Somatosensory evoked potentials during compound thumb movement.

The aim of the study was to assess the influence of a biphasic flexion-extension movement upon somatosensory evoked potentials (SEPs). Voluntary thumb flexion initiated a sequence of either single or single PLUS sustained electrical stimulation upon the median nerve. In cases of sustained stimulation the subjects had to overcome the induced tetanic thumb flexion. During movements the latencies of early components were longer compared to rest; during simple movements the amplitudes of most components were diminished compared to rest; the amplitudes of early components were further diminished in movements against tetanic contraction compared to simple ones; the suppression of SEP amplitudes was similar regardless of possibility to overcome the opposing tetanic contraction; the changes in SEP amplitudes were not dependent on training.