The visual kinetic depth effect is altered with Parkinson's disease.
People with Parkinson's disease (PD) 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.



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 Training stimuli appear as an opaque rotating ball and the Test stimuli appear as a rotating transparent ball.



Whereas all controls and all PD patients reported seeing the Training stimuli as a rotating ball, the patients with PD were significantly less likely to report the Test stimuli appearing as a 3D "ball" than were the healthy participants. Instead, seven PD patients often reported these bidirectional stimuli appeared "flat."



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.
Department of Psychology, University of Florida, Gainesville, FL, 32611, USA; Brain Rehabilitation Research Center, Malcom Randall VA Medical Center, Gainesville, FL, 32608, USA.
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White
Department of Neurology, University of Florida, College of Medicine, Gainesville, FL 32610, USA.
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Skidmore
Department of Neurology, University of Florida, College of Medicine, Gainesville, FL 32610, USA.
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Hammond
Brain Rehabilitation Research Center, Malcom Randall VA Medical Center, Gainesville, FL, 32608, USA; Department of Neurology, University of Florida, College of Medicine, Gainesville, FL 32610, USA; Geriatric Research Education and Clinical Center Malcom Randall VA Medical Center, Gainesville, FL, 32608, USA; Center for Neuropsychological Studies, University of Florida, Gainesville, FL 32611, USA. Electronic address: heilman@neurology.ufl.edu.
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Heilman
D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D003867:Depth Perception / Q000502:physiology*; D005260:Female; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D009949:Orientation; D010300:Parkinson Disease / Q000150:complications* / Q000523:psychology; D010468:Perceptual Disorders / Q000209:etiology*; D010775:Photic Stimulation; D011597:Psychomotor Performance
Disengagement; Global attention; Kinetic depth effect; Parkinson's disease; Structure from motion; Visual perception; Working memory