Sensory Threshold to Direct Current Stimulation in Schizophrenic and in Normal Subjects

Observations reported by Grabfield¹on the faradic current threshold as an index of "general nervous irritability" in patients with dementia praecox indicated that high thresholds were found constantly in 33 per cent of his patients and at times in as many as 48 per cent. As a preliminary to an investigation into the theoretical and practical significance of these observations, the present study was conducted to make certain of the existence of differential thresholds. The method employed by Grabfield was that of Martin,²which consists essentially of determining the threshold for make or break induction coil shocks. The second and third finger-tips of the observer's left hand were placed in liquid electrodes forming part of the secondary circuit. The experimenter, in another room, sent shocks of gradually increasing intensity (by tightening the coil coupling) until the subject pressed a key, indicating that he had experienced the shock. For