Objective: To determine the role of anticipatory and movement control processes for the coordination of bimanual target aiming in individuals post stroke.
Subjects: Thirty adults with chronic stroke and 30 individuals without stroke history.
Design: A two-group (stroke, control) by two-aiming type (unimanual, bimanual) by two-limb (paretic, nonparetic; left, right for controls) design with repeated measures on the last two factors.
Outcome measures: Kinematic analyses of performance and psychometric measures of reaction time, movement time, peak resultant velocity, time to and after peak resultant velocity and interlimb timing for movement initiation and target impact.
Results: Compared with unimanual aiming, the nonparetic limb exhibited a prolonged movement time in the bimanual condition; the locus for prolongation was primarily in the deceleration phase. This adaptive response allowed for a nearly simultaneous (both limbs) target impact in 81% of trials. Compared with the unimanual condition, the nonparetic limb exhibited a lower peak velocity (10%) in the bimanual condition. Conversely, compared with the unimanual condition, the paretic limb exhibited a higher peak velocity (4%) in the bimanual condition. This disociation between limb and condition was observed for the stroke group but not the control group.
Conclusions: The interlimb coordination that emerged for the stroke group revealed a complex and asymmetric contribution from each limb mediated through anticipatory and motor control processes. We suggest that this coordination may be harnessed for future bimanual intervention approaches to rehabilitation of upper limb function after stroke.