Cerebellar dysfunction of movement and perception.

This review describes some characteristics of patients with cerebellar lesions, including limb movements, changes in motor planning and disturbances in time-dependent perception. The delay in movement initiation can be explained by a delay in onset of movement-related discharge of neurons in motor cortex. Disorders of movement termination (hypermetria) are accompanied by asymmetric velocity profiles and by prolonged agonist and delayed antagonist EMG activity necessary to brake the movement. During complex movements in three-dimensional space, the cerebellum contributes to timing between single components of a movement, scales the size of muscular action, and coordinates the sequence of agonists and antagonists. The basic structure of motor programs is not generated exclusively within the cerebellum and patients with cerebellar lesions can use precuing information to improve their motor performance. Time-dependent perception in the auditory and visual domains are disturbed in patients with cerebellar lesions.