Evolution of myoelectrical and precentral cell activities during learning of a new amplitude of movement

Abstract

The object of these experiments was to determine if changes in precentral neuron activity may be related to learning of a new amplitude of movement. Data were obtained from two monkeys trained to stop, in a given position, an elbow flexion movement in order to get a reward. A screen prevented the animal from seeing its forearm. The terminal position was not indicated by a cue, and movements were self-initiated. Motor performance and cell activity were analyzed during the period of learning of a new amplitude of movement. The cells studied presented the reciprocal patterns of activity: they were active flexion but discharged during passive extension. Results clearly indicated that: (1) amplitude was the actual parameter which was learned; (2) the peak frequency of discharge of motor cortex neurons increased during learning, as did the frequency of reward; and (3) the peak frequency of discharge related to passive movements was not changed by conditioning. The results support the hypothesis that the increase of the activity tied to active movements which is observed during conditioning may not be related to an increase of peripheral feedback but expresses a greater 'corticalization' of the movement.