Waveform and habituation of sympathetic skin response.

The aim of this study was to investigate the relation of sympathetic skin response (SSR) waveform variation to latency, amplitude, and habituation. Twenty SSRs were recorded from the palm skins of 50 normal subjects by electrical stimulations. Reproducibility of SSR waveforms was also evaluated (n = 35). Waveforms were classified as one of two types, namely, the P type, in which the positive component was larger than the negative, and the N type, in which the negative component was larger than the positive. During successive stimulations, 14 of the 50 subjects had only P type waveforms (P pattern), 9 others only the N type (N pattern), and the remaining 27 both the P and N types (M pattern). The P pattern had a larger amplitude and shorter latency than the N pattern. Twenty-seven of the 35 subjects had the same SSR pattern in two tests conducted on different days. Habituation with time was more pronounced for the M pattern than for the other two patterns. It was suggested that changes in SSR waveform during successive stimulations reflected habituation. Most subjects with the M pattern had a distinct attribute in the development of habituation.