LEFT HEMISPHERIC-SPECIALIZATION FOR LEARNED, SKILLED, AND PURPOSEFUL ACTION

Three-dimensional motion analyses were performed on trajectories of re petitive ''slicing'' gestures by 4 participants with left-hemisphere l esions and limb apraxia, 6 participants with right-hemisphere lesions, and 7 neurologically intact participants. Left hemispheric lesioned p articipants with apraxia, but not right hemispheric lesioned participa nts showed impaired coupling of spatial and temporal aspects of wrist trajectories and deficits in interjoint coordination. Both groups of b rain-lesioned participants differed from control participants in the 3 -D plane of the wrist motion. The deficits of some right hemispheric l esioned participants in controlling the plane of wrist motion may be a consequence of left hemispatial neglect with rightward deviations. in contrast, the deficits of apraxic participants in controlling wrist t rajectories and coordinating joint motions seem to reflect a deficit i n these participants for the movement plan.