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Ocular Motor Physiology Lab

Faculty:


David S. Zee, M.D., Professor of Neurology, Ophthalmology, Neuroscience and Otolaryngology–Head and Neck Surgery.
Phillip Kramer, M.D., Assistant Professor of Neurology and Otolaryngology-Head and Neck surgery
Richard Lewis, M.D., Assistant Professor of Neurology and Ophthalmology
David A. Robinson, Dr. Eng., University Professor Emeritus of Ophthalmology and Biomedical Engineering.
Mark Shelhamer, Sc.D., Assistant Professor of Otolaryngology–Head and Neck Surgery and Biomedical Engineering
Mark Walker, M.D., Instructor of Neurology

Postdoctoral Fellows:

Grace Peng, Ph.D., bioengineer
Hiroaki Ichijo, M.D., otolaryngologist
Naoto Hara, M.D., ophthalmologist
Walker Marker, M.D., neurologist

Additional Staff:


Adrian Lasker, M.S., electronics engineer
Dale Roberts, M.S., computer scientist
Leaaron Cooper, B.A, vestibular testing technician.
Corena Bridges, vestibular testing and animal technician

General Description:

Our research is directed toward how the brain controls the movements of the eyes (including eye movements induced by head motion) using studies in normal human beings, patients and experimental animals. The focus is on mechanisms underlying adaptive ocular motor control. More specifically, what are mechanisms by which the brain learns to cope with the changes associated with normal development and aging as well as the damage associated with disease and trauma? How does the brain keep its eye movement reflexes properly calibrated? Particular emphasis is on 1)learning and compensation for vestibular disturbances that occur either within the labyrinth or more centrally within the brain, 2) the mechanisms by which the brain maintains correct alignment of the eyes to prevent diplopia and strabismus, and 3) the role of ocular proprioception in localizing objects in space for accurate eye-hand coordination. Our research strategy is to make accurate, quantitative measures of eye movements in response to precisely controlled stimuli and then use the analytical techniques of the control systems engineer to interpret the findings.

Specific Projects

1. Compensation for loss of labyrinthine function. In normal human subjects we are developing models to study the adaptive mechanisms that are engaged when humans suffer a loss of labyrinthine function. By artificially manipulating the visual surround while a normal subject is being rotated in a vestibular chair one can simulate the visual consequences of a vestibular lesion and so prod the brain to produce an adaptive change in its vestibuloocular (VOR) response. Specific interests now in normal subjects include 1) studying the contextual cues that can be used by the brain to gate in or out one or another learned response, 2) developing a versatile virtual reality stimulator for eliciting vestibular adaptation and potentially for use in programs of physical rehabilitation for vestibular disturbances, 3) studying the linear (translational) VOR and its adaptive capabilities using a linear sled that we have developed, and developing adaptive paradigms that simulate the problems created when their is an imbalance between the two labyrinths.. In patients with labyrinthine disorders, we are studying the strategies and adaptive responses that they use to compensate for a vestibular disturbance. Once we know the ideal stimuli and how they should be presented to best stimulate VOR adaptation, we will be able to optimize programs of physical therapy to promote recovery in such patients.

2. Cerebellar function. We are studying the control of eye movements in patients with cerebellar disease and monkeys with cerebellar lesions. Our emphasis in on using the latest techniques and mathematical approaches for measuring and analyzing the alignment of the eyes around all three axes of rotation (horizontal, vertical and torsional). Little is known about the brain mechanisms for adaptive control of "3axis" eye alignment and our experiments are testing the hypothesis that the cerebellum is central to this process. We are also studying the role of the cerebellum in generating smooth pursuit eye movements and their adaptive control. We examine these adaptive mechanisms in human patients with lesions confined to the cerebellum and monkeys with experimentally-induced lesions in the vestibulocerebellum, the presumed site where these adaptive mechanisms reside.

3. Superior oblique palsy. Both in patients with naturally-occurring paralysis of the superior oblique muscle and in monkeys with experimentally-induced trochlear nerve paralysis, we are studying the mechanisms by which patients adapt to misalignment of the eyes (strabismus). We are also investigating what types of prism therapies might best promote restoration of proper eye alignment, and what parameter might best predict surgical outcome. Our emphasis again is on using the latest techniques for measuring the alignment of the eyes around all three axes of rotation.

4. Eye-hand coordination and ocular proprioception. Accurate reaching toward objects of interest requires more than just the presence of its image on the retina; the position of the eye in the orbit (and of the arm relative to the head) must also be known so the brain can make the correct coordinate transformations for an accurate motor movement. We are interested in the contribution of ocular muscle proprioception to how the brain knows where its eye is in the orbit. Such proprioceptive information may not only be necessary for accurate pointing but may also contribute to the adaptive mechanisms that help maintain accurate eye alignment. We are investigating this problem in monkeys in which the flow of orbital afference has been experimentally interrupted. By testing the accuracy of limb as well as eye movements we can infer the contribution of ocular proprioception to the control of eye and hand movements.

5. Applications of nonlinear dynamics to eye movement function. Nonlinear dynamics is a mathematical approach to physiology that we are applying to eye movement control. We hope to better understand the algorithms by which the brain chooses to program a "reflexive" eye movement (such as the quick phase of nystagmus) of a particular size at a particular time. Understanding of such algorithms may be important for quantifying and localizing abnormal brain function.

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