism for hand

preference is not based on an asymmetry in control of fine movement. The

exact nature of this phenomenon requires further clarification.

A number of studies have suggested that perhaps motor control is a

relatively more bilateral affair for left-inverters than for left-normals

(Halsey, Blauenstein, Wilson, & Wills, 1980; Parlow & Kinsbourne, 1981;

Warshal & Spirduso, 1981; and perhaps Todor, 1980, and Wilke & Sheeley,

1979). This line of enquiry might be worth pursuing further, but It should

be noted that Peters and Durding (1979) did not find such a tendency among

their female subjects and Peters (1983) and Guiard and Hillerat (1984) were

unable to find any difference between left-inverters and left-.tormals in

fine motor control. Note also that this possible "bilaterallty" applies to

motor phenomena and not, as in :he original Levy and Reid hypothesis, to

verbal or spatial functions.

The neurological mechanisms of hand control are discussed in the next

section.

Mechanisms of Hand Control

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In their 1978 paper, Levy and Reid suggested that left-inverters

controlled their writing hand from the ipsilateral hemisphere and raised the

question as to whether this control was exerted via transcommissural

pathways or via uncrossed pyramidal tracts. While briefly expressing some
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279

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uncertainty as to which alternative was the more likely, by far the main •v'V^

thrust of Levy and Reid's discussion was directed to supporting the Idea of 'V'N'A"''*

uncrossed motor tracts. Levy (1982) has modified her speculations with

respect to hand control: Ipsllateral hand control In inverters Is now said

to be restricted to pathways for vlsuomotor reactions, and It Is allowed

that some left-handers with left hemisphere specialization for writing

would use transcommlssural pathways while others (for such vlsuomotor

reactions) would use Ipsllateral motor pathways. Cyüyi^C

The question remains, however, as to whether ipsllateral control for 'VCVNV

vlsuomotor responses does characterize a substantial group of inverters. '.<Ms,

Some support for this notion comes from the findings of Moscovitch and Smith • ^

(1979) and Smith and Moscovitch (1979). In these and other related studies, ".-

laterallzatlon of motor control Is inferred by assuming that manual 'v'V'^v"'!

responses will be faster to stimuli initially entering the same hemisphere

that controls the motor response than to stimuli entering the other

hemisphere. Levy (1982) also refers to McKeever and Hoff's (1979) data as

supporting this notion of Ipsllateral control in Inverters, but in fact only

8/15 of McKeever and Hoff's subjects showed the appropriate performance - a

random recult. A similar finding was also reported by McKeever and Hoff for

their 1983 study. It might perhaps be argued that given the bias of

possible spatial compatibility effects to favor a "contralateral" pattern,

even this result is suggestive. However, Bradshaw, Nettleton, and Spehr J\?f/bf,

(1982) investigated response times to visual stimuli with controls for •

spatial compatibility effects and found no difference in the performance of SJJVV

inverters and normals. Although Levy (1984) disputed Bradshaw et al.'s Cy!"-"!"-\

procedure, her criticisms were answered (Bradshaw & Umilta, 1984) and -"v ""\

further reaction-time evidence has been found (Guiard, 1983) which negates

the notion of ipsllateral motor control for inverters with respect to

vlsuomotor tasks. Bashore, McCarthy, Heffley, Clapman, and Donchln (1982) 9

found that with respect to readiness potentials over the sensorimotor area \y£"b'i'£

prior to writing, inverters showed the same contralateral control as did ^ -- -

normals. They further concluded that although movement may be ipsilaterally

controlled in a small number of left-handers, handwriting posture did not --^

seem to index this difference, and that perhaps both left- and right-handers

may vary in neurological control of hand movements. Herron, Galin,

Johnstone, and Ornstein (1979) also concluded on the basis of EEC measures bv'Vvl

that the right central region of the brain is involved in the control of '^•/ b

left-hand writing for both Inverters and normals. For vlsuomotor r\-'.'/;

activities such as wilting, it seems that the evidence pertaining to this OC'"''"^

modified speculation concerning ipsllateral control In Inverters is at best V^V«»*».

equivocal. Consideration of hand/posture variations does not seem to 9 --

account for the different findings of these studies. ;y\-0/^

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A further problem regarding the idea that motor control is ipsllateral !•.-/ ''•'

for inverters when responding manually to visual stimuli, is the question of

the nature of such control. Evarts (1980) states that motor cortex activity

prior to a given movement is the same regardless of whether the movement is

triggered by a visual or an auditory stimulus and studies such as that of

Haaxma and Kuypers (1975) suggest that intrahemlspheric fibers subserve

visual guidance of the premotor cortex. It would seem, on the basis of 'V^V-!

present knowledge, that the only neurological basis for the Moscovitch and Ni^"«^

Smith results is an abnormality of the visual system and/or its connections vftwWj

to the motor system. McKeever and Hoff (1979) suggest that isolation of + i

visual from motor areas within the left hemisphere of left-inverters may -vv^S

necessitate a double transcallosal transmission for a right-hand response to '^• p^

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the RVF stimuli. This idea is similar to that proposed and refuted by Levy

(1982, p.600), namely, that left-inverters have a single commissural relay

for the heterolateral condition (condition referring to visual field -

response hand) but a double such relay for the homolateral condition. Levy

argues that were tnis the case, one could expect mean reaction time to be

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280 ::•

longer in inverters and mean variabilities to be larger, which is not the

case for Moscovitch and Smith's (1979) and McKeever and Hoff's (1979)

findings where inverters showed shorter and less variable reaction times

than normals. However, if McKeever and Hoff's hypothesis is correct, we

would expect that for left-inverters, the right-hand/RVF condition would

show the longest reaction time, the left-hand/LVF the shortest, and the two

heterolateral conditions in between. This was indeed the case for McKeever

and Hoff's (1979, Table 2, p. 449) data, and it remains so even if 3 msec is

added to the two LVCconditions to eliminate right-hemisphere sensory

advantages. However, Moscovitch and Smith's (1979) findings do not follow

this pattern and so the hypothesis remains a very tentative one. McKeever

and Hoff's later (1983) investigation indicates that disconnection of motor

and visual areas does not characterize left-inverters after all.

Levy (1982, p. 600) refers to Jensen's (1980, cited in Levy, 1982)

finding that reaction time variation distinguishes retarded from normal

people more reliably than mean reaction time. Levy seems to be suggesting

that perhaps the more efficient pathways (ipsilateral for inverters,

contralateral for normals) will show less variability in reaction time than

other pathways. This is born out to some extent by the findings of

Moscovitch and Smith (1979) but not by those of McKeever and Hoff (1979).

Inverters in both studies also showed less variability under homolateral

conditions than did normals - a fact which tends to contradict the idea of

variability distinguishing between the two writing posture groups with

respect to the efficiency of pathways.

In further support of her contention regarding ipsilateral motor

control. Levy (1982, p. 599) argues against the contralateral

transcommissural hypothesis by referring to Hecaen and Sauguet's (1971)

finding that agraphia for left-handers with right-hemisphere lesions was

much less common than in either left- or right-handers with left-hemisphere

lesions. Levy argues that such facts are difficult to reconcile with the

postulate that the right hemisphere is crucial for control of left-hand

writing, either as a central programmer or as a relay station. Although the

left-handers of Hecaen and Sauguet's study did show a higher tendency to

agraphia following right-hemisphere lesions than did dextrals, this tendency

was not statistically significant. However, when interpreting Hecaen and

Sauguet's findings it is very important to note that their subjects were

heterogeneous with respect to location of lesion within the hemisphere. As

Hecaen, Angelergues, and Douzenis (1963) pointed out, there are at least

three different sorts of agraphia, each related to different lesion

locations (i.e. frontorolandic, temporal, and parietal). Atv evaluation of

agraphia findings should consider the type and degree of agraphia, the

location of the lesion, and if possible the writing hand/posture of the

person prior to the lesion occurring. Such analysis could be very helpful

to our understanding of the neurological basis of motor control.

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The findings of Brinkman and Kuypers (1973) and of Geschwind (1975)

indicate that not only Is there a distinction between motor skill

programming areas and those controlling specific segments of muscular

activity, but there is also a distinction between control of fine and gross

muscle-limb segments, both with respect to brain areas and brain-to-musclepathways. With respect to limb segments, this model Indicates that fine,

distal movements which are important in writing are controlled primarily

from the precentral gyrus via contralateral pyramidal pathways (and to a

lesser extent extrapyramidally via contralateral pathways). Writing also

involves some gross movements of the wrist, elbow, and shoulder and these

segments are controlled via ipsilateral pathways. Such gross movements

could produce writing although it is likely to be a cruder or slower form of

writing than that which also includes pyramidal fine motor control. The

location of the motor skill programming area remains unknown. Evarts (1980)

V.

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281

has suggested that such programming may occur In the cerebellum and basal

ganglia which strongly influence the motor cortex. However Phillips and

Porter (1977) argue that it is not possible to attribute motor skill

programming in this way, even though the interaction between the cerebellum,

basal ganglia, and motor cortex is an important one.

If inverters in fact possess ipsilateral control of writing movements,

one might expect them to be able to use the inverted posture of the

nonpreferred hand more easily (also controlled via ipsilateral tracts) than

to use the normal posture for either hand (requiring contralateral tracts).

Weber (1983) timed writers using each of the four hand/postures in turn and

had independent judges rank the coordination of the written product.

Contrary to the expectation deriving from the ipsilateral control

hypothesis, it was found that left inverters showed more skill using leftnormal posture than in using either right-normal or right-inverted posture.

Normal writers also adapted better to using the preferred hand with

nonpreferred posture compared to using either posture with the nonpreferred

hand. Such findings suggest that neural control of hand preference for

writing may be more important than any factors relating to posture and thus

ar_ compatible with the model described in the previous paragraph.

Furthermore, when forced to write with their right hand, both left inverters

and left normals showed greater skill using normal posture than inverted.

The latter fact suggests that perhaps inverted writing is largely an

adaptation to left-hand writing rather than a reflection of ipsilateral

pathways.

Anomalies of Midline Development

Although Levy (1982) stresses that the idea of callosal agenesis being

associated with inverted posture is highly speculative, she still devotes

some space to defending this notion. The simplest solution to this question

seems to be to determine whether known acallosal or partially acallosal

patients do in fact use inverted posture. No known studies of acallosal

patients mention inversion, including the recent review by Chiarello (1980).

Given the detailed investigations that have been done on such patients,

surely if inverted posture were a consistent feature it would have been

noted by now. Personal communication from one of the leading investigators

of callosal agenesis (M. A. Jeeves, 3 November 1982) states that such

patients do not invert. Using an indirect measure of callosal functioning.

Miller (1983) inferred normal interhemispheric communication on a word

recognition task from lowering of recognition scores when words were

presented in two visual fields rather than one. Such lowering of scores was

considered to reflect callosally mediated interference between the

hemispheres. The lack of such lowering of scores was interpreted as

Indicating lack of callosally mediated communication. Findings suggested

that there is less callosally mediated communication in left- than righthanders. There was, however, no clear difference in this respect between

left-normals and left-inverters and, as Miller himself points out, any

Interpretation of this measure as indicating midline anomaly is highly

speculative at this stage.

CONCLUSIONS

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Some research data do seem to support the hypothesis of an association

between writing hand/posture and cerebral lateralization of function, but

these positive findings are like tiny islands in a sea of otherwise

unsupportive results. Editorial policy of reporting more unusual or

positive findings rather than unsuccessful replications or inability to

confirm, would seem to give extra significance to the generally negative or

weak evidence concerning any relationship between hand/posture and cerebral

asymmetry.

^<*iWM*n«^
282

There are other factors which may help to account for the equivocal

findings which pervade the cerebral laterality field in general, not least

the Levy hypothesis. Sackeim, Weiraan, and Grega (198A) and Levy, Heller,

Banich, and Burton (1983) report that arousal-level differences between

hemispheres should be taken into account ?nd Harshman, Harapson, and

Berenbaum (1983) claim that level of reasoning ability is relevant. Perhaps

the most succinct way of taking such factors into account is that of

considering subject strategies. Informal post-task questioning of subjects

by Weber (1980) revealed that subjects were using a variety of strategies

on the syllable and dot-location tasks. These strategies not only varied

between subjects but also from trial to trial for any one subject, and

sometimes combined strategies were used on a single trial. It was noted

that most subjects reported using both verbal and nonverbal strategies on

each task.

Clarification of the contribution of strategies to laterality effects

perhaps even requires a totally different experimental paradigm, one that

goes beyond the usual specification of stimulus, response, and instructional

set factors. It needs to establish the subjects' actual mode of performing

the task, trial by trial. Ways could be devised for subjects to report

their strategies. The main practical problems would be limits in the

subjects' awareness of their strategies and their capacity to describe such

strategies. Overcoming such problems might require training subjects in

such self-awareness and self-report. It might also be necessary to

investigate and perhaps control for the possible influence of the mode of

reporting such strategies, upon the direction and extent of lateral

asymmetries.

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In summary, there seems to be little clear and consistent evidence that

would indicate a relationship between writing hand/posture and particular

aspects of cerebral functional asymmetry, even when considered with re.-pect

to Levy's (1982) modifications. At best there are some suggestions of

relatively more symmetrical motor function in inverters than in normal

writers, but even this is tentative and requires confirmation and more

precise elaboration. Such relative symmetry would also have to be

accommodate the apparent fact of contralateral pyramidal motor control in

such writers. In view of the above arguments, and the fact that the two

hand/postures cannot be easily dichotomized (Buchtel & Rueckert, 1984;

Peters, 1983) and have been subjected to a variety of distinguishing

criteria (Fudin & Lembessis, 1982), we should perhaps concur with Guiard and

Nillerat (1984) that an inverted hand/posture may be largely an adaptive

strategy for producing an adductive movement.

APPENDIX

All page references to Levy's work refer lo the 1982 publication.

Levy (p. 589) says that Weber and Bradshaw give a misleading picture of

the experimental findings, fail to take Into account relevant clinical

observations, and do not distinguish between descriptions of observations

and interpretations of those observations.

Reply; Weber and Bradshaw have received unsolicited support from other

researchers in the field concerning their 1981 paper. This support,

together with the careful reviewing system prior to acceptance for

publication, would seem to indicate that Levy's comments are unfounded. If

readers follow Veber and Bradshaw's methodology for analysing Levy and

Reid's work and look at the relevant literature they can check on the

validity of the conclusions reached in Weber and Bradshaw's paper

themselves.

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Levy (p. 591) attributes to Weber and Bradshaw the belief that any

reliable and valid index of lateralized function in left-handers reflects an

underlying and general pattern of cerebral asymmetry, regardless of the VLs"1..

specific process within the verbal or nonverbal domain that a task assesses. O"*-"^'

Reply; This statement is publically contradicted by the existence of

Bradshaw's (1980) review, and both authors were well aware of the evidence

relating to bilateral representation of language functions in both left- and

right-handers. Our focus on the more general language and spatial asymmetry

reflected our concern to evaluate Levy and Reid's proposals which were in

fact general.

Levy (p. 599) disagrees with Weber and Bradshaw's conclusion that the vv'^*-

relation between hand/posture and cerebral asymmetry is "almost certainly

not as predicted by Levy and Reid."

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Reply; Such disagreement by Levy is surprising in view of her current ^v'-S'

modification which seems implicitly to endorse Weber and Bradshaw's

statement.

Levy (p. 599) says that Weber and Bradshaw were incorrect in

attributing to Levy and Reid (1978) the claim that inverters control writing

via ipsilateral pathways and that Levy znd Reid actually considered both

this notion and that of transconunissural control.

Reply; Weber and Bradshaw agree that Levy and Reid raised both

possibilities but note that the great weight of Levy and Reid's argument was

In support of the ipsilateral pathway proposal, as indeed is also largely

true of Levy's (1982) discussion, although perhaps to a slightly lesser

degree. Thus, evaluation of Levy and Reid's proposals necessarily involved

focus on their ipsilateral control notion.

ijnDni

Levy (p. 599) states that Levy and Reid (1978) did not discount the <ScSi

case described by Hellman, Coyle, Gonyea, and Geschwind (1973) as asserted

by Weber and Bradshaw, and that Levy and Reid cited this case to show that ^•/

the transconunissural hypothesis could not be ruled out.

Reply: Certainly Levy and Reid (1978, p. 136) do mention that the

Hellman et al. case suggests that the transcoromlssural hypothesis cannot be

ruled out. However, they then proceed to discount its significance (p. 137)

by suggesting that long-standing brain damage might account for this unusual

case and continue to argue in favor of ipsilateral control. Thus Weber and

Bradshaw's (1981, p. 78) statement is an accurate representation of the

position of Levy and Reid.

v.

fe

Levy (p. 601) says that Weber and Bradshaw question Levy and Reid's

citations re the similarity In performance patterns between left-inverters

and callosal ageneslc patients.

Reply; In fact Weber and Bradshaw (p. 83) agreed with Levy and Reid re

this similarity.

Levy (p. 602 and elsewhere) says that Weber and Bradshaw converted Levy

and Reid's speculative notions into claims.

Reply; Weber and Bradshaw's evaluation focussed on the main thrust of s.'r*.'J\''

Levy and Reid's arguments. However, we are pleased to note that, as a wSSn

possible consequence of this evaluation. Levy is now differentiating between MAQHOI

fact and speculation.

Levy ffrt (p. 602) states that Francois, Eggerraont, Evens, Logghe, and
284

DeBock (1973) report a variety of anomalies of midline development in

association with call^sal dysgenesis. She also suRgests that Weber and

Bradshaw dispute this statement.

Reply: Weber and Bradshaw did not dispute this statement but rather

commented that this study by Francois et al. made no mention of pyramidal

nondecussation.

Levy (pp. 602-603) states that Levy and Reid's citing of Tennyson

(1970) was to point out that, apparently, axogenesis of presumptive callosal

fibers occurs in callosal agenesis, but the axons that develop fail to cross

the midline and not (as implied by Weber and Bradshaw) as evidence

supporting generalized anomalies of midline development in association with

callosal agenesis.

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Reply: Again, Levy is attacking a straw man. What Weber and Bradshaw

actually said (p. 84) was that Tennyson's paper was not at all concerned

with the corpus callosum or its pathology.

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Levy (p. 603) suggests that Dennis' (1976) partially acallosal patient

(whose intentional finger movements were accompanied by unintended, although

,>ot always homologous, movement in the fingers of the other hand) shows that

synkinesis does occur in such patients, and that this somehow contradicts

Weber and Bradshaw's challenge to Levy and Reid's logic concerning

synkinesis in acallosal cases.

Reply: This argument does not seem at all clear and the reader is

referred to pages 83 to 85 of Weber and Bradshaw's (1981) paper for the

appropriate context in which they referred to Dennis's study.

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differences in auditory and visual perception, Neuropsychologla, T_t 179-

187.

2B9

Weber, A- M., and Bradshaw, J. L. '981, Levy and Reld's neurological model

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Zaidel, E., and Peters, A. M. 1981, Phonological encoding and ideographic

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Zurif, E. B. and Bryden, M. P. 1969, Familial handedness and left-right "jäS

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INDIVIDUAL DIFFERENCES IN DYNAMIC PROCESS ASYMMETRIES IN THE NORMAL AND

PATHOLOGICAL BRAIN*

John H. Gruzeller,

Department of Psychiatry,

Charing Cross and Westminster Medical School,

Fulham Palace Road,

London, U.K. W6 8RF.

STRUCTURAL VERSUS DYNAMIC PROCESS ASYMMETRIES

Dynamic concepts of brain function have played an Important role In the

history of neuropsychology. They were Integral to Holism, a nineteenth

century school of thought which had Its origins in the empirical studies of

Flourens (1794-1869), who deduced from extirpation experiments with birds

that individual areas had specific effects ('action propre') but also

generalised influences, such that the removal of any part affects every

other part ('action commune'). This dynamic view was upheld by Lashley

(19?9) who proposed principles of mass action and equipotentiallty from

evidence that learning impairments in rats were inversely related to the

extent of the brain tissue destroyed (mass action), but the precise location

of the destruction was unimportant because of an equivalence of function

(equipotentiallty). Later Luria (1973) introduced the concept of a

functional system whereby complex processes Involve integratlve

participation of widespread regions, the involvement of which could alter

with maturation (Vygotsky, 1963).

Strict localisationlsm has been the more influential school of thought

on Western neuropsychology. Its empirical foundations arose from

discoveries such as those of Broca in 1861 and Wernicke in 1874 of the

relationship between focal lesions of the left hemisphere and specific

language disorders. Investigations of cerebral asymmetry have followed in

the tradition of strict localisationism, inlt'ally attempting to delineate

absolute differences in function between the hemispheres but now giving way

largely to a search for relative differences in function, in view of

evidence of recovery of function after gross unilateral lesions, and the

failure to find clear-cut asymmetries in the intact brain. Neuroanatomical

asymmetries, thought to provide a plausible foundation for language

laterilisation, do not support the high estimates of left hemispheric

dominance based on inferences from hand dominance; around 30% of dextrals do

not show structural asymmetries in favour of the left hemisphere.

Hemispheric equivalence of function is gaining popularity to account for

language lateralisation in a substantial proportion of s'nlstrals (Satz,

1979), and may contribute to gender differences as an account of language

*This research was supported by the Wellcome Trust, The Science and

Engineering Research Council and by the MRC inn the form of student

fellowships

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Fig. 1. The two classes of cerebral asymmetry (see text for details).

language lateralisatlon In females. Gender together with handedness form

the two widely accepted individual differences in hemispheric specialisation.

Disquiet at exclusively structural determinants of lateralisatlon has

arisen from consideration of the temporal variation in asymmetries seen

across trials or sessions in the same subject revealed by laterality

measures such as dichotlc listening, divided visual field pr3sentationl

haptic sorting and so forth (Cohen, 1982). These are attributed usually on

a post-hoc basis to factors such as unfamiliarity, fatigue, stress or shifts

in attention or cognitive strategy. Cohen (1982) p.104 posits a combined

structural-dynamic model. "To extend the power of the structural model so

as to explain this kind of variability, it is necessary to postulate some

form of dynamic mechanism which controls or influences the functioning of

fixed structures. Dynamic models therefore represent an extension or

amplification of structural models, rather than a distinct alternative.

Although an increase in explanatory power is achieved by marrying structural

and dynamic models, there is a corresponding loss of predictive power

because the principles which govern the dynamic mechanism are not at present

sufficiently well specified." Here preliminary attempts are made at the

apecification of dynamic process asymmetries.

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An adaptation of Cohen's model is shown in Fig. 1. On the one hand

there are cerebral asymmetries presumed to have atructural determinants such

as verbal versus visuospatial and analytic versus gestalt processes, etc.

On the other hand, there are asymmetries in dynamic processes such as

arousal and attention. One modification of the schema is to suggest that

instead of subsuming arousal under attention, that arousal and attention may

Involve different mechanisms. An example of this independence has arisen

from dichotlc listening studies of paranoid schizophrenic patients where a

presumed left hemispheric bias in activation seen in free recall has placed

a constraint on ear advantagea in cued recall when attention was directed to

the left car (Gruzeller, this volume Fig. 2).

.'V

The moat developed theory of a dynamic process in competition with a

atructural one belongs to Kinsbourne'a (1970, 1975) model of attention.

Klnabourne posits that hemispheric activation patterns are reciprocally

related in a finely tuned balance. Moment-to-moment imbalances determine

the direction of orlentatlonal responses in the lateral plane. Through

Incompatible expectancies as to the nature of the task, priming carried over

from preceding tasks, or distraction from concurrent tasks, attention may be

diverted away from the atructural process best suited for analysis. One of

the reasons we suggest why tests of the model have not always been

confirmatory Is because activational imbalances may be out of keeping not

only with atructural process requirements but also with attention. Dynamic

processes themselves may be in conflict.

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Activational asyratnetries Independent of attention have received scant

attention In noraal subjects, though there Is an extensive literature in

psychiatric patients (e.g., Gruzelier & Flor-Henry, 1979; Flor-Henry &

Gruzelier, 1983). One exception is found in the work of Tucker (1981) who

has proposed that anxiety through over-arousal places a processing load on

the left hemisphere giving rise to a right hemisphere processing dominance.

Our investigation of this proposition with a within-subject design will be

outlined because it exemplifies how a dynamic process can reverse structural

asymmetries. Ve examined the effect of anxiety on a divided visual-field

task using a life-stressor to manipulate level of anxiety (Gruzelier &

Phelan, 1986). The effect of the Stressor was validated with

psychophysiological measures of sympathetic reactivity and self-report

acales of anxiety. Thirty three medical students, of whom nine were female,

were tested before an examination and again at a relatively unstressful time

at least four weeks before or after, with order of testing counterbalanced.

Sympathetic activity was monitored with electrodermal activity throughout a

stimulus habituation paradigm consisting of 22 tones of 70dB SPL, 1 second

duration, 1000 Hz, with controlled rise and decay times, and 20-40 second

interstimulus Intervals. The 15th and 19th tones were of 690 Hz and 2160 Hz

to measure dishabituation. Three other measures were obtained; the rate of

habituation of orienting responses to non-signal tones, the number of nonspecific responses between tones, and levels of tonic activity. It has been

shown that electrodermal responses increase with anxiety, that tonic levels

rise and rate of habituation is retarded (Stern & ,Janes, 1973); studies

which have included the effects of examination stress on students (Maltzman,

Smith & Cantor, 1971). The IPAT anxiety questionnaire was administered in

each condition to a sub-group (N-18); seven had .scores above 40 which was in

the psychopathological range (Krug, Scheier & C^ttell, 1976).

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provided by the electrodermal measures. Rate of habituation of orienting

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responses is shown in Fig. 2. HaMtuation w..s retarded under stress

(p<0.OO6). Non-specific responses, shown in Fig. 3, were more frequent

prior to exams (p<0.0007), as were orienting responses (p<0.0009), shown

Fig. 4. Skin conductance levels rose from a mean of 21.56 mhos to 26.03

mhps (p<0.03, one tailed). Self-report anxiety increased from 28.A to 31.1

(p<0.05, one tailed), particularly the frustration-tension sub-scale which

Increased from 7.00 to 8.37 (p<0.03, one tailed).

Hemispheric asymmetries were examined with a divided visual-field task

shown to produce a left hemisphere advantage In normal subjects (Connolly,

Gruzelier & Manchanda, 1983). The task required discrimination between

consonants and vowels with a manual reaction time recorded to target stimuli

(vowels). Stimuli were presented randomly in either visual field for 240

trials, 81 of which were targets. Stimuli were of 50 msec duration and

subtended an angle of 4 degrees on either side of a centrally positioned 500

msec warning light which occurred 400 msecs before the stimulus. The

Interstimulus interval was 4 seconds.

In the non-anxious condition there was a nine msec right visual-field

advantage whereas in the anxious condition the left visual-field showed a

six msec advantage (p<0.02). The results are shown in Fig. 5. Between

hemisphere differences were both significant (p<0.05). Within hemisphere

po^-hoc comparisons revealed that the right hemisphere showed the greater

variation between conditions (p<0.01). Anxiety significantly improved right

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Considering individual subjects Fig. 6, 23/31 subjects showed a left

hemisphere advantage in the non-anxious condition while 21/31 subjects

showed a right hemisphere advantage in the anxious condition (p<0.001).

22/31 subjects showed a shift between conditions, towards superior right

hemisphere performance in the anxious condition. Thus, more than two-thirds

of subjects showed a reversal of a left hemisphere advanr - for verbal

processing under anxiety, an effect largely due to an en ement in right

hemisphere processing. Thus, there was support for the , diction that the

relative difference between the hemispheres under anxiety would favour the

right hemisphere, but there was no evidence of a deterioration in

performance in the left hemisphere as might be supposed if anxiety placed a

processing load on the left hemisphere. Nor would the model predict an

improvement in right hemispheric performance. This will be returned to in a

later section.

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RATE OF HABITUATION AND INDIVIDUAL DIFFERENCES IN CEREBRAL ASYMMETRY

A further Implication from the study of examinar on stress was that

rate of habituation of electrod^rmal activity, which varied with anxiety,

ay itself represent an individual difference with a bearing on hemispheric

activational balance. In support of this contention, correlations have been

found between rate of habituation of the orienting response to tones and the

lateral asymmetry In response amplitudes, an asymmetry which is presumed to

provide one reflection of hemispheric activation. This was discovered in

three experiments (Gruzelier, Eves & Connolly, 1981a) involving, in the

first, patients awaiting minor surgery in the Copenhagen General Hospital;

In the second, first year medical students at Charing Cross Hospital and,

in the third, hospital staff at the latter hospital. The tone series was

similar but shorter to the one above involving 13 70 dB tones in experiments

1 and 2 and 10 tones in experiment 3. For the hospital staff this was

followed by a 90 dB SPL series, with stimuli of five seconds duration and

with the 10th of the 11 tones of ten seconds duration. Correlations between

rate of habituation to a criterion of three successive failures to respond

and lateral asymmetries in orienting responses, calculated as a laterality

Index, 2(left-right/left+right), are shown in Table I for the three

experiments for the total nvakcr of subjects, for male and female subjects

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Table 1 Correlations between trials to habituation and lateral

asymmetries in orienting response amplitudes.

GROUP SEX Rho

Surgical Patients

Hospital Staff

Students

All Groups

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70-dB Tone Intensity

M 16 .53 .05

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M 71 .49 .001

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correlations were obtained. Fast habituation was associated with larger

left than right hand response amplitudes and slow habituation with larger

right than left hand response amplitudes. The relationship was found to be

true of males whereas in females it was weaker, falling short of

significance in the hospital staff and absent altogether in female students.

