EFFECT OF MANIPULATION AND FRACTIONATED FINGER MOVEMENTS ON SUBCORTICAL SENSORY ACTIVITY IN MAN

Previous studies have shown that the somatosensory evoked potentials ( SEPs) recorded from the scalp are modified or gated during motor activ ity in man. Animal studies show corticospinal tract terminals in affer ent relays, viz. dorsal horn of spinal cord, dorsal column nuclei and thalamus. Is the attenuation of the SEP during movement the result of gating in subcortical nuclei? This study has investigated the effect o f manipulation and fractionated finger movements of the hand on the su bcortically generated short latency SEPs in 9 healthy subjects. Left m edian nerve SEPs were recorded with electrodes optimally placed to rec ord subcortical activity with the least degree of contamination. There was no statistically significant change in amplitude or latency of th e P9, N11, N13, P14, N18 and N20 potentials during rest or voluntary m ovement of the fingers of the left hand or manipulation of objects pla ced in the hand. The shape of the N13 wave form was not modified durin g these 3 conditions. It is concluded that in man attenuation of corti cal waves during manipulation is not due to an effect of gating in the subcortical sensory relay nuclei.