Evoked Potential Tests of Augmenting-Reducing

Two evoked potential tests of augmenting-reducing, using flash and sine wave modulated light stimuli, were administered to 23 normal Ss to determine: a) generalizability between tests; b) short-term reliability; c) influence of electrooculographic (EOG) activity; d) relationships between perceptual discrimination of stimuli and evoked response measurements; e) correlation between evoked responses, extraversion and neuroticism (Eysenck Personality Inventory). Four months later 11 Ss were retested before and after pilocarpine fixation of the pupil in miosis, to assess long-term reliability and pupillary factors. Although mean amplitudes of sine and flash responses were significantly positively correlated, correlations between linear slope measures of their intensity-response functions were low. Both short- and long-term reliability were high for mean amplitudes, but relatively low for most slope measures. Ocular factors, as reflected in EOG and changes with pupillary miosis, appeared to exert relatively little influence on the evoked potential measures of augmenting-reducing. Subjective perceptual discrimination performance was not correlated with evoked potential measures. Extraversion was correlated with some evoked response augmenting indicators; neuroticism yielded inconsistent results. Generally, results varied with lead placement.     

Overextinction of the Evoked Skin Conductance Response: An EEG Study

The present study was designed to investigate Sokolov's (1963) proposal that overextinction of the orienting response (OR) is related to sleep onset. A series of 80 auditory stimuli was presented to 22 male and female Ss. Although re-evocation of the skin conductance response (SCR) component of the OR occurred, in the majority of Ss, after 40–50 stimulus presentations, this was not accompanied by any change in cortical alertness as measured by integrated EEG output in three frequency bands (2–4, 4–8, and 8–13 Hz). However, the results did indicate that Ss displaying SCR return required more stimulus presentations before initial SCR habituation and displayed more spontaneous fluctuations in skin conductance during the prestimulus period than did non-return Ss. Within the return group, latency of SCR return was negatively related to both spontaneous activity during the prestimulus period and number of stimuli to initial habituation.     

Amplitude and Latency Changes in the Visual Evoked Potential to Different Stimulus Intensities

Visual evoked potentials (VEPs) were recorded from five sites (T₃, T₄, C_z, O₁, O₂) to six intensities of light flashes. Peak-to-trough amplitudes were measured for the P100-N120 and N120-P200 waveforms as well as baseline (prestimulus)-to-peak amplitudes for each component (i.e. P100, N120, and P200). Different methods of defining augmenting/reducing were compared. These included subtracting the VEP epoch mean level from mean levels within a timeband corresponding to P100 and calculating slopes both for these values and for the P100-N120 amplitudes across intensities. The technique of using slopes to describe amplitude-intensity functions was found to be unjustified and misleading. The Augmenting/Reducing groups defined by the slopes of peak-to-trough amplitudes or slopes of the timeband “amplitudes” proved to be almost mutually exclusive. Results also showed that the frequency with which actual VEP peaks occur within the appropriate timeband is very low and differs topographically. Augmenting/Reducing was then defined by monotonic increases in the P100-N120 peak-to-trough amplitudes. Augmenters and Reducers differed from each other not only for amplitude-intensity patterns but on a number of latency measures. Hemisphere differences were also found between groups. An inverse relationship was found between occipital and vertex amplitude-intensity patterns such that vertex augmenting was accompanied by occipital reducing and vice versa. Temporal and vertex amplitude-intensity patterns were similar.     

Bilateral Skin Conductance and Skin Potential in Schizophrenic and Normal Subjects: The Identification of the Fast Habituator Group of Schizophrenics

Chronic schizophrenics from three different hospitals were compared to normal subjects on skin conductance parameters. In addition to “Responders” and “Nonresponders” as reported by Gruzelier and Venables (1972), a group of “Fast Habituator” schizophrenics was found. These subjects produce one or at most two responses before habituation in an orienting series. The SC waveform of fast habituator subjects shows long latency, slow risetime and long recovery, although the amplitude of response is within normal limits.     

Delayed Habituation of the Electrodermal Orienting Response as a Function of Increased Level of Arousal

Level of arousal was manipulated by having subjects perform arithmetic tasks during a habituation procedure, which consisted of 55 presentations or a 1000 Hz. 80 dB tone. For one group a threat of shock was added to the task performance in order to include aspects of stress in the arousal manipulation. These two groups were compared with a group who heard the same stimuli but were simply instructed to relax. The three groups differed in level of arousal according to KEG signs of drowsiness, skin conductance level, and frequency of spontaneous skin conductance responses, All three groups differed from each other in number of trials to habituation criterion for skin conductance responses to stimuli. Since the delay of habituation was seen tin- both the Task group and the Shock-threat group, it was concluded that the effect was not bound to aspects of stress but was a general effect of increased arousal. For vasomotor responses an analysis in terms of habituation was difficult to apply because the two high arousal groups were very unresponsive from the beginning.     

