Prehension with the ipsilesional hand after unilateral brain damage

Sensorimotor deficits in the hand ipsilateral to a brain lesion have been r eported in different motor tasks. We evaluated performance of the ipsilesio nal hand in 12 patients with either left (LBD) or right brain damage (RBD) by kinematic analysis in order to precisely characterize possible deficits in the two components of prehension (transport and grasp). Both patient gro ups exhibited performance deficits in the main kinematic parameters, e.g., reduced velocity of the transport component and prolonged movement time. Ho wever, while LED patients showed a more general slowing, RED patients prolo nged in particular the last phase of the movement toward the object. We sug gest that relevant visuospatial representations and the adequate mapping of motor processes may be impaired after RED. In contrast, LED caused a more unspecific disturbance pattern, supporting the view that the precise parame terization of motor programs is impaired. Maximum grip aperture was normal in both patient groups. However, since aperture could be biased by slowed m ovement, the notion that the grasp component was preserved remains speculat ive. The patient's ability to scale the maximum velocity of the transport c omponent to adapt to changes in movement amplitude and to scale the maximum hand aperture of the grasp component to adapt to object size was preserved in both groups. Thus both hemispheres can have competence for this scaling mechanism.