Inhibition of cortical evoked potentials and sensation by self-initiated movement in man.

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AN imposed, passive or externally paced displacement (EPD) of the index finger in man evokes brain potentials that differ in delay and waveform for postcentral, precentral and prefrental areas1. Displacement so imposed leads to less accurate subjective estimation of limb position from that obtained by self initiated movement2. This behavioural observation as far as we know has not been neurophysiologically investigated with cortical recordings from the human brain. Thus we compared the cortical potentials following passive or externally paced displacement, to those related with a similar but self paced voluntary displacement (SPD) of the left index finger. Not only is self-initiated movement manipulative, however, it also subserves acquisition of sensory information. To examine this aspect of finger movement in a second series of experiments we studied the evoked responses and the subjective sensation to brief electrical stimuli applied to the left median nerve at the wrist or the index finger during SPD and compared them with similar responses elicited with the subject at rest.