The olivocerebellar tract

Abstract

Neurons in the inferior olive nucleus, the sole origin of cerebellar climbing fi bers, project their axons to the cerebellum through the olivocerebellar tract. A single olivocerebellar axon gives rise to multiple climbing fi bers (about seven in rat) which typically terminate into longitudinal compartments in the cerebellar cortex. These compartments match with the longitudinal striped arrangement of aldolase C-positive and -negative Purkinje cell subsets. As a result of this topographic arrangement, the olivocerebellar projection relays the synchronous activity of the electrically coupled adjacent inferior olive neurons to complex spike fi ring of Purkinje cells in a narrow longitudinal stripe. Olivocerebellar axons show a dynamic morphogenetic process. An immature axon has abundant terminal branches that innervate multiple Purkinje cells. Several terminal branches (climbing fi bers) grows to eventually establishing a powerful one-to-one synaptic connection between a single climbing fi ber terminal and a single target Purkinje cell. Furthermore, these axons are capable of strong compensatory re-innervation after lesion even in adult.