The relationship also fell short of significance in sinistrals.

It is well documented that non-specific responses are typically more

frequent in subjects who are slow habituators; here correlations ranged

between 0.76 and 0.84 for the total samples. The same relationship held for

non-specific responses between lateral asymmetries in response amplitude and

the number of responses. A scatter plot is shown in Fig. 7. Correlations

ranged between 0.45 and 0.73 for the total samples, all significant at the

p<0.001 level, and were significant for both men and women.

This cerebral asymmetry has an important bearing on phasic reactivity

in the electrodermal system whether responses are stimulus specific or nonspecific. However, this relationship does not extend to tonic levels of

skin conductance activity. Correlations between asymmetries of orienting

responses and tonic levels ranged between 0.06 - 0.32 (ns). Furthermore,

the partialling-out of the influence of levels on amplitudes still gave

correlations of 0.39 and 0.49 (p<0.06 - p<0.002) between the asymmetry in

responses and rate of habituation. An independance of lateral asymmetries

In levels and responses has been a consistent finding in our studies, as can

be seen in two illustrative cases (Figs. 8a b). This dissociation

deserves further neurophysiological investigation and may imply a more focal

distribution of influences on phasic responses.

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of the lateral asymmetry In reponses amplitudes.

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Given that there was a reversal in lateral asymmetries, two types of

hemispheric influence may underly the effect on response amplitudes as rate

of habituation decreased. Either there is a reciprocal relationship between

the hemispheres, as Kinsbournc's theory might suppose, such that when the

balance is tipped one way habituation is fast and when tipped the other

habituation is slow, or alternatively control of habituation may be

unilateral such that when control is strengthened oc weakened, amplitudes

will show variation predominantly on the hand contralateral to the

controlling hemisphere. We reasoned that reciprocal control would lead to

correlations between rate of habituation and unilateral amplitudes that were

opposite in sign on one hand compared with the other, whereas unilateral

hemlspheiic control should provide significant correlations on one hand

only. The obtained correlations supported reciprocal hemispheric control.

They were negative (-0.25 to -0.45) with the left hand and positive (+0.28

to +0.69) with the right hand.

The importance for cerebral asymmetry of individual differences in rate

of habituation is underscored by the finding that rate of habituation of

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during presentation of a one second tone.

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Fig. 9. Race of habltuatlon Co flashes

slnlsCral mlgraineur.

The unfilled circle represenCs Che

elecCrodermal orienting responses is predictive of Che laterality of pain in

migraine in paCienCs where Che headache is constsCenCly laCeralised

(Gruzelier et al., 1986). Two experiments were undertaken recording race of

habitation between headaches. In Che firsC experiment stimuli were flashes

of lighc and, in Che second, moderate intensicy'(70 dB) Cones in a series

similar Co Che ones used in Che experiments above. It was hypoCheslsed,

thaC, as pacienCs ofCen reporC sensory discomforC preceding and during

attacks, central mechanisms regulating sensory imput may be deficient and

Chis may have a hemispheric basis. In Che firsC experiment, 5 left-sided

migraineurs were compared with 6 right-sided cases, 7 with bilaCeral Cension

headache and 12 medically fit control;. Rate of habituacion is shown in

Fig. 9. There was no overlap between left and right-sided migraineurs and

Che one sinistral was midway between Che groups. Patients with left-sided

headache were on average faster Co habiCuaCe Chan all ocher groups whereas

pacienCs with right-sided headache were Che slowest Co habituate. Extremes

of habituacion in migraineurs were replicated in Che second experiment,

where seven left-sided cases were compared with six right-sided cases, see

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Rignt-sided Le't-sided

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Fig. 10. Race of habicuation and number of orienting responses Co Cones in

migraineurs.
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Fig. 10. All were dextral and free of medication. Hert the extremes of

habituation found parallels in the number of non-specific responses and in

tonic electrodermal responsiveness measured as the difference between the

highest and lowest skin conductance level. In both experiments, the patients

were all severe cases having migraine attacks as often as one a week. The

laterality of headache was the only clinical feature that distinguished

them. The association of extremes of habituation of the orienting response

with the laterality of pain makes it tempting to conclude that hemispheric

imbalance is a predispositional factor in migraine. Of relevance here was

the link between cerebral asymmetry and individual differences in rate of

habituation.

A study of neurological cases with unilateral lesions had earlier shown

opposite extremes of electrodermal responsivity according to the side of the

lesion. Heilman, Schwartz & Watson (1978) examined seven right-sided

patients, five of whom had infarctions in the distribution of the middle

cerebral artery, one with a right temporoparietal glioma and one a putamenal

haemorrhage. All manifested flattened affect and contralateral behavioural

neglect. Four had participated in an earlier experiment revealing

impairments in the comprehension, discrimination and expression of

affectively intoned speech. They were compared with six left-sided patients

with comparable lesions, five having infarctions in the distribution of the

left middle cerebral artery and one a left-sided putamenal haemorrhage. All

patients exhibited dysphasia, three with Broca's aphasia and three with

anomic and conduction aphasia. These groups, matched for the site of the

lesion, were in turn compared with a group of patients of similar age but

without known structural brain lesions. Electrodermal activity (skin

resistance) was recorded from the hand ipsilateral to the lesion to two

blocks of five presentations of brief electrical pulses (10 sec ISI)

delivered to the forearm, the intensity of which was individually gauged to

present discomfort but non-pain:- X:0.4A in mA (right), "X:0.28 mA (left),

X:0.53 mA (controls). There were no statistical differences in the amount of

current delivered. Levels of electrodermal activity were significantly

reduced in the right-sided group (right < left < controls), and 5/7 patient

were non-responders. In contrast, on average, the magnitude of responses of

the left-sided group was approximately four times that of the controls.

m

mm

It is unlikely that the differences in reactivity could be attributed to

recording from the left hand in one group and the right hand in the other

because though hemispheric influences are asymmetric they are nevertheless

bilaterally mediated; while the evidence so far is sketchy, structural

lesions Including surgical ablation produce asymmetric responsivity in the

direction of larger responses on the contralateral hand (Gruzelier, 1979b

for review). Furthermore, the authors note that when recordings were

obtained in right-sided cases from the contralateral hand, three continued

to be non-responsive over a range of stimulus intensities. Nevertheless,

replication of the study with bilateral recording and a standardised

stimulus is desirable, for there was a broad range of individual variation

in the levels of the current delivered. These Incidental findings do not

detract from the major difference in responsivity between the left and right

hemisphere lesion groups. Moreover, support is found from other reports

showing that aphasic patients maintain an ability to show differential

responses to emotionally loaded versus neutral stimuli whereas patients with

right-sided lesions show no such discrimination (Boiler et al., 1978; Morrow

et al., 198.).

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Morrow et al., (1981) compared electrodermal responses in three groups

cf 1A patients classified according to whether they had dominant or nondominant hemisphere neuropathology or no known nervous system pathology; c.ie

of the dominant hemisphere group had a right-sided lesion and demonstrated

right-hemisphere speech dominance. With two exceptions, the patients all

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302 m

had vascular lesions and the dominant hemisphere group were all dysphaslc.

Electrodermal responses were recorded from the hand ipsilateral to the

lesion to a randomized sequence of emotional and neutral slides. Regarding

responsivity to the slides on which all groups differed significantly the

groups were ordered as follows:- non-dominant, < dominant, < controls. In

addition emotional slides produced larger responses than neutral slides in

nil but the non-dominant group. Thus the difference between the unilateral

lesion groups was in keeping with the results of Heilman et al. (1978)

despite the different nature of the stimuli. There was a discrepancy

between the reports in the degree of responsiveness in controls. However,

in view of the wide individual variation in electrodermal responsiveness

this may have affected differences in sampling. Leaving aside this

discrepancy, it is clear that comparable left and right-sided lesions do

have differential effects on phasic responsi^ity In the electrodermal

system. With left-sided lesions responsiveness is retained, and may in some

instances be augmented, whereas with right-sided lesions patients become

hypo-responsive. If we assume the opposite polarity of influences operates

In the normal compared with the damaged brain, then the left hemisphere has

inhibitory influences and th" right hemisphere excitatory influences on

electrodermal activity. Accordingly the evidence with neurological patients

is consistent with tha results above in normal subjects and with

migraineurs, in whom increased cortical excitability has been hypothesised

(Wilkins et al., I98A).

yj«

The association of fast habituation with the left hemisphere and slow

habituation with the right hemisphere is also consistent with theories of

hemispheric specialisation in attention and with empirical evidence linking

electrodermal responsiveness and habituation wich vigilance and selective

attention. The electrodermal response when elicited to a repetitive

stimulus is regarded as one manifestation of orienting behaviour which

reflects investment of attention in the stimulus, while non-specific

reactivity is thought to be related to cortical excitability and alertness.

In vigilance experiments parallel declines in vigilance and electrodermal

responses have been reported (Ross, Dardano & Hackman, 1939; Stern, 1966).

In a visual detection study examination of the temporal relationship between

electrodermal responses and correct detections and misses revealed that

responses (skin potential) were more frequent before hits than misses

(Surwillo & Quilter, 1965). Blakeslee (1979) found a similar relationship

when measuring the amplitude ol responses in time epochs before and after

the stimulus. Furthermore Kiupf<i, Ruskin & Bakan (1971) found that errors

of, commission were negatively related to reactivity.

The measurement of habituation rates prior to vigilance tasks has shown

an association between fast habituation and ^oor vigilance (Coles & Gale,

1971; Siddle, 1972; Crider S Augenbraun, 1975). On the other hand prior

habituation to a stimulus later employed as a distractor was shown to

minimise its potential for distraction (Waters, MacDonald & Karenko 1977).

On th" basis of this evidence we have argued that extremes in electrodermal

reactivity are associated with differences in attention such that fast

habituation is associated with focussed, selective attention, and slow

habituation with sustained, broad, vigilant attention (Gruzelier, Eves &

Connolly, 1981a). Focussed selective attention is a prerequisite of

analytic, sequential processing of the left hemisphere while broad vigilant

attention is compatible with the parallel, holistic processing of the right

hemisphere. In support of this, Dimond & Beaumont (1973) have found a right

hemisphere superiority on a task of sustained vigilant attention ir normal

subjects while Dimond (1980) reviews a series of experiments with visual,

auditory and haptic tasks in patients with total commissurotomy shewing

superior right hemisphere vigilance.

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303

MOTORIC SPEED AND INDIVIDUAL DIFFERENCLS IN DYNAMIC PROCESS ASYMMETRIES

It follows from theories that differentiate left and right hemispheres

on the grounds of positive versus negative affect (e.g., Flor-Henry, 1979b),

approach versus withdrawal (Klnsbourne, 1982) and motorlc versus sensory

processors (Tucker & Williamson, 198A) that Individuals with a left

hemisphere disposition would have an advantage In motorlc speed. We

examined this with a haptlc sorting task In which speed of sorting was

compared for each hand and a 'processing' time obtained by subtracting the

time taken to sort the objects without object identification, 'movement'

time, from the time taken to sort them by class. In view of the

contralateral mediation of active touch the right hand was used to index the

left hemisphere and the left hand the right hemisphere.

In a pilot study (N-20), two tasks were developed which produced normal

distributions in hemispheric advantages with the distribution on one task

displaced to favour the left hemisphere and the other task to favour the

right hemisphere. The left hemisphere task involved the discrimination of

letters from numbers, and was termed the verbal task. The right hemisphere

task involved the discrimination of straight from curved bordered digits and

was termed the spatial task. Thirty-two dextral medical students were

examined, subdivided by gender into two equal groups. The subjects were also

subdivided on the basis of hemispheric dispositional asymmetries defined as

the mean left-right processing difference over the. first 4/8 trials of each

sorting condition. A comparison of the extreme 257. of each lateral

disposition and gender indicated that movement times were faster in those

with a left hemispheric disposition (p<0.01). In other words, subjects whose

processing tlc.s were initially better with the .right hand, irrespective of

whether the task was verbal or spatial, showed faster movement times

bilaterally when objects were handled without identification (Baxter &

Cruzelier, 1984).

These results were replicated in a further experiment involving 64

subjects divided by gender and age (over or under 30 years). When they were

subdivided further on the basis of hemispheric disposition, the left

hemisphere group again showed a significant advantage for movement time

(p<0.02). Hemispheric disposition also interacted with age and gender

(p<0.007). Vs shown in Table 2 this was largely due to a marked slowing in

movement time in women over 30 years who had a right hemisphere disposition.

This result may have a bearing on the controversial evidence that ageing,

while leading to bilateral impairments, has more deleterious effects on the

right hemisphere (Botwinick, 1983). The predominant but by no means

unequivocal view about brain laterality and gender is that in women the left

hemisphere is superior to the right whereas in men the rijht hemisphere is

superior to the left (Harris, 1980). If the view (Flor-Henry, 1983) that

pathology affects the more vulnerable hemisphere - the left in men and the

right in women - is added to this, then a dlsadvantaged right hemisphere may

be more a characteristic of ageing women than ageing men. Thus, taking gender

Table 2. Movement time in seconds for subjects classified by age, gender

and hemispheric disposition in haptlc sorting.

Hemisphere <30 ye ars >30 ye ars

Disposition M F H F

Left 11.7 13 .05 13.95 12 .95

Right 13.6 12 .95 13.46 16 .95

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Into account may resolve some of the controversy surrounding cerebral

laterality and ageing.

HYPNOTIC SUSCEPTIBILITY AND INDIVIDUAL DIFFERENCES IN DYNAMIC PROCESS

ASYMMETRIES

Individual differences In asymmetries In haptlc processing times have

also been found to relate to hypnotic susceptibility. In one experiment

students (Fig. 11) and in another middle-aged subjects, all naive to

hypnosis, were tested on the verbal haptlc test before and while listening

to a tape recording of an induction of hypnotic relaxation. Prior to

hypnosis those who were later to prove to be susceptible to the induction

chowed faster left than right hemisphere processing times. Under hypnosis

there was an Increase In right but not left hand processing times, and in

students the increase in processing time was positively correlated 0=0.65,

p<0.01) with the degree of hypnotic depth (Gruzelier, Brow, Perry et al.,

1984). This Implies that the Induction of hypnosis produces a progressive

slowing of left hemisphere processes.

P5Ä

In a previous experiment, lateral differences in electrodermal

responses to tones in a session prior to hypnosis also proved to

differentiate subjects who were to be susceptible to hypnosis (Gruzelier &

Brow, 1985). Consistent with the haptlc processing asymmetries, for whom

susceptible subjects prior to hypnosis showed a left hemisphere advantage,

the electrodermal responses of susceptible subjects were larger on the left

hand (Fig. 12). Furthermore, under hypnosis susceptible subjects showed a

reversal in asymmetries and an Increase In habltuation to tones occurring

Incidentally midway through the induction procedure. Habltuation In

unsusceptible subjects was retarded relative to'the pre~hypnosls session.

When considered in the context of cerebral asymmetry in attention and the

dynamics of an initial left hemisphere advantage, its inhibition and a shift

to the right hemisphere provides a neuropsychologlcal framework for the

familiar conventions of hypnotic induction. Hypnosis typically begins with

the requirement to focus attention by fixating on a small object, which we

interpret as engagement of a left hemispheric process. This is followed by

suggestions of sleepiness and fatigue leading to a suspension of critical

attitudes and an abdication or letting go of planning functions - an

inhibition of left hemispheric functions. Coincidentally there is an

increasing engagement of right hemisphere processes such as sensory memory,

passivity, visual imagery, etc.

< Unsusceptible subjects as a group do not show a left hemispheric

activational bias prior to hypnosis in either haptlc processing or

electrodermal orientating responses. Nor do they undergo an inhibition of

left hemispheric processes. Their tonic levels of skin conductance activity

- 20

J

g- 15

* 10

r

Left *>

1 ^

L sRignt

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pre post pre

Hypnosis

post

Fig. 11. Haptlc processing time for left and right hands before hypnosis

and after hypnotic induction while hypnotised in susceptible

subjects (left) and unsusceptible subjects (right).

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305

UNSUSCEPTIBLE

Log.

Amplitude

-3.0

-3.5

-4.0

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-4.5

Log.

Anplltude

SUSCEPTIBLE

Left

TONES ---RigMt

Log.

Amplitude

J—

1 5 10 15

Trill

-3.0 r HYPNOSIS

-4.0

-4.5

Log.

Amplitjde

3.0 HYPNOSIS

3.5

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4.0

-

V

4.5

1 5 10 15

Trial

Fig. 12. Bilateral electroderaal response amplitudes to tones in

susceptibles (left) and unsusceptibles (right) in session I

(TONES) and in a later session under hypnosis (HYPNOSIS).

s

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w

during the initial stages of the induction do not show the same decline or

adaptation as those of «usceptibie subjects, non-specific responses are

initially more frequent and haptic processing times show a small bilateral

improvement. These results suggest a more defensive, anxious attitude and a

failure to comply with the instructions for relaxation. In the light of

these experiments hypnotic susceptibility is se^n to consist of two

components. The first is the ability to engage left hemisphere focused

attention and the second to undergo an inhibition of left hemisphere

planning functions. Unsusceptible subjects either do not engage left

hemisphere focused attention, retaining a state of right hemisphere broad

attention, or fail to let go of left hemisphere planning functions, i.e.,

undergo left hemisphere inhibition. Thus, individual differences in

susceptibility to the induction of hypnotic relaxation reveal an interplay

between dynamic and fixed process cerebral asymmetries.

ANXIETY AND INDIVIDUAL DIFFERENCES IN DYNAMIC PROCESS ASYMMETRIES

In our study of examination anxiety in students, a right visual field

advantage for the processing of verbal stimuli gave way to a left visual

field advantage, see Fig. 5. Tuc!-.er, Stenislie & Earnhardt (1978) had

earlier found evidence for what was described as a processing load on the

left hemisphere for high trait anxious students. This was inferred from two

results. High trait anxious students compared with low had an asymmetry in

favour of the right ear in loudness judgements, indicative of greater left

•.• «.• i
306

Table 3. Reaction cine in msecs to verbal and spatial stimuli presented

In the left and right visual fields in anxiety patients and

dextral and sinistral controls.

Croup Task

Verbal Spatial

LVF RVF

Patients 582 608

Dextral 464 436

Sinistral 509 545

LVF RVF

697 734

557 581

656 636

hemispheric activation, and at the same time displayed poorer right than 'X**?

left visual-field hemisphere processing of verbal and spatial stimuli. Our

results were somewhat similar showing poorer left than right hemispheres

processing in a verbal task when state anxiety was raised but this was shown

to be due to an improvement in right hemisphere performance, Fig. 5.

A left visual field advantage in the same task was subsequently found

in a group of eleven, dextral psychiatric patients (seven female), whose

primary complaint was anxiety (Gruzelier & Bennett, in preparation^. They

were compared with seven dextral controls (four,female) of similar age. In

addition to the verbal task there was a spatial task which in two studies

have shown a left visual field advantage in normal controls and psychotic

patients (Connolly et al., 1979, 1983). The task consisted of a 3 x 3 dot

matrix in which one dot was missing on target trials. Manual reaction time '>.->;

was measured with task and hand order counterbalanced in blocks of 40 trials -'-'v'*^

with 240 trials per task. The results are shown in Table 3. There was a ''y-Y

highly significant interaction between Croup by Visual Field by Stimulus '•" "-V}

(p<0.0001). The controls showed the expected left hemisphere advantage for

the verbal task and right hemisphere advantage for the spatial task yV-!

(p<0.0001). Patients showed a right hemisphere advantage for both tasks V'vS

(p<0.0001). The patients scored more highly on questionnaire measures of "'v

anxiety such as the IPAT and EPQ Neuroticism (p<0.001). In a test of

hemisphericity in cognitive style (Zenhausern, 1978) the patients

showed more left hemisphere reliance than controls (p<0.05). Thus, while

patients revealed a left hemisphere disposition in cognitive style, it was v7^

their right hemisphere which showed a speed of processing advantage for

verbal material as was seen in anxious students. Support for the role of

left hemispheric activation in anxiety has been clarified somewhat using

electrodermal measures. In the experiments reported above which revealed

the relation between rate of habituation and the lateral asymmetry of

responses (Cruzelier, Eves & Connolly, 1981), a subsequent analysis of !•.>

questionnaire measures in the 31 hospital staff and 62 students revealed a ^- '-•'

relationship suggestive of a switch to left hemisphere control under highest

levels of anxiety. For students, the larger sample permitted a comparison

of those who were fast or moderate habituators (N-22) with those who were

slow habituators. It is noteworthy that slow habituators were in the

majority, contributing to an impression gained from a series of experiments

that levels of stress in medical students are high. Civen the large number

of slow habituators it was possible to subdivide them further into those KS^SI

with larger responses on the right hand (N-18) and those with larger ^Vsfl

responses on the left hand (N-22). The latter could be regarded as an jSjflS

anomalous group with respect to the model of cerebral asymmetry and

habituation examined earlier where fast habituation was under left

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307

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Table 4. Anxiety scales for students (N 62) classified according to rate

of habituation and lateral asymmetry in orienting responses.

SCALE GROUPS

Slow R/L Slow V/R Slow

Habituators Habituators Habituators Habituators

(22) (40) (18) (22)

IPAT Total 27.15 31.16 30.09 32.27

Subscales

Low self-control 5.29 7.00 7.00 7.00

Instability 3.50 3.00 2.68 3.38

Suspicion 2.46 3.13 3.25 3.00

Apprehension 7.38 8.22 6.50 9.94

Tension-frustration 6.46 8.01 7.38 8.63

n•- v •

EPI Neuroticism 6.75 8.43 8.22 8.64

Spellberger

State

Trait

41.65

40.49

43.35

42.68

42.31

42.88

44.47

42.47

hemisphere control and slow habituation under right hemisphere control.

It can be seen in Table 4 that when comparing all subjects classified

as either habituators or slow habituators a relationship between anxiety and

retarded habituation was supported. All anxiety related scales, namely the

total IPAT score, EPI Neuroticism, and Spellberger State/Trait were all

higher in slow habituators. A novel finding was the evidence among slow

habituators of higher anxiety in those with larger left hand responses,

which. In terms of the model of cerebral influences on electrodermal

activity is Indicative of a dominance of left hemispheric influences.

Comparisons between scales indicated that left hemisphere anxiety was

characterised by the IPAT subscales of frustration-tension on which high

scorers are described as "tense, frustrated, driven, overwrought", and more

so by the apprehension subscale where high scorers are described as

"apprehensive, self-reproaching, insecure, worrying and troubled." These

scales Indicate a verbal cognitive component to anxiety.

In the smaller saaple of hospital staff the relationships were examined

with correlations. Measures included the IPAT and EPI scales. Here only

one significant correlation was found with an anxiety scale. This was

between the lateral asymmetry in the amplitude of non-specific responses and

the IPAT suspicion subscale, in the direction of higher scores of suspicion

In subjects with larger left hand responses, see Table 5. As the hospital

staff were a more heterogeneous group demographically, and in terms of life

situation, the correlations were re-examined in another study of medical

students (15 men and 15 women) aged between 20 and 23 years (Holland, 1984).

They were dextral, all but for one whose exclusion did not alter the

»

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308

Table 5. Cocrelations between electrodermal lateral asymmetries and anxiety

^S

:<;.

Subjects Electrodermal Measure Anxiety Scale

Hospital

Staff

(N 31)

Students

(N 30)

non-specific responses suspicion

Correlation

Rho

-0.A3, p<0.05

orienting responses

dishabituating tones

skin conductance level

frustration-tension

Anxiety total

Emotional instability

Frustration-tension

Anxiety total

Low 8elf-contr;ol

Apprehension

Frustratlon^tension

Neuroticism

-0.41, p<0.03

-0.44, p<C.03

-0.46, p<0.02

-0.49, p<0.02

-0.59, p<0.0001

•0.49, p<0.003

-0.32, p<0.04

-0.49, p<0.02

-0.52, p<0.002

results. The same moderate intensity tone sequence was used as In the

previous studies. A range of significant correlations were obtained. These

are shown in Table 5. All showed an association of higher electrodermal

reactivity on the left hand with high anxiety. The correlations were more

numerous with asymmetries in tonic levels of activity. Correlations

Included IPAT anxiety and EPQ Neuroticism. Of the IPAT subscales

frustration-tension again showed significant relationships and in this study

Included orienting and non-specific responses as well as skin conductance

levels.

i

The relationship between lateral asymmetry in electrodermal activity,

rate of habituation and individual differences in anxiety can be thought of

as having the following implications for the influence of anxiety on dynamic

process asymmetries (Fig. 13). Fast habituation and low anxiety reflect a

dominance of left hemispheric Inhibition. The shift in excitationinhibition balance seen in decreasing rates of habituation reflects a

reversal in hemispheric influences resulting in a dominance of right

hemispheric activation. Under states of high anxiety, control may revert to

the left hemisphere without influencing the excitation-inhibition balance

which remains in a state of excitation, as reflected in slow habituation.

The dominance of excitation, out of keeping with left-sided inhibition, may

overload the operation of fixed structures of the left hemisphere. The

schema in Fig. 13 Is the familiar inverted - U relationship between arousalanxiety and performance in a new guise. The behavioural disorganisation

which characterises over-arousal and the down-swing of the inverted - U is

depicted as a consequence of the shift in hemispheric control to the left

hemisphere that occurs with high states of arousal-excitation.

Predictions should follow as to individual differences in the quality

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309

Raght

Hemisphere

Left

Slow

Moderate

Fast

Slow

ANXIETY/AROUSAL

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Fig. 13. Conceptualisation of the relationship between anxiety/arousal and

lateral cerebral activation.

of anxiety according to the asymmetry in «ctivational dominance. It might

be anticipated that a left hemisphere dominance will underly cognitive,

ruminative forms of anxiety whereas a right hemisphere dominance will

underly generalised, free-floating forms of anxiety. There is some hints in

support of this from Che IPAT subscales. Those Chat showed an association

with Che left hemisphere activation dominance were Che Chree scales with

strong cognitive assocl.Ki.ons:- the 'frustration-tension' scale, Che

'spprehension-worrying' scale and the 'suspicion' scale on which a high

scorer is described as 'suspicious, jealour, hard-to-fool.' Whereas no

relationships were found with Che scale of 'emodonal instability' -

'emotionally unstable, easily upset, changeable', or Che scale of 'low selfcontrol' - 'uncontrolled, follows own urges, careless of social rules'.

Bearing in mind Che inadequacies of self-report scales ratings obtained on

clinical samples should provide a useful test of this hypothesis as

exemplified by Che approach of Rabavilas et al. (1979) who wich unilateral

recording compared rates of electrodermal habituation to very loud (100 dB

SPL) Cones in Cen obsessive-compulsive patients with ruminative thoughts and

in ten exhibiting ritualistic behaviour. The former group showed both

higher reactivity and slower habituation to the tones. A systematic attempt

combining ratings with bilateral skin conductance would be of interest. One

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310

such attempt in schizophrenia has produced theoretically Interesting results

and will now be reviewed.

SCHIZOPHRENIA AND INDIVIDUAL DIFFERENCE? IN DYNAMIC PROCESS ASYMMETRIES

In psychiatry the need for sub-claisification of schizophrenia is part

of the contemporary Zeitgeist (Kety, 1^80). Historically, since the time

Kraepelin (1855-1926) first described catatonia, hebephrenla and paranoia as

the «ingle entity, dementia praecox, attempts have been made to account for

the heterogeneity of the disorder with various principles of subclassification such as acute/chronic, process/reactive, good/poor prognosis,

good/poor pre-morbid, paranoid/non-paranoid. The contemporary need for subclassification has come about for a number of reasons. It is clear that

patients differ in response to neuroleptlcs some undergoing complete

recovery and others a mild amelioration of symptoms. Some disorders

spontaneously remit whereas others lead to chronic deterioration.

Constellations of symptoms show wide variation between anH within patients,

at one extreme depicting florid acute symptoms and at the other socially and

emotionally withdrawn, autistic, behaviour. While a neurological basis of

schizophrenia has always had its advocates, it is the evidence from X-ray

computed tomography that first gave this widespread credibility. However,

the view that only some patients show CT signs and that these are the ones

with cognitive deficits (Crow, 1980), has been based on the detection of

fairly gross forms of pathology. It is likely that as scan resolution

improves computed tomography together with techniques that explore the

functional activation of the brain through measures of blood flow and

metabolism (e.g., Sheppard et al., 1983; Gur et al., 1983) will reveal focal

signs of abnormal structure and function more la keeping with evidence that

all forms of schizophrenia possess at least transiently, central nervous

system signs (Cruzelier, 1985). The most developed neuropsychophysiological

theory of brain dysfunction in schizophrenia is currently one of

lateralisation, either taking the form of a unilateral disorder, with most

evidence implicating the left hemisphere, or because of faulty

interhemispheric communication - evidence for which is reviewed in

Cruzelier, this volume. There have been numerous reviews of these hypotheses

such as Flor-Henry (1974; 1979,a,b; 1983,a,b), Cruzelier (1979a; 1981a,b;

1983), Newlin, Carpenter & Golden (1981), Ualker & McGuire (1982) & Uexler

(1980), to name a few. Most researchers of lateralised function in

schizophrenia have taken a unitary view of the disorder, however evidence

will be briefly outlined showing that individual differences in the form and

course of the disorder may be unravelled through consideration of individual

differences in the balance of hemispheric influences on dynamic processes

(Cruzelier, 1981, 1983, 1984; Cruzelier & Manchanda, 1982). Undrugged new

hospital admissions with a diagnosis of schizophrenia made with the help of

the Present State Examination and CATEGO analysis (Wing, Cooper & Sartorius,

1974) were examined for rate of habituatlon with the moderate intensity tone

series described above. If they were non-responsive to the tones, as is not

uncommon In schizophrenia (Cruzelier & Venables, 1972; Bernstein ct al.,

1982), they were given a 90 dB SPL sequence of 1000 Hz tones of 5 second

duration (see Cruzelier et al., 1981 b). Patients were sub-divided

according to the direction of the lateral asymmetry in orienting responses

and compared for syndromes (CATEGO) and ratings on the Brief Psychiatric

Rating Scale (BPRS) (Overall and Gorham, 1962). Two experiments were run.

