The cerebellar contribution to eye movements based upon lesions: binocular three-axis control and the translational...

The study of human cerebellar patients and monkeys with experimental cerebellar lesions has taught us much about the role of the cerebellum in normal ocular motor control. Here we emphasize recent findings that point to a role for the cerebellum in (1) the control of the three-dimensional axis about which the eye rotates in response to visual and vestibular stimuli, and (2) the generation of the translational VOR. Findings in cerebellar patients include abnormalities of eye torsion during attempted fixation that suggest a cerebellar role in the control of torsion so that Listing's law is obeyed. Abnormal torsion during vertical pursuit suggests that central processing of information for smooth pursuit may be based upon a phylogenetically old, semicircular canal coordinate scheme. Inappropriate and disconjugate vertical and torsional eye movements ("cross-coupling") occur during brief, high-acceleration rotations of the head. This suggests a role for the cerebellum in the binocular control of the rotation axis of the VOR. Finally, abnormalities of the modulation of the translational VOR with near viewing in cerebellar patients, but with sparing of the very initial 25-30 msec of response, suggests an important role for the cerebellum in the translational VOR.