Galvanic skin reflex inhibition threshold: A new psychophysiologic technique. Psychosotn Med 24

sedative tolerance based on the EEG and behavioral response to intravenous sodium amytal, was introduced by Shagass in 1954.12 The sedation threshold has been claimed by him to be (1) a reliable measure of "mani-fest anxiety,"13 (2) an objective method for the differential diagnosis of depressive states,14 and (3) a useful means of predict-ing the outcome of electroconvulsive ther-apy.14 The practical and theoretical impli-cations of such a test open an interesting area for psychophysiologic research. Other investigators (Ackner and Pam-piglione, Boudreau, Fink, and Thorpe and Barker) have reported difficulty in deter-mining the sedation threshold by both the clinical and the EEG criteria described by Shagass. In a recent article, Seager, working at Shagass ' laboratory, clarified some techni-cal aspects with reference to these criticisms. However, he also acknowledged difficulty in obtaining reproducible results when the procedure was carried out by different ex-perimenters, even in Shagass ' laboratory