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Period Covered: June 15, 1966 to January 31, 1967

I. Summery

Certain key experimental findings obtained during this first phase or the research have been combined with earlier observations cited in the project proposal to produce a model of best fit for the electrodermal system. It encompasses both a dual peripheral effector mechanism and a central control system. It assigns little or no function to vascular mechanisms. It has been used to develop a new methcd for analysis of the skin conductance response which has been highly suczessful in accomplishipg sorting of qualitatively different behavisral states withcut utilizing response aaplitude as such. The new =ethod should lend itself readily to automation.

II. Specific Experimental Findings

A. Periphezal Mechanism

1. Mictoelectrode Observations:

kia potentials were simultaneously recorced from sweat pores and from areas on the palmar surface between sweat pores (epidermal sites), together with-a macroscopic recording fron a nearby 0.3ca² sice (25 subjects). Pure positive waves, pure negative waves and biphasic waves were usually obtained from either microscopic site with equal frequency, although in a few subjects, the epidermal sites showed predoninantly positive responses while the pores produced negative or biphasic waves. For the population as a whole, no pattern was detectable which allowed prediction of the particular weveform at elther type of microscopic site.

One observation of interest was the frequent occisions in which the microelcctrodes on the sweat pore and epidernis shoued only positive waves while the macroscopic site shoved pure negative waves (Fig. l). This is attributed to the fact that the macroscopic site was covered with electrode paste and

(150)

Fcbruary 15, 1967

Approved Dete 2 fer Relassa 7 1

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Fig. 1. Simultaneous microelectrode recordings from a sweat pore from the area between sweat pores, and fron a neerby macroscopic site all on zhe volar surface of the finger. In this example the gross site shows a negative response, despite the positive activity in the microscopic sites. Negative is upwards.

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with an clectrode while the microelectrode sites were exposed to air and were considerably drier. When dry macroscopic electrodes made of woven silvcr cloth (to allow the site to remain dry) were used, the same effect was obtained, namely prominent positive waves at the dry site, while negative waves or negative with weak positive components occurred at the wet site (Fig. 2). This effect is, consistent with the predictions of a hydration effect recently discovered at this laborazory and investigated further under the present contract. It points out that the presence of two areas in the skin with differcnt potentials must result in internal circuit currents. The potential observed at the surface is then determined by the value of the two generators and their internal resistances. If the interual resistance (which includes the sweat duct and the horny layer, as well as any membranes involved) is reduced, the surface potential will move in the direction of that generator whose internal resistance is affected. Thus, when sweat overflows into the dry corneum, it reduces the resistance of the horny layer and brings the surface potential closer to the potential of the epidermis which is less negative than the sweat pore, This mechanism makes it inperative to work with a completely hydrated preparation if this spurious effect is not to be confused with true positive potentials, such as mey be recorded with the site immersed in dilute saline.

Since the spiral duct appears to be relazively freely permeable to ions as it passes through the horny layer, the corneum acts as a volume conductor when noist and interferes with the separation of sweat gland and nembrane effects by means of súrface microelectrode recordings. To elininate this effect and also the hydration effect described above, the skin is now being prepared by slicing avay most of the corneum, so that the microelectrode may rest almost on the granular layer, or may be inserted directly into the exposed sweat duct at this level. About 12 exploratory experiments have been run to develop this technique and a series with a fixed experinental desiga has been initiated. Surprisingly, the potential at the surface pore is 10 to 20 mv more negative than the potential within the lumen of the duct at the granular or Nalpighian layer. This may be indlicative of a diffusicn potential across the spiral duct wali. Aiso surprising is the observation of positive as well as negative and biphasic waves from within the exposed lumen at the deeper level. Experiments entailing simultaneous microelectrode recordings from the duct and from the granular layer are in progress. These should hopefully furnish definicive information on the origin of the different forms of potential response.

