The objective of the proposed research is to learn more about the mechanisms underlying both normal eye movement control and human ocular motor disorders. The research strategy is to make quantitative measurements of ocular motor function in both human beings and monkeys and to use control systems analysis to interpret the findings. Our major interest is in the mechanisms that maintain ocular motor accuracy with particular emphasis on problems peculiar to binocularity, eye muscle proprioception and the cerebellum. We will emphasize the study of adaptive mechanisms that improve binocular functions -- specifically the capability to make disconjugate, orbital-position dependent adjustments that compensate for asymmetrical muscle weakness. We will then use the models of unilateral ocular muscle palsy, prolonged monocular patching and spectacle correction for anisometropia to elicit and to characterize disconjugate ocular motor adaptation. Using techniques to open the vergence disparity feedback loop, we will also study vergence adaptation -- specifically using the initiation of vergence as a measure of vergence dynamics. To define the neurophysiological substrate of these adaptive mechanisms we will study the effects of interruption of ocular muscle proprioceptors and of lesions in the cerebellar flocculus -- the potential anatomical substrate(s) for disconjugate adaptation. Our results will provide new information about (1) disconjugate and vergence adaptive control and how they relate to disorders of ocular alignment such as paralytic and nonparalytic strabismus, (2) the function of ocular muscle proprioceptors, long a glaring unknown in ocular motor physiology and (3) the role of the cerebellum in ocular motor learning and plasticity specifically related to disorders of binocularity.
| Shaikh, Aasef G; Zee, David S; Jinnah, H A (2015) Oscillatory head movements in cervical dystonia: Dystonia, tremor, or both? Mov Disord 30:834-42 |
| Shaikh, Aasef G; Wong, Aaron L; Zee, David S et al. (2013) Keeping your head on target. J Neurosci 33:11281-95 |
| Shaikh, Aasef G; Palla, Antonella; Marti, Sarah et al. (2013) Role of cerebellum in motion perception and vestibulo-ocular reflex-similarities and disparities. Cerebellum 12:97-107 |
| Schubert, Michael C; Migliaccio, Americo A; Ng, Tammy W C et al. (2012) The under-compensatory roll aVOR does not affect dynamic visual acuity. J Assoc Res Otolaryngol 13:517-25 |
| Shaikh, Aasef G; Zee, David S; Optican, Lance M et al. (2011) The effects of ion channel blockers validate the conductance-based model of saccadic oscillations. Ann N Y Acad Sci 1233:58-63 |
| Xu-Wilson, Minnan; Tian, Jing; Shadmehr, Reza et al. (2011) TMS perturbs saccade trajectories and unmasks an internal feedback controller for saccades. J Neurosci 31:11537-46 |
| Demer, Joseph L; Poukens, Vadims; Ying, Howard et al. (2010) Effects of intracranial trochlear neurectomy on the structure of the primate superior oblique muscle. Invest Ophthalmol Vis Sci 51:3485-93 |
| Shaikh, Aasef G; Wong, Aaron L; Optican, Lance M et al. (2010) Sustained eye closure slows saccades. Vision Res 50:1665-75 |
| Schubert, Michael C; Zee, David S (2010) Saccade and vestibular ocular motor adaptation. Restor Neurol Neurosci 28:9-18 |
| Shaikh, Aasef G; Hong, Simon; Liao, Ke et al. (2010) Oculopalatal tremor explained by a model of inferior olivary hypertrophy and cerebellar plasticity. Brain 133:923-40 |
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