Control of reach extent with the paretic and nonparetic arms after unilateral sensorimotor stroke: kinematic differences based on side of brain damage

Abstract

Scaling of reach kinematics to targets that vary in distance is indicative of the use of planning and feedback-based adjustments. The control of reach extent, however, has not been reported for the paretic arm after stroke. The purpose of this study was to determine whether individuals post-stroke utilized planning (scaling acceleration magnitude) and feedback-based adjustments (scaling acceleration duration) to reach to targets that varied in distance. Individuals with mild-to-moderate motor impairment after stroke and nondisabled adults reached with both arms to targets presented at three distances (8, 16, 24 cm). Kinematic data were used to determine scaling of peak acceleration magnitude and duration to target distance and compared between arms (control, nonparetic, paretic). Despite differences in the magnitude of movement variables, individuals post-stroke utilized both planning and feedback-based adjustments to meet the demands of the task with the nonparetic and paretic arms in a similar manner as controls. However, there was variability in the use of planning with the paretic arm, some individuals utilized planning while others did not. After right brain damage, differences in reach control related to the specialized role this hemisphere plays in endpoint control were found in both arms; no hemisphere-specific changes were found after left brain damage (LBD). The appearance of hemispheric-specific effects after right but not LBD were not due to age, degree of motor impairment, or time post-stroke, but, instead, may be related to relative differences in visual-motor processing ability, lesion characteristics, or interhemispheric inhibition changes between groups.