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2. Aninal Experiments:

A series of expcrinents was run on 6 cats to investigate the characteristics of conductance and potentiel response in the footpad as a function of the pattern of electrical stimulation of the plantar nerve. Following repetitive stimulation (c.g., 8/sec, 15 volts, 5 sec.) there is an initial augmentation of the conductance response to single shock stimuli. The amplitude of this response, tested at 30-second intarvals, drops progressively to about S0 percent of its initial value over the course of 4 minutes following the repetitive volley. When it reaches this level, another repetitive volley causes an immediate doubling of the response to the standard single shock (Fig. 3). The decay then progresses as before. This phenomenon also occurs when skin potential responses are monitored. It is not due to base level effects (base level may be altered by only 5 percent during the repetitive volley and may fully recover by the time the first highly augmented response is elicited).

Another experímental finding in these experinents concerned the behavior of a second response superimposed on a preceding one. The findings of an earlier study indicated that the amplitude of a second conductance response was the same as the first, except for the steepest portion of the recovery slope of the first wave, at which point the second wave was markedly attenuated. This phenomenon was confirmed and extended to potential response πeasures. The behavior of the potential summation processes was almost identical to that of conductance summation. In these experiments, for an unknown reason, attenuation of the second response on the downward slope was coasiderably greater than in the first series.

The above findings suggested numerous follow-up experiments which could help lay the basis for the calibration of electrical changes in terms of nerve activity. However, these experiments were halted when it was iearned that the sweat slands of the cat footpad are apocrine (G. H. Wang, The Neural Control of Sveating, 1964). This has profound implications with regard to the interpretation of measurements from th≥ cat footpad. It renders the extrapolation of such results to bunan measurements highiy suspect. Investigators have, however, for several decades utilized the cat footpad as an experimental eccrine prepatacion. 'an investigatot well ex-Consulzation withi perienced in working with the cat footpad, revealed that there is considerable question as to the validity of Wang's statement. Until this matter is cleared up, however, this series of experiments is potentially irrelcvant and will be suspended.

3. Nail Plate Recordings:

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ponses recorded from the nail plate, previously reported, were pot artifacts of potentials generated in normal skin on the opposite or lateral sides of the finger and transmitted to the nail electrode by virtue of the volumc conductor properties of the finger. A portion of the nail plate near the distal, Iateral portion of the finger was cut away to expose the intact nail bed. Two simultaneous microelectrode recordings were cbtained from this area. The nost common recordings were pure fositive SPRs. When one of the microelectrodes was pushed barely through the uppcrmost layer of the nail bed, the potential showed a conspicuous positive shift of the order of iSmv and potential responses were markedly attenuated at this eiectrode. The control electrode remained active (Fig. 4). Tn three of the four subiects thus exanined, puncture caused attencation of the response (to a word association test) to less than 5 percent of the control level; in two of these the response was essentially abolished. When the microelectrode was withdrawn and placed ou the surface of the nail bed adjacent to the point of entry, activity reappeared, The fourth subject showed the positive shift with puncture but response amplitude, initially lo, was not diminished.Although this evidence,added to the eariier indirect evidence.gave compelling support to the contention that the responses did in fact originate in the surface of the nail bed, some doubt was cast on the supposition that the nail ted represents pure epidermal tissue (free of sweat glands) as described by histologists. jreported the findirg of sweat ducts along the distal margin of the nail which iavaded the nail field (personal communication). photographs do show the spiral ducts entering the periphery of the nail bed for a distance of 1 to 2 an. Whether these treversed the nail bed much further is uncertain; since nail recordings, except for those described above. are taken as close to the center of the nail bed as possible, it is thought unlikely that the potential recordings are contaminated by the products of sweat gland activity. However, until this factor is clearly resolved, the evidence from the nair bed mus- be accepted wich reservations. Histological data is now being sought to settle this issue.

