Functions of the Cerebellar lobes and nuclei
The diagram (above, left) shows the main connections of the cerebellum.
The inferior cerebellar peduncle carries axons from the spinal cord (the spinocerebellar and cuneo-cerebellar tracts; and in addition a major pathway form the contralateral olivary nuclei. The axons of these fibres are known as 'climbing fibres', and their functions are discussed in the section of Cerebellar Physiology.
The middle cerebellar peduncle consists largely of the axons of pontine nuclei that carry a copy of messages sent down the corticospinal pathway; this occurs because the cortico-bulbar (cortico-pontine) neurones synapse on pontine nuclei. The terminals of these axons have a characteristic structure and are know as the 'mossy fibres'.
The superior cerebellar peduncle is the main efferent pathway from the cerebellum, and carries the axons of the deep cerebellar nuclei (shown in the diagram on the right). The fastigial nuclei belong to the oldest part of the cerebellum and project to the vestibular nuclei. The dentate and interposed nuclei project rostrally to synapse in the red nucleus of the midbrain and the thalamus (see the diagram below, right).
The vermis connects with pathways passing from the brainstem to the spinal cord (bulbo-spinal pathways) that descend to motoneurones and influence muscle tone. Two groups of bulbo-spinal pathways - medial and lateral are influenced by the vermis. This region also receives proprioceptive information from the spinal cord.
The hemispheres of the cerebellum project to the motor areas of the cerebral cortex, and are concerned with motor planning and execution. These connections were developed along with the growth of the cerebral cortex and cerebellum during the evolution of the upright posture.
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