bluuebunny/crossref_metadata_2025 huggingface dataset:
Data Tilting for Time Series
Authors: Hall Peter , Yao Qiwei
Published: December 2004

We develop a general methodology for tilting time series data. Attention is focused on a large class of regression problems, where errors are expressed through autoregressive processes. The class has a range of important applications and in the context of our work may be used to illustrate the application of tilting methods to interval estimation in regression, robust statistical inference and estimation subject to constraints. The method can be viewed as ‘empirical likelihood with nuisance parameters’.
Achieving a Comprehensive Peace: The Linguistic Factor
Authors: Wenden Anita L.
Published: December 2004

This paper is based on theories from critical linguistics, which view language not as a neutral medium for the description of reality but as actively shaping and giving meaning to human experience. It, therefore, argues that the linguistic factor be taken into account in the analysis of and prescription for problems deriving from social and ecological violence that challenge contemporary societies. To that end, it outlines the components of a linguistic framework that illustrates how language communicates ideologies, which shape group attitudes and justify social practices that sustain the use of such violence, and then it applies the framework to an analysis of two brief texts on environmental security and President Bush's September 20, 2001, address to Congress.
Discourse Resistance And Negotiation By Indigenous Australians
Authors: Synott John
Published: December 2004

In the context of intercultural relations, the boundaries between dominant and subordinated communities are constructed in a variety of ways. Language frames, or discourses, understood from a sociological rather than a linguistic perspective can be considered to constitute one of the main processes for determining the character of intercultural boundaries. Using this theoretical perspective, this article examines a number of discourses that have contributed to the construction of social relations between Australian Aborigines and the dominant nonindigenous cultural groups in Australia. Examples from the colonial period show the way in which indigenous people were oppressed along racial boundaries, even as they resisted, while more recent instances chart the process of indigenous people in renegotiating social relations and in asserting the process of self‐determination and cultural celebration.
The poetry of nationalism*
Authors: Aberbach David
Published: December 2004

The poetry of nationalism has roots in ancient literature, particularly the Hebrew Bible, but is mostly a product of nationalism since the French Revolution. Many national poets are politically active and serve in government. Asserting artistic individuality, they express national individuality, though nationalism can also suppress creativity. Calling for moral regeneration, poets inspire their people with memories of heroism, real or imagined, and with myths unique to the nation. Their poetry often springs from defeat but anticipates national liberation and independence. Yet there is also a dark side to some national poets, particularly in their glorification of violence and lust for revenge against oppressors. National poetry changed after the failed revolutions of 1848–9. National poets were less inclined to believe in liberal ideals and progress toward universal goals and there was greater disillusionment and ambiguity toward the national role. World War I severely limited the militarist tendency in national poetry.
Prefrontal cortex: Links between low frequency delta EEG in sleep and neuropsychological performance in healthy, older people
Authors: Anderson Clare , Horne James A.
Published: December 2004

Low frequency (<1 Hz) delta EEG in sleep is of increasing interest as it indicates cortical reorganization, especially in the prefrontal cortex (PFC). Other research shows that delta power in sleep is positively linked to waking cerebral metabolic rate. Such findings suggest that<1 Hz activity may reflect waking performance at neuropsychological tests specific to the PFC. We investigated this unexplored area. Sleep EEGs (Fp1–F3, Fp2–F4, O1–P3, O2–P4) were recorded in 24 healthy 61–75‐year‐olds. We found significant associations between 0.5–1.0 Hz power from the left frontal EEG channel, in the first non‐REM period, and performance at tasks more specific to the left PFC (e.g., nonverbal planning and verbal fluency). This association was absent from the posterior channels. Neither age nor response times were confounding factors. This potential sleep EEG marker for PFC neuropsychological function in healthy, older people also points to further uses of the sleep EEG in understanding the role of sleep.
Representation of the standard: Stimulus context effects on the process generating the mismatch negativity component of event‐related brain potentials
Authors: Sussman Elyse , Sheridan Karen , Kreuzer Judith , Winkler István
Published: December 2004

In the auditory oddball paradigm, the frequent occurrence of a sound (the “standard”) forms the basis of deviance detection. The incoming sounds are compared with the cortical representation of the standard and those sounds that do not match it elicit the mismatch negativity (MMN) event‐related brain potential. Here we address the issue of whether the relative probability of the sounds in a sequence was a critical factor influencing which sounds would be represented as standards in the deviant comparison process. One frequent (F1) and two infrequent (D1 and D2) sounds that differed only in duration were presented in a sequence. D1 occurred proportionally as frequently with respect to D2 as F1 occurred with respect to D1. If the proportional relationship of sounds were critical then D1 could serve as a “standard” to D2 and thus D2 should elicit two MMNs. However, D2 elicited MMN only with respect to F1. This result as well as those obtained in two control conditions suggests that “standards” are not established on the basis of relative probability; they emerge as a result of global characteristics, the longer‐term context, of the sound sequence.
Effects of cycling exercise on the soleus H‐reflex and state anxiety among men with low or high trait anxiety
Authors: Motl Robert W. , O'connor Patrick J. , Dishman Rod K.
Published: December 2004

