Pontocerebellar fibers

The middle cerebellar peduncle consists entirely of pontocerebellar fibers and is the largest pathway of the cerebellum.

Anatomy

The fibers are horizontally oriented, forming bundles which pass dorsally through the pons among the pontine nuclei and interweave with the perpendicularly oriented corticospinal fibers.

Termination

The pontocerebellar fibers terminate throughout the cerebellar cortex except the flocculonodular lobe in an arrangement corresponding to the cortical origin of the pathway: efferents of the primary motor cortex project to the vermis and paravermal zone; efferents of the premotor, somatosensory, and association cortex project to the cerebellar hemisphere cortex. Additionally, the fibers also issue collaterals to the dentate nucleus.

Pathway

The entire pathway begins and ends in the cerebral cortex, and its entire course is the following:

(Motor and sensory areas of) cerebral cortex → corticopontine fibers → (ipsilateral) nuclei pontis (synapse) → pontocerebellar fibers (decussation within pons) → middle cerebellar peduncle → (contralateral) (cerebellar cortex and (collaterals) dentate nucleus of) posterior lobe of cerebellum (synapse) → cerebellothalamic tract → superior cerebellar peduncle → mesencephalon (midbrain) (decussation of tract at level of inferior colliculus) → (ipsilateral) (ventral lateral nucleus of) thalamus → (ipsilateral) motor (cerebral) cortex (predominately premotor cortex and primary motor cortex)