Three Ascending Tracts Activated from Group I Afferents in Forelimb Nerves of the Cat

Abstract

Publisher Summary Group I muscle afferents in hindlimb nerves activate two ascending tracts—the dorsal and the ventral spino-cerebellar tract (DSCT and VSCT). Group I afferents in forelimb nerves activate three ascending pathways. The rostra1 spino-cerebellar tract (RSCT) originates from cell bodies at, or slightly above, the level of the dorsal root entrance, ascends ipsilaterally in the middle third of the lateral funiculus, and terminates in a characteristic manner in the anterior cerebellar lobe. It receives monosynaptic excitation from high threshold group I muscle afferents, identical with tendon organ afferents. The cuneo-cerebellar tract contains one component that is monosynaptically activated from very low threshold group I muscle afferents, identical with muscle spindle afferents. The third pathway is a projection to the cerebral cortex of large muscle spindle afferents. The group I afferents ascend in the dorsal funiculus and activate monosynaptically cells in the main cuneate nucleus, which give origin to a component of the medial lemniscus.