BILATERAL VESTIBULAR FAILURE IMPAIRS VISUAL-MOTION PERCEPTION EVEN WITH THE HEAD STILL

VISUAL motion perception of a single object, moving with a constant an gular velocity of 40 min of arc/s in four orthogonal directions, was m easured in eight patients with chronic bilateral vestibular failure (B VF) with the head stationary. Perception of object motion was more sev erely impaired for horizontal than for vertical directions and the imp airment was more pronounced in the dominant eye than the nondominant e ye. Impaired motion perception in patients with BVF is best explained by a central visual mechanism that suppresses oscillopsia due to the i nvoluntary retinal slip caused by the defective vestibule-ocular refle x (VOR). This mechanism cannot be switched off with the head stationar y (inactive VOR) and thus causes a measurable deficit of motion percep tion. (C) 1998 Rapid Science Ltd.