Galvanic Skin Reflex Inhibition Threshold: A New Psychophysiologic Technique

Abstract

The galvanic skin reflex has been used as a bioelectrical measurement in the evaluation of sedation induced by barbiturates. The experimental technique utilizes the intravenous injection of sodium thiopental at the rate of 0.5 mg/kg of body weight per minute. The subjects verbally respond to taped digits offered to them at 20 second intervals. The injection of barbiturate is continued until the subject no longer responds, either behaviorally or bioelectrically (GSR), to the stimulation. The amount of thiopental in mg/kg of body weight necessary to inhibit the GSR has been termed the GSR inhibition threshold. In our preliminary study on 20 normals, 10 psychoneurotic depressed, and 8 psychotic depressed patients, we have found that the GSR inhibition threshold is a simple and objective method that seems to differentiate, at a high level of reliability, between psychotic and psychoneurotic depressed patients. The values for psychotic depressives, psychoneurotic depressives and normals are respectively 1.81, 3.44, and 3.32 mg/kg.