Sensorimotor interactions following callosotomy

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The proposed research is concerned with how people select, plan, and produce coordinated behavior. Many skilled behaviors require that the movements of the two hands be integrated in order to achieve a common goal. However, in many actions, the two hands may be engaged in essentially independent actions such as when holding a telephone with one hand and using a computer mouse with the other. Whether the hands are used to complete a common action or are engaged in different tasks, there are fundamental constraints on these movements, indicating various levels of interaction in both planning and execution stages of control. The study of split-brain patients provides a unique opportunity to study the operation of each cerebral hemisphere in relatively isolation. The proposed experiments provide a programmatic attempt to characterize the levels of representation at which integration of response components occurs. First, the temporal components of the movements are examined. Neurologically normal individuals show strong patterns of temporal coupling when producing bimanual movements. Are these phenomena observed in individuals with split-brains and if so, in a manner similar to that observe when the two hemisphere are connected? Second, the interaction of the spatial and force components of left- and right=handed movements is evaluated. Third, previous results have suggested that the existence of a shared implementation system limits performance when the two hands are used in distinct tasks. This limitation is observed even after callosotomy. A series of new experiments will rigorously assess this hypothesis. As a while, the studies should provide important insights into the psychological and neural mechanisms of coordinated behavior.