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Keith White, Frank Skidmore, Kenneth Heilman; The visual kinetic depth effect is altered with Parkinson's disease. Journal of Vision 2018;18(10):127. doi: 10.1167/18.10.127.
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© ARVO (1962-2015); The Authors (2016-present)
Background People with Parkinson's disease (PD) have sparse dopamine and often have visual-perceptual disorders. The goal of this study was to learn if they can develop a three dimensional (3D) percept that depends on the kinetic depth effect; that is, the viewer's ability to spatially integrate over time images that are moving along many trajectories. Methods Sixteen patients with PD and 12 healthy matched controls were presented with stimuli that were comprised of a circular region of randomly placed dots that moved as orthographic projections of a sphere. With a normal kinetic depth effect, the unidirectional Training stimuli appear as an opaque rotating ball and the bidirectional Test stimuli appear as a rotating transparent ball. Results Whereas all controls and all PD patients reported seeing the unidirectional Training stimuli as a rotating ball, the patients with PD were significantly less likely to report the bidirectional Test stimuli appearing as a 3D "ball" than were the healthy participants. Instead, seven PD patients often reported these bidirectional stimuli appeared "flat." When viewing stimuli that were mixtures of unidirectional and bidirctional frames, adding some proportion of unidirectional motion rescued the reports of "ball" for these seven patients. Conclusions This study has revealed that some patients with PD have impaired spatio-temporal integration of bidirectional visual motions, but the mechanism accounting for this loss, as well as why only some patients had this deficit, needs further study. When the driver of a moving vehicle fixates upon a stationary target in the surroundings, bidirectional retinal image motions may occur. Failure to perceive 3D structure in such moving scenes can be plausibly suspected to contribute to adverse events such as auto accidents. Drivers with PD have been reported to have increased risk for auto accidents.
Meeting abstract presented at VSS 2018
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