[Correlation of subjective assessments with somatosensory evoked potentials to electrical stimulation of the finger in man].

The relationship between 5 positive components of somatosensory evoked potentials (EPs) and subjective response to electrical stimuli, which were recorded in the same human subjects, was assessed in the present study. Five levels of tactile stimuli and 6 levels of noxious stimuli were applied to the tip of the right index finger. The relationship between the magnitude of subjective response and stimulus intensity was well expressed by a power function. Of 5 major positive components in an EP, P30 and P50 were localized at contralateral primary somatic projection area, while P90, P190 and P270 were at the vertex area. The amplitude of the 5 components systematically increased as increasing stimulus intensity, and also increased with the magnitude of subjective response. A significant correlation between the amplitude of P30 or P50 and stimulus intensity was found when the effect of subjective response was partially out. By contrast, the amplitudes of P190 and P270 were associated with subjective response when the effect of stimulus intensity was partially out. These results suggest that the earlier EP components reflect sensory signal processing, while the latter ones concern the subjective evaluating system.