The present study examined the effects of low‐ and high‐intensity cycling exercise on the H‐reflex and state anxiety among men having low (n=20) or high (n=20) trait anxiety. Participants completed measures of state anxiety and underwent elicitation and recording of the H‐reflex in the soleus muscle before and 10 min after three 20‐min conditions: (1) quiet rest, (2) cycling at 40% V̇O2peak, and (3) cycling at 70% V̇O2peak. We found that (1) exercise, but not quiet rest, resulted in a reduction of the H‐reflex; the magnitude of the reduction did not differ between men having low or high trait anxiety; (2) exercise and quiet rest resulted in similar reductions of state anxiety, and the magnitude of the reductions was larger for men having high trait anxiety than low trait anxiety; and (3) reductions of the H‐reflex were unrelated to reductions of self‐reported state anxiety across all three conditions. Contrary to prior opinion, the postexercise reduction in the H‐reflex reported by previous researchers and in the present study appears to be unrelated to self‐reported anxiety after exercise.
Electrophysiological evidence for altered early cerebral somatosensory signal processing in schizophrenia
Authors: Waberski Till D. , Norra Christine , Kawohl Wolfram , Thyerlei Dinah , Hock Dorothee , Klostermann Fabian , Curio Gabriel , Buchner Helmut , Hoff Paul , Gobbelé René
Published: December 2004

Various studies have indicated an impairment of sensory signal processing in schizophrenic patients. Anatomical and functional imaging studies have indicated morphological and metabolic abnormalities in the thalamus in schizophrenia. Other results give evidence for an additional role of cortical dysfunction in sensory processing in schizophrenia. Advanced analysis of human median nerve somatosensory evoked potentials (SEPs) reveals a brief oscillatory burst of low‐amplitude and high‐frequency activity (∼600 Hz), the so‐called high frequency oscillations (HFOs). The present study explores the behavior of HFOs in a cohort of schizophrenic patients in comparison to a group of controls. HFOs in the group of patients appeared with a delayed latency. In the low‐frequency part of the SEPs an increase in amplitude was found. These results are interpreted to reflect a lack of somatosensory inhibition in the somatosensory pathway, either at a thalamic or a cortical level.
Menstrual cycle phase effects on prepulse inhibition of acoustic startle
Authors: Jovanovic Tanja , Szilagyi Sandor , Chakravorty Subhajit , Fiallos Ana M. , Lewison Barbara J. , Parwani Arti , Schwartz Marion P. , Gonzenbach Stephen , Rotrosen John P. , Duncan Erica J.
Published: December 2004

Prepulse inhibition (PPI) represents an attenuation of the startle reflex following the presentation of a weak prepulse at brief intervals prior to the startle eliciting pulse. It has been shown that increases in striatal dopamine levels decrease PPI; because dopamine release is sensitive to estrogen, it is likely that PPI varies across the menstrual cycle. Cross‐sectional studies looking at estrogen effects suggest that this may be true. In this study, we compare effects of menstrual phase on PPI in a between‐group design (men, follicular phase women, and luteal phase women) as well as a within‐subjects design (women across the two phases). The study found a between‐group as well as a within‐subjects effect of phase on PPI. PPI in follicular phase women did not differ significantly from PPI in men. However, PPI was reduced in luteal women compared to follicular women. These data provide evidence that ovarian hormones affect sensorimotor gating.
Brain potentials and behavioral responses associated with attention to hard‐ and easy‐to‐discriminate passive knee joint movements
Authors: Smid H. G. O. M. , Hauser U. , Weiler H. T. , Awiszus F. , Hinrichs H. , Heinze H.‐J.
Published: December 2004

We investigated event‐related brain potentials (ERPs) to passive ramp movements of the knee joint. The knee movements were either attended or unattended and were either very easy or very hard to detect. We used special methods to ensure that movement only activated muscle spindle and joint receptors. The first movement‐related ERP started 20 ms after movement onset, and had a contralateral maximum. This initial ERP did not differ as a function of attention and movement discriminability. Signal detection analysis of the behavioral data suggested that hard‐to‐detect movements could be discriminated above chance level, but were not reported because of a decision bias. At 60–100 ms, an ERP was observed that discriminated detected from undetected hard‐to‐detect movements. Starting at 80 ms, we found an ERP that was unique to movements that were attended and easy to detect. We discuss that (1) the initial ERP reflects activation of preconscious sensory processors, (2) the second ERP may reflect detection that fails to attract attention, and (3) the third ERP reflects active focusing of attention on the movement.
Processing sentence context in women with schizotypal personality disorder: An ERP study
Authors: Niznikiewicz Margaret A. , Friedman Michelle , Shenton Martha E. , Voglmaier Martina , Nestor Paul G. , Frumin Melissa , Seidman Larry , Sutton John , McCarley Robert W.
Published: December 2004