4. A\_teration of SPR Waveform with Surface Solutions:

An earlier study had demonstrated that total amplitude of the e\_ectrodernal response, conductance or prcential, could be altered by the exposure of the site to various solutions, A follou-up study was undertaken to determine whether the positive and negative components could be selectively altered by this procedure. The exposure of palmar sites to 1M AlCl, was found to potentiate the positive response by an average o 750 percent (average on 7 subjects). The negative response was attenuated to 54 percent of control. but this may simply reflect the cancelling effect imposed by the increase in amplitude of the

……

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Fig. 4. Simultaneous microelectrode recordings from the nail bed showing positive responses to word associations. In the center penel, one aicroelectrode has been pushed through the gerninating layer and responses have disappeared. To the right, this electrode has been withdrawn again and replaced on the şurface near che puncture.

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positive wave in the complex (Fig. 5). It is of special significance zhat the earlier study on the conductance response showed an average of over 6cpercent increase in this measure. This suggests that the conductance response may be associated with the positive wave.

Another agent tried was SM NaCl. This had not been tested
for its effect on amplitude of conductance response, but had
been shown to reduce resistance to S percent of control level.
The effect on the potential response waveform was a conspicuous
potentiation of the "e" wave, a negative overshoot which
sonetimes follows the posit.e wave. Uniphasic negative waves
were unafiected (Fig. 6). Until the effect oa the resistance
response is determined, this effect cannot be fully interpreted.
It is presently considered to reflect a lytic effect on an
ionic barrier, presumably the semi-permeable merbrane res
ponsible for the positive wave. This membrane, according to
earlier studies from this laboratory, must be accessible to surface agents, and behaves as an imperfectly selective cation
perneable membrane. The initial phase of the response is seen as an increase in the permeability to cations, zesulting in a hyperpolarization, i.e., in a negative wave. As the breakdown of membrane resistance proceeds, the relative impermeabilicy to chloride is apparently lost and depolarization occurs, resulting in a positive wave. As the integrity of the meabrane is restored, the first effect is thought to be recovery of the relative impermeability to anions. If the recovery period is prolonged, there may be an appreciable delay before the permeability to cations is reduced to normal. During this phase, the membrane will be hyperpolarized, resulting in a second negative wave or overshoot, terned the "c" wave. A concentrated electrolyte such as 5M NaCi is thought to loosen membrane structure (to wit, the profound reduction in resistance) so that recovery is prolonged, accentuating the negative overshoot.

The above concept of the membrane process in the elestrodermal response also explains the effect of AlCiz. The absorption of the aluminum ion by the fixed negative charges of the membrane would cause partial neutralizetion and incipient loss of selective impernieability to anions. When the nembrane breakdcwn occurs during the response, the loss of impermcability to anions is therefore much more marked, resuiting in greater depolarization and a stronger positive wave. Although this explanation and that for the effect of 5M NaCl are hypothetical, they are consistent with a number of other experimental observations and in part form the basis of the newly formed model of elestrodernal activity.

二日

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5. Production of a Positive Potential Response by Local Mechanical Effect:

In 192l, Ebbecke discovered that a local dccrease in skin resistarce could be produced by pressure, electricity or heat and he interpreted this as the response of an epithelial ccil layer. Several years later, Rein found that a-positive potential response could be produced by the sane means. This phenomenon subscquently drew little attention, although it was confirmed by 7 It was reported to be obtained from various parts of the body but not from the palms or soles, a finding which suggests that sweat glands are not involved in the ptoccss. In an effort to facilitate the investigation of the properties of the positive response in the present research, a method was devised which would produce a fairly reproducible nechanical effect. Electrical stimulation did not appear desirable because of the numerous structures which it might activate. Pressure was thought undesirable because of the possible production of electrode artifact. The nechanical method chosen consists of taping to the volar surface of the finger a small inflatable bag. The tape is applied to the lateral sides of the finger such that inflation of the bag to 180m Hg exerts a stretch on the dorsal skin under the electrode. Inflations are made for 5 seconds at 30-second intervals and produce a square wave stretch. The response consists of a very rapid positive segment fo'lowed by a more gradually inçraasing segment (Fig. 7). In this recording, as in all others, two sites on separate fingers are subjected to the sttetch stimulus. A third site on another unstimulated finger is used to monitor any response of reflex origin. The locai responses (L) resemble the responses to word association (W) in general form and anplitude, but are not present on the non-stimulated control finger (C).