The first involved 23 undrugged patients selected for a drug trial in which

florid symptoms were one criterion for selection, and the second involved 25

consecutive undrugged admissions.

m

• * »I

.•v.v,

The two groups classified on the basis of a dynamic process lateral

«symmetry differed on 13/38 CATEGO syndromes and 8/19 BPRS ratings. To

sharpen the clinical description, the syndromes were examined for those

features applicable to the present patients as each syndrome is usually made

If, ^- A. f-V- ^w- V- ^

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311

Table 6. Symptoms of the two schlzophranid syndromes

Left hemisphere activation

Heightened self consciousness (simple ideas of reference)

Exaggerated self opinion and conviction of unusual ability (grandiosity)

Exaggerated concern about bodily welfare (hypochondriasis)

Euphoiia (hypomania)

Situational anxiety; avoids situations; phobias

Pressure of speech

Flight of ideas (hypomania)

• * .^ • • .

N." \

m

S

m N

• "j« *J«'^ '

V V • V

JW,

..N .N .N .V

Right hemisphere activation

Lack of self confidence

Social withdrawal

Uncooperative (resistance, resentment, unfriendliness)

Irritable to hostile

Emotional withdrawal

Reduced emotional tone (blunted affect)

Motor underactivity ,

Slow speech

Muteness, restricted quantity of speech

Inefficient thinking (muddled, slow, not goal directed)

» .'• .

up of more than one symptom or sign. A discriminant function analysis was

also undertaken to determine those syndromes and ratings which most

economically distinguished the groups. This enlarged the profile Co include

a further six variables. A synthesis of these analyses is shown in Table 6.

The groups were positioned at two extremes of an activation dimension

involving self concepts, emotion, cognition, and motoric behavior.

i

The syndromes had an affinity with Chose described by Kety (1980).

Consistent with Bleulerian schizophrenia patients with larger right

hand responses had more blunted affect, reduced emotional tone, emotional

withdrawal, slowness, restricted quantity and content of speech, reduced

energy level, uncooperativeness, social withdrawal and conceptual

disorganization. Consistent with the clinical profile of drug responsive

schizophrenia those patients with larger left hand responses had many more

florid features including hypomania, pressure of speech, flight of ideas,

siir.ple ideas of reference, delusions of grandeur, sexual and fantastic

delusions, depressive delusions and hallucinations, and hypochondriacal

delusions.

v.v,v/.;3

• •

v

• • « '

S%53

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The syndromes overlap but are not to be confused with the distinction

between acute, reactive, paranoid schizophrenia and chronic, non-paranoid

schizophrenia, a classification which has revealed differences in cognitive

functions (Magaro, 1980; Lang & Buss, 1965). What appears essential to

draw out Che difference is Che coupling of paranoid features with a

reactive, emotional component. This is the combination of features seen

here, where, for example ideas of reference and hypomanic features such as

i-V«. . I* /' »".v*AV,V,' '/'",'»'« «'<y.-'.'--'•' • »."* •"•_"r. •"•'• ""^-'»••.•-"•'^" •- •.1^" •• ^> ».• ^ •'• ' ^.- •

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312

pressure of speech were ranked first in the step-wise -liscriminant function

analysis (Gruzelier, 1981b). The same components, this time with emotional

reactivity defined psychophys<ologically, distinguished paranoid and

nonparanoid schizophrenic patients in an earlier dichotic listening study of

hemispheric functions (Gruzelier & Hammond, 1979; 1980; see Gruzelier, this

volume. Figs. 1 and 2).

Accordingly in schizophrenia activational dominance determines the form

the psychosis will take, producing a florid psychosis when left hemisphere

activation is dominant and a non-florid psychosis when right hemisphere

activation is dominant. Schizophrenic patients whose responses were slow to

habituate and who possessed heightened emotional reactivity showed the same

lateral asymmetry as anxious normals, namely larger left hand responses.

The group of patients with the opposite asymmetry possess right hemispheric

activation, as was found in slow habituating normals whose levels of anxiety

nay be higher than average yet not as high as those slow habituators with

the opposite asymmetry.

^ \* ¥

WWKX

TOOT

The model of hemispheric imbalance in the two syndromes is consistent

with a neuropsychological Interpretation of symptoms. The pressure of

speech and flight of ideas of the florid syndrome implies an activation of

left hemisphere verbal processes whereas the sluggish thinking, muteness and

restricted quality of speech of the non-florid syndrome implies an

underactivation of the left hemisphere. The association of euphoria with

the left hemisphere and depression with the right hemisphere is in keeping

with much evidence about the association of different polarities of mood

with the two hemispheres (Sackheim et al., 1982).

As diagnosis of schizophrenia on the basis of hallucinations and

delusions is widespread and not restricted to the diagnostic procedure

employed in our scudies, it follows that other studies of schizophrenia

measuring lateral ized functions should similarly reveal asymmetries of two

kinds in different patients according to syndrome type. A review

(Gruzelier, 1983) was undertaken and evidence was sought for two forms of

asymmetry. Dimensions which have a bearing on the electrodermal syndrome

may be age, chroniclty, prognosis, paranoid versus residual or catatonic

schizophrenia, anhedonic schizophrenia and in a recent report 'dominant'

compared with 'non-dominant' hemisphere syndromes. The review did provide

evidence of two syndromes in schizophrenia provided the measure reflected

imbalances in hemispheric activation or attention and so belonged to the

class of dynamic process asymmetries. The syndromes were consistent in

character with those delineated by electrodermal responses. Furthermore in

each case the nature of the asymmetry, perhaps with one exception, showed

left hemisphere over-activation coupled with right hemisphere

underactivation in acute, reactive, paranoid, good-prognosis schizophrenia,

and left hemisphere unJeractlvation coupled with right hemisphere

overactivatlon in chronic, residual, poor-prognosis schizophrenia. A wide

range of measures revealed bidirectional asymmetries in schizophrenia.

These included levels of electrocortical activity as seen in the

electroencephalogram (EEG), cortical evoked potentials to sensory stimuli,

lateral eye movements to questions designed to stimulate the hemispheres

independently, Che recovery curve of the Hoffman reflex to somatosensory

stimulatio: , measures of auditory processing including the shadowing of

dichotically presented textual passages, the recall of digits presented

dichotIcally, and thresholds to very brief stimuli, a test of somatosensory

extinction whereby competing textures are presented to the palmar surfaces

simultaneously and finally left-handedness (references in Gruzelier, 1983).

It is noteworthy Chat all but the last measure reflect processes that are

dynamic and reversible. Some vary with the activation levels of the

hemispheres: electrodermal responsiveness, electrocortical activity, the

Hoffman reflex and lateral eye movements; others with the direction of

's *•>^^'

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313

attention in the lateral plane: eye movements, auditory processing and

aomatosensory extinction. Handedness apart, in measures which belonged to

the fixed process class, such as the recognition of verbal or spatial

stimuli presented tachistoscoplcally, or the more traditional methods of

neuropsychological test batteries, a left-sided abnormality proved to be

ubiqi'i tous. Thus the need to distinguish between the two classes of

hemispheric asymmetry was critical.

More recent reports are compatible with the hemisphere-syndrome model.

Rabavilas, Liappas & Stefanis (1986) have examined bilateral electrodermal

activity in positive symptom paranoid schizophrenic patients. Correlations

between symptoms and lateral asymmetries in specific and non-specific

responses showed that the larger the asymmetry in favour of the left hand

the larger were ratings of conceptual disorganisation, tension, grandiosity,

suspiciousness and hallucinatory activity. Here, the ratings of tension and

suspiciousness were consistent both with the schizophrenia model and with

the results of the IPAT anxiety subscales in anxious normals outlined above.

Further consistency w .s found in the relationship between symptoms and

lateral asymmetries in tonic levels of activity. Comparisons were made

between the six patients with the dextral preponderance in levels and the

remaining 22 patients. Those with the rightward asymmetry in levels had

higher ratings on negative symptoms such as emotional withdrawal and blunted

affect and were rated as less tense. There were two ratings that were

inconsistent with the model. Conceptual disorganisation was associated with

both asymmetries, however, this is an ambiguous rating and only where it

reflects anergia in thinking is it clearly a negative symptom. There was

also less evidence of depression in the patients with the dextral

preponderance in levels, which is out of keeping with other ratings of

negative affect.

•-'•'V'.:

White, Svali & Charles (1986) has also found results consistent with

the model with telemetric recording of bilateral skin conductance in chronic

negative symptom schizophrenics. When compared with controls, patients were

differentiated by higher right hand levels in tonic skin conductance under

conditions of social stress when required to mime. Prolonged reaction time

latency was also positively correlated with right hand levels of skin

conductance.

Andrews et al., (1986), who divided patients on the basis of the CATEGO

analysis of Gruzelier & Manchanda (1982) into active and withdrawn symptoms,

found that this delineated a group of patients without the normal asymmetry

in somatosensory evoked potentials to unimanual stimulation. Those with an

abnormal symmetry in responses, which it is posited may reflect abnormal

interhemispheric transfer or the development of abnormal ipsilateral

pathways, belonged to the negative syndrome and had higher ratings of social

withdrawal and slowness.

«ÄSi

CW. WC

•v:

The relevance of the syndromes has also been extended to vlsuo-motnr

performance In tasks belonging to both structural and dynamic asymmetry

classes (Gaebel, Ulrich & Frick, 1986). They compared 20 schizophrenic

outpatients with 20 normal controls measuring lateral deviations in visual

fixation of a stationary spot of light, and eye movements during a letter

matrix search task. Individual differences were examined with the BPRS.

Rightward deviations (left hemisphere activation) were associated with the

rating of excitement and the factor score of activation. Leftward

deviations (right hemisphere activation) were associated with emotional

withdrawal. A long search time and search route, as in serial processing,

was associated with the rightward deviation in eye fixation and less

emotional withdrawal. Patients with the rightward deviation also had poorer

search performances than controls. Remarkably, the patients with leftward

«ye deviations, who had the more severe ratings of psychopathology overall,

• v». •. -«

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f^^^fwv^^rw^ ' wt wjw wv wwwv ^-v ww »^ »wwwwwwi»"»-» - •-•

314

had performance as good as controls. Their short search times and search

routes were characteristic of parallel processing, a right hemispheric

process. Right hemispheric activation was also consistent with their

leftward eye movements and negative symptoms.

CONCLUSION

A small contribution has been made towards specifying dynamic process

«symmetries with Implications for individual differences. The independent

variables have Included asymmetries in rate of habituation of electrodermal

orienting responses, non-specific electrodermal responses, and speed of

haptic sorting. The process of 'attention', though integral to habituation

of the orienting response, and involved in the cognitive tasks and hypnotic

induction, does not have the applicability that 'activation' does in its

unifying potential as a substrate for the behaviour under study, including

the broad repertoire covered by the psychiatric ratings. Here 'attention'

is subordinate to 'activation'.

In optimal circumstances hemisphere activation may be in consort with

structural asymmetries. Levy et al. (1983) provide compelling evidence

that the extent of right visual-field advantages in a syllable ',■■' .''

Identification task was associated with asymetries on a free-vision, fareprocessing task such that as leftward asymmetries became larger, indicating

Increasing right hemispheric activation, right visual-field advantages on

the verbal task diminished. Thus the extent of a structurally based

asymmetry in one task was associated with an activation based asymmetry in oRSfl

another. This is in contrast to the dissociation between activation and JMsn

structiue in states of anxiety found by Tucker et al. (1978), shown here in

the divided visual-field experiments in students under stress and in anxious

patients, and implicit in the electrodermal asymmetries in highly anxious

normals. Evidence points to an explanation of this dissociation in anxiety

in terms of an overactivation of the left hemisphere giving rise to an

overload of structurally based processing resources with a consequent shift

in processing to the right hemisphere. However, this explanation is

Inferential and requires both concurrent monitoring of activation

asymmetries under anxiety and manipulation of activation in order to provide ^ <«

validity for the interpretation of left hemispheric overactivation and W *

overload. /:

Levy et al. (1983) also found that the subjects with strong right W

visual-field advantages rated theJr performances pessimistically and those "

s

"

with reduced or no asymmetries rated their performance optimistically.

Research by Bear & Fedio (1976) into personality in unilateral temporal lobe

epilepsy has shown a similar association of pessimism with the left

hemisphere and optimism with the right from evaluations based on

discrepancies between how patients rated themselves and how they were rated

by their relative. The association of negative affect and the left

hemisphere and positive affect and the right hemisphere is at odds with the

jhemisphere-syndrome model outlined above in schizophrenia. Aside from ".-'-Xv O^l1

.- considerations of the adequacy cf self-rating this conflict is mentioned '-^'

here to acknowledge that the cerebral asymmetry of mood is but one of the

controversial issues that surrounds the localisation of dynamic processes.

An adequate discussion of this is outside the scope of the Chapter, suffice

it to say that the fact that the controversy exists is probably not that one -,;-.,

side of the argument is wrong, but that current models are Jv*

oversimplifications. What is true of psychosis is unlikely to be true in "v*"^

all aspects for the more differentiated emotions of the normal brain nor is v'v"-]

a unitary model of all the psychoses likely to be viable. Nevertheless, -SSic

unifying principles have been drawn here between the normal «.id pathological •\^ V

1

brain on the basis of activational asymmetries. But the range of pathology ]

covered has included only morbid anxiety and schizophrenia, and in tha l'*v'v'

WA?
WWH^V^BV

315

normal personality Individual differences have considered only anxiety.

Apart from the one cognitive activation measure in which cerebral

asymmetry in haptic processing was predictive of bilateral motoric handling

speed, electrudermal responsiveness was the measure of activation. The

literature on cerebral asymmetry and bilateral electrodermal responses is

complex and notable for conflicting results. However, the central centres

influencing electrodermal activity are also complex (Wang, 1964) and this

complexity has seldom been recognised in the design of the experiments to

date. Cognitive requirements in most have usually been multi-faceted with

no converging operations to delineate discreet processes. Here the

empirical consistency between replications and the theoretical consistency

across studies may have arisen for two reasons. The first is that a

standardised paradigm has been used throughout with only minor variations,

usually in the number of trials. Secondly, the task is a passive one with

minimal cognitive demands and no motor requirements. Holloway & Parsons

(1969) have shown Chat when comparing brain damaged patients with controls,

differences relating to the unilaterality of lesions were actually enhanced

during passive stimulation compared with both resting conditions and motor

and perceptual tasks. Asymmetries in controls also appeared to be larger

under conditions of passive stimulation.

In this chapter, individual differences in asymmetric cerebral

activation have been found predictive of rate of habituatlon to non-signal

tones and flashes, the laterality of pain in migraine, the induction of

relaxation under hypnosis, normal and pathological anxiety, syndromes in

schizophrenia and individual variation in processes dependent on structural . ; ,,

asymmetry such as verbal and spatial processing in both visual and v"^"V

somatosensory modalities. Just as handedness and gerMor are acknowledged as

important variables to control for In studies of fixed process asymmetries,

recognition should also be given to the need to control for individual

differences in hemispheric activation.

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THE EVOLVING OF THE HOMEOSTATIC BRAIN: NEUROPSYCHOLOGICAL EVIDENCE

Michael Miran and Esta Miran

University of Rochester,

Rochester, N.Y.

New York, U.S.A.

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Abstract

The purpose of this paper Is to explore brain functioning as an

integrated honeostatlc system with laterallzatlon and localization of brain

function. The central question is what Is the nature of the relationship

between hemispheres as the brain processes information using specialized

areas, neural pathways and whole brain interactions.

This paper discusses the neuropsychologlcal, evolutionary, and

developmental literature supporting the existence of homeostatic functioning

within the brain. It cites the perceptual systems as a model and then

reviews examples of laterallzed and homeostatic functioning in motor and

frontal systems. The inter- and intra- species evolutionary evidence for

laterallzatlon and homeostatic functions are reviewed. The role of

developmental processes in adaptation to brain damage are discussed as

exemplifying the role of homeostatic functions in the brain. The need fcr

future research on the homeostatic process of the brain and the Information

flow from micro- to macro- systems within the brain are discutsed.

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INTRODUCTION

Left, right, "ight, left, like a patient being examined by a

neuropsychologlst, neurosclence's attention has shifted from hemisphere to

hemisphere. Each new finding identifies a relative localization of one

attribute or another on the right or left hemisphere. Broca (1863) proposed

and Sperry (1968) expanded cur understanding of cerebral asymmetries.

Localization of function describes the operation of two subsystems i.e. the

left and right hemisphere. This localized approach, however, leaves many

loose ends and unresolved questions. One characteristic of studies of

hemispheric asymmetries is that they show a broad range of individual

differences, especially in populations other than right-handed males.

Studying one hemisphere or the other can provide valuable data, yet the

researcher risks neglecting the impact on the total brain of a specific

stimulus.

The brain functions as an integrated homeostatic system in which

information is transferred on anterior-posterior, laterallzed, and subcortical levels (Miran & Miran, 1984a, b & c). As we have reviewed the

literature on cerebral asymmetries, we have become aware that the brain is

organized as a hierarchy of homeostatic systems. This hierarchical system

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321

codes and processes information. The smallest point in this hierarchy is

the neuron and immediate neural networks. These microsystems are organized

into mesosystens involving localized areas such as the occipital cortex.

These mesosystens include specialized cell groups which may be dedicated to

a specific function. The brain is organized into macrosystems including the

anterior-posterior, right-left, and whole brain systems.

The Perceptual Mesosystems

The potential Interconnections of localized functions allows for the iJXf'vSj) V«v. diversity, spontaneity and complexity of human behavior. While speech is ,

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"localized" in Broca's and Wernicke's areas and visuospatial imaging and vW^w]

affective recognition are "localized" on the right side of the brain, the >

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important fact about human communication is that both affect and speech ^»NAJ

information are processed simultaneously to let us communicate with each

other. As well as emphasizing the bi-cameral and divided nature of the

brain, we emphasize the similarity, reciprocity^and coordination that is

characteristic of human brain function. '•"A".-'."-'

The compelling question for further research is how does the brain •'^■■^^>J

process information both in the Integrative mode and the localized mode i.e.

to what extent do areas of the b.'ain function Independently and >to what

degree to they interact during any one cognitive event. In this interactive v'v'v^v«

system how are the diverse areas of the brain Involved in any one response? •' rfSS

Specifically, the identical sensory stimuli can trigger a variety of s t.f.i

behavior. In order to select one of several potential behavioral patterns,

the whole brain may function. It is quite possible that the brain selects

one localized aiea to respond from, but In selecting, it is likely that the J**^/-*. •,

whole brain is scanned. Research using PET (Positron Emission Tomography), v/',''%'rJ

rCBF (Regional Cerebral Flow), and EEG has demoftstrated activity throughout 'v'-'/-f<'

the brain during cognitive tasks, with relatively greater activity in ^.'.^.^i

specialized areas. Depending on the task, specific areas of the brain are

activated In different orders. (Gur, 1983; Cur, Packer, Reivich, and

Weinberger, 1978; and Flor-Henry, 1983).

FROM PERCEPTION TO COGNITION: THE WORKING OF THE HOMEOSTATIC BRAIN ^V)

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The perceptual systems show very little lateralization, yet they art a nJOVvSa

good model of how the brain functions as an integrated homeostatic system. "NüVVN

At a micro level, the perceptual systems are organized on a point by point

homeotopic basis with bilateral representation (Hartline & Ratcliff, 1957;

Hubel & Wiesel. 1962; and Hubel & Wiesel, 1967). Virtually all of our

sensory experience reaches both hemispheres simultaneously. This bilateral

representation establishes a stored data base for both hemispheres.

Evidence for the Integrated brain model can be found in the perceptual

systems of seeing, hearing, smelling and body sensing. For example Von

Bekesy's (1968) model of the auditory system goes beyond the simple Inputoutput connections to describe the more complex feedback interconnection, '/^^/

I.e., homeostatic processes. He cites the role of lateral Inhibition at the V'v*V V

sense organs and aid-brain levels which sharpens new "images" and inhibits '/.'y^^/

"ground", thus providing a clear figure/ground relationship. He points out vV-jS^i

that these same organizing principles hold for higher order stimulus coding WMftofl

as well as basic stimulus impulse transdu,.Ions.

Von Bekesy's (1968) article highlights, that from the moment a stimulus /vVv'

is turned on, that simultaneous homeostatic Inhibitory and excitory trends VVJ^SS

occur. Thus, hearing a sound or seeing a light begins an active stimulus .'VWINI

sharpening and coding process in the auditory or occipital corticles. At

the same time that the stimulus is being registered on the display of the

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322

sensory cortices, it is also impacting the retlcular activating system and

arousing many other cortical areas in preparation for possible activity.

The stimulus is registered on the sensory cortex, and then it is

contrasted to other available sensory images for recognition involving

primary and secondary cortical areas. It is also mediated and shared via

areas of multimodal sensation i.e., posterior parietal, anterior occipital

lobe and association areas (Roberts, 1984). The stimuli can then be

transferred in three directions: forward in each hemisphere, across the

corpus rallosum, and to subcortlcal areas (Allen, 1983; and Andreasen,

1984). The brain is now prepared for a number of responses; from the fight

or flight responses of the affective limbic system to the sophisticated

symbolic and conceptual analyses of speech and non-verbal prosody (Thompson,

1967). As the stimulus progresses from the* perceptual system to the motor

strip, temporal lobes and frontal lobes, more complex coding and response

options are generated.

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A possible transitional area between perceptual systems and the motor

systems is the somatosensory cortex. This area is organized ot\ a pattern of

site specific representation based on innervation and activity of the sites

Involved. Our hearing and sight are closely interconnected with our bodily

perception, sense of self, and the perception of our bodies in external

space.

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The somatosensory system also serves as one of the systems that

completes a feedback loop for the motor system by making the individual

aware of movement that has occurred and the somatosensory status of the

body. We can relax and concentrate on the experience of our body at rest,

or we can "do" something active and feel its impact on other areas of our

body. The joint functions of perceiving changes in the state of our bodies

and serving as a feedback loop are significant in a homeostatic model of the

brain. The somatosensory system is bilaterally represented, and is adjacent

to somatomotor areas.

The current models of homeostatic brain functioning provide new ways of

looking at dichotic listening tasks and their results. Von Bekesy's (1968)

model, of lateral inhibition in the auditory system, suggests that many of

the processes described in the dichotic listening literature may be a result

of processes involving the cochlear nucleus and basilar membrane. He

provides an example of localization of the sound of a click via complete

Inhibition of other sou .ds including a delayed click. This inhibition

occurs within one millisecond of the first click. The right versus left

preferences, observed in dichotic listening tasks, may reflect the

preattentive processes of retlcular activation or the executorial and

Inhibitory processes in the sub-cortical parts of the auditory system.

Dichotic listening studies demonstrate the interaction of perceptual

and motor sets in shifting attention from hemisphere to hemisphere

(Broadbent, 1970; Cherry, 1953; Moray, 1970; and Swets and Sewall, 1964).

They note that switching sets is related to the time it takes from a subject

to alternate between two attentional stimuli. This type of information

exchange at neuronal and network levels underlies many of the processes by

which homeostatic regulatin of behavior occurs.

Evarts, Shinoda, and Wise (1984) study higher brain functions in terms

of "neural switching". They specifically discuss the relationship between

perceptual and motor "seta" in preparing for responses. In tern of

laterallty the authors present data describing speech as an interaction with

the motor activity of the mouth that depends on open-loop control in

multlarticular coordination.

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In summary, the neural Input sets are linked to a variety of behaviors

through the flexibility of switching of neural pathways. This process «?Äfo .

involves the rapid and efficient use of stored information or memory. ^''v-"*

Inhibition and activation are the key processes in neural switching.

Patterns of inhibition and activation relate to localization of brain

function. Many of the laterallzed individual differences in PET and EEG

studies appear to be examples of neural switching within a horaeostatic brain

system. The exact nature of these patterns is yet to be completely J^Jc/v

delineated. ''i's'i'

The conclusions regarding the perceptual system are: 1. It provides a

bilaterally represented data base for the brain, 2. Through the processes 7.V^>^J

of lateral Inhibition and excitation, stimuli are coded at sense organ, mid- ^ -.-'J

brain, and cerebral levels, and 3. Neural networlTs are developed which

connect perceptual and motor systems facilitating response patterns.

Motoric Mesosystems

As Von Bekesy (1968) describes a homeostatic process of inhibition £ud «.».•

activation in the perceptual system, similar homeostatic networks are 38l8r^

functioning within the motor and somatosensory systems. Netter (1980 p. 75)

provides a thorough visual illustration of motoric system as an interactive

feedback loop. The motor cortex is reciporically linked to the cerebellum

and the basal ganglia. These structures may act as a servomechanism, with

the subcortical areas acting as comparators (Heilman, 1979). Every muscle

group, like the biceps and triceps, has reciprocal inhibition and activation

which is necessary both to maintain resting ton,us and do work. The

cerebellum is involved with rapid movement (Ballistic); while the basal ^y;

ganglia is involved with slow movement (Tonic) (Heiiman, 1979).

While localized in opposite hemispheres, movement and verbal areas of >"'/'/*J

the brain are integrally and reciprocally connected. Geschwind (1965) foÄ'J

proposes the connection linking language to the elicitation of motor '-»'•/"/'J

behavior by using neural substrates. Specifically, stimuli travel along the WnHM

auditory pathways to Heschl's gyrus (primary auditory cortex), and then are

relayed to the posterior superior portion of the temporal lobe (auditory

association cortex). From there the stimuli travel by the arcuate EJJj

fasciculus to the premotor areas (motor association cortex), and then to the Vv^'

primary motor area. Through these pathways, a behavior is initiated and wÄ.

monitored (Geschwind, 1965). '&jwJS

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There is an interesting contrast between the functional and anatomical

differences in lateralization of the motor and speech systems. In the

speech system there is an apparent correspondence between the areas

functionally associated with speech production and interpretation; and a

specific set of brain locations i.e. Broca's area, Uernike's area, and the

enlarged planum temporalls. The speech system is highly laterallzed. In

contrast, the motor system is highly laterallr.ed i.e. one hand is usually

preferred; yet, the neuroanatomical and cytoarchitectonic basis for this '•! /. ;

lateralization of motor behaviour is not as clear cut as it is for speech.

Although the "dominant" hand may be associated with a slightly longer motor •"v"^'-""

strip on the contralateral side of the brain, there is no clear gross "V"/v

anatomical differences between the two sides of the brain which are Ä'

associated with a preference or greater dexterity of one hand over the v^."^

other. •IJS'VVJJ'

Motor systems do not function in isolation, but involve perceptual and v'v'v*'

verbal systems as a means of effecting complex human behavior. Behavior is '/-i'v"'

a stream of reciprocal and homeostatic events Involving many systems and

subsystems of the brain. Particular subsystems continue to operate after a

behavior has been initiated. The perceptual system continues to process

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inconing Information while other cognitive and behavioral events are

occurring in other systems of the brain. Hence, the individual can walk

down the street, chew gum, and listen to a "Walkman" at the same time.

Lateralization of specialized Abilities: Speech and Visuospatial

Research over the last two decades has focused on the anatomical and

functional specialization of each hemisphere (Gazzaniga, 1979; Geschwind,

1984; ICinsbourne, 1978; Milner Taylor & Sperry, 1968; Sperry, 1958; Sperry,

Gazzaniga & Bogen, 1969; and Zaidel & Sperry, 1974). These studies

strengthen the concept of relative specialization of the hemispheres. Each

cerebral hemisphere is relatively specalized in functioning: the left

hemisphere is specialized for verbal identification and speech production,

and the right hemisphere is specialized for affective and visuospatial

functions. s*

Scheibel & Scheibel (1954 & 1955) relate extended dendritic systems,

Increase in size of neuron somata, and In number of neuroglial cells to

enriched functioning of gifted individuals. Scheibel (1984) studies

dendritic growth and hemispheric asymmetry. He finds that in t^ie non-verbal

period of life, there is greater a civity on the non-dominant side (the

right hemisphere); while with the beginning of speech and conceptualization,

there is a marked increase in ehe number of higher order dendritic branches

on the dominant side (the left hemisphere). This is a shift of dendritic

growth from the right to the left hemisphere.

.•:-:-;-:v>

In terms of development of specialized abilities, Scheibel (1984)

suggests that skills are related to enriched dendritic growth. One feature

of the brain, it may be hypothesised. Is that ft can "grow", and it can

generate more information processing ability. In a dendritic tree each

dendritic bifurcation represents a "go—no go" or "on-off" decision point.

In terms of information generating or processing, more branches may be

associated in a general way with "greater degrees of fteedom" and

"complexity" in thinking and behavior. Scheibel (1984) is careful to point

out that this is a chicken and egg issue.

