The role of the cerebellum involuntary eye movements

In general the cerebellum is crucial for the control but not the initiation of movement. Voluntary eye movements are particularly useful for investiga ting the specific mechanisms underlying cerebellar control because they are precise and their brain-stem circuitry is already well understood. Here we describe single unit and inactivation data showing that the posterior verm is and the caudal fastigial nucleus, to which it projects, provide a. signa l during horizontal saccades to make them fast, accurate, and consistent. T he caudal fastigial nucleus also is necessary for the recovery of saccadic accuracy after actual or simulated neural or muscular damage causes horizon tal saccades to be dysmetric. Saccade-related activity in the interpositus nucleus is related to vertical saccades. Both the caudal fastigial nucleus and the flocculus/paraflocculus are necessary for the normal smooth eye mov ements that pursue a small moving spot. By using eye movements, we have beg un to uncover basic principles that give us insight into how the cerebellum may control movement in general.