Bimanual coordination during reach-to-grasp actions is sensitive to task goal with distinctions between left- and right-hemispheric stroke

The perceptual feature of a task such as how a task goal is perceived influences performance and coordination of bimanual actions in neurotypical adults. To assess how bimanual task goal modifies paretic and non-paretic arm performance and bimanual coordination in individuals with stroke affecting left and right hemispheres, 30 participants with hemispheric stroke (15 right-hemisphere damage—RHD); 15 left-hemisphere damage—LHD) and 10 age-matched controls performed reach-to-grasp and pick-up actions under bimanual common-goal (i.e., two physically coupled dowels), bimanual independent-goal (two physically uncoupled dowels), and unimanual conditions. Reach-to-grasp time and peak grasp aperture indexed motor performance, while time lags between peak reach velocities, peak grasp apertures, and peak pick-up velocities of the two hands characterized reach, grasp, and pick-up coordination, respectively. Compared to unimanual actions, bimanual actions significantly slowed non-paretic arm speed to match paretic arm speed, thus affording no benefit to paretic arm performance. Detriments in non-paretic arm performance during bimanual actions was more pronounced in the RHD group. Under common-goal conditions, movements were faster with smaller peak grasp apertures compared to independent-goal conditions for all groups. Compared to controls, individuals with stroke demonstrated poor grasp and pick-up coordination. Of the patient groups, patients with LHD showed more pronounced deficits in grasp coordination between hands. Finally, grasp coordination deficits related to paretic arm motor deficits (upper extremity Fugl–Meyer score) for LHD group, and to Trail-Making Test performance for RHD group. Findings suggest that task goal and distinct clinical deficits influence bimanual performance and coordination in patients with left- and right-hemispheric stroke.