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Elizabeth Huber, Ione Fine; Changes in the understanding of visual depth cues eight years after sight-recovery. Journal of Vision 2009;9(8):850. doi: 10.1167/9.8.850.
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© ARVO (1962-2015); The Authors (2016-present)
Here we report changes in the visual performance of patient MM, who acquired sight during adulthood after becoming blind at age three. One year after sight-restoration, MM perceived 2D form and 3D form from motion but had difficulty inferring 3D structure from stationary 2D images. In particular, MM was insensitive to both shading and perspective cues, such that he did not readily perceive shaded circles as being concave or convex and was unable to identify shapes depicted by 2D line drawings. Further, he was not susceptible to the Shepard tables illusion (where perspective cues lead normal observers to misjudge table dimensions). MM was also immune to the Bex illusion, where control observers overestimate the speed of expanding or contracting radial gratings. This ‘radial motion bias’ has been attributed to an interpretation of these stimuli as having motion in depth. MM initially exhibited no radial motion bias, in spite of otherwise normal motion processing. Follow-up tests conducted 8 years post-operatively suggest that MM has gained some fluency with perspective depth cues. For example, MM now shows similar sensitivity to the Shepard tables illusion when compared to control observers, and he displays a radial motion bias of equal magnitude to that of controls. Yet he remains insensitive to cues for shape from shading. In contrast to control observers, MM is no better at detecting targets shaded to appear convex or concave among inverted distractors. These results imply specific improvements in MM's performance and suggest some influence of adult experience on his understanding of perspective cues.
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