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George E. Carvell, PhD, PT   University of Pittsburgh
 
DISTRIBUTED MOTOR CONTROL: CEREBELLAR SUBDIVISIONS
KS&J Fig 42-3, p 835
   The Vestibulocerebellum is important in control of eye movements; control of neck, trunk and limb girdle muscles involved in balance & postural control of head, neck, and body. It is also involved in coordination of gait. This circuitry is critical for the Vestibulocular Reflex (which allows you to have a stable visual gaze despite head motion).
     Spinocerebellar information about efferent and re-afferent activity provides the basis for 'on-line' error detection/correction. This information may be used as 'Knowledge of Results ' (KR) about the movement from individual and repeated trials of a task which may be critical in learning and refining skilled tasks.
The role of the Lateral Cerebellum in the initiation of movements 'generated' in Human Cerebral Hemispheres is suggested by recent brain imaging studies. The Cerebellum may have a key role in Sensorimotor tasks such as active touch where sensory input and motor output are intertwined as a reciprocating unit of processing. Some studies suggest a more 'cognitive' role for the Cerebrocerebellum than was previously demonstrated in animal studies. Lesions of the Lateral Cerebellum may show mild or no deficits when the standard battery of tests for cerebellar dysfunction are performed. Indeed, the decrement in performance of highly skilled, well-practiced tasks may be appreciated by the subject long before clinical evidence of involvement is manifested. Motor 'memories' may suffer and subtle changes may be seen as increased errors, and a slowing of action as the individual relies upon feedback in tasks that previously were so over-learned that they were automatic. The Lateral Cerebellum has appropriate cerebral cortical connections to account for high levels of Cerebellar Activation in complex skilled tasks.
Lesions of the Paravermis produce the classical signs of cerebellar ataxia in limbs ipsilaterally. Lesions of the Vermis produce proximal limb and axial (truncal) ataxia.