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Gilles Vannuscorps, Albert Galaburda, Eric Falk, Alfonso Caramazza; A developmental deficit in seeing the orientation of typical 2D objects. Journal of Vision 2017;17(10):28. doi: https://doi.org/10.1167/17.10.28.
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We report the results from a single-case study of an adolescent, Davida, with no remarkable medical history, normal neurological exam, brain MRI and electroencephalogram, who has a highly specific deficit in perceiving the orientation of static, moving, flashed and flickering 2D shapes such as black, grey or colored letters, arrows, abstract shapes and line drawing of objects and faces. Davida reports seeing multiple orientations of these stimuli concurrently (the correct orientation and the equivalent of its rotation by 90, 180 and 270 degrees). Davida's results in non-speeded tasks probing her perception of orientation through verbal judgments, visual illusions, direct copy, and directed movements corroborated this difficulty. For instance, when asked to point to the tip of an arrow shown on a computer screen, she typically pointed where the tip of the arrow would be if the arrow was rotated by 90, 180 or 270 degrees. In contrast, (a) the processing of orientation from auditory, tactile and kinesthetic information is intact; (b) visual judgments about the identity, shape, distance, color, size, movement and location of the same kind of stimuli are intact; and (c) the perception of the orientation of the same shapes (letters, arrows, abstract shapes) shown in 3D, under very low luminance contrast and very low spatial frequencies is intact. The dissociation between processes engaged in the perception of the orientation of 2D shapes under medium to high luminance contrast and spatial frequency from those involved in the perception of the identity, shape, distance, color, size, movement and location of the same kind of stimuli, and those involved in the perception of the orientation of low contrast and low spatial frequency 2D and 3D shapes raises intriguing questions about the interaction of dorsal and ventral visual processes across the two hemispheres.
Meeting abstract presented at VSS 2017
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