A fused minimum spanning tree framework reveals large-scale cortical network reorganization during dual-task standing...

Objective.Dual-task standing challenges postural regulation in older adults, but the associated cortical network reorganizations remain incompletely characterized. This study investigated how a visuomotor dual-task modulates postural dynamics and cortical network during unstable standing.Approach.Twenty-six community-dwelling older adults performed foam-surface standing under single-task and visuomotor dual-task conditions. Postural dynamics were quantified using center-of-pressure (COP) measures and stabilogram diffusion analysis (SDA). Cortical network organization was assessed using electroencephalography (EEG) functional connectivity (phase-lag index) and minimum spanning tree (MST) topology. To improve characterization of distributed cortical adaptation, a novel fused MST framework integrating theta, alpha, and beta-band connectivity was evaluated together with conventional band-specific MST.Main results.Dual-task standing significantly increased COP displacement and velocity in both anterior-posterior and medial-lateral directions, accompanied by altered SDA parameters across directional domains, indicating substantial changes in postural control dynamics. EEG analyses revealed task-related cortical network reorganization, with increased theta and alpha band overlap ratios and significant topology changes in the fused MST representation. Compared with band-specific MST representations, the fused MST framework provided an integrated characterization of task-related cortical network adaptation across frequency bands.Significance.Visuomotor dual-task standing induces substantial reorganization of both postural dynamics and cortical network topology in older adults under unstable conditions. These findings suggest that the fused MST framework may provide a useful quantitative approach for assessing cortical adaptation to dual-task balance challenges in older adults.