STUDIES OF MOTOR PERFORMANCE AFTER PARIETAL ABLATIONS IN MONKEYS

Abstract

Ablation of the parietal cortex of monkeys is followed by a characteristic motor deficit. There is a relative disuse of operated as compared with normal extremities, but this paresis can be clearly distinguished from that following lesions of the motor areas for, after parietal ablations, fine finger movements are possible when visual attention is focussed upon them, and any emotional excitement improves motor coordination; whereas, after lesions of the motor areas, fine finger movements are seriously affected and excitement increases the deficit markedly. Sensory impairment is manifested by bizarre postures during cage activity and by changes in the placing and hopping reactions. Absent or diminished knee jerks, together with diminished resistance to passive manipulation appear immediately after parietal ablations. Later, knee jerks may become hyperactive but resistance to passive manipulation never becomes increased.