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Jessica Holmin, Mark Nawrot; Characterizing Motion Parallax Depth Thresholds in Older Adults. Journal of Vision 2015;15(12):805. doi: 10.1167/15.12.805.
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© ARVO (1962-2015); The Authors (2016-present)
Successful navigation in the world requires effective visuospatial processing. Unfortunately, older adults have many visuospatial deficits, which can have severe real-world consequences. One visuospatial process, depth from motion parallax (MP), has been largely unexplored in older adults. Unambiguous depth from MP requires intact retinal image motion processing and an extra-retinal pursuit eye movement signal. Both the motion and eye movement systems are affected by age. Given these deficits, it follows logically that sensitivity to MP may be affected in older adults, but no one has investigated this possibility. The current study characterizes depth from MP in older adults and explores whether age-related changes in the motion and pursuit systems affect depth perception from motion parallax. Stationary younger (18-35 years) and older (60-75 years) observers performed depth-phase judgments on random-dot motion parallax stimuli. The stimuli translated laterally at one of three velocities (2.3, 10.1, and 25 deg/sec), generating the necessary pursuit signal. Dots within the stimuli translated laterally (0.013-0.92 deg/sec), generating constituent retinal image motion. The MP depth threshold at each pursuit velocity was quantified using the motion/pursuit ratio, which takes into account image motion, pursuit signal, and viewing distance. In addition, observers performed an analogous motion perception threshold task to assess age-related changes in motion perception. Age-related changes in the pursuit system were assessed with a step-ramp pursuit task at the three velocities used in the motion parallax task. Older adults have higher motion parallax thresholds at all pursuit velocities, as well as higher motion thresholds and lower pursuit gain, especially at higher velocities. We conclude that the threshold limit for unambiguous depth from MP is affected by age. Decreased sensitivity to depth from MP is tied to age-related deficits in motion perception and pursuit eye movements, both of which are necessary for unambiguous depth from MP.
Meeting abstract presented at VSS 2015
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