Mossy fibre and climbing fibre responses produced in the cerebellar cortex by stimulation of the cerebral cortex in monkeys

Summary1.Responses in the cerebellar cortex induced by stimulation of several areas of the cerebral cortex were recorded and identified electro-physiologically to be due to mossy fibre and climbing fibre volleys, and their distributions were explored in the anterior and the posterior lobes of the cerebellum in monkeys. Early mossy and late climbing fibre responses at latencies of 4–5 and 15–18 msec respectively were recorded in certain areas of the cerebellar cortex. They were usually predominant on the contralateral side to the stimulation.2.Stimulation of the lateral part of the motor cortex (forelimb and face area) evoked mossy and climbing fibre responses mainly in the ansoparamedian lobules and in the caudal part of the anterior lobe (including lobulus simplex) of the cerebellar cortex, stimulation of the medial part of the motor cortex (hindlimb area) provoked the responses predominantly in the rostral part of the anterior lobe, and that of the intermediate part (areas for trunk and proximal parts of the extremities) induced the responses preponderantly in the middle part of the anterior lobe of the cerebellum.3.Stimulation of the parietal association cortex (area 5) elicited mossy and climbing fibre responses chiefly in the anterior lobe of the cerebellum. The premotor cortex innervates wide areas of the anterior and posterior lobes on both contralateral and ipsilateral sides. The frontal association cortex showed the projections on even wider areas of the cerebellar cortex, although the responses were relatively small in size.4.The results were compared with those obtained in cats and considered in referring to the cerebro-cerebellar loops in monkeys.