Although the response is relatively stable, it varies with the staze of background activity of -neural origia. In Figure 8, the enhancement of the response by negative skin potential accivity is illustrated during the response to a sniff. This potentiation is typical and hes been reproduced numerous times on 12 subjects.

The local potential response (LPR) has aiso been obtained from the volar surface of the finger, despice Ebbecke's statement to the contrary, possibly because he did not use stretch. Its amplitude, however, is less thar. that from the dorsal surface. No local conductance responses were obtainable from the volar surface, though they were readily obtainable from the dorsua.

The LPR can also be produced by vascular engorgenent of the finger, produced by the sudden inflation of an arterial finger

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L

Fig. 7. Comparison of local potential response (LPR) and central SPR to a word association stimulus. Upper trace: L = local stimulus (stretch); W = word association stimulus. Traces labelled L show racording from fingers fitted wich stretch device. Trace labelled C is a control finger which responds to central neural activity only.

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Fig. 8. Increase of LPR emplitude produced by background negative activity of neural origin. The negative activity has been proiuced by having the subject sniff sharply at point "s" on the upper trace.

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cuff. Because of the relatively large area enco=passed by the cuff and the small finger volume distal to it, tha vessels of the distal portion are markedly engorged. The resulting LPR is corsidered to be caused by stretching of the skin by this process. If prior to cuff inflation the hand is clevated to head level to empty the veins, inflation of the cuff produces littele or no LPR.

Exsanguination of the finger for 15 minutes, produced by rolling.a tight rubber doughnut from tip to base of the finger, potentiates the LPR by about 20 percent (14 subjects). The positive skin potential response of central origin (SPR) is simultaneously depressed, sometimes to less than 25 percent of control. If the positive LPR and the positive S?R are reflections of the activity of the sane end organ, this must indicate that hypoxia exerts its effect on the nerve endings rather than on the effector organ. Ebbecke, in fact, reported eliciting the local conductance response (LCR) from day-old cadavers.

The exsanguination data suggest that the LPR is not produced by a vascular mechanisn. Added evidcnce is seen in the fact that the LPR like the SPR is susceptible to the effects of locally applied electrolytes such as 1N AICl3, 1N NazSO4, or 5M NaCl. An example of this effect is seen in Figure 9, in which IN NaSO4 causes reversal of the rapid portion of the response but not of the secondary slower portion. This effect is reversed when the finger is returned to 0.1 NaCl solution. The effect of 1N AlCl3 is rather variable, although clearly present. At tines it attenuates the LPR; at other times it potentiates it. A solution of 5M NaCl produced a marked potentiation (e.g., l00 percent) of both phases of the response which was readily reversed by 0.1N NaCl. Work with this agent has just conmenced and the inter-subject variability of this effect is as yet unknown.

The rapid and slow components of this local response are considered to originate in separate processes since they occasionally dissociate as in the case of the results of exposure to NazSO4. An occasional subject wil1 show inversion of the rapid phase, with a normal positive slow phase. Because of the rapidity of the first phase and its negligitle latency, it is possible that it reflects the direct effect of stretch on the horny layer. Earlier unpublished data from this laboratory shows that a collodion membrane shen transiently stretched manifests a sharp alteration in the diffusion potential established across it. The horny layer possibly behaves in a sinilar fashion. If this is so, however, one would have great difficulty in explaining the augmentation of this response imnediately efter negative

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activity of central origin. Moreover, a simiiar pattern of fast and slow components is produced when the site is compressed rather than stretched. In this procedure a standard finger cuff is inflated over the electrode site. To test for whethcr the effect was due to electrode artifact, the experiment was repeated in solution with the elcctrode at some distance frox. the finger. In three subjects thus tested, the typical wave-form described for the stretch method persisted. It is therefore concluded that both the fast and slow components represent activities of two different viable membranes accessible to the surface, both sensitive to mechanical stimulation but either located at different points or heving different electrochemical characteristics.