Accumulating evidence suggests that schizophrenic patients do not use context efficiently. Also, studies suggest similarities in clinical and cognitive profiles between schizophrenic and schizotypal personality disorder (SPD) individuals, and epidemiological studies point to a genetic link between the two disorders. This study examined electrophysiological correlates of processing sentence context in a group of SPD women in a classical N400 sentence paradigm. The study assessed if the dysfunction in context use found previously in schizophrenia and male SPD also exists in female SPD. We tested 17 SPD and 16 matched normal control women. The results suggest the presence of abnormality in context use in female SPD similar to that previously reported for male schizophrenic and SPD individuals, but of lesser degree of severity. In SPD women, relative to their comparison group, a more negative N400 was found only to auditory congruent sentences.
On the status of individual response specificity
Authors: Marwitz Michael , Stemmler Gerhard
Published: December 2004

The concept of physiological individual response specificity (IRS) was critically discussed. A review of empirical studies focused on IRS magnitude, stability, and personality correlates. Using difference scores, an average of 33% of the participants showed a significant IRS. IRS stability was found in only 15% of the participants. In some studies, IRS incidence was associated with neuroticism or stress coping styles. We suggest that the IRS concept should include not only purely constitutional but also situational and psychological determinants. Predictions from this revised biopsychological model were tested with a data set comprising 48 healthy male participants who completed six tasks, which were replicated three times in 1‐week intervals. At Session 1, 21% of the participants displayed a significant IRS. IRS stability was found in only 8% of the participants. Participants with a significant IRS at Session 1 reported higher levels of fear (anger and happiness as covariates) and of pounding heart. Between‐session IRS (trait‐IRS) but not within‐session IRS (state‐IRS) was associated with trait anxiety.
Postperceptual effects and P300 latency
Authors: Leuthold Hartmut , Sommer Werner
Published: December 2004

P300 latency is commonly thought to provide a chronometric index of the duration of perceptual processing. Because the evidence in favor of this assumption is controversial, we examined whether P300 latency is influenced by perceptual processes, response selection, and by motoric processes in two experiments using a two‐choice spatial stimulus‐response compatibility (SRC) task. Both experiments revealed additive effects of perceptual difficulty with spatial SRC in reaction time and P300 latency. In addition, Experiment 2 showed that P300 latency measured in average waveforms is insensitive to motoric processes. The influence of spatial SRC on P300 latency disagrees with the view that P300 latency is sensitive only to stimulus evaluation processes. However, P300 latency may be used to discriminate between influences on premotoric and motoric processing stages. A response conflict account for the SRC effect on P300 latency is suggested.
A test of the validity of the method of constant stimuli as an index of heartbeat detection
Authors: Schneider Tamera R. , Ring Christopher , Katkin Edward S.
Published: December 2004

A heartbeat detection task, based on the method of constant stimuli (MCS), requires participants to judge which of a series of tones presented at different delays following a heartbeat are coincident with the heartbeat. Two experiments were conducted to test the validity of the MCS in assessing individual differences in the ability to detect heartbeat sensations. The first experiment found the MCS to be valid, in that about one‐third of subjects met the criterion for classification as heartbeat detectors when the tones were presented with respect to their actual heartbeats, but only one subject met the criterion when the tones were presented with respect to previously recorded heartbeats. The second experiment manipulated the timing of the comparison intervals (i.e., R + 100–600 ms rather than R + 0–500 ms) to examine the validity of the median R‐wave to tone interval as an index of temporal location of perceived heartbeats, and found it to be a valid index.
Neurophysiological evidence for visual perceptual categorization of words and faces within 150 ms
Authors: Schendan Haline E. , Ganis Giorgio , Kutas Marta
Published: December 2004

The nature and early time course of the initial processing differences between visually matched linguistic and nonlinguistic images were studied with event‐related potentials (ERPs). The first effect began at 90 ms when ERPs to written words diverged from other objects, including faces. By 125 ms, ERPs to words and faces were more positive than those to other objects, effects identified with the P150. The amplitude and scalp distribution of P150s to words and faces were similar. The P150 seemed to be elicited selectively by images resembling any well‐learned category of visual patterns. We propose that (a) visual perceptual categorization based on long‐term experience begins by 125 ms, (b) P150 amplitude varies with the cumulative experience people have discriminating among instances of specific categories of visual objects (e.g., words, faces), and (c) the P150 is a scalp reflection of letterstring and face intracranial ERPs in posterior fusiform gyrus.
Secretory immunoglobulin A and cardiovascular reactions to mental arithmetic and cold pressor
Authors: Willemsen Gonneke , Ring Christopher , Carroll Douglas , Evans Phil , Clow Angela , Hucklebridge Frank
Published: December 2004

