Somatosensory-evoked potentials and perception of skin velocity.

Mechanical ramp indentations of constant amplitude and randomized velocities to the finger tip of human subjects were used to adequately stimulate the rapidly adapting Meissner corpuscles. The somatosensory-evoked potentials and the subjects' estimations were simultaneously recorded and analyzed off-line. The magnitude of perception showed a nonlinear, monotone-rising function approximated by a log or power function with respect to ramp velocity. The small, early components of the EP showed little correlation to stimulus velocity. The large, late components (120 ms or more) showed a stimulus response function similar to the psychophysical one. These large, late components resemble the alpha rhythm in frequency and distribution. It is concluded that although the large, late component of the EP show a similar relation to the psychophysical one, it is unlikely that there is a specific correlation between them.