The Latency Distribution of the Skin Conductance Response as a Function of the CS-UCS Interval

Latency distributions were obtained for the skin conductance response, by blocks of 5 trials, for groups (N = 13) conditioned with CS-UCS intervals of 3.5, 5.5, 7.5, 10.5, 15.5, and 20.5 sec. Another group (N = 13) received 5, 10, 15, 20, 25, and 30 trials respectively with a .5 sec CS-UCS interval. For all blocks of 5 trials, in the extended CS-UCS groups, the modal response occurred in the 2–3 sec latency range characteristic of the orienting response (OR). There was no significant difference in OR frequency as a function of the CS-UCS interval. There was no systematic increase in response frequency with repeated trials in any of the latency ranges scored. No significant difference in acquisition was obtained as a function of the CS-UCS interval in the extended CS-UCS groups for either frequency or for magnitude. Performance of the (composite) .5 sec CS-UCS group was superior to that of the extended groups. This difference was not attributable to differential OR frequency. The PC group also exhibited a modal response in the 2–3 sec (OR) latency range. Response frequency in the OR latency range was lower in the PC group than in the conditioned groups, but response frequency outside of the OR range was higher in the PC groups than in the conditioned groups.     

Probability Learning and the P3 Component of the Visual Evoked Potential in Man

Evoked potentials were recorded to stimuli (S1) which were predictive of stimuli (S2) worth different monetary values to determine if these waveforms reflected the probability and/or the value of the predicted event as the subject learned the relationship between S1 and S2. Both the monetary value of S2 and its conditional probability following S1 were systematically manipulated over a wide range of values. Subjects were required to use the conditional probability information (0.5,0.75,1.0) in order to make a correct behavioral response and receive the monetary payoff ($0, $1, $2). The results indicate that the amplitude of the P3 component of the average evoked response to S1 increases as subjects learn the relationship between S1 and S2, and S2 is a high value event.     

Average Evoked Potential Changes as a Function of Processing Complexity

Electrophysiologic potentials (average evoked potentials (AEP) and contingent negative variation (CNV)) recorded during simple recognition and discriminative responses to tachistoscopically presented letter-pair stimuli showed a systematic shift toward greater overall positivity (i.e., smaller CNVs and larger late positive components) during increased processing load. In addition, more positive P2 components were found in the right as compared to the left hemisphere during simple recognition, and this asymmetry was enhanced during the more complex processing condition.     

Skin Conductance Responses in Huntington's Chorea Progeny

To test the assumption that limbic dysfunctioning in Huntington's Chorea (HC) would be reflected in abnormal skin conductance responses, 25 patients were examined.Only 2 of these patient showed normal skin conductance response. A further sample of 52 first generation, asymptomatic offspring of diagnosed HC patentes were tested. Seventeen of the at-risk subject were non-responders compared with 2 non-responders in the control sample of 26 subjects. The finding could be interpreted to favor the hypothesis that the presence of the pathogenic gene is correlated with electrodermal non-responding.     

Anxiety and the Habituation of the Skin Conductance Response

The effect of threat of shock on the habituation of the skin conductance response (SCR) to a series of auditory stimuli was assessed. Skin resistance and heart rate were recorded during the presentation of 20, 1 sec, 1000 Hz tones in a control session and in a session at the end of which subjects were led to expect a painful electric shock. The effects of the threat of shock consisted of recovery of the SCR and an increase in skin conductance level and heart rate. They were restricted to the period during which subjects believed the shock to be imminent. Two possible reasons for the SCR recovery were offered, one in terms of Lader and Mathews' (1968) ‘maximal habituation’ hypothesis and a second in terms of a change in the stimulus complex.     

