The dissociation between visual agnosia and optic ataxia has been challenged by several researchers as not as strong as originally portrayed; Hesse and colleagues demonstrated dorsal stream impairments in patient DF; Himmelbach and colleagues reassessed DF's abilities and applied more rigorous statistical analysis demonstrating that the dissociation wasn't as strong as first thought.
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This suggests that perceptual awareness is modular and that in sighted individuals there is a " binding process that unifies all information into a whole percept ", which is interrupted in patients with such conditions as blindsight and visual agnosia . motion, and low spatial frequency contribute to, but are not strictly necessary for, an object's salience in blindsight.
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These variants of visual agnosia include prosopagnosia ( inability to recognize faces ), pure word blindness ( inability to recognize words, often called " agnosic alexia " or " pure alexia " ), agnosias for colors ( inability to differentiate colors ), agnosias for the environment ( inability to recognize landmarks or difficult with spatial layout of an environment, i . e . topographagnosia ) and simultanagosia ( inability to sort out multiple objects in a visual scene ).