6. VascuLar Effects and SPR:

In the first phases of the present investigation a series of experiments was undertaken to determine whether a vascular coaponent was involved in the skin potential response. Earlier work by Darrow and by Lader and Montagu had established that vasomotor activity did not account for any apprecieble porcion of the skin conductance response, but these authors did not investigate the relation to potential effects. Vascular changes weze induced by venous and arterial occlusioa, by means of pressure cuffs. Venous engorgement is known to produce a compensatory increase in venous tone. Arterial occlusfon produces a reactive hyperemia involving arteriolar dilation. Local cold causes a reflex vasoconstriction. If any of these local effects ate accompanied by a local potential change recordable on che skin surface, one must face the possibilicy that these may be present in the SPR.

Initial experiments were accomplished with venous occlusion (20 to 60 mm Hg). The cuff was placed on the arm with the reference electrode on the central side of it. The experinental site was on the volar surface of the middle segment of the finger. A site on the opposite hand was used to monitor central reflex effects incidental to the occlusive procedure. Out of a total of 69 occlusions on 7 subjects, 48 showed a negative local response of up to 3.7mv (averege 1.2mv). In later experinents, however, a' finger cuff was substituted for the arm cuff and the response disappeared or in some cases was positive. It was then determined, by varying the proximity of the reference electrode (outside the cuff) to the cuff, that the apparent local negative responses from the finger were in fact local pcsitive responses from the reference site, resulting fron mechanical deformation of the refererice area by inflation of the cuff.

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Fig. 9. Reversal of the fast LPR component produced by 1 N NazSO4. The reversibility of the effect upon substituting O.l N NaCl for the NazsO4 is shoun in the third panel. A,ccni rol; B, oie fin"er in XagSC4; C, rąturnel to NaCl.

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In cnother series of experiments exsanguination of the finger was accomplished by the method alrcady described, In four subjects exsanguination was terminated suddenly after 15 minutes by cutting the constricting toroid. The associated potential response was either minimal or absene. Further runs of this nature are scheduled as are simple axterial occlusions of varying durations. At present, indications are that vasomotor responses do not produce appreciable potential changes at the skin surface.

7. Testing of the

Experiments by lon the cat footpad have lead him to postulate that the electrodermal response can be explained entirely by the effects of filling the sweat ducts and hydration of the corneum, there being no necessity to consider the presence of an active membrane in explaining the electrical effects. Although at first glance an assortment of observations leads one to reject such a hypothesis, .has been successful in defending it from many points,of attack. To investigate the question as to whether Ihydration model or a menbrane model can best explain thè electrodermal response, the following test was perforaed.

Two similar active sites were exposed to constant current and constant voltage sources, each under dry and wet conditions. The dry condition would be expected, on the basis of J !nodel, to produce a larger response than the wet condition, whether a constant voltage or constant current source is used. The mämbrane model, because of the dead space (corneum) interposed betveen the electrode and the active membrane, predicts that responses should be reduced by the dry state with constapc voltage but not with constant curreat. Comparisons were run with dry plate electrodes against a preparation in which the corneum was allowed to hydrate with electrode jelly.

Observations on three subjects were all consistent with the membrane model in that responses were considerably higher with constant current than with constant voltage in the dry state; responses in the wet state vere higher than in the dry state when cpnstant voltage was used. These results imply the existence of an inactive resistance betwcen the surface and the site of resistance changes. Unless the hydration changes postulated by!jtake place in the deeper layers of the corneum, his model must be regarded as inconsistent with the results of these observations.

