Bilateral Electrodermal Activity, Lateralized Cerebral Processing and Sex

The present study involved the assessment of systematic differences between skin conductance measures recorded bilaterally and concomitantly from 59 right-handed subjects while they were exposed to three types of stimuli. The stimuli were 5 min each of: a quiet period, a period of music, and a period of listening to a series of paragraphs. The music and paragraph conditions served, respectively, as operational definitions of right and left hemisphere tasks. Sex and genetic handedness were also assessed. Results showed that subjects with a family history of sinistrality gave more frequent SCRs on the left hand than on the right hand under the verbal condition, while those with entirely dextral families showed no left-right differentiation. In addition, musical stimulation produced more frequent responses in males than females, while the reverse was true for verbal stimuli. Finally, tonic SCL was higher on the right hand in males and on the left in females. Stimulation intended for a specific hemisphere did not produce significantly greater electrodermal activity on the contralateral hand.     

Bilateral Electrodermal Activity During Differential Cognitive Hemispheric Activation

In an attempt to reconcile inconsistent results reported to date, 27 dextral males were administered two separate procedures to examine the effects of hemisphere-specific cognitive tasks on bilateral electrodermal activity. The first procedure used arithmetic problems and slide visualizations to activate the left and right hemispheres respectively; the second procedure used aural proverbs and visualization problems. Neither procedure produced the expected electrodermal response magnitude asymmetry across tasks. While the potential effects of uncontrolled variables are discussed, these results question the robustness of the relationship between differential hemispheric activation and asymmetric electrodermal response magnitudes.     

Lateralization in the Electrodermal System as a Function of Cognitive/Hemispheric Manipulations

Three experiments examined patterns of bilateral differences in skin conductance as a function of cognitive tasks intended to produce specific manipulations in the relative activation of the two hemispheres. Experiments 1 and 2 employed right-handed subjects, and examined the effects of Verbal (left-hemispheric) and Spatial (right-hemispheric) tasks. In both experiments response amplitudes were substantially smaller in the hand contralateral to the more activated hemisphere than in the ipsilateral hand. Experiment 2 also examined the effects of Music and Number tasks, intended to produce a similar level of activation in the two hemispheres: these tasks were not accompanied by reliable bilateral differences in electrodermal activity. Experiment 3 consisted of a replication of Experiment 2 with subjects (sinistrals) known, as a group, to exhibit little functional hemispheric specialization. In these subjects, bilateral electrodermal differences did not vary systematically as a function of tasks. These findings argue strongly for the presence of lateralized cortical influences on electrodermal activity, and their implications for psychological and neurophysiological models of electrodermal functioning are discussed.     

Hemispheric Asymmetry and Bilateral Electrodermal Recordings: A Review of the Evidence

Bilateral electrodermal recordings are often used in psychophysiological research as a measure of functional hemispheric asymmetry. Although significant differences between left and right hand recordings are reported in the literature, the obtained differences are often in different directions. The purpose of the present paper was to review empirical evidence related to the issue of bilateral electrodermal recordings in research on hemispheric asymmetry. Special reference is made to the current controversy concerning contralateral inhibition vs. excitation or facilitation as the underlying mechanism for reported differences in performance of typical hemisphere-specific tasks. After reviewing the evidence, which is contradictory concerning several of the more critical parameters, the conclusion is that bilateral electrodermal recordings have not been unambiguously related to hemispheric asymmetry. However, when asymmetry between the hands is clearly demonstrated, this reflects an asymmetry in the functioning of the cerebral hemispheres.     

An Automatic Voltage Suppressor For the Measurement of Electrodermal Activity

An automatic voltage suppressor is described which increases the resolution of skin conductance and/or skin potential responses, facilitates the measurement of the corresponding levels, and prepares both electrodermal quantities for automatic data processing. The device accomplishes: 1) scanning of the levels at preset moments, 2) digital storing of these values for the corresponding time intervals, 3) subtraction of the stored values (minus an adjustable reserve) from the input signals, and 4) amplification of the difference voltages. Easy and inexpensive construction of the apparatus is possible using a minimal number of highly integrated circuits.     

