MECHANISMS AND REHABILITATION OF UNILATERAL SPATIAL NEGLECT : ANALYSIS OF INTERACTION BETWEEN ATTENTION AND MOTOR EXECUTION

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The present study aimed to elucidate the attentional-representational and motor mechanisms that cause unilateral spatial neglect after right hemisphere damage and to develop diagnostic and rehabilitation technique for neglect.In the symmetric positioning task, patients with left neglect were presented with a test sheet where a central vertical bar and a right small circle were printed. They were required to mark a circle at the horizontally symmetric point on the left side. The movements of the eyes and the hand were recorded and analyzed to explore the characteristics of perceptual and motor interaction in neglect. When such a crossed response is required into contralesional space, the representational map for that space may be activated also in the brain of patients with neglect. Besides, preparation of a leftward response may result in an effective orientation of the eyes and the hand into the left space, which would be hardly explored in the ordinary stimulus-response compatible condition.A line image task using a computer display with a touch panel was devised to explore representational image for lines when patients with neglect were asked to touch the left endpoint and perceived the whole extent reliably. The image for a fully perceived line may be represented far enough into left space even when left neglect occurs after a lesion that involves the right parietal lobe. However, left neglect may occur in estimation of the subjective midpoint on the representational image, which may be explained by a rightward bias of attentional distribution.A system with personal computer and cordless tablet was introduced to record performances of patients with neglect in the Behavioral inattention test (BIT, PC version). This system enabled analysis of time course and spatial scanning and gave detailed information to improve detection of problems due to mild neglect.