Visuo-motor deficits induced by fastigial nucleus inactivation.

The contribution of the cerebellar vermal lobules Vic/VII and of the caudal part of the fastigial nucleus (cFN) to the control of saccadic eye movements has been established by converging neurophysiological approaches. The precise delineation of these saccade-related territories in the medio-posterior cerebellum (MPC) has stimulated the development of detailed investigations of its output nucleus, the cFN. In the present paper, we review recent studies that describe the deficits of the saccadic displacement of the line of sight (gaze) induced by a reversible cFN inactivation under different experimental situations (head restrained, head-unrestrained or body-unrestrained). These data first indicate that the MPC does not solely influence the generation of saccadic eye movements but also the accompanying head movements during saccadic shifts of gaze in the head-unrestrained animal. They also support, in agreement with anatomical data, a distributed influence of the MPC on several levels of the sensory-motor system for orienting gaze, rather than a limited control of the immediate pre-motor structures.