Waveform variation and size of sympathetic skin response: regional difference between the sole and palm recordings

Objective: The aim of this study was to investigate the regional difference in sympathetic skin response (SSR). The influence of SSR waveform from sole skin (S-SSR) on latency, amplitude, and habituation was also studied. Methods: Twenty SSRs were analyzed in 41 normal subjects. Waveforms were classified as either the P type, in which the positive component was larger than the negative one, or the N type, in which the negative component was larger the positive one. The occurrence patterns of these two waveform types were classified into three kinds, i.e. P, N, and M patterns. In the P or N pattern all the SSRs were of the P or N type. The M pattern had both P and N types during consecutive recordings. Results: In the S-SSR, the P pattern had a higher amplitude and shorter latency than the N pattern, and habituation was most pronounced in the M pattern. These were compatible with previously reported findings in SSR from palm (P-SSR). The waveform patterns were not always consistent between P- and S-SSRs. The maximum S-SSR and P-SSR were not simultaneously obtained in nearly half of the subjects. Conclusions: The size and waveforms of SSR were modified not only by the condition of the central component, but also the peripheral component of the reflex and the sweat gland.