Spinocerebellum

The spinocerebellum consists of the anterior lobe and portion of the posterior lobe. Its medial zone receives sensory input from proprioceptor, vestibular, and cutaneous somatosensory input from the trunk, altogether with auditory and visual input. The output from this portion of the spinocerebellum goes by way of the fastigial nucleus to the vestibular nuclei. It controls postural adjustments in response to sensory input by signaling to the axial muscles through the medial motor systems. In primates, the inactivation of fastigial nucleus causes animals to fall towards the side of the lesion.

The intermediary zone spinocerebellum obtains input from the cuneocerebellar and dorsal spinocerebellar tracts transmission proprioceptor and cutaneous somatosensory data and from the ventral spinocerebellar tract that imparts information about the activity of spinal motor circuits. Additionally, it receives inputs from the somatosensory and motor cortex through axon collaterals of the corticospinal tract which synapse with nuclei in the pons. These pontine nuclei give rise to fibers which cross the midline to enter the contralateral cerebellar cortex by way of the middle cerebellar peduncle. This corticopontine-cerebellar pathway, having 20 million axons, is one of the largest tracts in the CNS, and goes to the cerebrocerebellum.

The output of the intermediary zone spinocerebellum is through the interpositus nucleus that projects to the ventrolateral thalamus and the red nucleus. By this direction the spinocerebellum controls the lateral motor pathways into limbs. Inactivation of the interpositus nuclei has little effect on walking or standing but outcomes in a large amplitude tremor of the limbs whenever an animal attempts to reach for an object. This is termed as an intention tremor and is frequently seen in humans with cerebellar damage.