The Effects of Paced Tapping on Heart Rate, Skin Conductance, and Muscle Potential

The use of a tapping response as an indicant of interest or preference in studies of the physiological correlates of attitude and attitude change is discussed. The physiological effects of paced tapping, using rates that might be employed in attitudinal studies, were examined under conditions free of attitudinal import. Major findings were: (1) There is no significant difference in the effect on HR with rates up to 3/sec. (2) There is no significant difference in the effect on SCL with rates up to 7/sec. (3) When raw EMG scores are used as the basis of analysis no significant differences are found with rates up to 3/sec; however, when the square root transform of this variable is used, a significant effect is found for all rates used in at least one of the phases of the experiment. The results, taken as a whole, indicate the possibility of either controlling or mathematically compensating for the physiological effect of the tapping response, per se, in attitudinal studies.     

The Effect of Stimulus Significance on Skin Conductance Recovery

The relationship between skin conductance (SC) recovery time and stimulus meaning was investigated. Previous research has shown that a strong relationship between prestimulus electrodermal activity (prior activity) and recovery time makes it necessary to control prior activity before the relationship of recovery time and stimulus meaning can be evaluated properly. In this study prior activity was controlled by experimental design. We examined the effects of stimulus meaning on skin conductance recovery time and amplitude in 55 teenage and young adult subjects in a continuous performance paradigm. Tones were presented monaurally to left and right ears. Subjects were required to make a pedal press after any tone in the left or right ear that followed a right-ear tone. Recovery time was computed for left-ear and right-ear tones not requiring a press because they had been preceded by a left-ear tone. SC recovery was longer for signal (right-ear) than for nonsignal (left-ear) tones with the effects of prior SC activity and amplitude removed. These findings replicate those of a pilot study (Janes, 1982). We conclude that stimulus significance can affect SC recovery time and that in this paradigm differences in prior SC activity cannot account for the recovery time differences observed.     

Bilateral Asymmetry of Skin Conductance Responses During Auditory and Visual Tasks

Bilateral skin conductance (SC) was recorded while dextral subjects engaged in tasks designed to differentially engage the right (RH) and left (LH) hemispheres. Subjects compared strings of speech sounds (LH) and musical chords (RH). They also decided whether written words rhymed (LH) and viewed pictures of faces in a continuous recognition paradigm (RH). SCRs in the right hand were larger during the chords task than the syllables task. The left hand did not differ for the two stimuli. In the visual experiment a comparable effect was obtained in males only. SCRs in the left hand were larger for rhymes than faces; the right hand did not differentiate between stimuli. Sex differences in laterality are considered. Subjects who were more equally balanced in awareness of the two sides of their bodies and subjects with familial sinistrals were more likely to show task appropriate SC changes. Using rote repetition and visual imagery as mnemonics did not affect SC asymmetries.     

The Role of the Orienting Response in the Anticipation of Information: A Skin Conductance Response Study

Theoretical positions concerning the role of the orienting response (OR) in information-processing and attention have viewed the OR either as indexing an active increase in information-processing efficiency, or as passively reflecting the results of information processing. This paper reports a skin conductance response (SCR) study of a two-stimulus anticipation experiment, where a warning stimulus (WS) informed subjects of the nature of an impending imperative stimulus (IS). The subjects' task was to identify as much of the IS as possible. Both the WS and the IS varied in information content and stimulus duration. SCR magnitude in the WS-IS interval varied according to the anticipated information processing requirements and was more sensitive to IS variation than WS variation. It is concluded that these responses index an anticipatory, activating process closely related to that suggested of the OR by Sokolov (1966), and consonant with the functional characteristics of the autonomic nervous system. Registration of information appears to be neither a necessary determinant of OR magnitude, nor a parsimoniously useful part of OR theory.     

Effects of Changes in Verbal Stimuli on the Skin Conductance Response Component of the Orienting Response

This paper presents three experiments which were designed to investigate the effects of changes in verbal stimulus meaning on magnitude of the skin conductance response (SCR) component of the orienting response (OR). In Experiments 1 and 2, subjects received 12 visual presentations of a single word stimulus followed by a test trial involving change. The results of Experiment 1 (N = 48) indicated that a test stimulus which constituted change in meaning and taxonomic category induced larger responses than did a change in meaning alone, which in turn induced larger responses than did a control condition of no change. Experiment 2 (N = 64) investigated the effects of both semantic and acoustic changes and the results indicated that only semantic changes resulted in test trial SCRs which were larger than those in the control condition. Experiment 3 (N = 48) investigated the effects on SCR magnitude of within- and between-taxonomic category shifts following habituation training with 4 examples of the category. In this case, only the between-category change resulted in SCRs which were larger than those in the control condition of no change. The results of all three experiments were interpreted as support for Sokolov's (1963) claim that the meaning of verbal stimuli is encoded during habituation. Moreover, the results of Experiment 1 indicate that responsiveness on a change trial is a positive function of the amount of change, while the results of Experiment 3 suggest that when a number of examples of a word class are employed during habituation, the semantic characteristics of that class are encoded.     