8. Model of Peripheral Electroderal Process:

The above findings have been conbined with. previously knowa

O

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data to devise a model whici best explains the total observations. It rests on several tentative conclusicns drawn from available evidence, namely:

a. Vascular effects probably play a negligible role in accounting directly for either conductance or potential responses.

b. A negatively charged membrane accessible to surface solutions is responsible for the jet-like potential and conductance responses which xecover rapidly and completely following neural discharge. This membrane is largely responsible for the positive potential response component, but can produce a short initial negative cosponent when the membrane breakdown process is slowed. It can also produce a negative overshoot. The conductance charge associated with this process is of the rapidly recovering type. This membrane is tentatively regarded as identical uith that responsible for the LPR and is thought to be located in an epidermal layer rather than in the sweat gland or duct. Activity of this πesbrane is considered to be associated with reabsorption of moisture from the corneum.

c. Secretion of the sweat gland is not attended by appreciable conductance or potential effects but the filling of the duct produces a reduction in resistance and a negative shift in surféce potential due to reduction in generator internal resistance. The sweat diffuses laterally out of the duct into the corneum where it is absorbed at a rate indicated by the incensity of positive activity. If absorption is slos, the associated resistance and potential changes may persist, resulting in a slow rate of recovery as seen in the first waves of figure 10.

B. A New Approach to the Analysis of the Skin Conductance Response

The manner in which the fast-reccvering membrane component and the slow-recovering sweat component are thought to combine to produce various forms of potential and conductance wave forms is illustrated by the recording in figure l0 and by the schematic addition in figure 1l. From figure l1 it is seen that a measure of the telative sweat and membrane activity may be obtained by inspection of the recovery limb, namely by observing the point at which the curve breaks and noting the elevation of the gentler slope above starting level. In practice, these two processes are frequently partially fused so that the overall recovery rate may serve only as a rough index of the relative sweating and absorption rates. The recovery of the fast conductance component appears tc be exponestial, in which case the time required for 50 percent recovery should be

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Fig. l0. Comparison of skin potential tracing (upper) and skin conductance tracing showing the relations of their various wave foras. The first three wavzs (a, b and c) axe characteristic of the pure negative sweat response with minimal reabsorption. Nembrane activity is indicated by the appearance of the fast components superimposed on the sweat weves at c and d in both traces.

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independent of amplitude. The recovery half-time would be prolonged in accordance with the amount of swoating in the response. Thus, recovery half-time (t/2) should, as a first approximation, constitute a useful measure of the relative mcmbrane and sweat activity of a wave.

C. Behavioral Studies

1. Theoretical Approach:

Duzing a comprehensive exploration of the cat-brain while recording from the foot-pad, ishoved that positive or negative responses could be obtained by cortical stiaulation, but that only negative responses could be elicited by stimulation of the hypothalamus. The positive waves were obtained by stimulation of the premotor cortex (Brodmann Area ), an area responsible for fine motor coordination. Lesions in this area cause loss of motor inhibitory restraint and produce forced grasping. If a monkey with such a lesion (bilateral) lies on its side, the forced grasping is relaxed on the downward side, indicating that another inhibitory influence has takan over, perhaps aediated by the vestibular and cerebellar control mechanisms. Interestingly, a human subject with electrodes on each hand shows a depression of the positive SPR on the dowaward side when he lies on his side. This is suggestive of the elation of positive activity to fine motor coordination. It is hypothesized that the pre-motor area functions in the fine adjustment of the moisture content of the skin necessary for manipulative behavior. The positive wave, shown earlier to be associeted with water-reaosorption, is seen as an indicator of this regulatory process and therefore of a set for soaldirected anipulative behavior. Electrodermal activity of hypotha\_aπic origin on the other hand, tied as it is to the limbic system, is (in the absence of thermoregulatory denands) more indicative of, an emotional response associated with palmar and plantar sveating. In the light of the mechanical resiscance to abrasion afforded the skin by high levels of hydration, this is considered to be a protective maneuver. While,,sweating may be produced by stimulation of the premotor corrextype of sweating is viewed as delicately tegulating the moisture content of the palmar and plantar corneum and is likely to be accompanied by evidence of the reabsorption process manifested by positive activity. Non-thermoregulatory activity or hypothalamic origin is viewed as  primarily protective and would nct likely be ac ompanied by the reabsorption process; it should therefore not show the positive component. Obviously this approach must represent a gross oversimplification of the control process, which includes inhibitory as well as facilatory inizuences from many other parts of the brain, inclucing the extra-pyramidal systen and limbic structures. However, ic does establish a rationale for rating responses along a dimension from primarily defense reactions to primarily goaldizectec prcpaxetions. F:xther, it elaborates a behavicral

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model which may be woighed against future findings and modified as dictated by the facts. The quantitative data for evaluating responses would be obtaincd froa aaalysis of either thc potential response or the conductance response, but because of the greater number of complicating factors in the analysis of the SPR, the conductance response has becn chosen for first examination. The recovery half-time (t/2) has specifically been utilizec for this neasure.

