Disorders of attention and action are often produced by brain injury. Unilateral spatial neglect is the most common neurobehavioral syndrome following focal brain injury to the human right hemisphere. Neglect spontaneously recovers to some extent in most patients, and therefore represents an ideal model for studying mechanisms of neurological recovery. The long-term goal of this proposal is to understand the neural and cognitive mechanisms of spatial neglect, its recovery, and how they relate to normal attentional mechanisms. Our overarching hypothesis is that neglect reflects the malfunction of attentional systems that are localized in posterior parietal and frontal cortex. We ask three basic questions. First, what processing deficits most contribute to the syndrome of neglect, and are these deficits anatomically dissociable? For example, what is the relative importance of deficits related to spatial attention and perception, directional motor actions, and arousal, and do they map to different brain regions? Second, which of these processing deficit(s) is/are more closely associated with the recovery of neglect? Third, what are the neural correlates of neglect recovery? Does recovery depend on the degree to which activation recovers in the lesioned and/or non-lesioned hemisphere, or does it depend on the balance of activity across the hemispheres? To answer these questions we carry out a prospective longitudinal behavioral, anatomical and functional magnetic resonance imaging (MRI) study in a large group of neglect patients with single unilateral hemispheric strokes, and several psychophysical experiments in patients with lesions in core areas of the attention system.
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