Cerebellar control of voluntary movements is achieved by the integration of external and internal feedback information to properly adjust and correct ongoing actions. In the forelimb of primates, rostral-spinocerebellar tract (RSCT) neurons are thought to integrate segmental, descending and afferent sources and relay upstream a compound signal that contains both an efference copy of the spinal-level motor command and the state of the periphery. We tested this hypothesis by implanting stimulating electrodes in the superior cerebellar peduncle (SCP) and recording the activity of cervical spinal neurons in primates. To dissociate motor commands and proprioceptive signals we used a voluntary wrist task and applied external perturbations to the movement. We identified a large group of antidromically-activated RSCT neurons located in deep dorsal sites and a smaller fraction of post-synaptically activated (PSA) cells located in intermediate and ventral laminae. RSCT cells received sensory input from broad, proximally biased, receptive fields and were not affected by applied wrist perturbations. PSA cells received sensory information from distal receptive fields and were more strongly related to active and passive movements. The anatomical and functional properties of RSCT and PSA cells suggest that descending signals converging upon PSA cells contribute to both motor preparation and motor control. In parallel, RSCT neurons relay upstream an integrated signal that encodes the state of working muscles and can contribute to distal-to-proximal coordination of action. Thus, the rostral spinocerebellar system sends upstream an efference copy of the motor command but does not signal abrupt errors in the performed movement.
- motor control
- voluntary movements
- Copyright © 2016, Journal of Neurophysiology