Cortical involvement in stroke survivors for balance maintenance
Stroke survivors often experience balance impairments which may result in increased risk of falling. However, it is unclear whether and how a stroke changes cortical involvement for postural control. To clarify this issue, we assessed the effect of stroke on sway-based corticokinematic coherence (CKC), which is a measure of the coupling between cortical electrophysiological signals and postural sways. To that end, we recorded the center-of-pressure fluctuations and electroencephalographic cortical activity of 34 stroke survivors and 34 healthy participants performing balance tasks during which sensory information was manipulated, by either removal or alteration. We found significantly increased CKC derived from medio-lateral sway in stroke participants when standing on foam compared to healthy controls, suggesting an increase in cortical involvement to compensate for the decreased function of the hemiparetic side, even in highly functional stroke survivors. Moreover, a relationship was found between CKC and clinical scores (Berg Balance Scale and Fugl-Meyer). This suggests that CKC could be used as a biomarker to track progress beyond traditional functional recovery as measured by clinical scores.