Pathways for control of face and neck musculature by the basal ganglia and cerebellum.

The basal ganglia are believed to influence movement via thalamo-cortical projections. However, the basal ganglia may also affect brainstem areas involved in movement control such as the red nucleus. The red nucleus receives input from the cerebellum and projects to motor neurons and premotor neurons in the contralateral brainstem and spinal cord. Are there pathways that allow output from the basal ganglia to influence processing in the red nucleus? This study uses the bidirectional tracer, WGA-HRP, to demonstrate that regions of the cat red nucleus receive input from the basal ganglia as well as from the cerebellum. Output from the entopeduncular nucleus, the feline equivalent of the internal segment of the globus pallidus, provides a modest direct input to the red nucleus as well as a more substantial indirect input via projections to the zona incerta and the fields of Forel. Regions of the red nucleus with input from the basal ganglia also receive input from the cerebellar dentate nucleus and lateral regions of interpositus. The regions of the red nucleus receiving basal gangliar input project to the contralateral facial nucleus and upper segments of the cervical spinal cord. Therefore, the red nucleus provides a junction where output from the basal ganglia can interact with output of the cerebellum for movement control of the head and face. The pathway may provide a substrate for a variety of movement disorders that are seen with diseases of the basal ganglia such as cervical dystonia and Parkinson's facies.