A study of the normal values and habituation phenomenon of sympathetic skin response.

Sympathetic skin response (SSR) has been developed recently as a method of capturing the autonomic nerve response as a parameter of the sweat gland function. In this study, our aim was to obtain the normal values with regard to both amplitude and latency of SSR from 50 healthy subjects and to find out the habituation mode, which is one of the most characteristic phenomena of SSR. The measurements were recorded from the hand and foot by rectangular waveform electric stimulation. The correlation coefficient regarding hand and foot leads, amplitude, and latency were studied at normal values. The result was that no significant difference could be observed between the left and right leads with regard to amplitude and latency recorded from the hand and foot leads. However, between hand and foot leads, a significant difference was observed for both latency and amplitude. As for the habituation, electric stimulations were also applied to 20 healthy subjects (age range, 21-62 yr) in the same manner as that used in taking the normal values. For the latency and amplitude of the response in association with the stimulation trials (Rn), the mean values of the hand as well as the foot were determined by averaging the values recorded from both hands and both feet of the 20 subjects. These values were designated as the latency and the amplitude of the hand and foot from R1 to R15. The changes observed in response to the transition in the number of stimulations were statistically evaluated as a gradual decrease in the amplitude. This phenomenon is thought to be a result of learning. On the basis of the 15 consecutive stimulations, a decrease in amplitude to the 7th and 8th stimulations and constancy in the results thereafter was observed, although minor differences in the results were apparent between the hand and foot leads.