Reactivity to Heteromodal Stimulation as a Function of Stimulus Intensity and Inner Arousal

In a preliminary study, it was observed that when increasingly intense light stimuli were presented simultaneously with a loud noise, magnitude of the skin conductance response increased over the first three levels of increasing light intensity, and then exhibited a paradoxical decrease. The present study extended the previous one by adding more intense stimuli and by examining the influence of inner sources of arousal in the form of motor effort and tonic skin conductance. Twenty subjects, half of whom squeezed a dynamometer during stimulus presentations, were presented with four intensities of noise combined with four intensities of light in all combinations in a randomized Latin Square design. Compared to the previous study, an increase in paradoxical responding was observed. However, the results could not be interpreted by simply assuming a reflexive inhibitory response to high levels of total stimulation. Rather they suggested the occurrence of what we have referred to as “intensity learning,” which involves a selective diminution in reactivity to high intensity stimuli while reactivity and alertness are retained to low intensity stimuli.     

Attention and Vigilance: Performance and Skin Conductance Response Changes

The skin conductance response component of the orienting reflex was used to measure changes in attention during vigilance performance in order to test several hypotheses which have related aspects of vigilance performance to the occurrence and habituation of orienting or observing responses. Subjects detected irregularly presented visual signals among similar visual events during two 30-min tasks. Skin conductance responses were analyzed in epochs of time immediately preceding and following signals and in nonsignal-related time epochs. Magnitudes of skin conductance responses declined in both signal-related epochs (pre and post), but this decrement was correlated with performance changes only in the post-signal epoch. There was no decrement in SCR magnitudes during the nonsignal-related epochs. Skin conductance response magnitudes were significantly larger both before and after detected signals compared to misses. The data support the hypothesis that changes in vigilance performance over time are related to habituation of the orienting reflex evoked by signals. They also suggest that attentional processes preceding signals are related to successful detections.     

Active-Passive Coping and Skin Conductance and Heart Rate Changes

Sixty subjects were administered 33 tasks, selected from the Raven Progressive Matrices, in conditions that differed by type of monetary reinforcement (reward, frustration, and control group). Subjects were tested in pairs. One subject, assigned as the active one, was asked to solve a problem while the other was only a passive observer. Heart rate level and the amplitude of evoked skin conductance responses were measured. Statistical analysis detected a higher heart rate level in active versus passive subjects at the beginning stage of the experiment, as well as a faster heart rate decrease in the former versus the latter group during subsequent blocks of four tasks. Changes in skin conductance response magnitude during the ensuing task phases exhibited a descending trend in passive subjects and an ascending trend in active subjects. The monetary reinforcement manipulation was not effective. The results support a concept put forward by Fowles (1988), who maintained that tonic heart rate and skin conductance response amplitude may serve as indices of the behavioral activation system and behavioral inhibition system, respectively, as postulated by Gray's model of arousal.     

Electrocortical and electrodermal responses covary as a function of emotional arousal: a single-trial analysis

Electrophysiological studies of human visual perception typically involve averaging across trials distributed over time during an experimental session. Using an oscillatory presentation, in which affective or neutral pictures were presented for 6 s, flickering on and off at a rate of 10 Hz, the present study examined single trials of steady-state visual evoked potentials. Moving window averaging and subsequent Fourier analysis at the stimulation frequency yielded spectral amplitude measures of electrocortical activity. Cronbach's alpha reached values >.79, across electrodes. Single-trial electrocortical activation was significantly related to the size of the skin conductance response recorded during affective picture viewing. These results suggest that individual trials of steady-state potentials may yield reliable indices of electrocortical activity in visual cortex and that amplitude modulation of these indices varies with emotional engagement.     

The Status of Skin Conductance Recovery Time: An Examination of the Bundy Effect

The independent status of recovery of the skin conductance response has been an important assumption underlying work in which electrodermal responses to different task demands have been examined or in studies in which different psychopathological groups have been differentiated. Doubts on this issue have recently been raised by Bundy and Fitzgerald (1975). The present study examines data on this point from two samples and suggests that it is still worthwhile to treat SCR recovery as an independent variable.