Subcritical Shift of Brain Dynamics in Patients with Chronic Stroke: Evidence from Resting-State EEG

The healthy brain has been proposed to operate near a critical state, reflecting a balance between neuronal excitation and inhibition. In contrast, stroke disrupts neural activity and brain network function, yet its impact on critical dynamics remains unclear. In this study, we investigated whether brain critical dynamics are altered in persons with chronic stroke using resting-state EEG. Several criticality-related metrics were compared between stroke patients and healthy controls, including neuronal avalanche statistics, branching parameter, Fano factor, long-range temporal correlations (LRTC), and neuronal-avalanche-based LRTC. These complementary metrics provide a multifaceted assessment of critical brain dynamics. Compared with healthy controls, stroke patients exhibited a significant reduction in probability of large-scale neuronal avalanches, along with lower branching parameters and Fano factors. In addition, stroke patients showed frequency-specific alterations in LRTC, with significant reductions observed in the beta and gamma bands. The scaling exponent (α) derived from neuronal-avalanche-based LRTC was also reduced. These findings indicate that stroke induces a subcritical shift in brain dynamics and provide a novel understanding of post-stroke brain dysfunction from a dynamical systems perspective.