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

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.