Electrodermal Activity in Hyperactive Boys Who Are Methylphenidate Responders

Hyperactive boys being treated with methylphenidate medication were randomly divided into two groups. In one of the hyperactive groups (n = 18) methylphenidate was withheld for approximately 72 hrs before testing. Boys in the other hyperactive group (n = 20) continued to take their usual daily doses of methylphenidate. Normal boys formed a third group (n = 20). The following electrodermal measures were taken: basal resistance, frequency of non-specific responses, specific response amplitude to an auditory signal, and number of trials to habituation. Normal and off-drug hyperactive groups differed significantly on specific response amplitude, and trials to habituation. In addition, frequency of non-specific responses approached significance. These differences indicated lower reactivity in the off-drug hyperactive group. Off-drug and on-drug hyperactive groups differed significantly on frequency of non-specific responses. In addition, trials to habituation approached significance. These differences again indicated lower reactivity in the off-drug hyperactive group.     

Electrodermal Activity in Patients with Huntington''s Disease and Their Progeny

Skin conductance was examined in patients with Huntington's disease (HD) and progeny at risk for HD to determine if electrodermal characteristics had potential to identify those progeny likely to succumb to HD. The two experimental groups chosen for study consisted of 7 patients in the early stages of HD and 29 progeny of HD patients. Because the HD and at-risk groups differed in age and sexual composition, each was matched by age and sex to separate psychiatrically and medically healthy normal control samples. Skin conductance was recorded bilaterally while subjects listened to three series of stimuli: 8 85dB tones, 12 105dB tones, and two familiar sounds. Dependent measures included skin conductance level, number of nonspecific responses, number of responses elicited by each tone series and the sounds, the amplitude, latency, rise time, and half-recovery rime of the first tone-elicited response in each series, and habituation rate to the soft and loud tones. The data analysis was carried out by comparing each experimental group to its matched comparison sample. A variety of parametric and nonparametric tests were carried out; no significant differences emerged either between the HD patients and their control group or between the at-risk subjects and their normal comparison group. Ninety-seven percent and 86% of the at-risk and HD subjects, respectively, responded at least once to the experimental stimuli, compared to 90% and 86% of the corresponding control groups.     

Another Look at the Relationship of Electrodermal Activity to Electrode Contact Area

The present study was undertaken lo reexamine the hypothesis that the relationship between skin conductance and electrode size is monotonic and linear. Skin conductance activity was recorded from 48 right-handed male subjects using 6 different sixes of electrode collars ranging in exposed surface area from .131 cm² to .786 cm². The dependent measures were skin conductance level (SCL); skin conductance response (SCR) amplitude to a series of 8 loud tones; latency, rise time, and recovery half-time of the first tone elicited response; (he largest self-generated SCR; and the number of nonspecific responses. The results indicated a significant linear relationship between contact area and SCL, stimulus and self-generated SCR amplitude, and the number of nonspecific responses. Latency was not affected by electrode size although the other time-based measures were. Differences in skin conductance activity were found among different palmar recording sites. The observed linear relationship between electrode size and electrodermal measures has implications for current models of electrodermal activity and for the comparison of results across studies in which different electrode contact areas are used.     

A Major Effect of Recording Site on Measurement of Electrodermal Activity

Although the medial phalanx has been recommended as the preferred site for recording skin conductance activity, a review of articles published in Psychophysiology indicates that a large minority (34%) of studies employ the distal phalanx. Informal observations also suggest that the distal site may be more reactive than the medial site. This study formally tests this observation by recording skin conductance from both medial and distal phalanges. Twenty-four right-handed subjects (12 male, 12 female) were exposed to a series of 10 orienting and defensive stimuli. Electrodes were placed on the fore and middle fingers of each hand, with distal sites used on one hand and medial sites on the other for each subject. Skin conductance amplitudes were 3.5 times larger at distal than medial sites (p less than .002), while skin conductance levels were 2.08 times larger at distal sites (p less than .0005). A significant Site X Stimulus interaction (p less than .025) indicated that the distal site was more sensitive to habituation over trials and to increases in skin conductance amplitudes with increasing stimulus intensity than the medial site. On the basis of these findings it is recommended that distal sites be used in preference to medial sites in the recording of skin conductance activity.     

Electrodermal Recovery and Stimulus Significance

The validity of Edelberg's (1970) hypothesis that speed at which the electrodermal response (EDR) recovers is affected by meaning of the stimulus evoking it, has been challenged by subsequent work showing prior ED activity's (EDA) highly significant association with ED recovery time. However, prior EDA's association with ED recovery does not rule out the possibility that the stimulus meaning may also affect recovery. In the present study a within-subjects design (N = 10) was used to evaluate effects of stimulus significance on skin conductance response (SCR) amplitude and recovery time (rec t/2) while prior EDA was held constant. Amplitude was greater and rec t/2 longer (slower) when the stimulus significance increased, and the effect on recovery did not depend entirely on amplitude. Prior EDA also affected amplitude and recovery but stimulus meaning had an additional effect. These findings contradict the notion of the EDR as a unitary phenomenon, and imply that both peripheral and central mechanisms are involved in determining response amplitude and recovery. Stimulus meaning may affect recovery to an even greater degree than it affects amplitude.     

