Eye movements evoked by microstimulation of dorsal cap of inferior olive in the rabbit

Abstract

1. Microstimulation was used in an attempt to activate selectively neurons of the dorsal cap of the inferior olive in unanesthetized rabbits, and the eye movements evoked by this microstimulation were recorded. 2. Trains of microstimulation (20--50 microA, 0.1- to 0.2-ms pulses, 10--60 pulses/s, 2--8 s duration) evoked low-velocity conjugate eye movements directed toward the side of the stimulated olive. These evoked eye movements were interrupted by resetting eye movements in the opposite direction and could be evoked only if the rabbit was in darkness. 3. The velocity of the evoked eye movements increased during a stimulus train and gradually decreased after the stimulation was terminated. 4. The low-velocity eye movements appeared to combine with eye movements evoked by vestibular stimulation without any significant interaction. 5. After transection of the olivocerebellar pathway or destruction of the contralateral cerebellar flocculus, dorsal cap microstimulation no longer evoked ipsilaterally directed eye movements.