Secretory immunoglobulin A (sIgA) in saliva and cardiovascular reactions to mental arithmetic and cold pressor tasks were recorded in 16 healthy young men on two sessions, 4 weeks apart. Both tasks elicited significant increases in sIgA secretion rate, reflecting increases in both salivary volume and sIgA concentration. Whereas mental arithmetic elicited a mixed pattern of alpha‐ and beta‐adrenergic cardiovascular reactions, the pattern of reactions to cold pressor was predominantly alpha‐adrenergic. Task levels of sIgA secretion rate, sIgA concentration, and saliva volume showed moderate to high test–retest reliability (r= .52–.83), although test‐retest correlations were less impressive for change scores (r=−.19–.53). The pattern of correlations between change in sIgA secretion rate and cardiovascular reactivity variables was inconsistent.
Identifying psychophysiological risk for psychopathology: Examples from substance abuse and schizophrenia research
Authors: Iacono William G.
Published: December 2004

A problem confronting the search for psychopathology‐related genes concerns the difficulty identifying gene carriers. Psychiatric diagnosis provides imperfect identification of affected individuals, and unaffected gene carriers go undetected. Psychophysiological measures may assist molecular genetic investigations by indicating genetic susceptibility for psychopathology, thus increasing the probability of identifying affected and unaffected gene carriers. Research strategies based on these premises are applied to the study of psychoactive substance use disorders and schizophrenia. Data are presented illustrating (1) that individual differences in inhibitory control involving autonomic and antisaccade eye movement measures and the P3 component of the event‐related potential may be sensitive to susceptibility for substance use disorders, and (2) that eye tracking variables may identify genetic risk for schizophrenia.
Individual differences in P3 scalp distribution in older adults, and their relationship to frontal lobe function
Authors: Fabiani Monica , Friedman David , Cheng Jeff C.
Published: December 2004

There is evidence that frontal lobe function may diminish in normal aging. The P3 component of the event‐related brain potential (ERP) elicited by target events in an oddball paradigm becomes more frontally oriented in elderly subjects. It was hypothesized that the extent to which the P3 distribution is frontally oriented in old subjects may index less efficient frontal lobe function. In this study, bootstrapping methods were used to establish the reliability of the locations of maxima of surface brain activity obtained with ERP recordings from young and old subjects. The results indicated that brain activity maxima are reliable for a given individual. However, among the elderly only, there were also clear individual differences in the distribution of the P3 component elicited by target stimuli in an oddball paradigm. On the basis of these differences, the old subjects were divided into two groups. In line with predictions, those elderly subjects who showed frontal‐maximal P3 scalp distributions had lower performance on standardized neuropsychological tests of frontal lobe function than those elderly subjects who showed posterior‐maximal scalp topographies.
Event‐related potentials of verbal encoding into episodic memory: Dissociation between the effects of subsequent memory performance and distinctiveness
Authors: Fernández Guillén , Weyerts Helga , Tendolkar Indira , Smid Henderikus G.O.M. , Scholz Michael , Heinze Hans‐Jochen
Published: December 2004

Episodic memory encoding and distinctiveness detection were examined using event‐related potentials (ERP) in a single‐trial word list learning paradigm with free recall following distraction. To manipulate distinctiveness, encoding of high‐ and very low‐frequency words was contrasted. Amplitudes of the N400 and late positive component (LPC) were larger for low‐ than for high‐frequency words, and ERPs were more positive for subsequently recalled than not recalled words. This subsequent memory effect was dissociated from the correlates of distinctiveness by polarity for the N400 and by time course for the LPC and dissociable into two effects. The data suggest that the first subsequent memory effect, which occurred for both word categories, is more directly related to episodic memory formation, whereas the second effect, which occurred for high‐frequency words only, is related to processes influencing episodic encoding success indirectly.
Motor programming of response force and movement direction
Authors: Ulrich Rolf , Leuthold Hartmut , Sommer Werner
Published: December 2004

Effects of movement advance information were assessed on the prestimulus amplitude of the lateralized readiness potential (LRP), on the contingent negative variation (CNV), and on reaction time (RT). In a precuing paradigm with movement parameters hand, direction, and force, partial precues provided advance information about either hand alone, hand plus force, or hand plus direction, and the full precue specified all response parameters. The full precue produced the shortest RTs and the largest CNV amplitude, precuing hand and force or hand and movement direction produced somewhat slower RTs and a somewhat smaller CNV amplitude, and precuing only hand yielded slowest RTs and the smallest CNV amplitude. In contrast, the LRP amplitude was largest for the full precue and was the same for the remaining precues. The CNV appears to index the central assembling of a motor program, and the LRP represents the implementation of the program at more peripheral levels.
Error‐related processing during a period of extended wakefulness
Authors: Scheffers Marten K. , Humphrey Darryl G. , Stanny Robert R. , Kramer Arthur F. , Coles Michael G. H.
Published: December 2004

The nature of error detection as manifested by the error‐related negativity was examined in both a Sternberg memory search task and a visual search task. Both tasks were performed in conditions with consistent or varied stimulus–response mapping and loads of three or six letters. After subjects were trained extensively in all conditions, they performed the tasks throughout the night without sleeping. The data suggest that the effectiveness of error detection decreases over time because of a decrease in the quality of perceptual processing. Error detection also suffers when performance requires more search‐related resources. In both cases, the representation of the correct response is compromised. These results indicate that error detection depends on the same perceptual and cognitive processes that are required for correct performance.
The psychobiology of strained breathing and its cardiovascular implications: A functional system review
Authors: Fokkema Dirk S.
Published: December 2004

