Altered visuo-motor behavior during inactivation of the caudal fastigial nucleus in the cat

Abstract.

It is known that the medio-posterior cerebellar lobules VI/VII of the vermis and caudal part of the fastigial nucleus (cFN) are involved in the control of saccadic displacements of the visual axis in space (gaze). We have recently shown in the head-unrestrained cat that inactivation of the cFN severely impairs the accuracy of orienting gaze shifts toward visual targets by altering the amplitude of both eye and head components. In the present paper, we report additional data that indicate that the deficits induced by cFN inactivation are not restricted to saccadic gaze shifts but extend to the forward reaching movement of the whole body toward a visual target. Indeed, the path followed by the animal walking toward a visible food target was systematically curved toward the inactivated side. This deficit could largely be accounted for by an angular bias in the heading direction used by the animal to reach the target. These data suggest that pharmacological inactivation of the cFN leads to a general deficit in spatial orientation.