MESODIENCEPHALIC AND CEREBELLAR INFLUENCES ON OPTOKINETIC AND VESTIBULAR NYSTAGMUS

Electrodes were implanted in the mesodiencephalon and fastigial nuclei of the cerebellum of 14 cats. Concomitant electrical stimulation of the mesodiencephalon during optokinetic (OKN) or vestibular stimulation caused an increase in frequency of the nystagmic response when the stimulus was applied contralateral to the direction of the fast phase of nystagmus (e.g., stimulation on the right side when the eye movement was toward the left); ipsilateral stimulation caused a decrement in frequency. Electrical stimulation of the fastigial nuclei during OKN or vestibular stimulation led to a complete inhibition of the nystagmus (independent of the side stimulated) and a centering of the eyes. Results suggest that the cerebellar roof nuclei may be involved with mediating the responses necessary for inhibition of nystagmus through visual fixation. © 1969.