Strained breathing is a natural respiratory pattern, with cardiovascular implications. It is associated with social factors, attention, expectation, and anxiety and with defense behavior in animals. An inhibition of active behavior is characteristic. Strained breathing is based on the functional heterogeneity of the medullary postinspiratory neurons. In stressful circumstances, muscle tension and laryngeal reflexes induce a strong reduction of airflow in the glottis, resulting in a prolonged Stage I of expiration and an elevated intrathoracic pressure. The resulting elevations of blood pressure and CO2 level further stimulate the strained breathing pattern. The straining factor intrathoracic pressure is an important psychophysiological parameter. Functional aspects of strained breathing may be an elevated brain perfusion and the prevention of hyperventilation. It induces blood pressure oscillations and respiratory sinus arrhythmia. Frequent strained breathing may contribute to cardiovascular pathology and sleep apnea, creating a link between functional behavior and disease.
Gender differences in late positive components evoked by human faces
Authors: Oliver‐Rodríguez Juan C. , Guan Zhiqiang , Johnston Victor S.
Published: December 2004

Event‐related potentials (ERPs) were recorded in male and female participants in response to 32 male and 32 female faces. Participants were instructed to simply look carefully at each face; after ERP collection they were asked to rate each face on a 5‐point attractiveness scale. A positive correlation between average rating and average P300 scores to opposite sex faces was observed in male (r= .40) and in preovulatory (r= .41) and postovulatory (r= .44) female subjects. Correlations to same sex faces were only found in postovulatory females (r= .61). Male participants showed a much larger average P300 than did female participants, and the P300 evoked in female participants was unexpectedly larger to female than to male faces. Neither task relevance nor stimulus probability is a plausible explanations for these findings because they were experimentally controlled. These results support the emotional value hypothesis, according to which classical P300 processes reflect an affective evaluation of the stimulus, which in turn produces context updating.
Amplitude criteria and anticipatory saccades during smooth pursuit eye movements in schizophrenia
Authors: Ross Randal G. , Olincy Ann , Radant Allen
Published: December 2004

Increased frequency of anticipatory saccades during smooth pursuit eye movements is a potential marker of genetic risk for schizophrenia even in the absence of clinical symptomology. The operational definition of anticipatory saccades has often included an amplitude criterion; however, these amplitude criteria have often differed across studies. This study reports on the effect of varying amplitude criteria on the effect size in a comparison of 29 schizophrenic adults and 29 normal subjects during a 16.7°/s constant velocity task. The inclusion of small amplitude anticipatory saccades, with amplitudes of 1–4°, consistently increased effect size (largest effect size = 1.61). The inclusion of large anticipatory saccades, with amplitudes of 4° or greater, had an inconsistent impact on effect size. The separation of anticipatory saccades into leading saccades (anticipatory saccades with amplitude 1–4°) and large anticipatory saccades (amplitude >4°) deserves further exploration.
Secretory immunoglobulin A and cardiovascular activity during mental arithmetic and paced breathing
Authors: Ring Christopher , Carroll Douglas , Willemsen Gonneke , Cooke Jonathan , Ferraro Adrian , Drayson Mark
Published: December 2004

The role of the autonomic nervous system in secretory immunoglobulin A (sIgA) responses to laboratory challenge was explored in a study in which sIgA and cardiovascular activity were recorded at rest and during mental arithmetic and paced breathing. These tasks were selected to preferentially engage the sympathetic and parasympathetic nervous systems, respectively. Mental arithmetic elicited a mixed pattern of increased alpha‐ and beta‐adrenergic activity and a reduction in parasympathetic activity; diastolic blood pressure, total peripheral resistance, and systolic blood pressure increased, preejection period shortened, and heart rate variability decreased. In contrast, paced breathing primarily elicited an increase in parasympathetic activity; heart rate variability increased. Mental arithmetic also provoked an increase in sIgA concentration but no change in saliva volume, whereas paced breathing affected neither sIgA concentration nor saliva volume. These data suggest that sIgA responses to laboratory challenges are mediated by sympathetic rather than parasympathetic processes.
Contrasts between the cardiovascular concomitants of tests of planning and attention
Authors: Middleton H. C. , Sharma A. , Agouzoul D. , Sahakian B. J. , Robbins T. W.
Published: December 2004

