Point 16











Point: 16. Pontine Nuclei - Middle Cerebellar Peduncle

Pontine grey nuclei are involved in conveying information from the motor cortex to the cerebellum regarding intended movement(s) of CONTRA. arm and leg. There are lots of pontine grey neurons, indicating the importance of the cortico-ponto-cerebellar circuit in overall motor function.

Pontine grey neurons lie in the basilar (ventral) pons among the numerous bundles of corticospinal, corticobulbar and corticopontine fibers (there are a great many more of these than corticospinal and corticobulbar fibers). Corticopontine fibers arise in IPSI. motor associated cortical areas and provide the pontine grey neurons with information regarding intended movement(s) of the CONTRA. side of the body (remember that corticospinal fibers cross). Pontine grey neurons possess pontocerebellar axons that CROSS through the other side of the basilar pons, enter the MIDDLE CEREBELLAR PEDUNCLE (or brachium pontis) and terminate in the cerebellar cortex (neurons in the LEFT pontine grey project to the RIGHT side of the cerebellum via the RIGHT middle cerebellar peduncle).

Lesion in the pontine grey results in incoordination of the CONTRA. arm and leg. In contrast, a lesion of the middle cerebellar peduncle results in motor incoordination of the IPSI. arm and leg.

Other Note:
Extra tidbit! Since there is only one source of CLIMBING FIBERS (inferior olive), pontocerebellar (as well as cuneocerebellar and dorsal spinocerebellar) fibers terminate in the cerebellum as MOSSY FIBERS.