Cortical activity during balance and walking tasks in stroke patients: Functional near-infrared spectroscopy neuroimaging research

Background: Stroke survivors frequently suffer from balance and gait impairments, yet the cortical mechanisms underlying these functions remain unclear. This study addresses this gap by utilizing portable functional near-infrared spectroscopy (fNIRS) to map task-specific neuroplasticity. Objectives: We aimed to (1) compare cortical activation patterns during balance and walking tasks, (2) analyze functional connectivity (FC) and lateralization differences, and (3) explore correlations between neuroimaging metrics and clinical outcomes. Methods: In this cross-sectional study, 31 stroke patients (60 +/- 11.90 years; 29 % female) completed Tetrax balance training or AlterG treadmill walking. fNIRS measured hemodynamic responses in prefrontal, premotor, motor, somatosensory, and occipital cortices. Wavelet amplitude (WA) quantified activation; wavelet phase coherence (WPCO) assessed FC. Results: Bilateral premotor cortex (PMC) and contralateral primary somatosensory cortex (S1) activation significantly increased during walking (P < 0.001). FC strength increased between ipsilateral occipital cortex (iOC) and contralateral S1/M1 during walking (P < 0.05) but decreased in balance tasks. Negative correlation emerged between contralateral PMC activation and Fugl-Meyer scores during balance (r =-0.537, P = 0.039), while activities of daily living (ADL) scores positively correlated with motor/occipital activation during walking (r = 0.53-0.87, P < 0.035). No lateralization asymmetry was observed (P > 0.05). Conclusions: Enhanced S1/occipital activation highlights critical roles of sensory-visual integration in post-stroke locomotion. Contralateral recruitment compensates for ipsilateral deficits during challenging tasks, providing neurophysiological insights for targeted rehabilitation.