Hemispheric control of the initial and corrective components of aiming movements.

This study examined whether the left and right hemispheres play differential roles in controlling the initial and corrective components of aiming movements. A simple aiming task was administered to 31 normal control subjects and 29 unilateral stroke patients (14 with right hemisphere damage and 15 with left hemisphere damage). Movement amplitude was varied (25, 64 and 100 mm) and reaction time, movement time and accuracy were measured. Through a trajectory analysis, initial and corrective movements were separated. The stroke patients performed the task with their ipsilateral arm which was compared to the normal controls' right or left are performance. Regardless of the movement amplitude the left hemisphere group's reaction time was slower, and the execution of the initial movement component was less accurate than controls. No performance deficits were found on corrective movements. Performance was not impaired for the right hemisphere group on any measures. These results are discussed in terms of the hemispheres' possible roles in controlling movements which are largely open or closed loop.