We cannot say whether there is a genetic program determining dendritic

growth; or alternatively, whether environmental stimulation influences

dendritic growth patterns of the hemispheres. But it appears that there

are individual differences in patterns of dendritic growth. There is a

mathematical model called fractals that describes the symmetric and

asymmetric branching in naturally ocurring systems. According to Mandelbort

(1982), this model describes dendritic systems.

Speech. Strong support for specialization of function in each

hemisphere comes trom research demonstrating that speech is located in the

left temporal lobe above the plenum temporale — Wernicke's area (Springer &

Deutsch, 1981). Porac & Goren (1981) present data on the architectonic site

of the enlarged planum temporale and the greater length of the Sylvan

fissure in the left hemisphere. Yet Porac & Coren (1981) further state that

speech may not be completely located in the left hemisphere for most

individuals; but rather, it may be located to a greater or lesser degree in

the left hemisphere. Language may be bilaterally located for most

individuals, with individual differences as to the extent to which language

is located in the left hemisphere.

For the majority of the population speech is located in the left

hemisphere, yet for 12 to 42 of right-handed people and 252 of left-handed

people, speech is located in the right hemisphere (Porac & Coren, 1981).

Galaburda (1984, p. 20) cites evidence that anatomical differences are the

basis for lateralization for language: 1. There is a larger Broca's areas

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325

and associated Tpt a.id PC areas in 66Z of the population. 2. Postmortem

analysis of brains found asymmetries in proportion of pyramidal fibers

crossing from one side to the other in the decussations of the medulla. 3.

In the lower medulla, analysis of brains finds an aberrant circumollvary

bundle deriving from the pyramidal tract on the left side more frequently

than on the right.

While evidence points to a left hemisphere dominance, yet more careful

examination of the anatomical data on lateralizatIon reflects a wide range

of Individual differences. "In Broca's area architectonic asymmetries

fluctuate between 15:. and 259Z in favor of .he left side (Galaburda, 198A,

p. 19). These individual differences are observed in research on

architechtonic and behavioral studies of localization of speech.

Recent findings suggest that some speech a£y be located in the right

hemisphere. Gur et. al. (198A) show that in a left-handed callosotomy

patient, both left and right hemispheres were involved in language i.e.

writing. Gazzanlga (1983) describes a patient with language in the right

hemisphere (although it occurs infrequently).. Gardner (1982) discusses

evidence that the right hemisphere can think verially. Based on aphasia

studies. Geschwind & Galaburda (1984) suggest that language is bilaterally

represented to some extent in most of the population.

Cappa and Vignolo (1979) extend the localization of language from a

left-right hemisphere task to a task involving the thalamus. They found

aphasia after left thalamic lesions. Language may in fact Involve the

participation of subcortical areas of the brain.

The two hemispheres of the brain together produce streams of wordbehavior interactions. Thus, the first event in a speech sequence may be a

facial or tonal recognition,i.e. a right hemisphere task. Next, there is

the analysis of content, organization of a response, and finally the

response. The redundant and homeostatic quality of this system allows for

various solutions, i.e. subcortical-affectlve, visual-motor, and verbal

cognitive solutions to the same problems.

In conclusion, speech is a dynamic phenomena in which perceptual images

and words are combined via a variety of decision rules to create symbols

which are useful in communication to others, and to serve as an internal

communication system within the brain. As Plaget (1954) aptly points out,

speech is an extension of sensorl-motor concepts to include verbal stimuli.

The speech system, as we now understand it, can include both right and left

hemispheres, the thalamus, and other areas. The functioning of this

marvelously human symbol system requires multiple representations and events

on both sides of the brain to produce words and to coordinate action.

Visuospatial. Research has yet to arrive at a clear, specific,

consistent, definitive, right hemisphere task i.e., affect, facial

recognition, visual patterns, musical patterns, and prosody. What has been

designated a right hemisphere task for the purpose of research, may actually

involve more brain systems than was originally anticipated.

More recent research findings are contradicting earlier results on

right hemisphere functioning. Parsons (198A) replicated Kitnura's (1969)

visual dot-location task. In contrast to Kitnura's results of right

hemisphere superiority. Parsons (1984, p. 31) found "a significant overall

left hemisphere superiority".

The path that information takes in being processed may be other than

task specific. In fact, the processing of information in the brain may

depend on other factors such as speed of task. Marquis, Glass and Corlett

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(1984) describe EEC patterns of the same task, varying speed of task. When

the task Is performed at a slower speed (25%) than their self-chosen pace,

the Individual processes Information In the left hemisphere. Ir contrast,

as the pace Increases (25%) the Individual processes the same Information In

the right hemisphere. Marquis et al. (1984, p. 206) suggest: "A sequential

processing strategy Is being used at the slow pace whilst a parallel or

Gestalt processing strategy Is being used at the fast pace". In any

behavior there may be many combinations of inter- and intra-hemlspherlc

contributions.

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In conclusion, communication is the integration of speech and

visuospatial systems. Language is the product of a system involving

multiple locations in the brain. Language involves inputs and outputs from

and to perceptual, motor, frontal, and subcprtlcal areas. Thus, even in the

most classic case where anatomical evidence forlaterallzation is strongest

for speech located in the left hemisphere, the functioning of the

laterallzed hemisphere is constantly interacting with other areas of the

b. aln via the corpus callosum and anterior posterior fibers within each

hemisphere. ,

i

Actual communication between individuals and within the individual is a

whole brain process. For example, hearing the words involves auditory

cortex, reading and writing involves the visual cortex, and the verbal

content involves intellectual and affective interpretations. Andreasen

(1984) proposes that the language function works properly when special

cortical centers and the "writing" that connects them function properly.

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An example of whole brain function occurs when an individual picks up a

pencil. He/she sees the color, feels the shape, interprets the prospect of

having to work, and initiates the behavior of writing. Recognizing the

pencil «nd initiating appropriate behavior of writing words involves both

multiple brain are-s (speech and visuospatial), and interactive brain

processes.

The Frontal Lobes

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As we have progressed through the brain from the back to the front, we

have examined the brain's structure from hardwired sensory systems to hard

wired motor systems. What then do the frontal lobes do in this system?

They provide the internal monitoring feedback and modulating systems that

synchronizes and sequences activity. The frontal lobes can coordinate the

complex motoric sequencing and suppressing of subcortical systems; thereby

completing a feedback loop via activating or damping the motor potential,

subcortical response, and the reticular activation system. The frontal

lobe's role in the relative excitation and inhibition of other behaviors is

relatively well understood. A great deal has been learned since Phlneas

Gage's unfortunate accident!

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While the literature on hemispheric asymmetries has emphasized the role

of the corpus callosum in exchanging information between the left and the

right hemisphere within the brain, our review of the literature has pointed

to numerous other ipsilateral tracts. Notably these include the frontaloccipital, frontal thalamic, and frontal llmblc tracts, which provide input

and output for feedback loops involving the frontal lobes. The frontal

lobes play a modulating role in complex cognition by inhibiting subcortical

structures and motor structures. The anterior-posterior, right-left, and

cortical-subcortical tracts complete the feedback system and orchestrate the

activities of the homeostatlc brain.

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Evidence for and against asymmetry in the frontal lobes is hotly

debated. Porac and Coren (1981) present new evidence showing the right

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frontal lobe is generally larger, and blood pressure and volume are greater

in the right hemisphere.

In conclusion, the frontal lobes increasingly have the capacity for the

type of covert behavioral rehearsals that we call "thinking". The issue of

consciousness is less problematic if we assume that we are dealing with a

homeostatic system that is capable of monitoring its own behavior. Much of

the work of personality theorists has described the process of "insight".

The nervous system is organized to not only have the right hand know what

the left hand is doing in an on-line fashion; but more importantly, to allow

them to work in a coordinated fashion to accomplish a task, while the mouth

may be talking or the feet running — or emotionally, the heart may be

"breaking".

I

Brain Functions during Cognition *

PET studies show patterns of activation i.e. what happens when the

brain performs a cognitive task. Studies of regional cerebral blood flow

demonstrate that for different populations of, subjects, there are varying

patterns of brain activation. Gur, Skolnick, Gur, Caroff, Rieg«r, Obrist,

Younkin and Reivich (1985) examine patient and non-patient subjects and find

differences: 1. probe by probe, 2. resting vs. cognitive task, 3. male vs

female, 4. patient vs. non-patient, 5. spatial vs. verbal task, and 6, left

vs. right hemisphere. Variance in blood flow can be interpreted as variance

in brain activation. While one part of the brain may be more active for a

specific task, all parts of the brain are receiving a continual flow of

blood and are active in varying degrees.

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Using (rCBF), Sheppard, Gruzelier, Manchanda, & Hirsch (1983) record

patterns of symmetrical and asymmetrical responding in normal and

schizophrenic subjects. Subject's responding appear to be variable

depending on the specific probe studies i.e. which brain area In which

subject population is being studied.

EEG studies support the concept of a homeostatic integrated brain:

there are patterns of individual and group differences in hemispheric brain

activation and Inhibition (Glass, Butler & Carter, 1984; Etevenon, 1984;

Flor-Henry and Koles, 1984; and Rebert and Lowe, 1984). These studies show,

that when the brain performs a cognitive, spatial, or affective task in

varying subject populations, then different areas of the brain are

stimulated and activated.

THE ROLE OF EVOLUTION IN BRAIN DEVELOPMENT

In our study of human brain behavior relationships and the development

of laterality, let us start at the beginning. We take a change of scene

from the modern computerized neuroscience laboratories that we associate

with brain research and return to the African veldf of 3 million years ago.

What could such a trip teach us about human brain-behavior relationships?

Such a trip provides information on the origins of human brain functions and

the brain's evolutionary development of complexity and laterality.

The proposed homeostatic model delineates patterns of brain

organization existing prior to differentiation of the human species, and

then describes the interactive neuropsychologlcal patterns of brain behavior

relationships seen today. Evolutionary theory traces the development of

specific systems from general ones and complex systems from simple ones,

i.e., the nervous system from hormonal signalling mechanisms (Horridge,

1968). The evolutionary data expand and clarify the question of lateralized

cerebral asymmetries and integrated brain functioning in terms of: 1. Coevaluation of brain and behavior. 2. The evolution of improved neural
•• .'•J

328

sequencing and homeostatic regulation of complex behavior. 3. Evolution of

size and convultions. 4. The evolution of laterality.

Presented below are examples of other species that reflect the

evolutionary processes at work in the development of human lateralized

speech, and complex behavior. The echidna is an example of an animal that

evolved increased intelligence via increased brain size and convultions

without specific lateralization of functions. In contrast, the song bird is

an animal that evolved lateralization of singing without increased size and

complexity of convolutions. Non-human primates exhibit complex behavior

similar to humans; yet they do not consistently display laterality.

Australopithecines have a brain which is smaller than the human brain and

has many ape-like characteristics. Yet the Australopithecine's brain may

offer clues to the beginnings of hemispneric asymmetry. '-'CN'C*'"""-^

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Echidna

In exploring the evolution of the human brain, an examination of the

echidna provides valuable information. Fossil evidence indicates that this

species' brain increased in size and convolutions Just as the human brain

evolved. Echidnas are oonotremes. They lack a corpus callosum their

nervous system has commissures, and tracts in a relatively symmetrical brain, !

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but they do have two hemispheres. Yet, In the evolutionary process, they

demonstrate the importance of brain size and convolutions. Their neocortex

occupies A3', to A8Z of brain weight; almost as much as primates brains where

the neocortex occupies SAX. Their neocortex is expanded and nearly \''.'/^. * /<

spherical; while its surface is richly convoluted in a series of deep folds

and bumps. Although the echidna has many "reptilian" features such as

laying eggs, it functions behaviorally at the level of a cat or primate, and

demonstrates rapid learning on certain tasks (Gould, 1983).

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Song Bird

Song birds and canaries are vertebrates that demonstrate lateralized

sound production. Nottebohm (1984) points out that such birds are the only

vertebrates in which there is a relation between a naturally occurring

learned benavior and the brain pathways that control it. Although singing

is lateralized and occurs without ever hearing the song of other birds, such

a song is simple and lacks other social cues. For a bird's song, to reflect £'SCVJ8ÄI

the unique song patterns of particular species, it requires hearing, '''*/<^/'K

imitation, and learning. This study points out, that for a relatively *t*J\f\t

"hardwired" neurosystem to act, requires interaction with a specific social

environment.

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Primates ?% '%"" ."

Evidence for the co-evaluation of brain structures and complex human •\/-/\-V

behaviors can be found in primate research. Recent research highlights the :>^

issue of inter- and intrahemispheric information processing in macaques and

humans (Doty, Overman and Negrao, 1979; and Overman & Doty, 1982). While we

cannot study neurosystems and synaptic processes of prehoninids and early

horninids, and compare it to humans, we can compare and contrast non-human

primates and humans. The above mentioned studies of non-human primates and

humans demonstrate similar complex brain processes of interhemispheric

transfer and coordination; yet in laboratory studies, the primates

(Macaques) do not display consistent lateralization of task and behavior. SxMSr^"1

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Terrace (1985) compares speeh in apes with speech in humans. He vSöwS"

suggests that language has two levtls: words and sentences. While apes may CvSJ^VlK

be able to put two words together to make a simple sentence, only humans can * *\M

use language to express complex ideas and concepts. Language is processed
329

in a range from simple labelling to conceptual expression.

Australopitheclnes

Falk (198A) made endocasts (casts of the Inside of the bralncase) of

our earliest known human ancestors called "australopitheclnes". These

endocasts are dated approximately 2.5 - 3.5 million years ago. The major

distinction found between australopitheclnes and humans are ir brain

convolutions, density, and size; as well as organization. Falk (198A) cites

the evidence: "The organization of the australopitheclnes Is 'ape-like' in

that it identifies a particular groove, known as the fronto-orbital sulcus,

that courses from the side of the frontal lobe to Its surface. In place of

this feature, human brains display a particular pattern of convolutions"

(Falk, 1984, p. 38).

/*

LeMay & Culebras (1972) examined the endocasts of the Neanderthal man

who lived 30,000 to 50,000 years ago. The endocasts had typical sylvan

asymmetry of a longer, straighter left fissure on the right that turned up.

One aspect of this evolving pattern of convolutions Is the establishing of

patterns of cerebral asymmetries in the human brain. ,

The above authors' research further provides evidence showing that the

human brain evolved as a complex integrative structure. The human brain:

(a) is considerably larger than australopitheclnes' (1450 cc instead of 450

cc's), (b) has clearly Identifiable frontal lobes which are involved in

human higher-order cognitive and behavioral control functions, (c) has

identifiable fissures and gyrl which help provide more information

processing area in a more compact volume, and (d) has an identifiable

Broca's and Wernicke's areas, which are associated with hemispheric

asymmetry, specifically the human characteristic of speech.

The evolution of the human lateralized verbal system required the

following changes from "ape like" structures: 1. a Broca's area or

equivalent structure, 2. a voice box that is low enough in the throat to

permit human speech sounds, 3. a structure of facial muscles that can be

used for form human sounds. 4. the necessary innervation connecting the

brain and facial muscles, and 5. learning of socially relevant and

significant sounds.

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Based on the limited cases known so far, it appears that these changes

did not always take place in a synchronized fashion. In some cases, such as

the evolution from Homo habilis to Homo erectus to Homo sapiens

(neanderthal) to Homo sapiens (modern), the brain size appears to have

preceded the thinning of the skull and reducing of brow ridges (Holloway,

1974; Laltman, 1984). In other situations such as the transition from

Australoplthicus afarensis to robustus to zinjantrophus, the advent of

bidpedalism provided a basis for change in the angle of the head, and

eventually evolution of the voice box. The progress of human evolution has

been a result of change In many Interacting systems. These changes resulted

In an enlarged brain with a subsystem th.it permits the acquisition of speech

in a social environment that provides the necessary models and

reinforcement.

Johanson and Edey (1982) and Jolly (1972) highlight the following

behaviors evolved from australopitheclnes to humans: bipedalism, tool making

and use, speech and use of language, changes in reproductive behavior that

allows for genetic penetrance, and cooperative food gathering. Miran

(1983) cites the intergenerational storage and transmission of information

as a characteristic of human communities and the socialization of "creative"

behaviors. The increased brain size and complexity, as well as hemispheric

asymmetry, extends human mental abilities.
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There Is a question as to the relationship between the degree of

laterallty and the evolution of expanued and convoluted structures. Most of

the efforts to explain this relationship have oversimplified the complexity

of both phylogenetic and ontogentic processes. We can identify at least

three interrelated processes: (a) the establishing of layers of neuronal

tissue In phylogentic and developmental sequences. These cell layers are

the basis for the microjystems and cellular specialization, (b) tl.e folding

and refolding of these sheets of cells, and (c) the asymmetrical

arrangements of convolutions and cell layers into asymmetrical structures

associated with the behavior of speech.

Ve believe that these processes may reflect some underlying

evolutionary and developmental patterns that permit increasing complexity of

neural tissues. Although they are still at^an early stage of use in

neurosciences, there are mathematical models caHed fractals which describe

the symmetric and asymmetric distributions of a phenomena around an axis.

These models have been used to describe dendritic trees and neural

structures. They appear to be a good fit. What we observe as

lateralization may be a result of mathematicaj. functions that govern the

distribution of neural structures around a central axes (Mandelbrot, 1982),

may be speculated.

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Geschwind (1984) makes the point that the evolution of language

development includes internal cognitive information processing. The use of

internal language is a means by which an organism can self-regulate. He

suggests that internal language processing systems that exist in humans may

. o exist in other species.

In conclusion the human brain system evolved in a broad co-evolutionary

context. First the human brain systems and subsystems are distinct in terms

of increased brain size, density, and convolutions. Next the human brain

developed laterallty, each hemisphere is specialized for a function i.e. the

left hemisphere is specialized for verbal identification while the right is

specialized for visuospatial functions.

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DEVELOPMENTAL ISSUES IN THE NORMAL AND ABNORMAL BRAIN

In the preceding section we discussed the role of evolution in the

establishment of systems and subsystems of the brain. In particular, we

examined the development of lateralized functioning. In this section we

consider the developmental process and the influences of various types of

injury. By comparing child with adult brains, we can see the differences as

unique systems which have unique patterns of resonse to injury. Many

previous conceptualizations, such as "plasticity", can be evaluated in terms

of the interaction of systems and subsystems in a homeostatic brain.

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Some parts of the brain can compensate for damage to other areas

(Roberts, 1984). This compensation is often a result of shared equivalent

functions and the "plasticity" of behavior that is both fundamental to human

beings and capable of being developed through socialization (Miran, 1983).

It is possible that adaptation, learning, and recovery all reflect an

underlying inherent characteristic of neural tissue.

V

Previous research comparing brain function and dysfunction of children

with adults and senior adults has yielded problematic findings (Reitan,

1979; Telzrow, 1984; Towbln, 1978). Problems can be expected when you

compare one dynamic system with a dlfferent dynamic system; and essentially

we have two distinct brain systems i.e. infant and adult. These systems may

share many functions in common, yet these systems also may involve different

mechanisms. Miller (1984) suggests that, in comparing children to adults,

what we are seeing are different disease etiology, processes, and

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331

compensation. This makes statistical comparisons of normal and brain

damaged infants and adults problematic. St. James-Roberts (1981, p. A7)

states: "Valid comparisons are prevented by failure to control these

procedures, the status of residual system, diaschisic variables, recovery

periods and experimental variables ... and differences in surgical

techniques". What we can discuss is the brain mechanisms and related

diseases as the brain develops. The homeostatic brain model offers a

paradigm for examining brain damage in terms of age, location, and severity.

Infants-and-Children

At birth the human brain includes genetic encoding for "hard wired" or

"dedicated" areas, I.e. medullary and mid-brain regulation rf biological

processes perceptual and motor systems. Frvntal. temporal and association

areas are less clearly "dedicated" and to a greater degree are dependent on

environmental "software" I.e. socialization for their functioning.

At its earliest stage much of brain function can be compared to a

"computer core" which has the potential for memory but which has not been

"programmed" to any specific pattern or filled with data. In later

development this early system is progressively developed both

neuroanatomically and behaviorally, including tnyelination of the corpus

callosum. The child acquires behavior and increases synaptic and dendritic

connections. As this system develops neuroanatomically, it develops

functionally (Bigelow, Nasrallah and Rausche, 1983; Miller, 1984).

Miller (1984) describes the maturation of the brain and concludes that

in early stages of brain maturation (childhood), the brain may not be able to

carry out the functions of a mature brain (adulthood). Based on a primarily

sensori-motor input-output system, a process of development and interaction

Is initiated. Piaget (1954) describes the process of development as primary

circular reactions, the maturing of the perceptual-motor coding systems, and

the development of cognition and organized sensori-motorlc response

patterns. As each system develops, it enhances the devlepment of other

brain subsytems and systems.

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At birth the brain is hardwired for perceptual motor activities. The

frontal areas of the brain are relatively plastic i.e., the part of the

brain which later moderate" speech and higher level cortical functioning.

Towbin (1978) discusses damage to the cerebral system in pre- and

perinatals. He describes two phenomena: (1) reduction in cerebral function

— mental retardation; and, (2) distortion of cerebral function — the

uncontrolled motor patterns such as cerebral palsy, epilepsy, and related

pathology. The most common cause of cerebral damage in perinatals is

hypoxia or lack of oxygen. Damage leads to a system wide dysfunction. The

greater the damage, then the more severe the dysfuntion (Towbin, 1978).

Brain damage in infants and young children is most likely to Impact the

development of the total system. Miller (1984) cites malnutrition as a

similar system wide problem. A smaller less differentiated system is

affected in a relatively equal and generalized fashion than a larger more

specialized system.

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The diseases that attack children are different from those that attack

adults. Children are vulnerable to residual impairment from infectious

diseases, malnutrition, and cranial irradiation (Levin, Eisenberg, Uigg and

Kobayashi, 1982). These conditions do occur in adults but are more

frequently Identified in children. In terms of flexibility children appear

to have an advantage over adults. There is a great deal of still relatively

undifferentiated area in the brain. If there is damage to the left

hemisphere, then other brain subsystems i.e. the right hemisphere can take

over its functions. If unfilled memory banks are damaged, the child

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experiences no specific losses, but an overall delay in development.

Kertesz (1979) attributes plasticity in the young (before the age of 10-12

years) to the adaptability of Golgi Type II cells. The flexibility of these

ueurons man terminate in the teens by hormonal changes.

While evidence strongly supports developmental changes in brain

organization and function, individual differences remain a key concept.

Within this developmental sequence, the actual rate of growth or recovery

from damage differs for Individual children (Roberts, 1984).

Adults and Senior Adults

In the adult, the brain functions efficiently and effectively in an

interactive mode. Moscovitch (1979) finds that the right hemisphere plays a

supportive role in normal communication and memory. Deptula and Yo^awltz

(1984) examine depression as a right hemisphere deficit. Springer and

Oeutch (1981) examine normal subjects' hemispheric functioning. Attention

and task interference influence Information processing. Cognitive tasks

increase the activity in the brain as measured by EEC. This increase in

activity is related to specialization of hemispheric function (Glass, 198A).

In the adult the "core" has been filled with data and programmed for

specific functions. Damage to"the "core" results in specific deficits

(Heilige, 1983); yet malnutrition and starvation in adulthood do not have

such permanent devastating effects as seen in children. Wiesel (1970)

describes starvation conditions in the Nazi Concentration Camps; yet when

adequate nutrition was restored, these camp survivors have gone on to

function cognitively on a high level. They hav,e recorded their intellectual

functions.

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Another group of disorders in adults are system wide breakdowns.

Specifically, they are Huntington's Chorea, and similar disorders. These

diseases involve the breakdown of information processing and flow within the

brain. .». ^- >.

These diseases exemplify the problems of studying brain function and

dysfunction. Cain (1985) discusses Huntington's Chorea, a genetically

determined neurological degenerative disease. Yet the course of the

disease, the nature of the symptoms, and the speed of deterioration differs

between individuals. This type of disorder describes the breakdown of subsystems and eventually multiple sub-systems within the brain.

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Senior adults have problems of: strokes, progressive dementia, toxic

psychosis, anoxia, loss of blood supply to the brain, and related blood flow

and systems diseases. There is a progressive atrophy and loss of function

of cerebral tissue. Joynt and Shoulson (1979) and Scheff (1984) discuss

Dementia as a possible localized deficit, yet they caution that whole brain

functions are disturbed such as cognition, orientation, memory, abstraction

and reaction to stress.

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The brain diseases of adults and senior adults include tumors that may

or may not be cancerous; and strokes which involve the decrease of blood

flow to the brain. These cases are localized lesions of the brain and

affect specific subsystems, as well as specific microsystems.

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In conclusion, the integrated brain model provides a paradigm for

studying brain function and dysfunction. This is the study of multiple

areas of the brain as they interact in either a successful manner or a

damaged manner. Any head injury or deteriorative process affects the

homeostatic systems and sub-systems of the brain. The patterns of recovery

and deficits provide information as to the development of localized brain

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333

function at varying ages. The advantage of the horaeostatic brain model is

that it helps us understand the development of the brain and the effects of

damage at different ages.

CONCLUSIONS

Previous models of brain function have been based on lesion and deficit

models, split brain studies, and einer relatively rare conditions. While

these models describe aspects of brain function, they do not completely

describe LM complex and dynamic interactions taking place within the human

brain on a routine basis. We i.eed to understand how Information is

transmitted from micro to meso to macrosystems. While micro- and "molar"

processes are Important, the next step in bfain research is to develop the

means to study complex interactions of dynamic Structures and functions.

Our model of integrated homeostatic braia function takes into consideration

the complex and dynamic nature of brain behavior relationships.

Data from more recent studies suggest th^t, while there ia relative

specialization of hemispheres, the brain is more flexible in lateralization

of function than was originally believed. What is emerging is a concept of

brain function as a complex interactive systems process. One hemisphere may

be dedicated to a specific function; yet while the hemisphere is performing

the designated function, It Is in Interaction with the "whole" brain, both

simultaneously receiving and sending information. This is an internal

dynamic network in search of a homeostatic balance.

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One of the key features of the homeostatic brain model is that it takes

into consideration hemispheric asymmetry in providing a model for

understanding individual differences. The individual differences in size

and organization of the hemispheres of the brain underlies many of the

observed differences in hemispheric asymmetries. In a particular area of a

hemisphere which is "specialized for a function", the dendritic enrichment

appears to be associated with the development of specialized abilities such

as speech or visuo-motor skills. This model also permits a better

understanding of the role of the environment and socialization as necessary

conditions for the development of a complex skill such as speech.

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The homeostatic brain model has a significant heuristic value. The

concepts of development, plasticity, and compensation may all be different

words describing similar processes of adaptation to environmental Influences

or injuries. Many fundamental issues in psychology -ijch as cognitive

dissonance and repression are being formulated in terms of the right and

left brain model or more recently the idea of brain modules and

microprocessors.

One of the contributions of the model of the homeostatic brain is that

it makes us begin to rethink our definitions of Wellness, psychopathology,

and brain damage. The distinction between different types of

psychopathology and brain damage from normals may be more than a matter of

sice-specific deficits: it may be the disruption of homeostatic systems.

The next task is to evaluate empirically and operationally the

homeostatic brain model. We anticipate further research focusing not on

localized processes but on the functioning of systems and subsystems within

the homeostatic brain.

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338

TWO PROBLEMS IN SCHIZOPHRENIA RESEARCH

V

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AN ARGUMENT CONCERNING SCHIZOPHRENIA: THE LEFT HEMISPHERE DRAINS THE SWAMP

•_o

Rue L. Cromwell

Department of Psychology,

University of Kansas,

Lawrence,

Kansas, 660A5-2462, U.S.A.

Two «ajor traditions exist In the psychological study of schizophrenia.

One, stemming from cognitive theory, has focused upon attentlon.il and

Information-processing factors with minimal concern for braln-behavlor

relations. The other has been neuropsychologlcal, which focuses upon bralnbehavlor relations and topography of brain function with minimal concern for

cognitive formulation. The purpose of this chapter will be to recount some

problems in schizophrenia research and, in somewhat iterative fashion,

discuss what might be learned from the Interplay of cognitive and

psychoneurological concepts in understanding schizophrenia.

/•.' \V

Two of the many problems in current schizophrenia research are the

classification of individuals with only one data domain and the "merry-goround effect".

Classifying people as schizophrenic patients with only one data domain

(Cromwell, 198A, p.16) means that individuals are sorted out primarily on

the basis of what they say. Reported delusions, reported hallucinations,

•nd/or inference from verbal report about thought disorder are the defining

symptom features. Based upon this limited domain an arbitrary group is

designated who present problems to self and others and who are received by

health 'nstitutions for care and custody.

'■■■>'J

^n the other hand, it is indeed hazardous to assume that the necessary

antecedent conditions of this disorder all fall within that same verbal

domain. To the extent other .'actors, non-verbal in nature, are involved,

effective progress in classification (for purposes of intervention,

prevention and prognosis) may be curtailed.

The "merry-go-rou.id effect" (Cromwell, 1972) refers to how

investigators so often tend to view the antecedent-consequent relationships

in schizophrenia. Many tend to "ride only one horse in the carousel". They

af.end to variables on only one level of description (e.g., biochemical,

structural-anatomical, electrophyslological, information-processing, interpersonal communication, stress and expressed emotion, conceptual

uncertainty, or such), and they assume that their horse is "leading the

pack". Variables on othei levels of description are viewed as secondary

effects.

