Deficits in Performance on a Mechanically Coupled Asymmetrical Bilateral Task in Chronic Stroke Survivors with Mild Unilateral Paresis

Abstract

Typical upper limb-mediated activities of daily living involve coordination of both arms, often requiring distributed contributions to mechanically coupled tasks, such as stabilizing a loaf of bread with one hand while slicing with the other. We sought to examine whether mild paresis in one arm results in deficits in performance on a bilateral mechanically coupled task. We designed a virtual reality-based task requiring one hand to stabilize against a spring load that varies with displacement of the other arm. We recruited 15 chronic stroke survivors with mild hemiparesis and 7 age-matched neurologically intact adults. We found that stroke survivors produced less linear reaching movements and larger initial direction errors compared to controls (p < 0.05), and that contralesional hand performance was less linear than that of ipsilesional hand. We found a hand × group interaction (p < 0.05) for peak acceleration of the stabilizing hand, such that the dominant right hand of controls stabilized less effectively than the nondominant left hand while stroke survivors showed no differences between the hands. Our results indicate that chronic stroke survivors with mild hemiparesis show significant deficits in reaching aspects of bilateral coordination, but no deficits in stabilizing against a movement-dependent spring load in this task.

Neural Control of Stopping and Stabilizing the Arm

“…Metabolic costs of stopping may be different from those of trajectory control, and future work may be able to address how this impacts movement strategies. A recent study from our lab showed that stabilizing behavior was similar between stroke survivors and neurologically intact adults during a mechanically coupled bimanual task ( Jayasinghe et al, 2021 ) even though previous work using unilateral tasks have shown performance deficits in stroke survivors. There is clearly more to the story of stabilization than meets the eye, and future work can focus on different types of stabilization tasks—online correction, staying in a fixed position during perturbation to the same hand, bimanual stabilization, etc., to form a deeper understanding of this complex phenomenon and its specialization within the brain.…”

How virtual and mechanical coupling impact bimanual tracking

“…Finally, we would expect stroke survivors to show different lateralized behaviors to controls ( 57 ) and to observe lesion-dependent differences in their capabilities to use the task redundancy without impacting their performance ( 51 ). Therefore, the aforementioned results need to be tested on the relevant population before deciding on a design for bimanual rehabilitation devices.…”