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Simultanagnosia: When a Rose Is Not Red

¹ University of Pennsylvania School of Medicine, ² Moss Rehab Research Institute, Philadelphia, PA

Reprint requests should be sent to H. Branch Coslett, Department of Neurology, University of Pennsylvania School of Medicine, 3400 Spruce St., Philadelphia, PA, 19104 USA, or via e-mail: hbc{at}mail.med.upenn.edu.

Information regarding object identity ("what") and spatial location ("where/how to") is largely segregated in visual processing. Under most circumstances, however, object identity and location are linked. We report data from a simultanagnosic patient (K.E.) with bilateral posterior parietal infarcts who was unable to "see" more than one object in an array despite relatively preserved object processing and normal preattentive processing. K.E. also demonstrated a finding that has not, to our knowledge, been reported: He was unable to report more than one attribute of a single object. For example, he was unable to name the color of the ink in which words were written despite naming the word correctly. Several experiments demonstrated, however, that perceptual attributes that he was unable to report influenced his performance. We suggest that binding of object identity and location is a limited-capacity operation that is essential for conscious awareness for which the posterior parietal lobe is crucial.