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Laurie M. Wilcox, Jennifer Redwood, Deborah Giaschi; Does the loss of sensory fusion demarcate fine vs coarse processing?. Journal of Vision 2013;13(9):1178. doi: 10.1167/13.9.1178.
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© ARVO (1962-2015); The Authors (2016-present)
In recent experiments we have found that a coarse stereoscopic mechanism is available to support depth perception at large disparities in individuals with amblyopia (VSS 2012). These subjects all performed poorly on conventional tests of stereopsis, but were similar to controls when the stimuli were presented at very large disparities and appeared diplopic. While the data are suggestive of distinct underlying (fine and coarse) mechanisms which map onto 1[sup]st[/sup] and 2[sup]nd[/sup] –order disparity processing, further study is required to make this link. The experiments reported here use visually normal observers and stimuli with different interocular contrast ratios presented at a large range of disparities. The goal is to determine whether coarse processing is responsible for depth percepts under conditions where the stimuli are diplopic and/or poorly matched in the two eyes. Luminance patches with a diameter of 30 or 21 min were presented stereoscopically at five interocular contrast ratios ranging from 20:100 to 100:100. In Experiment 1 we assessed diplopia thresholds to categorize disparities as fine (fused) or coarse (diplopic). In Experiment 2 observers performed a depth discrimination task for disparities ranging from 3 to 72 min. Regardless of size, depth discrimination was unaffected by interocular contrast differences when the test disparities were outside Panum’s fusional area. Within the fused range, performance declined gradually at each contrast ratio with steeper slopes corresponding to larger ratios. These data suggest that the disparity at which sensory fusion is lost may mark a boundary beyond which only coarse (2[sup]nd[/sup]-order) disparity processing is available to support stereopsis.
Meeting abstract presented at VSS 2013
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