Some sources of variance in skin conductance

An attempt was made to identity some of the factors that might contribute to the variance associated with skin conductance. Results confirmed earlier findings that Blacks have lower levels of skin conductance than Caucasians. The precise role of skin albedo is difficult to determine because within these groups there appears to be a negative relationship between skin reflectance and skin conductance. Possibly peripheral blood flow differences are responsible. There were no differences in heart rate or in self-report measures of arousal between the groups, and the contribution of personality variables to skin conductance variance was, in part, anomalous.     

Random control procedures in classical skin conductance conditioning

There have been differences in opinion concerning what constitute proper procedures for providing random controls in classical skin conductance conditioning. The present paper is a comment on selected aspects of a methodological discussion of control procedures and permissable inferences provided by Furedy, Poulos, and Schiffman (1975).     

A microcomputer package for real-time skin conductance response analysis

A suite of programs has been developed to acquire data from a commercially available, highquality skin conductance meter, via a standard IEEE bus, on an Apple II or Apple lie microcomputer. These programs score and analyze stimulus-evoked skin conductance responses in a preset time window, and store the resultant data on disk, if required. Facilities for a manual override of the automatic scoring routine are available. The setup offers a method of scoring data as they are acquired; it uses currently recommended standards for skin conductance analysis and allows a high magnification of responses, without any need for continual monitoring, because of hardware facilities that automatically “back-off” a subject’s tonic skin conductance level.     

Generalization of extinguished skin conductance responding in human fear conditioning

In a human fear conditioning paradigm using the skin conductance response (SCR), participants were assigned to two groups. Following identical acquisition, group ABA (n = 16) was extinguished to a generalization stimulus (GS), whereas group AAB (n = 20) was extinguished to the conditioned stimulus (CS). At test, presenting the CS in group ABA yielded a strongly recovered SCR. Presenting the GS in group AAB, on the other hand, did not disrupt the effects of extinction. We conclude that extinguishing the CS (group AAB) is an efficient strategy to overcome the stimulus specificity of extinction observed otherwise (group ABA). Clinical implications are discussed.     

Fear relevance and diminution of unconditioned skin conductance responses.

According to Donegan and Wagner's priming model [1987], a signalled UCS will elicit a smaller UCR than an unsignalled UCS. Assuming that fear-relevant CSs are good predictors of aversive UCSs, while fear-irrelevant CSs are relatively bad predictors of aversive UCSs, the present study examined the effect of fear relevance on electrodermal UCR diminution during the acquisition phase of a single cue conditioning procedure. Four groups were studied, each of which consisted of 12 subjects. Group 1 had a fear-relevant CS (a slide of an angry face) paired with a UCS (7 mA shock), whereas group 2 had a fear-irrelevant CS (a slide of a happy face) paired with a UCS. Groups 3 and 4 had unpaired presentations of the CS and UCS and served as control groups for 1 and 2. There were 4 habituation, 8 acquisition, 4 recovery (UCS-only), and 6 extinction (CS-only) trials. While overall UCR levels were lower in the paired than in the unpaired control groups, it was also found that the size of UCR decrement and subsequent recovery was greater in the angry face CS-paired group than in the happy face CS-paired group. This finding is in line with the predictions that flow from the Donegan and Wagner model.     

A fiber-optic system for recording skin conductance in the MRI scanner

The acquisition of the skin conductance response (SCR) during functional magnetic resonance imaging (fMRI) raises significant safety issues, as well as practical ones, which need to be addressed in order for these experiments to be conducted safely and successfully. Metallic and conductive wires in the presence of time-varying gradient magnetic fields such as those present in fMRI experiments may induce heating, as well as electric fields, in these components and, if in contact with the subject, could produce severe burns and electric shocks. Moreover, these metallic and conductive components can significantly distort the magnetic field, resulting in image artifacts. A system for recording the SCR in humans simultaneously with fMRI is presented. The device is a fiber-optic-based transducer, which records the SCR from two fingers of the same hand, using electrodes containing inline radio frequency (RF) suppression filters and protective resistive loads. The fiber-optic SCR transducer was tested using 1.5 and 3.0 Tesla MRI scanners running EPI sequences. This system was able to safely record SCRs free of RF interference during an fMRI experiment, and the fiber-optic design of the transducer eliminated any artifacts on the MRI scan.     

Integrated circuit random foreperiod device and digital interval timer1

A digital integrated circuit computer that produces random (as opposed to pseudorandom) foreperiods is described. Also contained in the device is a precision digital interval timer.     

Cognitive factors in the concurrent differential conditioning of eyelid and skin conductance responses

The objectives of the study were to (1) determine if differential conditioning of eyelid responses ocurs only among subjects who accurately report knowledge of the CS-UCS relations, (2) assess whether differentially conditioned eyelid responding occurs only after the initial accurate interrial report, and (3) explore characteristics of differentially conditioned skin conductance responses (SCRs) obtained in an eyelid conditioning paradigm, with special attention to whether eyelid and SCR conditioning are similarly related to the subjects’ knowledge of the stimulus relations. Fifty-one male subjects were administered 80 differential eyelid conditioning trials, the CSs consisting of the 1,200-msec illumination of slides containing either grammatically correct or grammatically incorrect phrases. Significant differential SCR and eyelid conditioning was obtained for both V- and C-form eyelid responders, but only for subjects who accurately reported the CS-UCS relations. The initial appearance of SCR and eyelid differentiation was related within the trial sequence to subjects’ recognition of the stimulus relations. Eyelid and SCR conditioning were related similarly to knowledge of the stimulus relations, the exception being that subjects who recognized the stimulus relations late in the trial sequence did not develop reliable eyelid differentiation.     

Effects of stimulus omission and stimulus change on dishabituation of the skin conductance response

Three experiments examined the effects of stimulus omission and stimulus change on dishabituation of the skin conductance response. In all experiments, subjects received 17 tone-light or light-tone (S1-S2) pairings, and the primary manipulations were omission of and change in S2 on Trial 16. Responses to S1 and S2 on Trial 17 constituted the data of primary interest. Experiment 1 (N = 72) demonstrated that omission of an expected stimulus was more effective in producing dishabituation than was presentation of an unexpected but not experimentally novel stimulus. Experiment 2 (N = 60) indicated that both omission of an expected stimulus and presentation of an unexpected and experimentally novel stimulus produced dishabituation. Experiment 3 (N = 72) revealed that both the omission and the miscuing of 52 produced reliable dishabituation. The results are interpreted as indicating the importance of a comparison between current input and the stored representation of previous stimulation in the development of habituation.