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"Sequence Agnosia" in Bálint's Syndrome: Defects in Visuotemporal Processing after Bilateral Parietal Damage

University of British Columbia, Canada

Reprint requests should be sent to Jason J. S. Barton, Neuro-ophthalmology Section D, VGH Eye Care Center, 2550 Willow Street, Vancouver, British Columbia, Canada V5Z 3 N9, or via e-mail: jasonbarton{at}shaw.ca.

Bálint's syndrome is characterized by visuospatial dysfunction, with failure to attend to multiple objects in space and poor spatial localization manifested as impaired reaching and saccadic targeting. Less investigated in this disorder is perceptual processing along the dimension of time. We studied the performance of a patient with Bálint's syndrome on two oddity paradigms in which she had to indicate which of three objects was different in color, shape, or structure. Her initial difficulty with processing multiple objects present simultaneously in different locations recovered, but she had persistent difficulty processing objects seen sequentially at the same location. Further studies showed that this deficit was not due to impairments in sustained attention or in distributing attention over time, but to impaired processing of temporal sequences. The deficit was also present with auditory stimuli, indicating a multimodal failure of temporal sequencing. These findings show that bilateral parietal lesions affect not only the spatial but also the temporal organization of perception.