Hemispheric specialization for control of movement trajectory and steady state position.

Robert Sainburg
Department of Kinesiology, Pennsylvania State University

     Full text: Not available
     Last modified: April 28, 2007
     Presentation date: 08/10/2007 2:05 PM in MCC
     (View Schedule)

Abstract
Handedness has long been thought to results from a dominant system which is simply better developed to perform virtually any aspect of motor behavior. However, our research has suggested that each hemisphere/limb system has become specialized for different aspects of motor control. The dominant arm performs best in coordinating intersegmental dynamics and in controlling trajectory parameters, such as speed, direction, and curvature. Whereas, the nondominant arm tends to achieve more accurate and consistent steady state positions at the end of reaching movements. Studies that have examined interlimb differences in response to perturbations and in adaptation to novel task conditions have supported the idea that dominant control relies more on feedforward mechanisms to specify trajectory features, whereas nondominant control relies more on feedback mechanisms to modulate impedance. These different control strategies have been confirmed by interlimb differences in performance on tasks that vary either initial or final limb states, and are consistent with the performance of everyday bilateral activities, such as slicing a loaf of bread with the dominant arm while holding the loaf with the nondominant arm. We recently tested our model of lateralization in unilaterally lesioned stroke patients. We examined whether ipsilesional deficits following stroke might reflect loss of the functions for which the ipsilateral hemisphere has become specialized. Our findings strongly support this hypothesis, and suggest that the ipsilesional, ?non-affected? limb should be addressed from a remedial perspective in rehabilitation. This is particularly important in hemiparetic patients, when this limb most often becomes the lead-manipulator for activities of daily living.