THE EFFECT OF MICROSTIMULATION OF THE OCULOMOTOR VERMIS ON DISCHARGES OF FASTIGIAL NEURONS AND VISUALLY-DIRECTED SACCADES IN MACAQUES

The present study confirmed our previous reports that neurons in the fastigial oculomotor region (FOR) of the macaque show presaccadic bursts during contralateral saccades and that the burst duration is closely related to the duration of the accompanying saccade. Furthermore, when the burst duration was reduced by subthreshold electrical stimulation applied to the oculomotor vermis prior to the onset of the burst, the impending visually-directed saccade became hypometric. The reduction in the burst duration was closely related to the degree of the hypometria. Since saccadic burst neurons in the FOR constitute the sole output channel for saccadic signals of the oculomotor vermis, the findings support the hypothesis that the cerebellum can regulate the amplitude of eye movements.