1. Afferent connections. The three large whitematter tracts (peduncles) of the cerebellum convey afferent input to the cerebellar cortex from the cerebral cortex, pontine nuclei, the brain stem nuclei of the trigeminal, vestibular, and cochlear nerves, and the spinal cord. This structure contains the major output from the cerebellum, the dentatothalamic tract, which terminates in the ventral lateral nucleus of the thalamus. It contains one major afferent pathway, the ventral superior cerebellar tract. The middle cerebellar peduncle carries fibers of pontine origin. The inferior cerebellar peduncle carries fibers from the vestibular nerve and nucleus to the flocculonodular lobe and fastigial nucleus, and from the contralateral inferior olive to the cerebellar hemispheres (olivocerebellar tract), as well as proprioceptive input from the posterior spinocerebellar tract and fibers from the brain stem reticular formation.
2. Efferent connections. The cerebellar nuclei (fastigial, globose, emboliform, and dentate) project via the (contralateral) superior cerebellar peduncle to the red nucleus, thalamus, and reticular formation. The thalamus projects in turn to the premotor and primary motor cortex, whose output travels down to the pons, which projects back to the cerebellum, forming a neuroanatomical circuit. Cerebellar output influences (ipsilateral) spinal motor neurons by way of the red nucleus and rubrospinal tract. The inferior cerebellar peduncle projects to the vestibular nuclei and brain stem reticular formation (completing the vestibulocerebellar feedback loop) and influences spinal motor neurons by way of the vestibulospinal and reticulospinal tracts.
3.Posterior and Anterior Spinocerebellar Tracts
There are two such tracts on each side, one anterior and one posterior. Posterior spinocerebellar tract (Flechsig's). The fibers from the muscle spindles and tendon organs divide into numerous collaterals after entering the spinal cord. Some of these collateral fibers make synaptic contact directly onto the large ? motor neurons of the anterior horn. Other collateral fibers arising at thoracic, lumbar, and sacral levels terminate in a column-shaped nucleus occupying the base of the posterior horn at levels C8-L2, which is named the intermediolateral cell column or thoracic nucleus, or Clarke’s column. The postsynaptic second neurons with cell bodies lying in this nucleus are the origin of the posterior spinocerebellar tract, whose fibers are among the most rapidly conducting of any in the body. The posterior spinocerebellar tract ascends the spinal cord ipsilaterally in the posterior portion of the lateral funiculus and then travels by way of the inferior cerebellar peduncle to the cerebellar vermis. The anterior (Gowers') spinocerebellar tract (tractus spinocerebellaris anterior).The first neuron is common with the posterior tract. The cells of the second neurons are in the posterior horn. Their axons form the anterior spinocerebellar tract and stretch in the anterior parts of the lateral white column on their side and on the opposite side to which they cross through the white commissure. The tract ascends through the medulla oblongata and the pons - to the superior medullary velum where it again crosses to the other side. Then the fibres enter the cerebellum through its superior peduncles and terminate in the cortex of the vermis. Thus, this tract forms two decussations and proprioceptive sensibility is carried to the same side from which it had gone.
Cerebellar disorders have numerous causes, including congenital malformations, hereditary ataxias, and acquired conditions. Symptoms vary with the cause but typically include ataxia (impaired muscle coordination).