2. Application Demonstrating Specificity of Individual Stimuli:

In an earlier study it was shown that there is a qualitative difference between the electrodermal response to the alerting signal for a forthcoming task and to the subsequent signal for execution of the task. This difference which was independent of absolute amplitude was seen as a change in the ratio of the anplitudes of the palmar and dorsal finger response. This ratio, BD, increases with relative "sweatiness" of a response because of the marked difference in sweat gland œoncentration from the two areas. Although this method produced a denonstrable separation of responses, it was relatively insensitive and subject to numerous complications. Further, it did not lend itself readily to on-line automatic analysis. The recovery half-time measuré was applied to sone of these sare data. It was considerably more sensitive in terms of the percent difference between the responses to the alerting and execution signal, despite the fact that it utilized only a single site. A comparison of the two measures for alerting and execution signals in a simple perceptual task and in a reaction time task is given ia table 1. For this subject the t/2 measure was much more coasistent and more discriminating than F/D in the perceptual task. In the reaction time task, although it showed larger differences between the two types of response, it was not as consistent as was the P/D measure. Out of 7 subjects tested in a similar fashion to date, 6 showed t/2 to have a discriminative power equal to or better than the P/D seasure.

3. Application to Discernπent of Situational Differences:

In another type of experiment the measurenent of recovery half-time was applied to the separation of two stetes or prolonged activity, nanely rest and task performance in an effort to determine whether e shift in state of activation would be in evidence even when no change in amplitude of response occurred. The two situations were (1) relaxing in a seated posture, eyes open, awaiting the start of the task instruction, (2) engaging in an eggressive task. This task consisted oz calling aloud a serieș of numbers from 1 to 10 which the expe-imenter wculd attempt to guess, the purpose being to allow che experimenter the fevest number of correct guesses. The last three relatively pure wayes of the rest condition were chosen Eor anelysis. The

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first three waves during the task period which matched these in .olitnde were chosen for the comparison. Results for the 12 ubis are shown in table 2. Al1 12 showed the same resulcs, namely a shortening of the recovery half-time during the task period (Fig. 12). According to the theoretical framework underlying the analytic approach, this would indicate that the moistureregulating mechanism, supposedly activated for goal-directed manipulative behavior, was nobilized during the task which included the use of a push button signal by the subject. However, similar results were obtained even when no push button procedure was included. This suggests an extension of this motor preparation to problem-solving situations in general, even though the manipulation may be only syabolic.

III. Conclusions

Because of the relative simplicity and high sensitivity of the t/2 measure, it should lend itself well to automation. It is alsost, but not entirely, independent of response amplitude and thus constitutes a measure of the quality of response which is relatively free of the problem of assessing overall activation level of the electroderal system. It apparently can differentiate between behavioral shifts of relatively long duretion, as well as between the rapid shifts associated wich two successive brief sticuli of different qualitative meaning. Future efforts will be concerned with investigating its sensitivity zo various subjective states, especially the defense reaction and to deterining whether it is affected by changes in base level. At the same time efforts will be made to devise a system for automating extraction of this measure.

The pieces necessary to construct a faithful model of the peripheral electrodermal effector system are gzadually falling into place. Feur most promising areas for further study of this system include nicroelectrode expeximents, observations on the locally induced response, studies on the effects of various solutions,applied to the skin surface, end studies on the reabsorption process. These are presently occupying a major part of the laboratory effort and will continue to do so for an eppreciable period.