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STRATEGIES TO SOLVE THESE PROBLEMS

339 iü

Of the strategies (Cromwell, 1984, p.18-28) to circumvent these

problems, two deserve mention here: (a) the search for schizophrenia-related

variants (SRVs), and, (b) the search for the earliest information-processing

event In which something goes wrong among schizophrenic patients.

The SRV strategy

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A «chlzophrenla-related variant (SRV) is a variable which

(a) is associated with schizophrenia (though not necessarily erclusively,

since the boundaries for clinical definition of schizophrenia must remain

suspect),

(b) can be identified in patients before a.iJ after, as well as during, any

episode of illness, and.

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(c) is familial, e.g., can be identified in healthy first degree relatives.

The SRV strategy is directed toward variables in any domain of data. Since

they, by definition, must be antecedent to the manifest disorder, it is

hypothesized thai, they will serve more clearly as phenotypes for genetic

study than the later features which accompany or define the manifest

disorder.

?P

An analogy to the SRV strategy can be seen in the work of Annett (see

this volume; 1978; Annett & Kilshaw, 1983), wherein handedness is assumed to

be the final result of both genetic and environmental forces and, therefore,

not an appropriate phenotype for genetic study. Through her assumption that

right vs. left verbal dominance is indeed more clearly a phenotype, the

distribution of handedness as a combined result of sundry environmental and

underlying constitutional determinants becomes more clear. In similar

fashion, the SRV strategy takes seriously the commonly accepted notion that

schizophrenia is a product of hereditary and environmental factors. Then,

without the contradictory assumption that schizophrenia itself should be

pursued as a phenotypic target, the search is directed toward SRVs as

appropriate phenotypes.

Since schizophrenic symptoms emerge later in life than handedness, its

genetic and other constitutional determinants are more elusive. SRVs which

precede psychotic episodes may be useful not only for genetic study but as

potential risk predictors. However, since they also occur in relatives who

never become ill, they may help isolate and clarify the genetic and

environmental factors necessary for the precipitation of Illness. Thus, an

SRV is not a subclinical form or a one-to-one correlate of schizophrenia

which follows along later. It is a precisely defined variable which may or

may not be sufficient to presage a schizophrenic episode.

Since the SRV strategy is a new one, few SRVs have been Identified.

Some candidates for study are (a) reaction time cross-over, (b) span of

apprehension, (c) visual evoked response augmenting-reduclng, (d) blood

platelet monoamlne oxldase, (e) plasma dopamlne-beta-hydroxylasc, (f)

dlchotic listening intrusions, and (g) smooth pursuit eye tracking

disturbance (Cromwell 198A, p.33-34). In addition, lacono (e.g. lacono et

al., 1983; personal communication) has also studied (h) skin conductance

recovery and (1) capillary nallbed structure. Zubln and Stelnauer

(Reference Note 2) are also studying pupillary dilation, pupillary light

reaction, vigilance, heart rate and blink rate.

The implications of these variables for the present paper is that the

ones which currently appear to be most strong in meeting the SRV criteria

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are those which are Involved In the early stages of information processirg. * ' The implications of this for the understanding of the psychoneurology of 'N?S

schizophrenia and of normal brain functioning will be examined. rf-XS»

"Earliest Processing Event" Strategy \P&!u<

Another strategy for studying schizophrenic (or SRV-devlant)

individuals involves the search for the earliest event of breakdown in the

sequence of information reduction. Little attention had been given to this

area of cognition until recent years, and certainly no standard nomenclature

to lescribe these information-processing events has yet been agreed upon.

Yet, some convergent findings are worth mentioning.

The first set of events ordinarily examined are those involving sense

organ input. With these receptive and peripheral afferent events t-^

essentially no important impairments have been found to be specific to JSN

schizophrenic patients (e.g., see review by Shakow, 1963). '}>"'

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Once information reaches the central nervous sytem, iconic integrity

and decay represent the next candidacy in the search for schizophrenic Vbreakdowr. Spaulding, Rosenzwelg, Huntzlnger, Cromwell, Briggs and Hayes .'/I,

'v',"I

(1980) examined visual decay (and integration) features by presenting two '•""'•%>'

dot matrices separated by a variable interval without visual presentation.

If the second dot matrix entered the Icon before the first one had decayed fifij

then the subject could integrate the two dot patterns and report a two-digit

number. No number or other recognizable image was detectable when each dot

pattern was viewed separately. Schizophrenic patients were shown to be

remarkably similar to other comparison groups in this decay and integration >

,<v*\a

function. •W'J

Similar results were found earlier when Knight, Sherer and Shapiro > t

(1977) presented successive line fragment images separated by a variable 'vvv

interval. With smaller intervals the subjects were more able to recognize a «"v""^'

line drawing which resulted from the integration of the two fragment images. X'Jyft

Although schizophrenics again did not differ from control subjects, the ^"vS

differences in the decay function suggested that more than one mechanism may fV'.^n

be involved in this stage. i

Th*; next stage concerns processing from the icon. One aspect of this

has been studied through partial report span of apprehension. In this

procedure an array of stimuli (usually letters) are displayed tachlstosc'opically for 50 msec. The subject is preinstructed to look for either of ftSBi

two targets (such as a T or F). The subject then either reports or guesses

which of the two targets occurred. From the percentage correct performance,

the mean number of elements processed is calculated. This technique, along

with vigilance measures likely related to it, has revealed a wide range of

findings of schizophrenic deviance. Schizophrenics (Neale, Mclntyre, Fox &

Cromwell, 1969), remitted schizophrenics (Asarnow, Steffy, MacCrimmon &

Cleghorn, 1978), children at biological risk for schizophrenia (Asarnow,

Steffy, MacCrimmon & Cleghorn, 1977), and childhood schizophrenics (Sherman

& Asarnow, 1984) are all deviant on this task. Moroever, little or no

impairment is found when subjects are asked for "full report" of all they

have seen in the array (Cash, Neale & Cromwell, 1972). Thus, the impairment

appears to be related to the scanning and disengagement from irrelevant

stimuli rather than the scanning capacity and short term memory factors.

SSSM The next search for schizophrenia breakdown would be In the stages

where Information Is transformed to representational forms. These

representations would be the unit products which eventually lead to verbal

emissions. Here many redundant systems are likely involved, and the current

nomenclatui. for these stages of processing is even less clear. However,

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341

ample examples of schizophrenic breakdown appear to arise from this

"represented" or "labeled" information. Often these breakdowns are referred

to as distorted perceptions, such as in inkblot testing. The major point to

be remembered here is that the deficit already described above in visual

search inevitably carries forward faulty information for this

representational processing stage.

K/l^i

In the stages after representation, wnere verbal concepts have been

formed, numerous studies have shown schizophrenic impairment. In verbal or

other effector response, in executive decision process, and in use

(efficient retrieval) of long term memory, the impairments are so pervasive

in schizophrenia that it is difficult (and theoretically more interesting)

to identify where the schizophrenic is unimpaired. All of these deficit

measures involve focal attention and subject awareness. Indeed, as

indicated previously, the definition of the schizophrenic disorder itself

lies in these latter phases of processing.

The conclusion to be drawn from the foregoing data and their

Interpretations is that the schizophrenic deficit is not so diffuse as to

defy isolation forever. The deficit is not encountered in the very early

stages of informational input, but, once it does occur, the stages which

follow appear generally impaired.

Qualifying comment

Among the many statements of caution and qualifying assumptions when

interpreting attentional and information processing data a few are certainly

worthy of comment here.

In such a recent area of research, as already suggested, the useful

divisions of processing stages and the nomenclature are certainly not clear.

The methods are certainly subject to exploration and refinement. A best

possible outcome would be that the present modes of description become more

and more obsolete.

It is also important to remember that informational input does not corae

in discrete bits, even though this is attempted in the experimental

laboratory. Instead, with the continuous flow of input from all modalities,

the various stimuli and processing events do not occur in isolation.

In this respect some recent work is directed as to how the subject

disattends (disengages processing) from immediately prior stimulation. Such

disengagement mechanisms would appear important in order for the subject to

be prepared for the continuing stream of input. Posner (1982; see also

Posner, Cohen, Choate, Hockey & Maylor, Reference Note 1) has shown that

after successive visual processing from Site A to Site B, the subject can

more easily process Information from a third Site C than return to process

new information at Site A. This mechanism may be important in "clearing the

•late" in order to deal with continually new input in real life situations.

PRELIMINARY COMMENTS CONCERNING HEMISPHERIC FUNCTION

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Before discussing the implications of these cognitive findings in

schizophrenia for hemispheric brain functioning, it is appropriate to make

some preliminary statements and assumptions about the latter.

Proposed assumptions

The following proposed assumptions, all challengable but potentially

useful, represent a starting point for the final argument of this paper:
342

1. The right hemisphere Is primarily responsible for preattentlonal

processing, especially in the visual domain.

Here, as elsewhere, it is recognized that one can speak only of hemispheric

advantage, not of discrete functions.

2. This preattentlonal processing is Inevitably a massive effort in brain

function. Stated differently, the task to select, "group," and enhance the

"relevant", and to inhibit the "irrelevant", from the vast array of input

occurring at a given moment is massive as compared to the trivial

requirements to transform greatly reduced information into pathways of

verbal resolution, decision making, and action.

3. Tb sequence of processing on this preattentive level remains localized

primarily In the right hemisphere, at least in the stages of visuospatial

separations of figure from ground.

4. Information in these early preattentive stages must become sufficiently

reduced i be transferred across the corpus callosum.

5. After crossing to the left hemisphere the information is received and

further reduced through verbal coding and logical manipulation.

This stage is required to make the information storable in long term

memory (with the possible exception of memory for Images).

This stage is also required for performing output resolutions of

conscious thought, decision making, verbal response, and other effector

reaction.

Proposed hypotheses

If the foregoing crude picture of relative specialization is valid,

then one could hypothesize the following:

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1. The right hemisphere should have the relatively greater energy demand

since it is dealing with massive amounts of unreduced information.

2. The right hemisphere migat be expected to be structurally different in

order to accommodate to this specialized massive task. That is, if the

massive preattentlonal function (at least the visual one) is primarily and

most frequently located in the right hemisphere, one would well expect the

appropriate cell structure, vascular structure, and chemistry to differ on

the right side in a manner which would accommodate to this greater

preattentlonal and energy-demanding function.

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3. The functions of the left hemisphere might more easily be simulated

today by modern computers with "verbal" and logical algorithms which deal

with information after it Is already in reduced form.

Implications

1. Since the final stages of information processing are primarily in the

left hemisphere, and these are rhe stages of which we are most immediately

aware, they are the ones, historically, more likely to be studied and

identified first. Thus, we might be expected to label this side as the

"dominant" hemisphere. The present formulation would suggest that the left

side of the brain is dominant only in the sense that the side of the moon

which faces us is dominant. Likewise, one could call the surface portion of

•n iceberg the dominant portion.

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The formulation of dominant vs. non-dominant hemisphere has probably

retarded progress in the understanding of brain function. Better It would

be, if one can speak of relative advantage, that the left hemisphere has the

"later" and the right hemlsphare has the "earlier" processing functions. "AV"*

2. Although the right hemisphere is regarded as the locus of visual-spatial

"ability", it might more appropriately be viewed as the site of relative ÄJvSJSSl

advantage for certain visual processing stages. i'-l^'/yOv

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Evidence

Gur (this volume) has reported greater blood flow in the right

hemisphere. If blood flow is related to lateral energy demand, then the

right pide of the brain, as hypothesized above, should in general have the

higher rates. v."^-

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With respect to task-specific blood flow, tasks with strong visuospatial emphasis should be expected to put a greater demand upon the right

hemisphere, and tasks with strong verbal emphasis should put a greater

demand upon the left hemisphere. Again, Gur (this volume; Gur, Gur, Rosen,

Warach, Alavi, Greenberg & Reivich, 1983) has shown that this relative

difference in blood flow in the direction expected (verbal tasks elevating

left hemisphere blood flow and visual tasks elevating right hemisphere blood

flew). However, as might be expected, this difference is not as great as

the overall difference of right over left side. The massive preattentional

screening must be taking place regardless of the emphasis in the task being '.'K'-''-

performed.

Relevance for schizophrenia

When one attempts to fit the data of schizophrenic deficit onto the

topographic map of brain hemispheres there is ample reason for caution. To

begin, several reasons may be cited for this caution.

1. Little work in schizophrenia has been done with split field techniques;

therefore. Inferences usually oust be based upon bilateral Information

exposure plus some prior notion of how these are laterally specialized. '•jSrC'^SJ

2. As has been stated so often elsewhere (see this volume) one can at best ^j^iSKi

speak only of hemispheric advantage, not of unique hemispheric function. XLVNWI

Perhaps because of redundant systems in the brain which are topographically /•"^ '^"•''l"»'!

separated, functions can be acquired in one hemisphere when the other has

lost the flection. Nevertheless, a picture can be constructed of the

relative h ispheric advantage in the sequences of processing events earlier

described in the search for schizophrenic deficit. . ,

3. Contrary to the "staging events", abstracted and interpreted from the «C ' -"

attencional and information-processing research on schizophrenia, both the

input of stimulation and the monitoring and rhythm of the brain are ongoing.

They are not activated (set in motion) by a particular input at a particular

moment. 'J^HH

Given these and other appropriate cautions, the tentative formulation

concerning schizophrenia is as follows:

1. Sensory input and iconic storage functions have no significant

Impairment in schizophrenia.

2. Preattentional functions are faulty in the schizophrenic patient. To

the extent that the right hemisphere is at advantage for these functions,

then the right hemisphere Is faulty In this early phase of Information

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344

processing.

3. The information, reduced in faulty form, is transmitted across the

corpus callosum to the left hemisphere.

A. The left hemisphere, being the recipient of any fault arising from the

right hemisphere (or from transport therefrom), is therefore compromised in

performing the later stages of processing. It would not be unexpected that

the left hemisphere is often found deviant in arousal and other

psychophysiological indices (as reported by Flor-Henry, 1979; Gruzelier,

Jutai, Connolly & Hirsch, 1984; and others).

The essence of the present assertion is that deviant left hemisphere

functioning does not necessarily mean that the left hemisphere is the source

of the problem of schizophrenia. For the "later" left hemispheric

mechanisms to be operating smoothly and efficiently in the face of earlier

impairments in the chain of processing would be difficult to argue. If the

right hemisphere shows deviance (also reported by Gruzelier et al., 1984, and

see this volume) its effects should become evident in informational

products of the left hemisphere.

In short, the left hemisphere of the schizophrenic finds itself "up to

its 'crotch' in crocodiles under conditions while its major purpose is to

drain the swamp" i.e., to perform the final homeostatic stages of

information resolution.

*aa

5. As suggested by Venables (1984), visuo-spatial processing functions,

normally assumed by the right hemisphere, may have to be picked up by the

left hemisphere. If so, one could reasonably assume, as he does, that en

interference has resulted from the proximity of these earliei and later

processing functions. This formulation also would support the notion of

left hemisphere aberration as a secondary matter in schizophrenia.

However, it is important to note here that the proximity/interference

hypothesis is not necessary in order to account for the deviant functioning

in the left hemisphere as being a secondary feature. The mere transmission

of faulty information from the right heiUphere is sufficient to argue this

point.

CONCLUSIONS

1. Research on information processing stages might be useful for developing

a sequential dynamic, rather than a static ability, formulation of brain

function. Such a formulation would suggest that early (preattentional)

processing stages are primarily in the right and later (verbal, decisionmalting, executive action) stages ara primarily in the left hemisphere.

2. A formulation that the massive preattentional screening is primarily in

the right hemisphere might explain some of the empirical findings of lateral

differences in cell density, blood flow, and task-related blood flow.

3. Left, hemisphere hyperarousal and other left brain deviations would be

explained as secondary outcomes resulting from faulty information being

transferred to that hemisphere from earlier preattentional processing in the

right hemisphere.

REFERENCES

Annett, M. (1978). A single gene explanation of right and left handedness

and bralnedness. Coventry, England: Lanchester Polytechnic.

Annett, M. & Kilshaw, D. (1983). Right- and left-hand skill: II.

>:

/ W" ." JU
iP

m

Estimating the parameters of the distribution of L-R differences In tmm* A

males and females. British Journal of Psychology, 74. 269-283. yS's'^A^vJ

Asarnow, R.F. Steffy, R.A., MacCrlmmon, D.J. and Cleghorn, J.M. (1977). An äSOW^"''"

attentional assessment of foster children at risk for schizophrenia.

Journal of Abnormal Psychology, 86, 267-275.

Asarnow, R.F., Steffy, R.A., MacCrlmmon, D.J., and Cleghorn, J.M. (1978).

An attentional assessment of foster children at risk for schizophrenia.

In L. C. Wynne, R.L. Cromwell, and S. Machysse, S. (Eds.) The Nature

of Schizophrenia. New York: John Wiley and Sons. ?y^5£wS^

Cash, T.F., Nesle, J.M., and Cromwell, R.L. (1972). Span of apprehension In ^V'ÄJJJSA

acute schizophrenics: a full report technique. Journal of Abnormal WX-'V^

Psychology, 79, 322-326. " ^ "

Cromwell, R.L. (1972). Strategies for studying schizophrenic behavior.

Psychopharmacalogla, 24, 121-146.

Cromwell, R.L. (1984). Preemptive thinking and schizophrenia research. In

W.D. Spauldlng and J.K. Cole (Eds.) Nebraska Symposium on Motivation. •""" ^v'-X

Lincoln, NE: University of Nebraska Press, 1-46. '^V^/^^

Flor-Henry, F, (1979). Commmentary on theoretical issues and Sf^fiTiTi

1

^

neuropsychological and electroencephalographic findings. In J.H. , ^ • ' Gruzelier and P. Flor-Henry, (Eds.) Hemisphere Asymmetries of Function £\-'v''VN

'"v^

in Psychopathology. Amsterdam: Elsevier/North Holland Co., 189-222. ,

r

'yv'vV-""%

Gruzelier, J.H., Jutai, J.W., Connolly, J.F. & Hirsch, S.R. (1984). iS-Vvv/vi

Cerebral asymmetries in unmedicated schizophrenic patients in EEC <^yJS*\,'Vvjy

spectra and their relation to clinical and autonomic parameters. In J. •.'•"."•".">'."•. . j

Mendelwicz and H.M. van Praag (Eds.) Advances in Biological Psychiatry. iow«J

Basel: S. Karger. 'v'vv'.

Gur, R.C., Gur, R.E., Rosen, A.D., Warach, S., Alavi, A., Greenberg, .'■■.'/' ','

J., & Reivich, M. (1983). A cognitive-motor network demonstrated by >^"v •

positron emission tomography. Neuropsychologia, 21, 601-606. u'&iOk'"'/ '*

lacono, W.G., Lykken, D.T., Peloquin, L.J., Lumry, A.E., Valentine, R.H., & •.-4jf»ii • _

Tuason, V.B. (1983). Electrodermal activity in euthymic unipolar and

bipolar affective disorder^. Archives of General Psychiatry, 40, 557-

565.

Knight, R., Sherer, M., and Shapiro, J. (1977). Iconic imagery in v/^,,v

s

j>v>'V

overlncluslve and nonoverlncluslve schizophrenics. Journal of Abnormal

Psychology, 86. 245-255.

Neale, J.M., Mclntyre, C, Fox, R., and Cromwell, R.L. (1969). The span of .....*.

apprehension in acute schizophrenics. Journal of Abnormal Psychology,

74, 593-596.

Posner, M.I. (1982). Neural systems control of spatial orienting.

Philosophical Transactions of Royal Society, London, B 298, 187-198.

Shakow"j D. (1963). Psychological deficit In schizophrenia. Behavior

Science, 8, 275-305.

Sherman, T. & Asarnow, R.F. (1984). The cognitive disabilities o

f

the

schizophrenic child. In M. Slgman (Ed.), Children with Dual

Disabilities: Mental Retardation and Emotional Disorders, Orlando,

Florida: Grune & Stratton. ''%''N'"-/,V'">*

Spauldlng, W.D., Rosenzweig, L.H., Huntzinger, R.S., Cromwell, R.L., Briggs, '* ''*•'''•'•S'-^»

D., and Hayes, T. (1980). Visual pattern integration in psychiatric *

patients. Journal of Abnormal Psychology, 89, 635-643. SSxvSvM

Venables, P. (1984). Cerebral mechanisms, autonomic responsiveness and ••/-•NvC£v'"v

attention In schizophrenia. In W.D. Spauldlng and J.K. Cole (Eds.) WJMMM>3

Nebraska Symposium on Motivation. Lincoln: University of Nebraska AwwAAjfl

Press, 47-92. " ITCSWNNWHXI

•

Reference Notes

1. Posner, M.I., Cohen, Y., Choate, L., Hockey, R. & Maylor, E. Sustained

concentration: Passive filtering or active orienting? Paper delivered to

the meeting on Preparatory Processes, sponsored by NSF and CNRS. Ann Arbor.

Michigan, August 1982.
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346

2. Zubln, J. & Steinhauer, S. Psychobiologlcal indicators in

schizophrenics and their siblings. Unpublished manuscript.

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347

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CEREBRAL LATERALITY & SCHIZOPHRENIA: A REVIEW OF THE INTERHEMISPHERIC

DISCONNECTION HYPOTHESIS

John Gruzelier,

Department of Psychiatry,

Charing Cross and Westminster Medical School,

Fulham Palace Road, London W6 8RP. U.K.

INTRODUCTION

The disorders of Interhemlspherlc communication revealed by the animal

experiments of Sperry & colleagues In the 1960's (Sperry, 1964), and by the

patients of Bogen & Vogel undergoing callosectomy (1962), gave Impetus not

only to basic research on hemispheric specialisation but also provided

theoretical concepts of relevance to neurology and psychiatry (Geschwind,

1965; Galin, 1974). The splitting of psychic functions which gave

schizophrenia its name was plausibly seen to stem from disconnection in

neurological terms between a rational, verbally mediated left hemisphere and

a holistic, nonverbally mediated right hemisphere. Conceivably, the

observed dissociation between affect and cognition may have a similar origin

to the dissociation between verbal and facial expression sometimes seen

after callosectomy. Alternatively, a disorder of hemispheric specialisation

which disrupted the normal processes of interhemlspherlc integration might

be at fault; the popular presumption was that this was likely to be leftsided in view of the linguistic disturbances of schizophrenia. Acordingly,

the split mind of the schizophrenic night arise from a split brain.

Substance to these ideas was added by two influential reports. Flor-Henry

(1969) surveyed the lateralisation of epileptic foci in patients with

temporal lobe epilepsy combined with schizophrenia or manic-depressive

features. Schizophrenic-like psychoses were associated with left-sided or

bilateral foci and manic-depressive psychoses with right-sided foci.

Rosenthal & Bigelow (1972) reported that the only pathology found in an

examination at post-mortem, admittedly of the right hemisphere only, in ten

schizophrenic patients was an enlargement of the corpus callosum.

Subsequent research polarised initially around these competing ideas, though

by Che time of a conference called to review the findings (Gruzelier & FlorHenry, 1979) they were seen to be mutually compatible.

Now there are a number of theories about the nature of lateralised and

interhemlspherlc dysfunction in schizophrenia:- 1). There is a functional

reversal of normal hemispheric specialisation for verbal and nonverbal

processes. 2) Right hemisphere deficits are the forerunner of left

hemisphere dysfunction. 3) The left hemisphere problem is primary, but

opinions diverge as to whether this produces a loss or overactivation of

function. 4) The interhemlspherlc pathways play a primary role. 5)

Opposite states of hemispheric balance in activation lead to a relative

dominance of the left hemisphere in acute, reactive, florid, remitting

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348

schizophrenia and right hemispheric dominance in chronic, retarded

schizophrenia. These theories have been recently reviewed by the author

(Gruzelier, 1986) and this chapter will be concerned only with the role of

the corpus callosum in schizophrenia.

The origin of the theory that madness arises from incongruous and

independent actions of the hemispheres has been traced by Harrington (1986)

to the 18th century, when it was said of the insanity of Pascal 'madness and

wisdom each had its compartment or its lobe, the two sides separated by a

fissure' (La Mettrie, 17A7). However it was Wigan (18AA) who fully

elaborated the thesis in a book 'A New View of Insanity: Duality of Mind'.

He proposed that the normal exertion of control over one hemisphere by the

other is lost and the resulting interhemispheric conflict is manifested by

psychosis. At the time this view did not gain hold for several reasons, one

of the more persuasive of which has been the puzzle of agenesis of the

corpus callosum. William Ireland (1891) writing in the British Medical

Journal 'On the discordant action of the double brain' expressed this

puzzlement 'It is, however, surprising that the complete absence of this

organ has been noted half a dozen times without entailing any apparent

functional deficiency, for examination of the literature shows that where

there has been imbecility there has always been some other grave defect. On

the other hand .... where the brain is otherwise well developed there may be

no disturbance of mobility, co-ordination, general or special sensibility,

reflexes, speech, or intelligence, whether the defect of the corpus callosum

be primary or secondary. This view has also been confirmed by observations

of destruction of the corpus callosum from disease".

Research on callosal agenesis up to the present day has not resolved

this problem. It is now thought that sparing of the anterior commissure in

acallosals may permit interhemispheric transfer, or that compensation has

occurred through duplication of functions bilaterally with or without

dependency on highly developed ipsilateral fibres (Bogen, 1985). Nor is the

callosal agenesis model appropriate for callosectomy; acallosals show few of

the disconnection deficits seen in split-brain patients. Needless to say,

this along with the existence of coincidental noncallosal pathology, does

not bode well for the application of the acallosal model to schizophrenic

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The split-brain model also appears inappropriate for schizophrenia.

After callosectomy neither acute nor chronic clinical signs have any

resemblance to psychosis and in cases of organic pathology of the callosurr

psychotic symptoms occur only rarely. Notwithstanding the relevance of such

symptoms to some of the accompanying features or subclinical disorders of

schizophrenia, the origin of the symptoms appears outside of the callosum.

These are what Bogen (1985) terms 'neighbourhood signs'. He concludes a

discussion of the mental symptoms by saying "In my experience, patients with

anterior callosal lesions often do have 'a certain apathy'. This

'imperviousness' occurs in patients with acute or progressive callosal

lesions - especially the malignancy which is sometimes called a 'butterfly

glioma' because it spreads its wings into both frontal lobe^. The patient

who is impervious to instructions will eventually respond, and often

appropriately (but sometimes incompletely), but after repeated requests and

considerable delay. Ue are now inclined to attribute this symptom not to

involvement of the genu of the corpus callosum (which is, to be sure,

involved) but rather to involvement of the medial aspects of the frontal

lobes including the anterior cingulate gyri. And we suppose the

imperviousness to be a milder form of akinesia, often approaching a mute

immobility, of a patient who has what is sometimes called 'the subfrontal

syndrome' consequent to bleeding from an anterior cerebral artery aneurysm,

- with a third ventricle tumor".

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349

lesions, although It Is probably not a result of callosal interruption.

This seems, in retrospect, a good example of anatomic relationships being

important clinically, although misleading from the point of view of

physiological theory".

"Neighborhood signs have also been rotcd with posterior callosal

lesions, with involvement of the hippocampi. Translating Escourolle et al,

(1975) (see Bogen, 1985):

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A certain number of our tumors of the splenium (twice as common as genu

gliomas) were accompanied by memory dysfunction, whereas the anterior tumors

were more often manifested by akinetic states with mutism, probably because

of bilateral anterior cingulate involvement."

Thus structural lesions in and around the callosum vary along an

anterior-posterior axis in their behavioural effects, and these bear little

resemblance to the fundamental deficits of schizophrenia.

Theory aside, the real impetus to current interest in the callosum in

schizophrenia arose from the post-mortem study of Rosenthai & Bigelow (1972)

which revealed callosal enlargement. However, this has been qualified in a

recent replication (Bl^elow et al., 1983) where enlargement was restricted

to anterior and medial aspects and was confined to a subgroup of mostly

nonparanoid patients with disorders of early onset. Another publication on

the same series of patients which examined the callosum for gliotic cells

(Nasrallah et al., 1983) cast yet a different light on the findings.

Cliosis was associated with a thinner callosum in posterior regions and

occurred in late onset paranoids as well as in manic-depressives. This may

imply regional differences, both with respect to the nature of the pathology

and the associated clinical syndromes, and possibly the functional

implications of the interhemlspheric transfer deficit. A cautious

interpretation is probably warranted for Nasrallah et al. question the

pathological significance of so-called 'enlargement' in view of the fact

that the dimensions of the callosal cross-section In schizophrenic patients

were no larger than in medical and surgical controls.

The inappropriateness of models of defective interhemlspheric transfer

in schizophrenia on the basis of agenesis of the callosum, or callosectomy,

or for that matter organic lesions of the callosum, is clearly apparent.

Nevertheless, this does not rule out a more subtle problem of

interhemlspheric integration in schizophrenia. The nature of the problem

may lir in faulty transmission such as a poor signal to noise ratio (Butler,

1979) or a loss of contralateral inhibition. Logically a disorder of

interhemlspheric transmission may not simply involve a problem in the

interhemlspheric pathway but in the transmission or reception of the signal

in either hemisphere, thus a problem in interhemlspheric Integration may

coexist with a lateralised disorder.

