Cortical Network Reorganization During Balance Control in Chronic Stroke: Premotor-Parietal Behavioral Uncoupling and Directional Prefrontal Compensation.

Background: Balance control is essential for independence in activities of daily living, and its impairment is a leading contributor to falls in stroke survivors. Stroke-induced brain reorganization alters cortical activation patterns; however, localized changes do not reveal the underlying network dynamics critical for the exchange of task-related information. How stroke affects balance-related cortical network dynamics remains unclear. Methods: We studied cortical functional connectivity during a challenging balance task in fifteen chronic stroke survivors and fifteen age- and gender-matched healthy adults. Whole-head electroencephalography (EEG) was recorded while participants performed a balance sway-referenced task. Balance-related cortical sources were localized to the supplementary motor area/premotor area (SMA-PM), posterior cingulate cortex (PCC), and bilateral lateral prefrontal cortex (LPFC). Directed task-related functional connectivity was estimated across multiple frequency bands. Results: Stroke participants demonstrated elevated gamma-band SMA-PM to PCC connectivity, ipsilesional LPFC to SMA-PM connectivity, and SMA-PM to contralesional LPFC connectivity compared to healthy participants. Stroke participants also showed poorer performance on both the clinical Berg Balance Scale (BBS) and the laboratory-based balance task. Stronger SMA-PM to contralesional LPFC connectivity, but not SMA-PM to PCC connectivity, was associated with better BBS scores in stroke survivors. Conclusions: These findings suggest less reliable SMA-PM to PCC sensorimotor pathways and a compensatory recruitment of SMA-PM to contralesional LPFC pathway for the control of balance post-stroke. Cortical network reorganization after stroke leads to directional connectivity changes adaptive to functional needs, with implications for designing targeted interventions to reduce fall risk in stroke survivors.