The extent of polysynaptic responses in the dorsal spinocerebellar tract to stimulation of group I afferent fibers in gastrocnemius-soleus.

We investigated the extent of the distribution of polysynaptic connections to the dorsal spinocerebellar tract (DSCT). Recording from a randomly selected population of DSCT units, we found that over 60% responded to maximal stimulation of group I afferent fibers in the gastrocnemius-soleus muscle nerve. Most of the responses had a time course or latency consistent with polysynaptic activation. The extensive distribution of this input into the pool of DSCT neurons suggests that input from muscle nerves in general is widely distributed to these neurons. The results further imply that the DSCT plays a more integrative role in the transmission of information from the hindlimb to the cerebellum than has been previously supposed.