THE ROLE OF THE VESTIBULAR COMMISSURE IN THE GAZE HOLDING OF THE CAT

Recent theoretical studies have proposed that the vestibular commissur e is a major component of the horizontal gaze-holding system. In order to test this hypothesis, we disrupted the vestibular commissure of th e cat by a parasagittal cut running between an abducens nucleus and th e adjacent medial vestibular nucleus. Successfully lesioned cats suffe red of a characteristic syndrome. In the light, gaze holding was impai red when the animal was looking toward the side of the lesion, but nor mal when looking toward the opposite side. We conclude (1) that the ve stibular commissure is a component of the gaze-holding system, (2) tha t the vestibular commissure is less essential for gaze holding than ot her structures as the nucleus prepositus hypoglossi, and (3) that the horizontal gaze-holding system consists of two halfs, each being more active in ipsilateral than in contralateral gaze.