Dysmetria of fast phase of optokinetic nystagmus in cerebellectomized rabbits

Abstract

The whole cerebellum except for the lobulus petrosus was removed in young rabbits, which were kept alive for 3–4 months before studying eye movements. The general motor disturbances were similar to those described in the literature for other species. Recovery was slow and very incomplete. Eye movements elicited by moving a striped drum around the animal were precisely recorded. Sinusoidal movements of the drum were followed in the same way as by normal animals, however, with fewer saccades. Steady drum rotation produced an extreme eye deviation from the midposition (up to 40°) with insufficient correction by saccades. A similar reaction was elicited by darkness. Once the eye reached this extreme position, it continued spontaneously with a very small nystagmoid movement (slow drift to the periphery, saccade to the middle). This condition, sometimes lasting more than an hour, was often uninfluenced by any drum movement. The amplitude-maximal speed relationship for saccades was similar to that in normal animals. I concluded that the cerebellum is indispensable for the correct programming of fast eye movements.