VV3

AUDITORY PROCESSING

Dichotic listening studies of schizophrenic patients have a bearing on

callosal dysfunction. Split brain patients have shown an abnormally large

right ear advantage for verbal material which may reflect an Impairment of

left ear input across the interhemlspheric pathway. Comparisons between

binaural and monaural hearing have provided the somewhat unusual finding

that acute schizophrenic patients under some circumstances perform more

poorly under the more natural binaural condition. Considering first the

dichotic listening paradigm, split-brain patients have shown an abnormally

large right ear advantage to verbal material due to a reduction in the

recall of words heard in the left ear (Milner et al., 1966; Sparks and

Geschwind, 1968; Springer and Cazzaniga, 1975). This evidence has been
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Fig. 1. Ear differences in frte recall of digits.

used Co validate dichocic listening as a method for investigation of

hemispheric effects via contralaferal auditory projections; the ipsilateral

auditory projections having been functionally occluded, apparently by virtue

of competition of input In either ear. The failure of split-brain patients

to recall much of the verbal input to the left ear implies that the normal

route of transmission extending from left ear to right hemisphere via the

contralateral pathway and then across the callosum has been prevented by

commissurotomy. Transmission does not occur via the Ipsilateral pathway.

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controls (x: 10.25), see Fig. 1. Two thirds of each group were at acute

stages of illness but chronicity had no bearing on the data. Subsequently

the results were interpreted by one of the authors as evidence of abnormal

left hemispheric overactivation in paranoid patients (Nachson, 1980); a

callosal disconnection interpretation has also been offered (Walker et al.,

1981).

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Larger than normal right ear advantages have also been reported in

recalling consonant-vowel-consonant trigrams and common words, again in a

subgroup of »chizophrenic patients (Lishman et al. , 1978). These were male

patients with active symptoms, auditory hallucinations at some time of their

clinical history, and no genetic association with schizophrenia. Colbourn

and Lishman (1979) went on to examine these effects using consonant-vowel

syllables and cor.e contours The majority or schizophrenic patients showed

normal left ear recall of the syllables but on this occasion the majority of

male patients failed to show a right ear advantage. The authors concluded

that the normal left ear recall indicated no support for a callosal

transmission impairment while the reduction in right ear recall in male

patients suggested a left hemisphere impairment. There was no impairment in

recall of the tone contours in the seven patients tested.

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Cruzelier and Hammond (1979, 1980) carried out essentially the same

experiment as Lerner et al. (1977) with two modifications. In addition to

the free recall condition they included blocks of trials where subjects were

instructed to recall all the numbers heard in one ear before the other, a

conventional procedure for varying the direction of attention to either ear.

Additional blocks involved intensity manipulations where digits were 20

decibels louder in one ear than the other. Eighteen chronic, male

schizophrenic patients were tested, and as was found In the Israeli study,

the extent of the right ear advantage depended upon a clinical history of

paranoid symptoms; paranoid patients showed a larger than normal right ear

bias. In this study non-paranoids showed less of a right ear advantage than

controls. Psychophysiological recording revealed that the majority of

paranoid patients were autonomically responsive, as shown by the frequency

of electvodermal responses to moderate intensity tones, whereas nonparanoids for the most part were non-responsive. The ear differences are

shown in Fig. 1.

The conditions in which directed attention and intensity were

manipulated had a particular bearing on the callosal hypothesis. It can be

seen from Fig. 2 that the paranoid patients In the conventional free recall

condition showed a right ear bias similar to that where attention was

directed to the right ear, or where stimulus intensities were 20 decibels

louder in the right ear than the left. It was as though in ordinary

circumstances their attention had been directed to the right ear. It is

important to note that they could reverse the ear advantage when

instructions or stimulus conditions favoured the left ear. The dynamic

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nature of the ear advantapes would not support an interhemisplieric 2S2

disconnection theory based on a structural impairment of the callosum. The

results were more in keeping with a dynamic imbalance in intra- and

Interhemispheric processing. Paranoid patients showed an imbalance

advantaging the left hemisphere and disadvantaging the right. As a

consequence they were not as competent at directing attention leftward as

controls and non-paranoid patients, the latter of whom were particularly

proficient at -ailing left ear material. Non-paranoid patients revealed

the opposite asymmetry, a dominance of the right hemisphere over the left.

The effects were reliable across six experimental sessions given at

fortnightly intervals and were not influenced by the withdrawal of

medication for four weeks, or its reinstatement for a further four weeks.

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Interhemispheric interactions were also implicit in the condition where

subjects were required to withold the recall of louder digits until after

the recall of quieter digits. Here 13/18 patients had greater difficulty

when witholding recall of right ear digits whereas controls (10/16) had

greater difficulty in withholding left ear digits. This would imply in

patients greater excitatory influences from the left to the right

hemisphere, an issue returned to in discussing evoked potential findings.

Two other dichotic listening studies involved longitudinal testing on a

different type of patient - new admissions. Wexler & Heninger (1979)

examined 8 schizophrenic, 6 schizo-affective and 12 patients with primary

depression admitted while unmedicated to a research ward and then retested

while undergoing treatment. Stimuli were nonsense syllables consisting of

stop consonants preceded and followed by 'a'. Apart from five patients with

reliable left ear preferences, ear differences were on the whole labile.

There were no ear asymmetries when symptoms were severe but with recovery

from symptoms the normal right ear advantage emerged. Symptoms in these

patients were predominantly of the positive type:- paranoid behaviour,

hallucinations, odd and unusual thoughts, thought disorder, verbal anxiety

ard expressed anger; while negative symptoms included psychomotor

retardation and depressive mood.

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The second dichotic study (Johnson & Crockett, 1982) also involved

acute patients - 16 schizophrenics and 16 depressives - tested first on

admission while unmedicated and again when symptoms remitted on drugs. They

compared the recall of words anu trukical chords. For verbal material their

results were consistent with ... e earlier study. Once again on admission the

schizophrenic patients showed no ear advantage for words yet on recovery,

when medicated, right ear advantages were clear. Curiously on admission

they showed the expected left ear advantage for chords but on recovery the

ear advantage reversed. It is conceivable, though this remains to be

tested, that the reversal in ear advantage for chords from the normal right

hemisphere advantage in admission to the abnormal right ear advantage on

recovery was due to drugs. This is in view of the fact that a number of

reports on the effects of antipsychotic neuroleptics in schizophrenia are

consistent in showing enhanced left hemisphere functions on medication

(Serafetinides, 1972, 1973; Hammond & Cruzelier, 1978; Gruzslier & Hammond

1979).

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Reconciliation of the dichotic listening studies requires consideration

of three factors:- syndromes, outcome, and severity of symptoms. Patients

with acute disturbance and patients attending outpatient clinic (Colbourn &

Lishman, 1979; Wexler & Henninger, 1979; Johnson & Crockett, 1982), both

signs of a remitting form of schizophrenia, do not show the expected right

car advantage for verbal material, which in view of the normal right

hemisphere specialisation for tone contours and musical chords (Colbourn &

Lishman, 1979; Johnson & Crockett, 1982) suggests a left hemisphere

impairment and a sparing of the right hemisphere rat.ier than a hemispheric

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reversal of functions. Chronic patients on the other hand show abnormal

right or left ear advantages for verbal material with the direction of ear

advantage depending on the pyndrooe:- a right ear-left hemispheric bias in

the reactive, florid, paranoid syndrome and a left ear-right hemisphere bias

in the nonreactive, chronic, retarded syndrome. All experiments support the

dynamic nature of the ear advantages. This rules out callosal impairment of

the structural, disconnection type.

The relevance of chronicity is also becoming clear in results with

another auditory procedure which compares the effects of monaural and

binaural listening on story comprehension. P. Green & Kotenko (1980)

examined twenty schizophrenic outpatients who had evidence in case histories

of auditory hallucinations, ten normal controls and ten neurotic patients.

After excluding four schizophrenic patients, two for poor performance and

two because of left ear advantages, the remainder were found to exhibit

poorer left ear performance and poorer binaural performance relative to the

monaural conditions. The results were interpreted as evidence of impaired

callosal transfer on two counts. The impaired left ear performance was in

accord with the callosectomy model, while it was hypothesised that the

binaural impairment may follow from faulty interhemispheric integration via

the interhemispheric pathways.

Both results were replicated in a second study (Green et al., 1983)

which involved 26 acute and 22 chronic patients, again compared with

neurotic patients and normal controls. 18/26 acute and 7/22 chronic

patients, a considerably smaller number than before, showed abnormally

reduced left ear scores. As before the acute group showed binaural

listening that was Inferior to the preferred monaural ear. This time about

half the patients showed a left ear preference. The authors also examined

13 children at genetic risk for s<-hizophrenia and 13 control children. The

high risk group had poorer comprehension overall and showed the binaural

impairment seen in acute patients. Ear differences did not reach

significance but the children were deficient in a test of speech sound

perception suggesting left hemisphere involvement. Thus, the studies of P.

Gteen and colleagues revealed a deficiency in binaural listening relative to

the better monaural condition which was confined to acute schizophrenic

patients and children at genetic risk for schizophrenia. In the acute

patients the binaural deficit coexisted with poorer ear performance. In

chronic patients on the other hand there was no sign of the impairment in

binaural listening, yet there was a loss of right ear advantages, and in

fact the opposite asymmetry was found in about half of them.

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Replications using the same comprehension tests have been attempted by

Kugler and colleagues (Kugler 1983) and by E. Green (1983). Examining

chronic patients Kugler lound that performance on both ears was reduced but

there was no abnormal asymmetry in either direction. She also adapted the

task for dichotic listening with competing stories in either ear and

instructions to shadow one ear. While there was no evidence of attentional

difficulties in shadowing, patients showed negligible right ear advantages

and reduced performance overall. The lack of a right ear advantage was In

keeping with evidence of impaired left hemisphere performance and was

consistent with the absence of a right ear advantage in the chronic patients

by P. Green and colleagues. Another replication by E. Green (1985) involved

twelve acute and twelve chronic schizophrenics who were compared with normal

controls and patients with borderline to mild mental handicap. The binaural

impairment and right ear advantage found by P. Green in acute patients was

replicated. The chronic patients also produced results consistent with the

earlier studies namely no impairment in binaural listening and no ear

advantage in monaural listening.

One other instance of poorer performance with binaural than monaural

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354

listening h.is been reported (Gruzelier & Hammond, 1979). This was found in

comparing reaction times to monaural stimuli which were the words 'left' or

'right' presented in a response compatability paradigm (Simon, 1969).

Schizophrenic patients at different stages of the illness and drug treatment

were compared. Those with active, positive symptoms were alone in showinp

slower reactions when the words were heard binaurally (x: 700 msecs) than

when heard in the left ear (x: 650 msecs) or right ear (x: 67A msecs).

This provided evidence that the performance deficit with binaural listening

was restricted to patients with active, positive symptoms of schizophrenia.

Thus, auditory studies in schizophrenia have revealed a performance

decrement in acute patients when binaural listening was involved. This has

been interpreted as an interhemispheric integration deficit and it coincided

with a larger than normal right ear advantage in monaural listening for

story comprehension. In chronic patients, the right ear advantage was lost

and in one study was replaced in half the patients by a left ear advantage.

In chronic patients there was no binaural hearing deficit and the results

were consistent with a left hemispheric deficit. In acute patients the

right ear advantage accompanying the binaural deficit nay reflect either a

right hemisphere and Interhemispheric deficiency or a left hemisphere

dysfunction, possibly of an overactivation type. In children at genetic

risk, for schizophrenia it was found to coincide with impairments in speech

sound perception, presumably Involving the left hemisphere. The association

of opposite ear advantage; with chronicity is compatible with the

hemispheric imbalance syncrome model mentioned in connection with the

dichotic listening studies. An overactive and dysfunctional left hemisphere

could also underly a binaural, verbal integration deficit.

<*.v.v:

The dichotic and story comprehension results are compatible in showing

relationships between ear advantages and syndromes having an affinity with

acute or chronic schizophrenia. Yet they are incompatible with respect to

the absence of the ear advantage in verbal dichotic listening in the acutely

disturbed patients compared with the right ear advantage in story

comprehension in acute patients. This may signify that level of processing

is important such that thm dependency on deeper levels of processing in

story comprehension places a greater reliance on left hemispheric functions.

Alternatively the descrip:or 'acute' may be too vague and may disguise

differences between the s:udies in severity of psychopathology.

HAPT1C PROCESSING

Haptic tasks involving intermanual transfer have provided another test

of interhemispheric communication in schizophrenia. Up to the time of

previous reviews (Gruzelier 1979, 1981, 1983) there was little in the way of

conclusive evidence. However, recent evidence indicates transmission

problems in a subgroup of patients co-existing with lateralised aspects. P.

Green (1978) had studied 20 mainly outpatient, medicated patients and

compared them with normal controls and neurotic patients. Green found that

the schizophrenic patients showed poorer learning of tasks involving

intermanual transfer, nevertheless there was no control for drugs or

intelligence, and the tasks on which the schizophrenic patients experienced

difficulty were the more complex ones and hence the effect could have simply

reflected task difficulty. Subsequently Carr (1980), attempted to control

for intelligence by equating patients and controls for socloeconomic status

and employment. She compared 10 chronic medicated patients with age and sex

matched normal controls. The task required subjects to remember an array of

objects palpated without vision after an interval of up to three minutes.

Unfatniliarity of objects and increasing delay made the task harder for both

groups but only the patients experienced more difficulty than controls when

tasks involved intermanual transfer. These results support a transfer

deficit unless the effects could be attributed to medi.ation.

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355

Dimond et al. (1979, 1980) performed tests known to show impairment

«fter commissurotomy. The 24 schizophrenic patients were insritucionalised

and middle-aged (mean age: 52 years). They were compared with six normal

controls and six cases of severe anxiety or depressive Illness requiring

long term care. Unfortunately, errors in performance were summed over

patients making the results difficult to interpret. Evei so it was clear

that impairments in intermanual transfer in hand tapping, touch localisation

and object naming did occur in some patients, but these were often

transient, for example on the second of the four monthly test sessions no

patient showed anomia.

Weller and Kugler (1979) also selected tests on the basis of the

callosectomy model. These included touch localisation, reproduction of

imposed posture, and identification of inscribed digits. They managed to

include some patients free of neuroleptics in their sample of 2A acute

schizophrenics and 16 chronic schizophrenic patients. These were compared

with schizoaffectives (N - 8), depressives (N 11) and normal controls.

Close inspection of the results (see Gruzelier 1979, 1983) suggests some

evidence of a lateralised left hemisphere deficit but is ambiguous with

respect to callosal transfer. Further experiments by Kugler and Henly

(1979) involved intermanual matching of objects and measures of the time

taken and errors made in discriminating shapes, letters and numbers. They

found left-sided rather than ca losal transfer deficits. < .-

New evidence by Huret et al. (198A) using a collection of tests of

parietal function found a variety of deficits. These implicated the left

hemisphere in tests of righc-left disorientation, finger agnosia and

dyscalculia, all components of Cerstmann's left parietal syndrome. Less

prevalent were problems in interhemispheric transfer which were seen in

tactile dyslexia occurring bilaterally or on the left side alone, and from

motor and praxic features of left dysgraphia. Some patients also displayed

constructional apraxia suggesting right parietal involvement in keeping with

a small body of evidence implicating right parietal dysfunction in

schizophrenia. All-in-all, these results are exemplary of trends in the

research on lateralisation and interhemispheric deficits in schizophrenia

with respect to the relative incidence of left-sided, Interhemispheric and

right-sided deficits. Clinical correlates remain an unexplored issue in

tests of haptic and mororic processing but should prove informative as it is

apparent from the existing reports that patients vary in patterns of

deficits.

VISUAL PROCESSING

In the visual modality, divided visual-field studies have provided

measures of callosal crossing time. No evidence of interhemispheric

transmission impairments in schizophrenia has been found. Yet most studies

have provided evidence of left hemisphere deficits. The conventional

finding in these reports is slower processing of verbal information

presented in the right visual-field which passes directly to th'.- left

hemisphere for processing than when the same material is presented in the

left visual-field and reaches the left hemisphere for analysis via the

callosal pathway (e.g. Connolly et al., 1979. 1983). Cur (1978) found that

this extended to inaccuracies in verbal performance, but so far this is an

isolated finding - typically the problem is one of speed of processing

rather than inaccuracy, indicating that the left hemisphere remains

specialised for verbal analysis in schizophrenia as it does in the normal

brain (see Walker & McGuire, 1982).

•v-v

^

Estimates of callosal crossing time revealed no suggestion of a deficit

(Connolly et «1., 1979, 1983; Shelton t Knight, 1984). In Connolly et al's

(1979) experiment the response involved the time taken to identify vocally

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numbers in a sequence of letters and numbers (verbal task) or the absence of

a dot on a 3 x 3 matrix (spatial task). Absolute differences between visual

fields were no different for schizophrenic patients and controls. This was

despite the apparent need for two crossings of the callosum in the case of

spatial processing of stimuli presented in the right visual field - the

first crossing from left hemisphere to right for the spatial analysis and

the second from right to left for the vocal report.

356

Bilateral heml-field presentation requiring the matching of stimuli in

opposite visual Melds provides some evidence of matching difficulties

(Beaumont & Dimond, 1973; Eaton, 1979). Nevertheless tho possibility

remains that these could be a function of the greater attentional demands of

binocular presentation. These studies, together with a third which did not

replicate the bilateial matching impairments (Magaro & Page, 19b3), were all

consistent in showing right visual-field impairments In letter matching

(Beaumont & Dimond, 1973), name matching (Eaton, 1979), and in one,

impairments in face, letter and chape matching in nonparanoids as distinct

from paranoius (Magaro & Page, 1983).

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A final visual study used the acallosal model of disconnection and

accord'ngly requires a cautious interpretation of the role of the

interhemispheric pathway. This entailed the moncular viewing of a rotating

pattern and the interocular transfer of movement after-effects, the transfer

of which is absent in acallosals. About two thirds of sixteen, medicated,

enronic male patients reported reliable after-effects. Unexpectedly these

were of shorter duration in patients (Tress et al., 1979).

SOMAT0SENS0RY EVOKED POTENTIALS

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Another approach has been to examine somatosensory cortical evoked

potentials bilaterally in response to unilateral stimulation, on the

assumption that the ipsllateral potential is generated via callosal fibres.

The results are confusing, because investigators have produced deficits

unique to their study and are in conflict as to the putative role of

interhemispheric and ipsllateral pathways. Nevertheless, all are invoked in

support of interhemispheric integration problems in schizophrenia! The

common assumption is that the ipsllateral response occurs in response to

stimuli transmitted from the contralateral cortex (via the callosum)

resulting in an attenuation of amplitudes and a delay in latencies. The

effects have been found to be more pronounced in children, a result in

keeping with the known maturational development of the cerebral commissures

throughout childhood (Salamy, 1978). To date, in comparisons between

schizophrenic patients and controls, the supposedly clear-cut picture of

contralateral dominance is seldom seen in controls let alone patients. In

accounting for this Gulmann et al. (1982) reveal the uncertainties that

surround contribution of interhemispheric and intrahemlspheric influences

on the homolateral somatosensory potential. According to Regan (1972)

bilateral representation occurs only for components later than 63 msecs,

yet Gulmann et al. (1982) deduce that it Is unlikely that all components

later than 65 msecs depend on callosal transmission because of evidence

from ir.farct cases in whom only early contralateral components were normal,

yet who did have abnormal late ipsllateral components. This implies that

later components were generated secondarily in the ipsllateral hemisphere

from the earlier component dependent on callosal transfer (Gulmann et al.,

1982). It is evident that more basic research in normal subjects and

patients with well defined neurological lesions is imperative before

results with psychiatric patients can be interpreted.

Problems of interpretation are further compounded by the results found

Ir. achizophrenic patients. These do not follow straightforward predictions

from disconnection theory. Ipsllateral responses are not attenuated nor are

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latencies delayed. The opposite situation often prevails. Evoked potentials are either symmetrical in amplitude, latency, or both, or latency

differences imply shorter transmission times in patients than controls.

Perhaps not surprisingly authors tend to be coy about their hypotheses and

Invoke post hoc explanations invoking abnormal ipsilaterdl influences, or

accelerated transmission across the cerebral hemispheres, or abnormal

development of ipsilateral pathways secondary to a defective callosum.

Tress et al. (1979) using a tap to the forearm, which produced results

similar to median nerve stimulation, found abnormal ipsilatcral latencies.

Twelve male, medicated, chronic patients were compared with seven normal

controls. Schizophrenic patients shared an attenuation of ipsilateral

amplitudes with controls but the ipsilateral latency of the component about

30 msecs was not delayed as it was in controls. This effect was

subsequently re-examined la another group of patients and compared with

welve controls (Tress et al., 1983). The groups again differed in

latencies with less evidence cf longer ipsilateral than contralateral

responses in patients than controls. The components showing the differences

often differed from the previous study and ranged from 25 - 60 nsecs. In a

third study another 13 patients were tested, eleven on two occasions where

on the second of which pindalol or placebo had been added to neuroleptic

medication. On the first occasion the normal advantage to contralateral

latencies was found at 33 msecs but not at 23 or 30 msecs. On retesting,

the peak at 25 msecs failed to show the contralateral advantage in those

patients on placebo.

Thus it can be seen that in the three experiments of Tress et al.,

latency rather than amplitude measures showed abnormal contralateralipsilateral relationships. Contrary to disconnection theory, ipsilateral

latencies were shorter not abnormally long in patients. However, the

components varied both across experiments and with retesting within the saine

experiment: experiment I, P30; experiment II, P25, N35 and P50; experiment

II session 1 P25 and P50; session 2 P25. At the same time the other

components which included N60 and P75 did show the expected asymmetr/

throughout. With respect to a neuropsychological interpretation, the

authors noted that the contralateral-ipsilateral differences .'n controls

were too small to meaningfully reflect a delay due to callosal transmission.

The authors referred to ipsilateral influences and 'more rapid spread of

activity, in the schizophrenic subjects from the ipsilateral primary

receiving area to other areas'.

The report of Jones and Miller (1981) is the most controversial on this

phenonomen. Jsing vibration ot the finger, the critical feature of which

was a sudden extension of the finger (Jones and Miller, 1982), they reported

responses that were symmetrical In amplitude and latency in both patients

and controls.

An attempted replication had a different outcome. Andrews et al.

(1984) compared 19 schizophrenic and 9 manic-depressive patients with 10

normal controls. They used a vibratory and kincsthetic stimulus modelled on

the Jones and Miller procedure with electrodes placed over parietal cortex.

Their procedures took account of various methodological criticisms advanced

by Shagass et al. (1982) of the Jones and Miller work. In addition in a

pilot study they compared the vibratory stimulus with median nerve

stimulation. In general, amplitudes to both stimuli were larger over

contralateral cortex, especially in the earlier peaks at P30 and P43 which

were the most clearly identifiable. They concluded that ipsilateral

responses in normals were too small to be reliably identifiable and this did

not permit an accurate estimate of inter-hemispheric transfer time.

Furthermore, :>eak identification was unreliable bilaterally in about a third

of Che patients who were discarded from the analysis. In the remaining

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358

subjects three patterns of response were observed, one of which was specific

to patients. All three groups had a similar incidence of symmetrical

responses whereby stimulation on one side produced appreciable ipsilateral

activity in addition to the contralateral responses. The third pattern

which was seen only in schizophrenic patients and one manic-depressive

patient with a sister with schizophrenia consisted of symmetrical responses

from stimulation of either forefinger.

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1

The schizophrenic patients with the bilateral responses were

distinguished by clinical symptomatology. A syndrome analysis was

undertaken after that of Gruzelier & Mancnanda (1982), (sec Cruzelier, this

volume) who found that patients with a predominance of negative symptoms of

schizophrenia in combination with Schneiderian symptoms were homogeneous in

the direction of the asymmetry of electrodermal responses compared with

patients with predominantly positive symptoms who showed the opposite

asymmetry. Evidence from both electrodermal and electrocortical recording

(Cruzelier, 1983, 1984; Cruzelier et al., 1985) indicated that the group

with the negative symptoms possessed an imbalance in hemispheric activity in

the direction of higher right than left hemisphere activity. This would

make a comparison of hemispheres in the Andrews et al. study of considerable

interest. They were cautious in the interpretation of the abnormal

bilateral response pattern seen in about half of the patients, concluding

that in these patients there is 'a demonstrative abnormality of early

cortical registration of somatosensory Information which tends to an

excessive ccrtical response ipsilateral to the stimulated finger'.

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Median nerve stimulation has been used in one study of schizophrenia.

Culmann et al. (1962) examined 10 chronic medicated schizophrenic patients

and 10 age and sex matched normal controls. Reliable ipsilateral responses

were found after 63 msecs. Contralateral versus ipsilateral latency

differences distinguished patients from controls when the right arm was

stimulated. Transmission time was in fact shorter in patients, not longer,

as a callosal disconnection theory would predict. When expressed as a ratio

the effect was restricted to male patients and lost significance when female

patients were added.

In summary, none of the studies found evidence in keeping with

callosectomy or an impairment in callosal transmission akin to abnormally

delayed maturation. When lateral differences arose these were only in early

components up to about 63 msecs and varied with the stimulus methods

involved. There is reason to question whether these could reflect callosa)

influences in view of their short latency or because the ipsilateralcontralateral differences in normals were too small to reflect interhemispheric transmission times. If the finding of Culmann et al. (1982)

relating to the P63 component is exempt from these qualifications then the

abnormality in patients was restricted to information transmitted from left

to right, and not vice versa, and indicated faster than normal transmissions

in patients, not delayed transmission. If this is a reliable finding, even

for a subgroup of patients, and if the interpretation is valid, it suggests

an important lateralised anomaly and may imply a reduction in left

hemisphere inhibitory influences over the right hemisphere. Finally,

assuming that the ipsilateral responses recorded by Tress et al. (1979,

1983), Jones and Miller (1981) and Andrews ct al. (1984) are not

artefactual, then the results appear to reflect an abnormal spread of

activity in the homolateral cortex to somatosensory stimulation. The

findings of Andrews et al. suggest that this may be restricted to patients

with a predominance of negative symptoms, patients who have been shown

elsewhere to possess an imbalance in hemispheric activity in favour of the

right hemisphere, (see Cruzelier, this volume).

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CONCLUSION

359

iT.v.'

There is now suf.uient research on lateralisaclon and interliemispheric

relationships in schizophrenia to reveal some consistent patterns of results

across studies. These offer rays of hope for elucidating the nature of

brain functional organisation in a disorder notorious for a lack of

replicable findings about basic neural mechanisms. Though the Implications

from these results raise more questions than answers, some clear guidelines

«re offered for future research.

Firstly there is no evidence Co suggest that a disorder of

interhemispheric relationships is a unitary deficit in schizophrenia.

Anatomical and histopathological studies of callosal structure, together

with neuropsychological measures of function suggest that Che type of

dysfunction nay relate Co clinical syndromes which have a bearing on

chronicity and sympComs. As has been discussed, Gruzelier, this volume, and

•ee Gruzelier (1981; 1983; 1985; 1986) for more detailed accounts, there is

reason Co suggest an Important distinction between symptoms associated with

acute, reactive, florid, remitting schizophrenia and chronic, retarded, poor

prognosis schizophrenia. These nay be loosely termed posicive and negative

syndromes, provided Schneiderian symptoms are seen as a separate syndrome

one which may coexist with the other two. In tests of Che callosal

hypothesis Che need for this disdncCion has been shown in measures of

dichoCic lisCening, story comprehension and in somatosensory evoked

potentials. These combine with a more extensive range of variables from

studies of lateralIsation:- electrodermal orientating responses, EEC,

cortical evoked potentials, the Hoffman reflex, conjugate lateral eye

movements, somatosensory extinction and handedness to provide support for

the syndrome-asymmetry model (Gruzelier, 1983). Recent tests which

explicity test the model find support from an EEC spectrum analysis of

visucl evoked potentials (Gruzeliei et «1., 1985) and from lateral

deviations in visual fixation, visual search and pupillary dynamics (Gaebel

and Ullrich, 1986). It appears that hemispheric balance is one

neuropsychological dimension that distinguishes the syndromes:- greater

left than right hemispheric activation in the posicive syndrucie and ehe

opposite state of imbalance in the negative syndrome. A further refinement

to the model is here suggested from comparisons of blnaural and monaural

listening; this relates to a chronicity dimension. The posicive syndrome in

acuce patients may co-exist with a problem of interhemispheric integration,

a coexistence not seen in chronic patients with the positive syndrome who do

not show the integration deficit. However, further tests of this hypothesis

are required and these should include racings of symptom severicy Co give

precision to ehe acuce/chronic disdncCion.

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S

.v.v:

Evidence Co date suggests little in Che way of Che funccional

dlsconneccion ChaC would follow scruccural impairments in incerhemisphcric

pachways akin Co calloseccomy or agenesis of Che callosum. Only in Che

somatosensory modality in Che evoked potential studies (Tres^ et al., 1979,

1983; Gulmann et al., 1982; Andrews et al., 1985) and Che behavioural

sCudies of Carr (1980) and Hurec et al. (1984) were Chore implications for

a nonfunccional callosum. In ehe Andrews et al. study this was restricted

Co Che negative syndrome patients and in the Carr study the patients were

institutionalised and therefore may also have been characterised by negative

features. The interesting possibility arises that the negative symptom -

right hemisphere syndrome, a.so co-exists with an as yet unspecified callosal

dysfunction. Ihis would provide an alternative account to the one of a left

hemisphere loss of function for the poverty of speech, which may extend in

some cases to mutism, and other features of cognitive reduction and motoric

retardation seen in the negative syndrome.

