Primary afferent collaterals and spinal relays of the dorsal and ventral spino-cerebellar tracts.

Abstract

Summary.The experiments were performed on cats under nembutal anaesthesia.Successively more caudal midline sections of the spinal cord abolished the ventral spino‐cerebellar tract (VSCT) discharge evoked on hamstring nerve stimulation, only when the sections were performed at the lower part of the L V segment. This indicates that the column of VSCT cells extends to a level caudally of Clarke's column.The mass discharges in the dorsal and ventral spino‐cerebellar tracts (DSCT and VSCT) were simultaneously recorded on stimulation of the hamstring nerve. The decrease of the discharges after sections of the dorsal funiculi at different segmental levels showed that the collaterals from Golgi tendon organ afferents to both DSCT and VSCT neurons are given off at the same segmental level. This level corresponds to the location of the VSCT neurons, caudally of Clarke's column. Both types of muscle spindle afferents ascend in the dorsal funiculi, and give off collaterals to the DSCT neurons at a more cranial level, which corresponds to the caudal‐most part of Clarke's column. It is suggested that the collaterals of the Golgi tendon organ afferents are common for the two tracts and that these collaterals branch to give secondary collaterals to the VSCT neurons and other secondary collaterals which ascend within the gray matter to terminate on the DSCT neurons.