The purpose of this grant application is to increase the understanding, detection, and recovery of human ocular motor and related visual disorders. Experiments will determine the affect of posterior brain injury or transcranial magnetic stimulation on the detection and discrimination of hemifield motion. Studies of the recovery of these visual processes after injury are proposed. The ability to encode spatially-accurate saccades after frontoparietal brain lesions is examined. Disruption of a corollary discharge involving the frontal eye fields may disrupt the spatial accuracy of saccades in the double-step paradigm. Extraretinal signals from smooth pursuit may provide ineffective information for spatially-accurate saccades during pursuit. Injury to the smooth pursuit system may also injure the ability to disengage fixation and initiate visually-guided saccades. Posterior parietal lesions produce unidirectional deficits in smooth pursuit that have not been explained by a loss of unidirectional pursuit neurons or neurons involved in motion vision processing. The possibility that these unidirectional asymmetries in smooth pursuit velocity are caused by unidirectional asymmetries in the discrimination of retinal slip velocity errors is tested. A reliable clinical method that selectively tests frontal and posterior saccade or smooth pursuit pathways would be valuable. Studies of the affect of regional transcranial magnetic stimulation on saccades and smooth pursuit responses may lead to such an important new clinical and investigative method. All of these studies are unified by the premise that understanding how the visuomotor brain normally responds to injury may lead to logical approaches for facilitating its repair.
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