Sympathetic Nerve Activity Underlying Electrodermal and Cardiovascular Reactions in Man

The paper summarizes results of micro-electrode recordings of sympathetic activity in human muscle and skin nerves. The nerve activity was correlated with blood pressure, plasma noradrenaline, electrodermal and/ or plethysmographic activity. Baroreflex and thermoregulatory mechanisms were studied as well as effects of arousal or emotional stimuli.     

Auditory Vigilance Correlates of Electrodermal Response Habituation Speed

The present study was designed to test the hypothesis that individual differences in the speed of habituation of the phasic eleclrodermal response (EDR) reflect characteristic rates of attentional decrement with stimulus repetition. Subjects selected for the extrems of EDR habituation speed to a pure tone were subsequently tested in an auditory vigilance task. Slow habituators showed a high and substained rate of signal detection, while Fast habituatos showed a lower overall rate and a time-on-task decrement. Further analyses employing signal detection theory measures indicated that these detection differences were due to group differences in response criterion levels rather than to differences in the rate of attentional decrement. The implications of this finding for understanding individual differences in EDR habituation speed are discussed.     

Bilateral Electrodermal and Electrocortical Activity in Anticipation of Sensorimotor Tasks

The present study investigated the relationship between lateralized sensorimotor activation and lateralized elevation of electrodermal activity. Within a two-stimulus reaction time paradigm skin conductance responses (SCRs) were recorded from both hands, while subjects awaited and performed unilateral sensorimotor tasks. A tactile warning stimulus was applied 6 s prior to a tactile imperative stimulus either to the same or to the contralateral hand; the imperative stimulus was associated with a choice reaction time task. Task-dependent lateral asymmetry with larger skin conductance responses contralateral to the involved hemisphere indicated contralateral facilitatory processes rather than inhibition. This asymmetry disappeared with repeated stimulation (across trials). Only right-hand (left hemispheric) tasks proved to be sensitive to habituation. The asymmetry, recorded in slow brain potentials (SP_s), assured that lateralized cortical processing was induced through the present experimental arrangement. The brain potentials specified the time course of lateralized processing, exhibiting larger late negative shifts at the precentral areas contralateral to the hand involved in the sensorimotor task and larger early negativity and a more pronounced positive evoked potential (late positive complex, LPC) contralateral to the hand stimulated by the tactile warning stimulus.     

Prior Activity as a Determinant of Electrodermal Recovery Rate

This study attempts to assess Bundy's 1974 report that electrodermal recovery rate (ERR) can be accurately predicted by a variable, X, based on the recency and amplitude of prior activity. Five different types of assessment were made with the following results. (1) ERR was significantly related to X in two paradigms which avoided the temporal constraints of Bundy's experiment. (2) ERR of responses to repeated reaction time stimuli could be altered by controlling the magnitude of X. (3) A change in stimulus from a reaction time signal to a loud noise failed to change ERR when the value for X was held constant and when response amplitude was treated as a covariate. (4) The rank order of ERRs for reaction time signals and for loud sounds could be reversed by controlling the magnitude of X. (5) Differences in ERR associated with a cold pressor exposure and a mirror tracing task were reevaluated taking into account prior activity. Analysis of covariance with Bundy's X as the covariate failed to erase the difference. However, with a new covariate, namely the number of electrodermal responses in the 15 sec before the measured response, the difference in ERR became nonsignificant. In agreement with Bundy, prior activity appears to represent a major determinant of recovery rate. It is suggested that for those studies reporting ERR differences, attention should be focused on the biobehavioral implications of the likely differences in prior activity.     

Differential Responsiveness of Two Electrodermal Indices to Psychological Stress and Performance of a Complex Cognitive Task

Sixteen high trait anxious and 16 low trait anxious male Ss were assigned to a high stress (HS) or a low stress (LS) condition and were given differentially stressful instructions. All Ss were then required to perform a complex cognitive task, the Halstead Category Test. Adjusted indices of tonic and phasic exosomatic electrodermal activity were monitored throughout the experiment. Level of tonic skin conductance (SC) was only minimally responsive to the manipulation of psychological stress but increased greatly during cognitive and perceptual activity. Phasic activity increased significantly following psychological stress but not following cognitive and perceptual activity. It was concluded that these results support a multiple component theory of electrodermal activity. Phasic electrodermal activity appears to increase with psychological as well as physical threat and was suggested to be a good index of autonomic emotional arousal. Tonic SC appears to change mainly as a function of cognitive activity.     

