Aberrant beta-band network alteration preceding freezing of gait in Parkinson's disease

Background: Freezing of gait (FOG) is a debilitating motor symptom observed in the advanced stages of Parkinson's disease (PD), characterized by an abrupt inability to initiate or continue forward walking. Whole-brain functional connectivity analysis has shown promise in elucidating the underlying pathophysiology and identifying potential biomarkers in PD. However, the specific changes in local brain networks during the transition from normal gait to freezing remain unclear. Objectives: This study aimed to investigate changes in brain network organization during the transition to FOG compared with the transition to voluntary stopping. Methods: Eighteen PD patients with FOG performed walking tasks designed to trigger either freezing or voluntary stop events, while undergoing simultaneous ambulatory electroencephalography (aEEG) recording. Functional connectivity was estimated using phase-locking value (PLV) across multiple frequency bands, measuring the consistency of phase synchrony between brain regions, and examined network organization using graph modularity, an index of how strongly the brain segregates into functionally specialized subnetworks, focusing on the 2-second time windows preceding each event. Results: Transitions to freezing were characterized by increased local beta-band connectivity within right frontoparietal, middle-frontal, parietal-occipital, visual, and bilateral insula regions, alongside reduced connectivity between frontal and posterior areas in lower-frequency bands. Conclusions: Increased local beta segregation and reduced fronto-posterior connectivity may reflect network alterations that precedes freezing episodes. Such patterns could help identify neurophysiological markers for predicting and potentially preventing FOG in PD.