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L. Kiorpes, T.A. Price, J.A. Movshon; Deficits in Global Form Perception in Amblyopic Monkeys . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3592.
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Purpose: Recent studies in human and nonhuman primate amblyopes reveal substantial losses of form and motion perception, beyond those expected from amblyopes’ deficits in basic visual detection and resolution. We have previously shown deficits in contour integration in amblyopic monkeys which were larger than expected from contrast sensitivity loses (Kozma and Kiorpes, 2003). The contour integration deficits could indicate a general disorder of higher–order form vision, or they could be peculiar to the task’s requirement to link elements over large distances. Methods: Glass patterns are global form stimuli defined by the distribution of local signals carried by paired dots. We tested amblyopic monkeys on Glass pattern detection and contour integration; amblyopia was characterized by measuring full contrast sensitivity functions. Amblyopia developed as a result of either experimental strabismus or anisometropia. For Glass pattern detection, the animals choose which of a pair of stimuli comprised of oriented dipoles had ordered structure; the structure could be linear or concentric. For contour integration, the animals indicated the location of a ring of co–circular Gabor patches imbedded in a field of "noise" Gabors. Thirteen monkeys participated; five monkeys were tested on both tasks. Results: All amblyopic monkeys showed deficits on these tests of form perception regardless of etiology. Eight also had losses with fellow eye viewing. 6/9 monkeys tested with Glass patterns were unable to detect the structure with the amblyopic eye; 2/8 tested on contour integration were unable to reliably indicate the location of the ring. For the 5 monkeys tested on both tasks, the degree of loss was similar across tasks. Conclusions: We conclude that amblyopes have a general disorder of form vision, which is not predictable from losses in contrast sensitivity, and may involve neural changes downstream of V1.
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