Physiological response stereotypy is a well‐established psychophysiological construct. Unfortunately, specifying parameters of tasks that evoke differing physiological responses has proved difficult. We have recorded cardiovascular activity while subjects carried out executive and attentional tasks that differed not only psychologically but also in their sensitivity to brain pathology and to pharmacological manipulations. Finapres recordings were made of 30 healthy, normal subjects (mean age 24 years) performing two tasks involving differing aspects of sustained attention and two tasks involving differing aspects of spatial working memory and planning. Measures of heart rate and blood pressure, heart rate and blood pressure variability, and their spectral derivatives revealed differing patterns of cardiovascular adjustment between the “attentional” and “planning” tasks. Each test raised blood pressure, but changes in blood pressure and heart rate variability were confined to the attentional tasks. These findings suggest distinct brain mechanisms subserving different forms of arousal.
Brain responses reveal the learning of foreign language phonemes
Authors: Winkler István , Kujala Teija , Tiitinen Hannu , Sivonen Päivi , Alku Paavo , Lehtokoski Anne , Czigler István , Csépe Valéria , Ilmoniemi Risto J. , Näätänen Risto
Published: December 2004

Learning to speak a new language requires the formation of recognition patterns for the speech sounds specific to the newly acquired language. The present study demonstrates the dynamic nature of cortical memory representations for phonemes in adults by using the mismatch negativity (MMN) event‐related potential. We studied Hungarian and Finnish subjects, dividing the Hungarians into a naive (no knowledge of Finnish) and a fluent (in Finnish) group. We found that the MMN for a contrast between two Finnish phonemes was elicited in the fluent Hungarians but not in the naive Hungarians. This result indicates that the fluent Hungarians developed cortical memory representations for the Finnish phoneme system that enabled them to preattentively categorize phonemes specific to this language.
ERP indicators of disturbed attention in mild closed head injury: A frontal lobe syndrome?
Authors: Solbakk Anne‐Kristin , Reinvang Ivar , Nielsen Christopher , Sundet Kjetil
Published: December 2004

The purpose of the study was to examine the hypothesis that distractibility is a fundamental characteristic of mild closed head injury (MHI). The claim that cognitive symptoms in MHI are due to a mild type of frontotemporal injury was also investigated. Cognitive event‐related potentials (ERPs), accuracy and reaction time to target stimuli in a dichotic listening paradigm, and neuropsychological test results were studied in patients with MHI (N= 15), patients with verified frontal lobe damage (N= 10), and healthy controls (N= 13). Information processing reflecting target detection (N2, P3b) and sustained selective attention (processing negativity) was studied. The MHI and frontal patients did not differ on behavioral measures, except that the MHI group had significantly longer reaction times to target stimuli in the ERP task. Both patient groups had deviant ERPs compared with controls, but their ERP patterns differed in important respects. Contrary to expectations, the MHI patients had the most abnormal ERPs. They showed significantly smaller N2 and Nd amplitudes than frontal patients and controls, indicating that the mediating cognitive mechanisms were not equivalent in MHI and frontal injury. The data suggest that MHI patients allocated less processing resources to the task than either the control subjects or the patients with frontal lobe damage.
Early attention effects in human auditory‐evoked potentials
Authors: Hoormann Jörg , Falkenstein Michael , Hohnsbein Joachim
Published: December 2004

A fundamental question in attention theory concerns the earliest processing stages that can be modulated by selective attention. A series of experiments is reported in which very early attention effects are found under specific conditions in the frequency‐following potential (FFP), a brain stem response to low‐frequency tone stimuli. In two experiments, stimuli of two different modalities were applied, and attention directed to one of the modalities. In two further experiments, only auditory stimuli were presented. In the first of these last two experiments, a dichotic paradigm with sustained attention to one ear was used, in the second a monotic paired‐stimuli paradigm was used, in which the first stimulus served as reference for the second one. Only in the last experiment significant attention effects were found in the latency, but not in the amplitude of the FFP. The results show that a very early attention effect on the latency of the FFP can be demonstrated, but only under highly specific conditions. The size and preconditions of the attention effect suggest that it reflects subtle intramodal tuning mechanisms in the cochlea or in the lower brain stem.
Removing electroencephalographic artifacts by blind source separation
Authors: Jung Tzyy‐Ping , Makeig Scott , Humphries Colin , Lee Te‐Won , McKeown Martin J. , Iragui Vicente , Sejnowski Terrence J.
Published: December 2004

Eye movements, eye blinks, cardiac signals, muscle noise, and line noise present serious problems for electroencephalographic (EEG) interpretation and analysis when rejecting contaminated EEG segments results in an unacceptable data loss. Many methods have been proposed to remove artifacts from EEG recordings, especially those arising from eye movements and blinks. Often regression in the time or frequency domain is performed on parallel EEG and electrooculographic (EOG) recordings to derive parameters characterizing the appearance and spread of EOG artifacts in the EEG channels. Because EEG and ocular activity mix bidirectionally, regressing out eye artifacts inevitably involves subtracting relevant EEG signals from each record as well. Regression methods become even more problematic when a good regressing channel is not available for each artifact source, as in the case of muscle artifacts. Use of principal component analysis (PCA) has been proposed to remove eye artifacts from multichannel EEG. However, PCA cannot completely separate eye artifacts from brain signals, especially when they have comparable amplitudes. Here, we propose a new and generally applicable method for removing a wide variety of artifacts from EEG records based on blind source separation by independent component analysis (ICA). Our results on EEG data collected from normal and autistic subjects show that ICA can effectively detect, separate, and remove contamination from a wide variety of artifactual sources in EEG records with results comparing favorably with those obtained using regression and PCA methods. ICA can also be used to analyze blink‐related brain activity.
Age‐related decline in inhibitory control contributes to the increased Stroop effect observed in older adults
Authors: West Robert , Alain Claude
Published: December 2004