Other results suggest that the nature of disordered interhemispheric

•

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relationships in some patients may stem from faulty transmission such as 360

would occur through disruption of the fine tuning of patterns of excitation

and inhibition that underly intcrhemispheric communication. Little is

understood of these dynamics in the normal brain and to date the influence

of contralateral inhibition has received the most consideration (Denenborg,

1979; Flor-Henry, 1983). Two strands of evidence have been mentioned which

suggest that there may be an asymmetry in these relationships, such as

excessive excitation, or conversely a failure of inhibition in a left to

right direction (Gruzelier & Hammond, 1979, 1980; Gulmann et al., 1982).

There is another study which has also provided tentative support for leftsided origin to a callosal transmission impairment in schizophrenia

(Buchsbaum et al., 1979). Visual evoked potentials were measured Co flashes

of variable intensity presented to the nasal hemi-retinae while patients

Ignored or attended to the temporal sequence. Sixteen unmedicated

schizophrenic pati «ti were compared with patients with left or right-sided

temporal lobectony. The schizophrenic patients resembled the left temporal

lobectomy patients In failing to show an increased N12G response to stimuli

transmitted by the indirect callosal pathway to the left Cemporo-parietal

region. This represented a failure in callosal transmission of a signal in

a leftward direction. However, when this is seen in conjunction with a

left-sided impairment (left lobectomy in the neurological cases), it would

appear that the disruptive influence was transmitted from left to right and

hence was in keeping with the other reports.

The most clear cut evidence of an impairment in iaterhemispheric

integration arose from evidence of poorer reaction times and story

comprehension with binaural than monaural listening. This occurred in the

case of the reaction time impairment only in actively disturbed patients

with a predominance of moderate-to-severe positive symptoms. The

comprehension impairment occurred in acute patients and in those whose

symptoms had abated to permit their treatment as outpatients. The

impairment also occurred in asymptomatic children with a schizophrenic

parent. Thus the binaural integration impairment is not a

neuropsychologlcal concomitant of acute, positive symptoms but may instead

reflect a trait marker for the remitting form of schizophrenia.

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While a problem of interhemispheric integration is a reasonable

inference as to the nature of the neuropsychological deficit, it was

mentioned at the outset that a problem of interhemispheric transfer could

also stem from a lateralised deficit. There is little doubt that in acute

patients, without resorting to the literature on lateralisation in

schizophrenia which does not concern itself with interhemispheric deficits,

the bulk of evidence implicates the left hemisphere:- the exaggerated right

ear advantages in dichotic listening, the absence of impairments in

nonverbal dichotic listening and spatial hemi-retinal processing, the

verbal-right visual field deficit In tachistoscopy, and the greater

prevalence of right than left hand deficits in haptic processing.

Nevertheless, a smaller body of evidence implicates the right hemisphere in

perhaps a subgroup of patients, seen here In the results of Huret ct al. If

the evoked potential experiments «re correct In suggesting an abnormal

development of ipsllateral pathways in some patients with S'-hizophrenia then

interpretation of the auditory studies In schizophrenia is »laced on a

different footing. The neuropsychological model of dichotic listening which

provides the basis for the belief that the simultaneous presentation of

competing monaural input causes a suppression of the ipsilateral auditory

pathways may not hold in schizophrenia. However, before this theory

warrants further consideration, basic research is needed on ipsilateralcontralateral relationships in normal subjects. Research in our laboratory

has shown that a dominance of contralateral over ipsilateral evoked

potential relationships to monaural stimuli occurs in only 50* of normals,

and, while a significant group effect in favour of contralateral dominance

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361

Is obtained with repeat sessions, the effect is not reliable within subjects

(Connolly «t al., 1985). Andrews et al. (1984) did find reliable responses

to somatosensory stimulation at retest intervals of one year, but again only

50Z of their normal subjects displayed the contralateral dominance

phenomenon. Whether there is asymmetry in the instances of ipsilateral

dominance would be a worthwhile question.

>:

Finally, two other, possibly interrelated, factors require

consideration. These are levels of processing and regional localisation

within the interhemispheric commissures. The evidence of Bigelow et al.

(1983) and Nasrallah et al. (1983), though inconsistent with one another,

do raise the possibility of regional differences in structural impairments

which appear Co have clinical counterparts. This may account for the reason

why studies of visual processing with tachistocopy, unlike auditory and

•omatosensury measures, have failed to support the interhemispheric

relationship hypothesis in schizophrenia. Interhemispheric commissures

which are devoted to the relatively low order processing required in the

various divided-visual field studies nay escape impairment in schizophrenia.

Level of processing may also be relevant to interhemispheric and lateralised

dysfui on as seen in the discrepancy between ear advantages in the

different auditory procedures in acute patients.

Thus, regional localisation within the cerebral interhemispheric

pathways, as well as levels of processing, are added to the many factors

that require consideration in future attempts to test the model of impaired

interhemispheric relationships in schizophrenia. The other factors

described in this chapter included dynamic versus structural processes,

positive versus negative syndromes, acute versus chronic stages of the

disorder, lateralised versus interhemispheric pathway deficits, leftward

versus rightward interhemispheric influences, and the concept of

disconnection versus disordered communication. The callosal theory of

schizophrenia holds promise of continuing to fulfil an heuristic role in

delineating the nature of brain disorder in schizophrenia.

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schizophrenic patients with stable abnormalities of laterality of

somato-sersory cortical evoked responses. Paper presented at the Second

Interna ional Meeting of the International Organisation of

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Beaumont, J.C., & Dimond, S.J. (1973). Brain Disconnection and

schizophrenia. British Journal of Psychiatry, 123, 661-662.

Bigelow, L.B., Nasrallah, H.A., Raauscher, F.P. (1983). Corpus callosum

thickness In chronic schizophrenia. British Journal of Psychiatry, 142,

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Bogen, J.E. (1985). The Callosal Syndrome. In Oxford: K.N. Heilman and

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and Post, R.M. (1979). Hemispheric differences in evoked potential

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Butler, S. R. (1979). Interhemispheric relations in schizophrenia. In J.

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mmtmmmmm^nv^r ^n "v^v vr» r» v^ u^ trt.- vr » B^* »^ -«

* w~m i » -^ -* -» -• -». -. -v.

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366

INTRODUCTION

INDIVIDUAL DIFFERENCES IN CEREBRAL LATERALIZATION: HOMEOSTATIC BRAIN

FUNCTIONS OF SCHIZOPHRENICS

Michael Miran & Esta Miran

Strong Memorial Hospital,

University of Rochester,

Medical School,

Rochester, New York,

U.S.A.

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One of the typical experiences of a psychiatrist or psychologist

interviewing a schizophrenic patient is the feeling that if they asked the

right question, they would get a coherent answer. Yet each new question

produces a tangent, a circumstantial response, and a fragmented piece of

fictious perception with the gestalt never completed. After a while the

clinician finds elements of an underlying theme. This elusive and

inconclusive search for the right question and answer is typical of our

scientific study of schizophrenia. Eat n new study and theory gives us yet

another fragment in our search for understanding and ultimately for better

treatment methods. ;fe

Let us consider a more specific example of the communication process

with schizophrenic patients. The following is an excerpt from a therapy

group described by Rokeach (196^), p.53.

"Sir," Leon began, "1 told them my sincere belief but these gentlemen

also stated their sincere belief. 1 don't care to lead their life, and

they have a right to live their own."

Then he turned to Joseph: "Captain Davy Jones, will you fet up there

and talk about your subconscious institution pertaining to your

character? Therefore, do you have any part subconscious reflections

Chat you wondered about pertaining to? Do you have any dreams?

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"I'm Just simply Cod and I work for the cause of the English," Joseph

answered.

"Sir, Jesus Christ, man!" Leon ex^ ..Ij\ed. "I have to disagree with you

on that because England..."

This interaction between two of the throe Christs of Ypsilanti

highlights the difficulties schizophrenics have in communicating with ea>h

other as well as other normal individuals. Schizophrenics' language, as in

this example, is not just grammatically faultv, but it is organized around

different principles and premises than is the case with normal communication

(Abse, 1971).

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367 This ihapter foiuses on the role of intrahcmispherir and interhemispherlf communii-ation in sihizophrenia. Wc propose that the defiilts in

coRnitlor., perreptlon, and i onmuniiat ion that are typical of sihizophrenlrs

can be understood as breakdowns in the internal communication processes

within a homeüstatic brain. This chapter examines the literature on models

of schizophrenia.

THEORIES Öl- LEFT AND RICIH HEMISPHERIC DYSFUNCTION

Flor-Henry (1969) began studying the role of the left hemisphere in

schizophrenia when he noticed that there were many similarities between the

behavior of temporal loSe epileptics and schizophrenics. Further studies

Flor-Henry, Koles, Howarth, & burton (1979); Flor-Henry & Kolc«; (1980); and

Flor-Henry, Koles, & Tucker (1982) provide evidence for the hypothesis» of a

left temporal lobe overactivat ion in schizophrenics.

In their latest work Flor-Henry, Koles & Sussman (1984) and Flor-Henry

& Koles (1S(- .) use sopliisticaued statistical techniques to compare the

performance of the two hemispheres in different populations on verbal and

visual tasks. Flor-Henry finds changes in the Interhemispheric organization

of schizophrenics and other psychotics. The Interhemispheric coherence of

schizophrenics appears to be lowest of all psychotic groups, lie also

highlights that In normals, during verbal and block design asks, there are

partial shifts of latcrallty. He finds that there are anterior posterior

shifts In psychoses.

$

Based on current theories of left- and right-hemisphere organization,

Flor-Henry (1983), Cruzelier and Hammond (1976), Gruzelier and Manchanda

(1982) and Cur (1979), have examined schizophrenia in terms of dominant

(usually left) temporal lobe overactivation, frontal lobe deficits, and

right hemisphere deficits. Cur (1979) used a tachistoscope and reported

that schizophrenics tended to "overactivate their left dysfunctional

hemisphere." Using regional cerebral blood flow (rCBK), Cur, Packer,

Reivich and Weinberger (1978) further supported the hypothesis of left

hemispheric overactivation. In their most recent research Cur, Cur,

Skolnick, Caroff, Obrist, Resnick, and Reivich (1985), using (rCBF), find:

"Schizophrenics, however, had no change in hemispheric asymmetry of flow for

the verbal task and the greater left hemispheric Increase for the spatial

task." Cur's research reflects the role of individual differences and

inconsistent variance in the functioning of both hemispheres during verbal

and visual task perfirmance in schizophrenics. While intra- and

interhenispheric coordination appear to be significant factors in

schizophrenic dysfunction, the exact nature of this lack of coordination

needs further investigation.

Based on data from electrodermal lateral asymmetries, Cruzelier O^^i)

presents evidence for two syndromes in schizophrenia: "A florid syndicme is

coincidental with left-hemispheric overactivation, and a nonflorld syndrome

with right-hemispheric overactivation." Using electroencephalographic

measurement, Cruzelier (1983b) found: "...asymmetrical electro-cortical

activity in both directions in schizophrenia, with right-hemisphere

abnormalities coincidental with the retarded syndrome and left-hemisphere

abnormalities with the more florid one." Gruzelier's evidence suggests that

in schizophrenia there are individual differences in hemispheric

functioning. Gruzelier Interprets the differences as showing that the

florid schizophrenics that respond to treatment are more like normals, ind

that the more chronic schizophrenics appear more like brain damaged

patients.

A series

Brain Research

of papers presented at the European Winter Conferences On

in Chamonix, France highlight many of the issues in EEC

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studies of cerobrjl asymmetries in si hizophreniis. Tuiker (1984) sutj^ests -jfig

that anxiety is a function of dopamine systems. Scrafetinides (19^4)

distinguislies left hemispficrii- dysfunction as associated with thought

disorder symptoms and rißht hemispheric dysfunction with symptoms of

anxiety. He hiphlights that there is a change in the EEC functioning of

schizophrenics in the course of treatment. He also cites several references

which reflect changes in right left patterns in schizophrenia. Etevenon

(1984) makes the point that there are major intrahemispherlc as well as

interhemispheric changes in EEC potentials in schizophrenics.

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Another study by Etevenon, Pidoux, Rioux, Peron-Magnan, Verdeaux and

Dcniker (1979) compare the spectral analysis of the EEC's of two groups of

schizophrenics and a control group. They find both intrahemispheric and

interhemispheric difference between the schizophrenics and the control

groups. Roemer, Shagass, Straumanis and Amadeo (1979) examine auditory and

somatosensory evoked potentials in schizophrenics, nonpsychotlc psychiatric

patients and normals. They find that only the auditory evoked potential

results augmented the previous visual evoked potential evidence of left

hemisphere involvement In schizophrenia. A comparison is made by Toonc,

Cooke & Lader (1979) of electrodermal activity In patients who had

temporal lobe surgery to determine if the same type of responses would be

Identified in temporal lobe patients as are seen in schizophrenics. They

found no differences between the operated and non-operated sides of the body

and between control and temporal lobe patients on electrodermal responding.

The evidence from these researchers fails to establish a single

consistent localized deficit in brain structure. However, their results

highlight a breakdown in feedback, synchronization, and effective

co-processing between the hemispheres in schizophrenics. In addition to the

individual differences discussed above, the literature has a number of

instances of failures to identify left temporal lobe overactivation.

Schneider's (1983) findings contradict this hypothesis: "Unlike normals,

schizophrenics' left-hemisphere function appeared to be inferior to the

right-hemisphere function in the perceptual task". These disparate findings

suggest a process which unpredictably oscillates in its Impact on the right

and left hemispheres. The cause of this oscillating is in the process of

being delineated through ngoing research in this area.

THEORIES OF CORPUS CALLOSUM DYSFUNCTION

Other researchers suggest that schizophrenia is the result of a corpus

callosal dysfunction and enlarged ventricles. Beaumont and Dimond (1973)

used a four screen tachistoscope to project stimuli into the separate

hemispheres of the brain by presenting them into a particular visual field.

Their result showed that schizophrenics performed significantly poorer than

controls in conditions requiring cross-matching of stimuli between

hemispheres; while schizophrenics showed no deficit in separate hemispheric

identifications.

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Iienn & Nasrallah (1962) discuss schizophrenia in terms of brain

disease. Bigelow, Nasrallah & Rauscher (1983) found significantly

thicker corpus callosums in 21 early onset chronic schizophrenics; as

compared to 8 late onset schizophrenics, 13 neurological patients and 14

with other psychiatric diagnosis. Nasrallah, Jacoby, McCalley-U'hitters &

Kuperman (1982) used computed tomography to show that: "55 young men with

chronic schizophrenia and 27 ag^- and sex-matched control subjects showed a

significantly higher ventricle-brain ratio (VBR) in the patients with

chronic schizophrenia." Nasrallah, McCal ley-Whitters, & Jacoby (19b2) found

cignificantly enlarged ventricles in manic and schizophrenic groups, as

compared to normal controls. "Cerebral atropny was more frequent in

schizophrenia, while cerebellar atrophy was more frequent in mania ...

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Cerebral «trophy was not associated with ventricular enlargeircnt In either

disorder." Studies of corpus callosal dysfunction In schizophrenia first

suggested that there were enlarged ventricles and a thickened corpus

callosum. Further Investigation Is providing more specific evidence

supporting or refuting structural varianrr between schizophrenics and normal

controls.

Dimond, Scammell, Pryce, Huws & Gray (1980) used Intermanual and crosslateral transfer to study split-brain symptoms in chronic schizophrenia.

Patients were compared to a mixed group of depressed and anxious patients.

The results showed a failure of interhemlspheric transfer in performance in

schizophrenic patients. Researchers suggest that the deficit is a "noisy

channel" that produces the failure in the transmission of information. The

researchers stress Chat performance is inconsistent, i.e., that infortratlon

transfer is "inefficient" rather than "disconnecter." Jaynes (1976) makes a

similar point highlighting that normal people change hemispheres during a

task at a rate of once per minute while schizophrenics appear to change at a

rate of once in 6 minutes. Many studies suggest a difficulty in

interhemipheric information processing in schizophrenia.

Other studies have examined right and left hemisphere functioning in

schizoplireuics. Tress, Caudrey & Mehta (1983) did an evoked potential

study using tactile evoked potentials. They find differences between

schizophrenics and controls. The schizophrenics did not show a

"lateralizatton effect" suggesting that schizophrenics were not receiving

tactile evoked potentials transmitted across the corpus callosum.

Walker, Hoppes & Emory (1981) have reinterpreted earlier studies as

reflecting a deficit interhemlspheric transfer rather than left hemisphere

over-activation. Magaro and Page (1983) specifically postulated an

interhemlspheric deficit in schizophrenia. The findings of their study

supported a left hemisphere deficit not an interhemlspheric deficit.

Cazzaniga (1983) presented data on cerebral asymmetries in split brain

patient with right-hemisphere language. The patient had his corpus callosum

severed to control epileptic seizures. The patient functioned normally in

his everyday life. As he functioned in his dally routine, information was

being fed separately and simultaneously to both hemispheres. In the

experimental condition, stimuli were simultaneously presented to the left

and then the right hemisphere of the brain. Specifically, the stimuli

consisted of a story: "MARY ANN MAY COML VISIT INTO THE TOWNSHIP TODAY".

Stimuli to the left hemisphere sequenced alternately. "MARY MAY VISIT THE

SHIP." Stimuli to the right hemisphere sequenced alternately: "ANN COME

INTO TOWN TODAY." Thf> brain then had to integrate this Information without

the help of the corpus callosum. The patient's response was: "Ma ought to

come into town today to visit Mary Ann on the boat." In an attempt to

Integrate the stimuli, the patient became confused and confabulated a story

similar, but not necessarily identical, to what we might interpret as

schizophrenic responses.

Considering the evidence for callosal dysfunction from a homeostatic

brain model, it appears that the corpus callosum plays a role in generation

of schizophrenic symptoms. However, the evidence suggests a dynamic i.e.

information flow deficit. Further investigations are needed in order to

draw specific conclusions as to the relationship between structural and

biochemical variations in the corpus callosum and deviant behavior.

FRONTAL LOBE DYSFUNCTION

A cerebral blood flow study by Ingvar and Franzcn (1974) identified

schizophrenics as having hypofrontality and lower levels of frontal lobe

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aruusal. A later study by Cur, Skolniik, Cur, Carotf, Relper, Obrist, 370

Younkin & Reivich (1983) has shown that when a verbal or visual task is

involved these eftects diminish and are replaced by lateral izod di t teremes.

Sheppard, Cruzelier, Mamhanda, Hirsch, Wise, Franckowiak & Jones

(1983) find no hypoactivity in the frontal lobes of schizophrenics. They

find evidence that metabolism within the basal ganglia is reduced in

schizophrenics. They state: "suppport was obtained for the hypothesis that

an abnormality in hemispnere laterality may underlie schizophrenic illness."

Although (rCBF) studies have produced negative findings on frontal

lobe dysfunction, the homeostatic brain model suggests that the frontal

lobes may be involved in producing schizophrenic symptoms. First, the

dopamine system which is influenced by psychotropic medication is heavily

represented in frontal lobe areas. Secondly, the frontal lobes have

interconnections with many other areas of the brain via ascending and

descending tracts. We suspect that at least some of these anterior

posterior tracts are involved in the generation of schizophrenic symptoms

such as slowed and inaccurate responses. The use of leucotomy and lobotomy

may have acnieved results because they interrupted dysfunctional circuits

involved in psychotic behavior. However, the surgical technique is so

unselective that it cuts many functional channels and disrupts many

behaviors which are not "psychotic".

COMPARISONS OF SCHIZOPHRENIC AND BRAIN INJURED PATIENTS

Davison and Bagley (1969) review many schizophrenic-like organic

conditions. They provide a model of organic brain disorders in the

aetiology of schizophrenic-like symptoms. The model they use to discuss the

aetiology of schizophrenia includes physical stress, social stress,

psychological stress, genetic predisposition, alcohol, amphetamines,

Parkinsionianism, and narcolepsy. These factors contribute to biochemical

changes (along with organic brain disorder) which lead to specific brain

dysfunction and to schizophrenic experience and behavior.

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Thcy cite parallels between schizophrenics' behavior and various types

of brain damage from different aetiological entitles. These studies do not

provide evidence of any one specific site in the brain which produces

schizophrenia. Rather they suggest many types of brain damage result in

schizophrenic-like symptoms. In terms of schizophrenic symptoms, areas like

the temporal lobes and diencephalon seem particularly important.

Cruzelier (1983a, p.276) discusses Taylor's (1975) study of temporal

lobe epileptic patients. He cites evidence for and against "alien tissue"

I.e. small tumors, hematomat , and focal dysphasias, as a basis for

psychosis. His conclusion is: "Civen that many alien tissue lesions occur

at early stages of brain development, the relatively late occurrence of

psychosis may involve the breakdown of compensatory mechanisms." Flor-Hcnry

(1983) makes the connection between the symptoms of schizophrenia and left

temporal lobe epilepsy.

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Many schizophrenics have behavioral deficits typical of brain damaged

people. However, their deficits are not reliably associated witii a speciflc

location in the brain or aetiology. Further, neuropsychological

investigation into schizophrenia may provide more definitive brain behavior

relationships.

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Many schizophrenics have behavioral deficits typical of brain damaged

people. However, their deficits arc not reliably associated with a specific

location in the brain or aetiology, further, neuropsychological

investigation into schizophrenia may provide more definitive brain behavior

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DEFICITS IN PARIETAL AND OCCIPITAL FUNCTIONING

371

Given that many of the key symptoms of schizophrenia involve gross

perceptual defects such as halluiinations and body schema distortions, it is

reasonable to examine the fidence of rear brain involvement. Erwin and

Rosenbaum (197^) did a study comparing schizophrenics and patients with

known parietal lobe lesions. Tiey found that schizophrenics and parietal

lobe damaged patients had similar impairments in weight discrimination when

compared with controls. The parietal lobe damaged patients showed a deficit

in tactile sensory perception. Schizophrenics showed disturbances in body

image. Tiiey Interpret these findings as reflecting different types of

neurological dysfunctions.

Despite difficulties in controlling for attentional and cognitive

artifacts, most of the studies of visual and auditory functions in

schizophrenics do not find a difference between schizophrenics and normals

in the functioning of their visual and auditory systems. However, when

tasks become more complex and generalization or inhibition of responses

becomes part of the task, then schizophrenics have significant problems.

Polyakov (1969) wrote an article examining the problem of perceptual

and cognitive deficits in schizophrenia. He describes the breakdown in

schizophrenics' cognitive functioning in terns of a scries of links with a

fundamental (biochemical) process being the initial link in the series. He

compared schizophrenics to a control group of sixty normals on a series of

experimental tasks. He studied generalization and comparison using an

experimental method based on the work of Meleshko (1965). The first series

of problers consisted of asking the patients to make comparisons of 12 pairs

of objects. In the second experiment 39 objects pictured on cards were

shown to the subjects, and they were asked to divide the cards into groups.

Polyakov (1969) finds: "...if their logical, operational schema of activity

is preserved, schizophrenics are able to abstract any attribute and on the

basis of the attribute make a generalization as well as the normal person."

Schizophrenics auditory perception was also studied by Polyakov (196°).

A "muffled word" was used as the target stimulus. They used "strong,"

"medium," and "weak" noise levels; and measured the percentage of correct

identifications. Under the strong noise condition there was little

difference between normals and schizophrenics, because the stimulus was

overwhelmed by the noise. In the weak noise group the schizophrenics scored

only slightly worse than normals. On the intermediate level of difficulty

Schizophrenics were best at perceiving unlikely endings and normals were

best at perceiving likely endings.

A similar study was conducted of visual perception among schizophrenics

(Bogandov, 1965). Subjects were presented with blurred pictures of objects

which they were asked to identify. In this study schizophrenu s had the

highest thresholds for identifications when common standard images were

presented. On unusual images schizophrenics h.-^d lower thresholds i.e.

faster recognition than normals.

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Investigations by Cornblatt & Erlenmeyer-Kimling (1985) show global

attentional deviance is a marker in children at risk of schizophrenia.

Knight, Elliott, & Freedman (19P5) study backward masking of information in

schizophrenics. They find "the perceptual-organization-deficit hypothesis

best accounts for the apparent disruptions in poor premorbids' short tern

visual memory."

Two recent studies illustrate the difficulties doing neuropsychological

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372

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research with sihizophrenirs. Knight Pt al. (19H5) examined short term

visual memory functjoninj.' with cognitive and backward masks. They find

significant differences between ^ood and poor premorbid schizophrenics.

poor premorbid schizophrenics treated both cognitive and backward masks

equivalently and showed deficits. The results are discussed in terms of a

theory of visual-input dysfunction in schizophrenia. In a second study,

again uslnp a visual information processing task, Knight, Youard and Wools

(1985) report a general difference between schizophrenics and normals but no

specific differences in various conditions. The results are discussed as

reflecting a generalized cognitive disturbance. They relate the level of

difficulty on particular tasks to the amount of capacity required to

complete processing. Knight et al. (1985) discuss the difference between

their study and others in the field.

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The point that we would emphasize is the contradiction between findings

on one hand of a specific visual Information processing deficit; and on the

other hand, broader cognitive processing deficits. The schizophrenia

literature has many of these contradictions. The finding of both ipeclfic

deficits and general information processing difficulties may reflect the

multiple levels of dysfunction characteristic of schizophrenics. W° believe

this occurs because of the malfunctioning of homeostatic processes within

schizophrenics' brains.

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DEFICITS IN NEUROPSYCHOLOGICAL FUNCTIONING

Current studies discuss neuropsychological test results of

schizophrenics (Green & Walker, 1985; Gruzelier, 1983a; Lewis, 1979).

These studies find that schizophrenics do not have the specific deficits

typical of lateralized stroke or head injury patients; yet their test

responses are different than "normals''. Lewis (1979) found that

schizophrenics tend to be slower than normals on many tasks. As discussed

by Gruzelier (1983a), schizophrenics have problems with both right and lett

hemisphere tasks which may reflect dynamic processing problems rather than

the type of structural neuropsychological problems usually identified via

neuropsychological test batteries.

Lewis (1^79) compares various levels of chronicity and length of

hospitalization. Lewis finds that these variables do not, in and of

themselves, account for most of the variance in the deficits of

schizophrenic;' behaviors. In her study, s»hizophrenics had difficulties on

Reaction Time, Receptive Speech, Expressive Speech, Writing, Arithmetic,

Pathognomic and Intelligence Subscales of the Luria Nebraska

Neuropsychological Battery. She also discusses the role of deficits on the

Motor Rhythm, Receptive Speech, Arithmetic, and Memory Subtests. Another

study (Purisch, Golden & Hammeke, 1983) used the Luria Nebraska to

discriminate between schizophrenic and brain injured patients. A similar

neuropsychological study by Selin and Gottschalk (1983) compared

schizophrenics, depressives and conduct disorders. They found that

schizophrenics have deficits in rhythm, perception, abstraction, and on EEC

measures•

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Green and Walker (1985) compare schizophrenics with positive and

negative symptoms on a battery of neuropsychological tests. They summarize

their findings as follows: "The central finding from this study is that

positive and negative symptoms are associated with diffe-ent patterns of

performance deficit on neuropsychological tests. Negative symptoms are

associated wit'., poorer performance on tests that measure visual-motor and

visual-spatial skills. The positive symptoms, on the other hand, are

related to deficits on tests that involve short term verbal memory. These

findings are not consistent with the notion that negative symptoms are

uniquely associated with generalized cognitive impairment. Instead, it

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appears that the situation is mure complex and that both types of symptoms

are associated with characteristic performance deficits (Green and Walker,

1985 p.A66)." Cruzelier (1983) finds electrodermal ditferences in patients

with positive and negative symptoms. Their symptom patterns are consistent

with coRnitlve deficits discussed by Green and Walker (1983).

Holden, '.>.>: Stock & Itil (1985) study neuropsychological deficits in

chronic treatment resistant schizophrenics. They find that therapy

resistance was positively correlated with scores for organic impairment on

the Modified Word Learning Test. They find positive correlations between

their neuropsychological measures. They also collect EEG data. They find

that their treatment resistant patients had a greater incidence of low

frequency bands (3-8 Hz bands). They find that the Modified Word Learning

Test was the most useful tool for measuring organic deterioration in their

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SCHIZOPHRENIA: THE BREAKDOWN OF THE HOMEOSTATIC BRAIN vi^<-vj

Brain Systems: Micro-, Meso- , and Macrosystf-ns "'V"v'V'S

In the human brain, information is coded and processed as a hierarchy

of homeostatic systems from neurons to whole brain functions: from micro- Co

meso- to macrosystems. Evidence suggests that there are microsystems

breakdowns in schizophrenic brain functioning. Microsystems consist of

neurons and their immediate neural networks. Schizophrenic behavior

patterns include generating stimuli which do not correspond to external

stimuli i.e. hallucinations. This may reflect random and unsynchronized • . , ^ ^ *

firing of neurons or groups of cells in the brain. VvV

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Mesosystems consist of specialized cell groups organized into localized ^/^/•'r

areas such as the occipital cortex, perceptual, and motor systems, and each

hemisphere. These localized areas perform a specific function. Evidence

from EEG studies (Klor-Hcnry, Koles & Sussman, 196A; Flor-Henry & Koles,

1984; and Koukkou, 1985); (rCBF) stulies (Gur, 1979); and behavioral studies

(Lewis, 1979) suggest that in schizophrenia there may be a breakdown in »•V»>^,>jj

infon. ation processing in communication between these localized areas. MA'SV«.!

