The role of cognitive load on motor performance of the ipsilesional arm in stroke survivors with severe hemiparesis.

Background: Ipsilesional arm motor deficits post stroke vary with the side of brain damage. Although stroke leads to both cognitive and motor impairments that can affect movement performance, the lateralized effects of cognition on motor control remain unclear.

Objectives: To examine whether changes in cognitive processes post stroke affect ipsilesional arm motor performance differently depending on the side of brain damage.

Methods: We designed a cognitively challenging upper limb reaching task on the Kinereach virtual reality motion tracking system to examine ipsilesional arm movement in 15 chronic stroke survivors with severe hemiparesis (6 left hemisphere damage, 9 right hemisphere damage; age 58 years +/- 3.09 SEM). Participants completed 170 trials in which they needed to internalize a set of pictorial instructions in order to locate and reach for the correct target.

Results: We found that reaction time and movement error each increased with increased cognitive load (p < 0.0001). With increased cognitive load, there were differences between groups with respect to reaction time (p = 0.012), spatial efficiency of hand paths (p = 0.017), and movement accuracy (p = 0.032).

Conclusion: We found evidence of lesion side differences with respect to key measures of ipsilesional arm motor performance during a reaching task with an added cognitive challenge. Thus, these findings suggest that rehabilitation strategies should be tailored based on the side of lesions to better address hemisphere-specific motor and cognitive impairments, particularly considering that day-to-day tasks involve both motor and cognitive processes.