Past research has demonstrated an age‐related increase in the Stroop effect. Some theorists have suggested that this increase results from a decline in the ability to inhibit word information on incongruent trials, whereas others have suggested that the decline reflects general slowing. These two hypotheses were evaluated using event‐related brain potentials (ERPs) measured while younger and older adults performed the Stroop task. As expected, the Stroop effect was greater for older than younger adults. The ERP data revealed a selective age‐related attenuation of two modulations reflecting the inhibition of word information on incongruent trials. Latency of the P3 wave did not increase to a greater extend for older than younger adults from the congruent to incongruent trials as expected based on the general slowing hypothesis. Taken together, these findings support the inhibitory deficit hypothesis by demonstrating an age‐related decline in a conceptual level inhibitory process that supports the suppression of word information in the Stroop task.
The visual N1 component as an index of a discrimination process
Authors: Vogel Edward K. , Luck Steven J.
Published: December 2004

Many previous studies have demonstrated that the visual N1 component is larger for attended‐location stimuli than for unattended‐location stimuli. This difference is observed typically only for tasks involving a discrimination of the attended‐location stimuli, suggesting that the N1 wave reflects a discrimination process that is applied to the attended location. The present study tested this hypothesis by examining the N1 component elicited by attended stimuli under conditions that either required or did not require the subject to perform a discrimination. Specifically, the N1 elicited by foveal stimuli during choice‐reaction time (RT) tasks was compared with the N1 elicited by identical stimuli during simple‐RT tasks. In three experiments, a larger posterior N1 was observed in choice‐RT tasks than in simple‐RT tasks, even when several potential confounds were eliminated (e.g., arousal and motor preparation). This N1 discrimination effect was observed even when no motor response was required and was present for both color‐ and form‐based discriminations. Moreover, this discrimination effect was equally large for easy and difficult discriminations, arguing against a simple resource‐based explanation of the present results. Instead, the results of this study are consistent with the hypothesis that the visual N1 component reflects the operation of a discrimination process within the focus of attention.
Changes in spinal excitability during choice reaction time: The H reflex as a probe of information transmission
Authors: Hasbroucq Thierry , Akamatsu Motoyuki , Burle Borís , Bonnet Michel , Possamaï Camille‐Aimé
Published: December 2004

The aim of the present study was to investigate the modulations in amplitude of H reflexes elicited in a hand muscle, the flexor pollicis brevis, during the performance of a choice reaction time (RT) task in which this muscle was directly involved. Ten subjects were to choose between a left‐ or a right‐thumb key‐press according to the lateral location of a flash of light. The stimulus–response mapping was either compatible or incompatible. Hoffman reflexes were elicited at different times during the RT by stimulation of the median nerve. Twenty‐five milliseconds before the voluntary response, the amplitude of the H reflex suddenly increased when the muscle was involved in the response and decreased symmetrically when the muscle was not involved in the response. Mapping compatibility exerted no detectable influence on the changes in spinal excitability. The latter result supports the assumptions that are at the core of Sternberg's additive factor method.
Acute changes in carbon dioxide levels alter the electroencephalogram without affecting cognitive function
Authors: Bloch‐Salisbury Elisabeth , Lansing Robert , Shea Steven A.
Published: December 2004

The partial pressure of carbon dioxide in the arterial blood (PaCO2) is usually tightly regulated, yet it varies among healthy people at rest (range ∼32–44 mmHg) as well as within an individual during many natural life situations. The present study examined whether modest changes in end‐tidal PCO2 (PetCO2; a noninvasive measure of PaCO2) affect electroencephalographic (EEG) activity, cognitive function, and vigilance. Nine adults were ventilated mechanically using a mouthpiece; respiratory rate and breath size were held constant while PetCO2 was set to levels that produced minimal discomfort. Despite discrete changes in EEG, neither acute PetCO2 increases (mean = 47 mmHg) nor decreases (mean = 30 mmHg) from resting levels (mean = 38 mmHg) affected performance on cognitive tasks, latency or amplitude of the N1, P2, or P3 event‐related potential, or alertness. Modest changes in PetCO2 may cause significant alterations in the EEG without disturbing cognitive function.
Statistical control of artifacts in dense array EEG/MEG studies
Authors: Junghöfer Markus , Elbert Thomas , Tucker Don M. , Rockstroh Brigitte
Published: December 2004