Electrodermal Lability and Visual Information Processing

Individual differences in electrodermal lability have been related to performance in vigilance and reaction time tasks. The goal of the present study was to employ an "additive factors" approach to identify the stages of information processing that might underlie these effects. Nineteen labile and 17 stabile subjects performed a choice reaction time task in which a visual imperative stimulus was presented under two conditions of intensity (presumed to affect the speed of pre-processing operations) X three conditions of degradation (which influences later encoding processes related to feature extraction). Measures of both reaction time and movement time were obtained. The major findings were: (a) labile subjects had faster reaction times than stabiles, and (b) lability interacted significantly with stimulus degradation. Labiles also tended (p less than .10) to have faster movement times. This pattern indicates that labiles and stabiles differ in the performance of later encoding operations, and possibly in the speed of motor processes as well. However, they do not appear to differ in the early pre-processing of the simple physical attributes of a stimulus.     

Learned Asymmetry of Localized Electrodermal Responses

The present study investigated the possibility of establishing bilateral electrodermal responsivity of skin on the digits following the pairing of electric show applied to one hand in conjunction with the visual presentation of a triangle. Ten subjects (Ss) displayed significantly larger electrodermal responses on the hand previously shocked when presented with the image of a triangle without shock. No bilateral differences were observed during the presentation of a neural stimulus a circle, These results are interpreted as supporting the notion of learned a asymmetry of localization electrodermal responses.     

A Comparison Between Commercially Available Electrode Gels and Purpose-Made Gel, in the Measurement of Electrodermal Activity

Despite general agreement that a standardised procedure is desirable for the measurement of electrodermal activity, several types of electrode gel are in common use. In this study, 20 volunteers listened to a series of tones while skin conductance was measured at four sites using four different gels, namely K-Y Jelly, Beckman, Neptic, and purpose-made 0.05M NaCl in methyl cellulose. Prestimulus conductance level, response amplitude, change in conductance level, response latency, and response probability were measured. Analysis of variance showed a significant between-gels effect for prestimulus conductance levels, with Beckman and Neptic giving higher levels than K-Y Jelly or 0.05M, as predicted. There were no between-gels effects for the other variables. There were no effects due to placements or channels. The results are discussed in relation to the theoretical requirements of electrode gels used for measuring electrodermal activity.     

The Relationship of Symptomatology and Medication to Electrodermal Activity in Schizophrenia

An electrodermal assessment procedure using mild innocuous tones, task-relevant tones, and loud white noise was administered to a sample of schizophrenic patients (n = 77). The present study investigated the relationship of schizophrenic symptomatology and anticholinergic level of neuroleptic medication to electrodermal variables. Each patient was evaluated for positive (florid) and negative (defect) symptoms. The neuroleptics that patients received were rated according to their anticholinergic effect. No significant differences in symptomatology were observed between electrodermal responders and nonresponders; however, nonresponders showed a nonsignificant tendency to have more positive and negative symptoms than responders. Both negative symptoms and anticholinergic levels were significant predictors of lower tonic levels of skin conductance. Patients receiving high anticholinergic neuroleptics showed significantly reduced measures of electrodermal responsivity and tonic levels. Thus, both symptomatology and type of neuroleptic are related to electrodermal measures, with the anticholinergic effect of neuroleptic medication being more pronounced.     

Electrodermal Responsivity in Young Hypotensive and Hypertensive Men

Electrodermal responses were recorded during the presentation of 16 moderately intense (1000 Hz, 90dB) tones in three groups of young men: borderline hypertensives (138/79 mmHg), normotensives (112/65 mmHg), and hypotensives (104/63 mmHg). Electrodermal response habituation was measured as a decline in response over trials, number of trials to a response criterion of three successive nonresponses, and number of inversions of response amplitude (larger responses following smaller responses) in the stimulus sequence. Habituation was fastest in hypotensives. Nonspecific electrodermal responses at rest and during tone presentations were most frequent in borderline hypertensives, least frequent in the hypotensive group, with the normotensive group falling in between. There were no significant differences in electrodermal level. The rapid habituation rate in hypotensives is discussed in terms of cursory information processing associated with impulsive behaviour. The higher nonspecific electrodermal activity in borderline hypertensives is interpreted to indicate increased sympathetic nervous system activity.