Point 16
Intro
Point: 16. Pontine Nuclei - Middle Cerebellar Peduncle
Function:
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.
Pathway:
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).
Deficits:
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.