Effect of dorsal cerebeliar vermal lesions on binocular eye movement control

Purpose. Previously we reported that the dorsal cerebellar verm is of the monkey participates in the on-line and adaptive control of saccades and pursuit, in this study we test the hypothesis that it also participates in the control of binocular alignment and disconjugate and disjunctive eye movements. Methods. The dorsal cerebellar vermis (predominantly lobules 6 ancTTTwas surgically aspirated in three rhesus monkeys trained to follow visual targets. We tested (1) tonic vergence (phona), (2) disparity-induced vergenece, (3) combination of saccades and vergence, (4) binocular yoking of the eyes during saccades, (5) phoria adaptation and (6) disconjugate saccade adaptaion. Visual targets were presented on a video monitor or by using LEDs aligned in depth. To induce adaptation M Frenzel prism was pasted on a translucent goggle in front of one eye (filling the whole (paradigm(S)) or half (paradigm(6)) field). Results. Post-lesion each monkey developed a comitant esopnona of 2 deg. Vergence and combined saccade-vergence showed no changes in amplitude or dynamics. Binocular saccade yoking and disconjugate saccade adaptaion were not affected. In two of three monkeys, horizontal phoria adaptation was decreased to a large (10 diopters) base-out prism. Vertical phoria adaptation was unaffected by the lesion. Conclusions. The dorsal cerebellar vermis is related to control ot baseline binocular alignment and to a slight degree, phoria adaptaion. With respect to saccades, the dorsal vermis seems primary concerned with control of the Cyclopean eye.