Eye movements induced by electric stimulation of the cerebellum in the alert cat

The surface and interior of the cerebellum were electrically stimulated in alert, cervically-transected cats. A variety of patterned eye movements were produced which included horizontal, rotatory, upward and downward eye movements. These eye movements resemble those produced by semicircular canal nerve stimulation. Horizontal eye movements were evoked from the tuber vermis and from the area of the fastigial nuclei. Straight upward and downward eye movements were induced by stimulation of the midline vermis in the anterior and posterior lobes. Downward rotatory eye movements were induced from the region of the interpositus nuclei, from a small area of overlying dorsal cortex, and from the lateral portions of the nodulus and uvula. Rotatory upward eye movements were evoked from ansiform lobes and from the region of the dentate nuclei. Pure rotatory eye movements (wheel rotations) were induced from an area which centered over the brachium conjunctivum at the level of the superior vestibular nuclei. Homotopic cerebellar points gave similar but reversed responses. Ocular responses algebraically summated when two points were simultaneously stimulated. By summating the ocular responses induced by stimulation of different cerebellar points, eye movements could be induced in any spatial plane. These experiments suggest that there is a topographic separation of the neural organizations which produce eye movement in various spatial planes in the cerebellum.