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In a normal brain, a stimulus is going to be attenuated as a result of

lateral inhibition. In a schizophrenic's brain the stimulus is not

modulated. Repetitive cycles are established which lead to -.epeatinR

behavior without change. This can be seen, for example, whjn a patient '' /"-/'s''

rocks and rocks all day. This involves the malfunctioning of information V'/'vS«

feedback loops and is seen in perceptual, motor, and cognitive systems. v'r•!'•l'^',

Processing time is slow and there are many errors. Schizophrenics show •/r/W

individual variability in their functioning.

The whole brain functions as a macrosystem. This includes the S£vJ,*»'*".v

anterior-posterior, right-left, and whole brain systems. The normal brain

has a relative synchronicity of EEG which varies depending on the task and

reciprocal inhibition of right and left sides of the brain. This helps the

individual remain focused on a specific task and utilizes the brain

effectively to perform that task. In schizophrenia, the individual does not

stay focused. Tangential information is processed as if it were the main N'S'N'»'.

thought. :-.^--:.

Schizophrenic behavior and .'aterality tasks

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The homeostatic brain model can be used to evaluate the behavior of '/W^v'

schizophrenics on laterality tasks. The search for a specific locus of •i's^

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Schizophrenic deficit is confounded with the tasks used to study it, and

more importantly with the endogenous "tasks" that schizophrenics themselves

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374

use routinely. In many studies, Morstyn, Duffy 4 McCarley (19b3); Shnw,

Colter & Resek (1983); Bernstein, Taylor, Starkey, Juni, Lubowsky & Paley

(1981); Abrams & Taylor (198U); and Hirarnatsu, Kameyana, Saitoh, Niwa,

Rytnar & Itoh (198A) there is a conflict between the task demands of the

experiment, and covert verbal and visual activities of schizophrenic

patients i.e. the patients are generatinp their own stimuli. For example.

In resting EEC and (rCBF) studies schizophrenics often show left hemisphere

arousal. Such a phenomena could occur if schizophrenics were actively

involved in repetitive ideas and covert speech. The problem with laterality

tests of schizophrenics is that the Internal stimuli to themselves, conflicts

with the external stimuli of the experiment. The internal information

processing of schizophrenics interferes with the experimental tasks, and

produce anomalous results.

One study explores the cortical and subcortical arousal processes in

schizophrenia, and they (Pfefferbaum, Horvath, Roth, Tinklenburg &

Kopell, 1980) find deficits in cortical but not subcort'eal arousal in

schizophrenics. Other studies such as Siegel, Waldo, Mizner, Adler &

Freedman (1984) have studied sensory gate keeping and inhibition in

schizophrenics. Schizophrenics were Impaired in their ability to inhibit

and had abnormalities in wave length and power. An EEC telemetry study is

particularly interesting. Stevens and Livermore (1982) find slow activity

and le&s alpha activity In schizophrenics than normal controls. During

periods of abnormal behavior, they showed the "Ramp Spectra" often associated

with epileptic spikes. No epileptic spikes were observed.

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There is a dichotomy between what schizophrenics think and do, and

external reality. In addition to interhemispheric dysfunction, Etevenon

(198A) cites the role of intrahemispheric dysfunction. Thus, a stimulus

presented to one hemisphere is not effectively coded i.e. a stimulus may be

inhibited, "lost," transferred, or greatly amplified. The inter- and

intrahemispheric communication problems led to some of the more bizarre

behavior of schizophrenics. Stimuli generated within the brain are treated

as if they are external realities, and external realities are not responded

to as such. The breakdown contributes further to changes in body

perception, confusion, and disorganization of thinking.

Individual differences in the course of the schizophrenia process

To gain a better understanding of the progression of schizophrenia from

acute to chronic states and lateralizatlon of function, we can consider a

sample case and the major charges in his life. In the classic case of Dr.

Daniel Paul Schrcber, we see an individual who hac' a relatively good

premorbid adjustment, some family history of mental illness, and a previous

hypochondriacal episode from which he recovered successfully. During a

period of stress, Schreber becomes highly anxious, hypersensitive tu stimuli,

withdraws socially, and develops increasingly bizarre and idiosyncratlc

ideas. The symptoms include sleeplessness and hypochondriacal behavior.

Following this Initial stage of high anxiety and perceptual distortion, his

bizarre experiences and idiosyncratic ideas become organized into a

delusional system. Aftei many years of hospitalizatlon, his symptoms

subside to a point where he can again be released to the community (Freud,

1968).

Serafetlniaes (1984) discusses the advantages of examining EEC findings

as a "temporary disequilibrium, with an onset, course and resolution, either

towards a normative pattern or towards a pathological one..." If we

translate Dr. Schreber's experiences into patterns of hemispheric

activation, we would see the following changes in terms of onset, course,

and resolution. In terms of onset wc would see very high levels of

activation in one or both hemispheres. During the course of his psychosis,

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wc would expect to find poor interhemisplierlc »oordinat Ion. In the residual

stage wc would expect lowered arousal and a predominance of right hemisphere 375

oriented behaviors.

Several studies find behavioral and EEC changes during the course of a

schizophrenic process (Frith, Stevens, Joliiistone, & Crow, 1982; lacono,

1982; Koukkou, 1985; Rlzzo, Albani, Spadaro 2, Moroculti, 1983; Rizzo,

Spadaro, Albani, & Moroculti, 1984). The findings in these studies are that

acute schizophrenics who remit show more normalized EEC's than

schizophrenics who remain symptomatic. "Chronic" schizophrenics' EEC's

continue to show a variety of differences from normal and remitted

schizophrenics.

The main point about this analysis is that it reflects a dynamic

process of brain behaviour relationships as the individual experiences

different levels of dysfunctional adaptation. The course of the illness, as

seen in both EEC (Scrafetinides 198A) and factor analytic studies (Carr,

1983), reveals that it is difficult to Isolate a specific localized deficit

related to schizophrenic behavior. What you have is a progressive loss of

the person's overall ability to function, and then a regaining of functions.

Schizophrenia is a dynamic process with levels of dysfunction, and with an

onset, course and resolution. The dynamic processes should be seen to a

lesser extent in individuals at risk for schizophrenia than In

schizophrenics. Children of schizophrenics, who are at risk of

schizophrenia, show some of the same EEC and ncuropsychological functions

that are seen in schizophrenics (Prentky, Salznan, & Klein, 1981).

Likewise, schizotypal people show some of the same characteristics but to a

lesser degree. These people have some characteristics of schizophrenics,

but do not develop schizophrenia (Braff, 1981). Without the intense

stressert and subsequent stages of deterioration, these people do not

exhibit schizophrenic symptoms. Since children at risk show some

similarities to schizophrenics, they provide the beginning and important

stages in the development of schizophrenia. Further study of these children

will add to the body of knowledge on predictors of schizophrenia. This then

can be applied to early intervention and treatment.

Implications for assessment of schizophrenics

Excellent research is being done using EEC and brain imaging, yet this

research has not provided the field with practical methods to assess

schizophrenic patients. Our high technology imaging techniques provide new

information about hemispheric functioning, but the data is not easily

translatable into categories of schizophrenia associated with specific

bcain-behavior dysfunction. There is a schism between factorial validity or

other forms of validity, and clinical judgment (Cromwell, 1983). To

increase the validity of clinical assessment, what is needed is a way to

apply the results of the EEC and brain imaging studies to assessment of

schizophrenia.

One area where clinical assessment and research findings have converged

is the study of positive and negative symptoms of schizophrenia. Cromwell

(1983) and Holden et al. (1985) point out the significance of positive and

negative symtoms for understanding and treating schizophrenia. Type I,

positive symptoms, appear to be identified with left hemisphere

overactivation. The patients have hallucinations, delusions, and thought

disorders. Their behavior is bizarre, disturbed, and sometimes dangerous.

Type II, negative symptoms, appear to be associated with right hemisphere or

bilateral activation. The patients become passive, and their affect

flattens. Behaviorally th»y stay at home, fail at school or their jobs, and

take on virtually no household responsibilities. This diagnostic categorization has direct implications for treatment, management, medication, and

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prognosis. 376

Based on a homeostatir model, rliniial assessment of schizophrenia can

be made more iccurattf and applicable to treatment. The way to do this is to

develop assessment instruments whirh examine feedback loops within the

brain. It is possible to Identify subtypes of schizophrenia in terms of

systems functions and dysfunctions: 1. Arousal homeostasis; 2. Motor and

perceptual systems, especially proprioceptive feedback; 3. Interhemispheric

balance and reciprocity; 4. Anterior-posterior feedback; 5. Corticalsubcortical feedback systems; and, 6. Whole brain functioning.

The evidence of slowing of responses in schizophrenia sußgests another

assessment method. Schizophrenia can be examined in terms of the speed

(reaction time) and accuracy of information processing. Neuropsychological

tasks to assess the roles of inhibition/excitation and feedback within brain

areas need to be developed. Much of the future focus in assessment should

be on dynamic processes. This can be done by improving our existing: (a)

neuropsychological techniques;(b) EEC techniques; (c) brain imaging

techniques; (d) clinical Interview and assessment techniques.

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Implications for treatment of schizophrenia

In light of the above evidence let us reconsider our treatment of

schizophrenics. Holden et al. (1985) found that: "some chronic

schizophrenic patients do have neuropsychological and neurophysiological

profiles consistent with organic brain dysfunction." If schizophrenics, and

especially treatment resistant schizophrenics, have organic brain

dysfunction, then it makes sense to treat them like brain damaged | ople.

Yozawitz, Charters, Iskander & Reiter (1985) describe a system of

assessment and rehabilitation of psychiatric patients with

neuropsychological deficits. They combined cognitive habilitation

techniques with traditional activities of daily living (ADL) skills. The

patients showed pest treatment improvement on Performance I.Q., the

Similarities, Digit Span, and Block Design Wechsler subtests, and the

Arithmetic Subtest of the Wide Range Achievement test. Control subjects,

only receiving the ADL program, improved on the Wechsler Information Subtest

only. Their results can be interpreted as indicating that

neuropsychological interventions will be effective with schizophrenic

patients.

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There is an example of an intensive treatment program for brain injured

adults which may provide a model of possible treatment programs for

schizophrenics. Hooflen & Ben-Ylshay (1982) and Ben-Ylshay, Rattok,

Lakln, Plasetsky, Ross, Sliver, Zlde & Ezrachl (1985) present a description

of a treatment program for brain Injured adults. Treatment Includes: " (a)

Intensity (dally treatment), (b) communallty (emphasis on group-therapy) and

(c) cognitive remediation (Improvement of cognitive functions by special

techniques of learning). Treatment Is evolved In three stages: assessment

(two weeks); Intensive treatment (nine months); vocational experience

(unlimited duration). According to follow-up data, about 80X of the

patients achieve positive rehabllltatlonal results." Considering that

schizophrenics appear to be brain Injured, this type of Intensive program

may help them recover their functioning. We are not Ignoring nor minimising

the substantial differences between brain damaged and schizophrenic patients

In premorbldlty, history, course of Illness, life experience, and behavior.

Rather, we are emphasizing the potential utility of cognitive retraining and

psychosocial rehabilitation.

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A second treatment technique derived from the hon.eostatic brain model

Is to tralr schizophrenic patients to Improve the functioning of feedback '..

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loops within their own brains; and thereby imrease their ability to 37

modulate, inhibit, and roordinate their behavior. Several experimental

treatments are possible. Using biofeedbaik teehniquei iueh as those used in

studies of meditation and EEC (Kamiya, 1969), sihizoplirenies could be

reinforced for increasing the inter- and intrahemisnheric coherence of their

EEC's.

177 &&S

Schneider and Pope (I9»2) did a study conditioning EEC changes in

schizophrenics through biofeedback. Using biofeedback, they trained

schizophrenics to "mimic the EEC changes that have been shown to occur with

nejroleptic induced clinical Improvement." A related approach is to help

reduce the levels of psychotropic medication with side effects such as

Tardive Dyskinesia. Biofeedback techniques could be used to train the

patients to use other techniques to obtain the effect of the drug. The

introduction of biofeedback should produce the therapeutic effect, while

decreasing the level of dm;.

There is evidence from innovative programs that schizophrenic are able

Co revive feedback loops and regain competent daily functioning and a sense

of self-worth (Katz and Katz, 1983). They use art to help recreate or

revive feedback systems in the brain. Their treatment program has focused

on the self-esteem and living skills of the artist/patients. The Katzs'

suggest that the patients are developing new brain behavior relationships by

expressing themselves through their ait work.

CONCLUSION

Our conclusions are as follows:

1. The two hemispheres play a role in production of schizophrenic symptoms

and states, however, the situation is not as simple as that a single

dominant hemisphere is over or under active. The lateralization problems in

schizophrenia reflect a breakdown in reciprocity, synchronicity, inhibition

and coherence between the two hemispheres.

2. Schizophrenia is a multileveled breakdown in the functioning of the

brain. Specific neural functions and neural transmitter mediated functions

are disrupted (best understood in the dopamine circuits). There is a

breakdown in what Walsh (1981) calls "arousal homesotasis" involving both

cortical and mid-brain areas. Multiple perceptual, motor, and cognitive

systems are impaired. The particular systems involved show wide individual

differences. Interhemispheric and whole brain cognitive functions are

impaired.

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3. Schizophrenia is a breakdown in intra- and interhemispheric feedback

systems. This breakdown has periods of synchronicity and functioning, and

periods of dissynchronicity and dysfunction. The process is similar to the

electrical disorganization which occurs in an epileptic seizure. Yet

schizophrenics do not have as dramatic behavioral and EEC abnormalities as

do epileptics. Their behavioral and EEC functions are disturbed compared to

normals, but do not reflect the specific spike and wave and convulsions of

epilepsy.

4. The acute phases of schizophrenia have the potential for patients to

return to normal or near normal states. Continuation of schizophrenic

states results in functional and neuropsychological deterioration similar to

that seen in other types of brain damage.

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5. The assessment of schizophrenia is undergoing a transition.

Neurophysiological, neuropsychological and familial studies suggest

revaluation of the symptom oriented classification of schizophrenics. It is

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recomniended that the classitication of schizophrenics be based on the

feedback systems within the brain which are impaired. 378

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6. The -outlook for treatment of schizophrenics may be improving. In

addition to biochemical methods, intensive neuropsychological intervention,

EEC, and Bioleedback techniques can be used to at least reduce som»' of the

severity of schizophrenic symptoms. The groups of schizophrenics most

resistant to current treatments appear to represent the groups most in need

of neuropsychological intervention.

7. Research on the neuropsychology and neurophysiology of schizophrenia

should focus on homeostatic processes and feedback processes within the

brain.

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382

CEREBRAL LATERALITY AND PSYCHOPATHOLOGICAL DISORDERS

« . • . ^_ V

E. A. Serafetlnides,

Veterans Administration Medical Center

West Los Angeles, (Brentwood Division),

and The Department of Psychiatry and

The Brain Research Institute,

UCLA School of Medicine,

Lo Angeles, California, USA.

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INTRODUCTION

In a previous report (Serafetlnides, 1965), I presented evidence

suggesting not only a marked presence of aggressive behavior in, mostly

young, male temporal lobe epileptics (TLE), but also a left dominant

hemisphere focus for the majority of them. Indeed, looking at the results

again, It can be seen that out of 100 TLE cases, 36 were diagnosed as

aggressive, 25 of which had a left (L) focus vs. only 11 with a right (R)

focus. The 64 non-aggressive TLE cases were evenly split between the two

hemispheres (33 R and 31 LTL focus respectively). This difference is

significant at the p < .05 level. Discussing tne implications, then, I

stressed the significance of the dominant hemisphere for learning, linking

defect of the latter with frustration in coping, and aggression as a

maladjusted form thereof.

THE EVIDENCE

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Indirect supportive evidence for this argument is provided by Camp

(1977) and Camp, Zimet, van Dornick and Dahlem (1977) who found indeed that

verbal abilities are impaired in aggressive boys. The children studied had

an IQ of 90 and above. A few verbal tests were found to be significantly

inferior in aggressive boys as compared to normals, but much mjre

importantly, what differentiated the two groups was what the authors termed

verbal medlational ability. The hypothesis Is made that "both learning and

behavior problems in aggressive boys may be symptomatic of an Ineffective

linguistic control system". These boys are characterized by a rapid

response style and when speculating about control, and thus dyscontrol

mechanisms, one ought to consider that, as will be touched upon later, the

dominant hemisphere for speech might be involved in "pacing" response styles

through mechanisms similar to those it employs in "pacing" production of

speech.

Additional such evidence is presented by Krynlcki (1978). In two of

three male adolescent groups that he studied, 7 with a history of multiple

assaultive incidents and 6 with an organic brain syndrome, the results of

neuropsychologlcal tests and of EEC examination were indistinguishable,

showing poorer performance on the tests and paroxysmal type EEC

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abnormalities compared to a third group of 8 adolescents with an antisocial

behavior pattern but without assaultive Incidents. The nonassaultlve

patients had also a better established hand dominance, fewer perserveratlon

errors and a better verbal memory. It Is Interesting that the EEC

abnormalities were of a frontal distribution which the author considered as

evidence of fronto-temporal limblc connections.

A negative report was published by Hare (1979). Tachlstoscoplc letter

recognition tasks administered to the right and left visual fields of 55

prison Inmates, divided according to psychopathy ratings (high, medium, low)

failed to differentiate among the groups thus tested. Sandel and Alcorn

(1980) also failed to discern any laterallzatlon In 25 antisocial patients

by employing the conjugate lateral eye movement Index. In contrast,

however, to these reports, other investigators have reported on the

following laterallzlng evidence. Prltchard, Lombroso and Mclntyre (1980),

reported on 56 temporal lobe epileptic patients, among whom 36% were found

to have developed "psychological complications". Psychopathology, including

antisocial manifestations, was seen more often In patients with left

temporal lobe spike foci (43Z) and In males (A2Z) but the authors stated

that these trends did not attain statistical significance. Yeudall, ErommAuch and Davles (1982), examined the possibility of neuropsychologlcal

Impairment In 99 consecutively admitted Juvenile delinquents (64 males and

35 females). By using the Halstead-Reltan Battery and 12 additional tests

and comparing the results to a control group's findings (47 Ss) they

concluded that delinquents presented more abnormal profiles and their

pattern of deficits implicated the right or non-dominant hemisphere.

However, further analysis disclosed that the delinquent group In question

Included a significantly lower than average number of violent adolescents

and/or a correspondingly higher percentage of delinquents with depression.

The neuropsychological state of adolescent delinquent boys was also

Investigated by Wolff, Waber, Bauermeister, Cohen and Ferber (1984). In

contrast to controls the delinquent boys showed Impairment on all language

measures and, by implication, impairment of the dominant or left hemisphere.

It is Interesting to Juxtapose to this report the findings by Welntraub and

Mesulam (1983) on 14 patients with neurologic and neuropsychologic signs

consistent with right-hemisphere dysfunction. These patients were

characterized by shyness, vlsuospatlal disturbances, and Inadequate

parallngulstlc communicative abilities which Impaired their Interpersonal

skills. Although of average Intelligence, they were poor In arithmetic and

finally despite their difficulty in conveying their feelings (avoiding eye

contact and lacking the gestures and prosody that normally accompany speech)

there was no evidence that they were unable to experience affect. Hare and

McPherson (1984) employing a verbal dlchotlc listening task on 146 male

prison Inmates and control group of 159 male non-criminals found that

psychopathic prisoners (according to DSM-III and other criteria) exhibited a

less laterallsed performance than the other groups. The authors raised the

possibility that language processes are not strongly laterallzed In

psychopaths.

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Returning to epileptic patients, in an attempt to determine the

relationship between unilateral temporal lobe epileptic focus and behavior,

Bear and Fedio (1977) analyzed quantitatively 18 Inteiictal traits selected

on the basis of prior reports and pilot tests. The samples consisted of 27

epileptics (15 RTL and 12 LTL) and 2 control groups, one of 12 normal adults

and one of 9 patients with neuromuscular disorders. In terms of laterality,

RTL epileptics reported more elation, LTL epileptics more anger, pararola,

and dependence. Observers rated the RTL group as higher In terms of affect

and the LTL group as higher in terms of paranoia. In reinterpreting these

findings In the light of my own experience I would formulate the differences

between R and LTL epileptics thus: In LTL epileptics, aggression can be

teen as either a variation of the catastrophic reaction or an expression of

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the paranoid trait; In RTL epileptics, aggression can be seen as an

occasional manifestation of a basically unstable affect.

It teems, thus, on the evidence presented so far, that >j>

psychopathological disorders of an assaultive type are associated with

language or communication difficulties and thus by implication with

dysfunction of the left or dominant hemisphere. The e-iployment of %

alternative coping strategies, relying more on non-verbal as well as vW'v

"illogical" mechanisms, are hypothetical explanations which might be worth Ä^

considering in discussing the origins of violent behavior in psychopathic >^J\Vv

disorder». XN^V

SPECULATIONS AND HYPOTHESES

The evidence for the role that the dominant hemisphere for speech plays

in the control of aggressive Impulses cannot be overlooked. Whether this

role depends largely on the neocortlcal elements involved in learning,

especially verbal learning, or is drawn from the related subcortical

elements, is an area needing further research. Certainly the importance of

the amygdala in rage reactions cannot be denied nor the role of hippocampus

In learned behavior. The question that could be asked is whether the limbic

system of the dominant hemisphere for speech has a dominant role in the

generation or control of aggression, either in connection with other aspects

of learning, or, independently.

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In previous publications I discussed the three principles >*vV.vj

characterising cerebral dysfunction, namely those of deficit, disinhibition LMN'*^

and adaptation (Serafetinides, 1980; 1981; 198A). I also alluded to various

hemispheric specific assumed impairments implicit in such conditions, 1'S^v'

namely, impairment not only of speech but also of time-sequencing and pacing c*it/

of mental events in relation to dominant hemisphere dysfunction, paralleled, ^

in non-dominant hemisphere dysfunction, with impairment of the spatial '.•-V-V-V-'

"framing" of mental events. The resulting behavioral pattern, in the case '"Wv""^

of dominant hemisphere disorders, is thus postulated to be characterized by Jv!VvV

an explosive simultaneity of mental output, stemming from the impaired

ability to "hold" or "defer" the expression of such output, as would

normally be the case. In non-dominant hemisphere disorders an analogous

pattern is postulated, i.e., that of mood implosion, resulting from the

Inability to maintain a stable perspective of the self vis a vis the

Internal or external environment, as perceived.

.

In epilepsy (Serafetinides, 1980) such a formulation has to accoroodate

the phenomena associated with seizure discharges and their significance in

terms of stimulation or hyperconnection and inhibition or disconnection.

Thus, somatosensory symptoms and signs, such as the ones present in

convulsions, can be considered as phenomena of the first type (stimulation- "•"

hyperconnection) whereas aphasia and cognitive or amnestic symptoms, can be

considered as phenomena of the second type (inhibition or disconnection).

Furthermore, the organism might show in the end a host of other phenomena as

well, which as they tend to represent its overall response to functions

perceived as having been interfered with, can be understood as (mal)

adaptation or compensation phenomena depending on the case and the

circumstances. These can include aggression, paranoid thinking,

catastrophic reaction, anxiety, tension, g-andiositv and depression. As the

terms imply, such (mal) adaptation or compensation phenomena can follow

Impaired function of either hemisphere, at least theoretically; in practice,

however, some empirical correlations seem to surface again and again, such

as those of aggression, paranoid thinking and catastrophic reactions with

lesions of the dominant hemisphere, and depression, anxiety and grandiosity

with non-dominant ones.

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385

Proceeding from the specific case of epilepsy to the more general one

of psychiatric disorders, a further hypothetical formulation (Serafetinides

1981; 198A) runs as follows: dominant hemisphere dysfunctions can manifest

themselves as perturbations of consciousness of either a quantitative nature

(e.g. excitement or withdrawal) or of a qualitative one (e.g. paranoid

delusions). Associated phenomena such as inappropriate affect or obscure

somatic symptoms might represent in this respect (mal) adaptation or

compensation phenomena arising from a deregulated non-dominant hemisphere.

Symptoms directly attributable, on the other hand, to non-dominant

hemisphere dysfunction can be considered as those arising from perturbations

of awareness (visuo-spatial and self) of either a quantitative nature (e.g.

mania or depression) or of a qualitative one (e.g. bodily delusions). Here

the associated ruminative or verbal phenomena, such as stereotype thoughts

or flight of ideas can be considered as (mal) adaptation o** compensation

phenomena arising from a deregulated dominant hemisphere.

Thus, as can be seen from the above attempts at formulating testable

schemes of brain-behavior relationships various complexities of such

relationships have to be constantly redefined and notions such as the ones

presented here (e.g. direct vs Indirect symptoms, excitation vs inhibition,

(mal) adaptation vs compensation) might prove useful in these redefinitions.

In the end, however, only further research can determine their -at present

only heuristic - value.

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Acknowledgement

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The author wishes to acknowledge the support of the VA Medical Research

Service.

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387

LIST OF CONTRIBUTORS

MARIAN ANNETT, Department of Applied Social Studies, Coventry (Lanchester)

Polytechnic, Coventry, CV1 5FB, U.K.

PAMELA, J. BION, Psychology Department, Lancaster University, Lancast- r, LAI

4YF, U.K.

NIELS BIRBAUMER, Department of Clinical and Physiological Psychology,

Gartenstrasse 29, University of Tubingen, Tubingen DA700, F.R. Germany.

JOHN L. BRADSHAW, Department of Psychology, Monash University, Clayton

Victoria, Australia 3168.

STUART R. BUTLER, Department of Anatomy, Medical School, University of

Birmingham, Birmingham B15 2TJ, U.K.

RUE L. CROMWELL, Department of Psychology, University of Kansas, Lawrence,

Kansas, 660A5-2462, U.S.A.

THOMAS ELBERT, Department of Clinical and Physiological Psychology,

Gartenstrasse 29, University of Tubingen, Tubingen D7A00, F.R. Germany.

P. FLOR-HENRY, Alberta Hospital Edmonton, Box 307, Edmonton, Alberta, T6G

2C3, Canada.

ALAN GLASS, Department of Anatomy, Medical School, University of Birmingham,

Birmingham B15 2TJ, U.K.

JOHN GRUZELIER, Department of Psychiatry, Charing Cross and Westminster

Medical School, 22/24 St. Dunstans Road, London.

RAQUEL E. GUR, Brain Behavior Laboratory, Departments of Psychiatry and

Neurology, University of Pennsylvania, Philadelphia, Pennsylvania 19014,

U.S.A.

RUBEN C. GUR, Brain Behavior Laboratory, Departments of Psychiatry and

Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, 19014,

U.S.A.

DEBRA L. KIGAR, Department of Psychiatry, McMaster University, Hamilton,

Ontario, Canada.

Z.J. KOLES, Department of Applied Sciences in MediciiH, Edmonton, Alberta,

T5J 2J7, Canada.

WERNER LUTZENBERGER, Arbeitsbereich Klinische und Physiologische

Psychologie, Gartenstr. 29, D-4700 Tubingen, F.R. Germany.

JOHN C. MARSHALL, Neuropsycholcgy Unit, The Radcliffe Infirmary, Woodstock

Road, Oxford, 0X2 6HF, U.K.

KATHRYN H. MCWEENY, Psychology Department, Lancaster University, Lancaster,

LAI 4YF, U.K.

MICHAEL MIRAN, Department of Psychiatry, University of Rochester Medical

Centre, Rochester, New York, 14642, U.S.A.

ESTA MIRAN, University of Rochester, Rochester, New York, 14642, U.S.A.

DENNIS L. MOLFFSE, Department of Psychology and School of Medicine, Southern

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Illinois University, Carbondale, XL 62901, U.S.A.

VICTORIA J. MOLFESE, Department of Psychology and School of Medicine,

Southern Illinois University, Carbondale IL 62901, U.S.A.

THOMAS R. CCONNELL, Counselling Department, University of North Dakota,

U.S.A.

LELON J. PEACOCK, Department of Psychology, University of Georgia, Athens,

Georgia 30602, U.S.A.

ANTONIO E. PUENTE, Department of Psychology, University of North Carolina at

Wtlimington, North Carolina, 28A03, U.S.A.

WILLIAM J. RAY, Department of Psychology, Penn State University, University

Park, Pi. 16802, U.S.A.

.T.R. REDD0N, Alberta Hospital Edmonton, Box 307, Edmonton, Alberta, T6G 2G3,

Canada.

BRIGITTE ROCKSTROU, Arbeitsbereich Klinische und Physiologische Psychologie,

Gartenstr. 29, D-4700 Tubingen, F.R. Germany.

S.J. SEGAL0W1TZ, Department of Psychology, Brock University, St. Catharines,

Ontario, L2S 3A1, Canada.

E.A. SERAFETINIDES, Veterans Administration Medical Center West Los Angeles,

(Brentwood Division), and The Department of Psychiatry and The Brain

Research Institute, UCLA School of Medicine, Los Angeles, California, U.S.A.

W.N. SCH0FIELD, Department of Experimental Psychology, University of

Cambridge, Downing Street, Cambridge, CB2 3EB. U.K.

THOMAS B. SCOTT, Counselling Department, University of North Dakota, U.S.A.

DON M. TUCKER, Department of Psychology, University of Oregon, Eugene,

OR97A03, U.S.A.

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A.M. WEBER, Department of Psychology, University of Victoria, P.O. Box 1700,

Victoria, B.C., VBW 2Y2D, Canada.

SANDRA F. WITELS0N, Department of Psychiatry, Faculty of Health Sciences,

McMaster University, Hamilton, Ontario, L8N 3Z3, Canada.

ANDREW W. YOUNG, Psychology Department, Lancaster University, Lancaster, LAI

4YF. U.K. i

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