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 Once achieved, the climbing fibers no longer send “error” signals to the cerebellum to change
the performance.

5. FUNCTION OF THE CEREBELLUM IN THE OVERALL MOTOR CONTROL.

The cerebellum coordinates motor control functions at three levels:

1. The vestibulocerebellum. This consists principally of the flocculonodular cerebellar lobes,
which lie under the posterior cerebellum, and of adjacent portions of the vermis. It provides
neural circuits for most of the body's equilibrium movements.
2. The spinocerebellum. This consists of most of the vermis of the posterior and anterior
cerebellum plus the adjacent intermediate zones on both sides of the vermis. It provides the
circuit for coordinating mainly movements of the distal portions of the limbs, especially the
hands, fingers and face.
3. The cerebrocerebellum. This consists of the large lateral zones of the cerebellar hemispheres,
lateral to the intermediate zones. It receives all its input from the cerebral motor cortex and
adjacent premotor and somatosensory cortices of the cerebrum. It transmits its output
information in the upward direction back to the brain, functioning in a feedback manner with
the cerebral cortical sensorimotor system to plan sequential voluntary body and limb
movements, planning these a fraction of a second in advance of the actual movements. This is
called development of "motor imagery" of movements to be performed.

5.1. Vestibulocerebellum functions.

The vestibulocerebellum originated at about the same time that the vestibular apparatus in the inner
ear developed. Loss of the flocculonodular lobes and adjacent portions of the vermis of the cerebellum,
causes extreme disturbance of equilibrium and postural movements.

But, what role does the vestibulocerebellum play in equilibrium that cannot be provided by other
neuronal machinery of the brain stem?

The answer is that in people with vestibulocerebellar dysfunction, equilibrium is more disturbed during
performance of rapid motion than during stasis, especially when these movements involve changes in

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