Strabismus, the misalignment of the two eyes, is a disorder of unknown etiology, caused by problems related to either the central innervation sent to the eye muscles and/or the eye muscles and orbital tissues themselves. Improving our understanding of the central and peripheral aspects of eye movement control is an important and necessary first step for an effective clinical diagnosis and treatment of strabismus patients. Our understanding of how the brain controls eye movements has benefited enormously from the comparison of neuronal activity with eye movements and the quantification of these relationships with mathematical models. Whereas this task has been very successful when considering eye movements in a single direction, mainly uncertainty, controversy and conflicting hypotheses currently exist when considering oculomotor control in three-dimensions. Part of the problem arises because arguments related to these controversies have been largely limited to behavioral observations. Very little data currently exist regarding the discharge properties of motor and premotor neurons for oculomotor control in 3D. Such a paucity of neurophysiological data includes the recent histological discovery of extraocular muscle pulleys and their postulated role in 3D eye movements (active pulley hypothesis). The long-term goal of these studies is to characterize neural activity during eye movements in 3D and to quantify these relationships with existing or expanded mathematical models of the oculomotor system. In this application, we propose a systematic series of experiments that, for the first time, will provide the missing link between behavior, imaging and modeling in understanding the role of mechanical and neural factors in 3D eye movement control. Accordingly, single unit recordings from motoneurons and premotor neurons during saccades, pursuit and the VOR will attempt to provide a comprehensive data set upon which existing and revised models of oculomotor function in 3D will be evaluated. Results from these experimental/modeling studies are fundamental in resolving these controversies and providing a comprehensive understanding of oculomotor function in health and disease. ? ?
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