THREE AXIS OCULAR MOTOR CONTROL BY THE CEREBELLUM

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The goal of this career development proposal is to provide the educational and research training necessary for a career in ocular motor neuro-ophthalmology, with an emphasis on the role of the cerebellum in the three-axis (horizontal, vertical, and torsional) control of eye movements. The research plan involves a combination of experimental and modeling approaches with parallel studies in human cerebellar patients and non-human primates. Additional training components include formal instruction in statistics and data analysis, control system approaches to the ocular motor system, mentoring in neural modeling techniques, and additional instruction in clinical neuro-ophthalmology and strabismus. Although much has been learned about the cerebellar control of horizontal and vertical eye movements, studies of the cerebellar control of torsion are much more limited. The experiments in this proposal take advantage of recent advances in three-axis techniques to investigate the vestibulocerebellar, and particularly the floccular, contribution to eye torsion. Using a three-axis magnetic search coil technique, recordings will be made in human cerebellar patients and in primates before and after surgical floccular lesions. Experiments will address the control of three-axis eye velocity during eye movements evoked by visual (pursuit and optokinetic) and vestibular (low- and high-frequency) stimulation. The control of static torsion and binocular alignment will also be investigated. Later experiments will focus on the cerebellar contribution to the linear VOR and on the effects of lesions in other cerebellar regions on three-axis eye movement behavior. These experiments should provide a greater understanding of the pathophysiology of vestibulocerebellar lesions, as well the three-axis representation of visual and eye movement signals in the cerebellum. They also complement other recent studies dealing with peripheral mechanisms of torsion control. Finally, they may lead to a greater insight into the role of the cerebellum in compensating for lesions elsewhere in the ocular motor system, such as superior oblique pareses and other causes of strabismus. This might lead to better treatment for these disorders.