With the advent of dense sensor arrays (64–256 channels) in electroencephalography and magnetoencephalography studies, the probability increases that some recording channels are contaminated by artifact. If all channels are required to be artifact free, the number of acceptable trials may be unacceptably low. Precise artifact screening is necessary for accurate spatial mapping, for current density measures, for source analysis, and for accurate temporal analysis based on single‐trial methods. Precise screening presents a number of problems given the large datasets. We propose a procedure for statistical correction of artifacts in dense array studies (SCADS), which (1) detects individual channel artifacts using the recording reference, (2) detects global artifacts using the average reference, (3) replaces artifact‐contaminated sensors with spherical interpolation statistically weighted on the basis of all sensors, and (4) computes the variance of the signal across trials to document the stability of the averaged waveform. Examples from 128‐channel recordings and from numerical simulations illustrate the importance of careful artifact review in the avoidance of analysis errors.
Interfacing mind and brain: A neurocognitive model of recognition memory
Authors: Mecklinger Axel
Published: December 2004

A variety of processes contribute to successful recognition memory, some of which can be associated with spatiotemporally distinct event‐related potential old/new effects. An early frontal and a subsequent parietal old/new effect are correlated with the familiarity and recollection subcomponents of recognition memory, respectively, whereas a late, postretrieval old/new effect seems to reflect an ensemble of evaluation processes that are set by the task context in which retrieval occurs. Both the early frontal and the parietal old/new effects are differentially modulated by the informational content (e.g., object forms and spatial locations) of recognition and seem to rely on brain systems damaged in amnesia. The late frontal effect appears to reflect prefrontal cortex activation. A neurophysiologically based model of recognition memory retrieval is presented and it is shown that coupling recognition memory subprocesses with distinct old/new effects allow examination of the time course of the processes that contribute to correct and to illusory memories. In conjunction with event‐related functional magnetic resonance imaging activation patterns the brain systems recruited by various aspects of episodic memory retrieval can be identified.
Mental fatigue and task control: Planning and preparation
Authors: Lorist Monicque M. , Klein Merel , Nieuwenhuis Sander , de Jong Ritske , Mulder Gijsbertus , Meijman Theo F.
Published: December 2004

The effects of mental fatigue on planning and preparation for future actions were examined, using a task switching paradigm. Fatigue was induced by “time on task,” with subjects performing a switch task continuously for 2 hr. Subjects had to alternate between tasks on every second trial, so that a new task set was required on every second trial. Manipulations of response–stimulus intervals (RSIs) were used to examine whether subjects prepared themselves for the task change. Behavioral measurements, event‐related potentials (ERPs), and mood questionnaires were used to assess the effects of mental fatigue. Reaction times (RTs) were faster on trials in which no change in task set was required in comparison with switch trials, requiring a new task set. Long RSIs were used efficiently to prepare for the processing of subsequent stimuli. With increasing mental fatigue, preparation processes seemed to become less adequate and the number of errors increased. A clear poststimulus parietal negativity was observed on repetition trials, which reduced with time on task. This attention‐related component was less pronounced in switch trials; instead, ERPs elicited in switch trials showed a clear frontal negativity. This negativity was also diminished by time on task. ERP differences between repetition and switch trials became smaller with increasing time on task.
Facial reactions to happy and angry facial expressions: Evidence for right hemisphere dominance
Authors: Dimberg Ulf , Petterson Maria
Published: December 2004

Previous research on asymmetric effects of emotional expression and brain‐hemispheric asymmetry has supported opposing theories of hemispheric dominance in the control of emotional reactions. In the present study, 32 subjects were exposed to pictures of happy and angry facial stimuli while facial electromyographic (EMG) activity from the zygomatic major and the corrugator supercilii muscle regions was detected from the left and right sides of the face. The subjects reacted spontaneously and rapidly with larger zygomatic EMG activity to happy facial stimuli and larger corrugator EMG activity to angry stimuli. These distinct reactions were significantly larger on the left side of the face. It is concluded that the present results support the hypothesis that the right brain hemisphere is predominantly involved in the control of spontaneously evoked emotional reactions.
Optimal signal bandwidth for the recording of surface EMG activity of facial, jaw, oral, and neck muscles
Authors: van Boxtel A.
Published: December 2004

Spontaneous pericranial electromyographic (EMG) activity is generally small and is contaminated by strong low‐frequency artifacts. High‐pass filtering should suppress artifacts but affect EMG signal power only minimally. In 24 subjects who performed a warned simple reaction time task, the optimal high‐pass cut‐off frequency was examined for nine different pericranial muscles. From four experimental conditions (visual and auditory reaction signals combined with hand and foot responses), 1‐min EMG recordings were selected (bandwidth: 0.4–512 Hz) and divided into 60 1‐s data segments. These segments were high‐pass filtered, the −3‐dB cut‐off frequency varying from 5 to 90 Hz, and subjected to power spectral analysis. Optimal high‐pass filter frequencies were determined for the mean power spectra based on visual estimation or comparison with a theoretical spectrum of the artifact‐free EMG signal. The optimal frequencies for the different muscles varied between 15 and 25 Hz and were not influenced by stimulus or response modality. For all muscles, a low‐pass filter frequency between 400 and 500 Hz was appropriate.