Cortical Projection of Proprioception in the Cat and Monkey.

Abstract

The effect of proprioceptive impulses on the corticogram was studied in cat and rhesus monkey by passive flexion and extension of an extremity, stimulation of the peripheral end of a ventral spinal root with condenser discharges, and stimulation of the central end of a muscle nerve. Excitation was indicated by disappearance of "Dial" potentials and/or increase in amplitude and frequency of background potentials. That tension receptors were primarily involved was shown by the fact that a stimulus of S1, subthreshold as far as the cortical effect was concerned, became effective if the muscles contracted isometrically or under load. The principal area of the cortex which was excited by proprioceptive impulses was the sensori-motor area in the cat and the precentral motor cortex in the monkey. In several cats the excitation induced by proprioception was spread diffusely throughout the contralateral hemisphere except for the extreme poles, but the excitation was greatest in the sensori-motor area. In the monkey the cortical effect was more restricted and appeared in the precentral motor cortex (area 4 and 6) and, to a lesser extent, in the adjacent part of the postcentral sensory cortex. When proprioceptive impulses were elicited in a hindleg of a monkey the area of greatest change of potentials was in a hindleg point of the contralateral motor cortex. Lesser degrees of excitation were seen in arm and face area and also in the ipsilateral leg area. It is suggested that proprioceptive impulses to area 4 are involved in voluntary movements. Their absence accounts for the loss of voluntary movements of the deafferented limb in the monkey although no change occurs in its responsiveness to electrical stimulation of the motor cortex.