Altered Visuomotor Network Dynamics Associated with Freezing of Gait in Parkinson's Disease.

Background: Freezing of gait (FOG) is a common gait disorder that often accompanies Parkinson's disease (PD). The current understanding of brain functional organization in FOG was built on the assumption that the functional connectivity (FC) of networks is static, but FC changes dynamically over time. We aimed to characterize the dynamic functional connectivity (DFC) in patients with FOG based on high temporal-resolution functional MRI (fMRI).

Methods: Eighty-seven PD patients, including 29 with FOG and 58 without FOG, and 32 healthy controls underwent resting-state fMRI. Spatial independent component analysis and a sliding-window approach were used to estimate DFC.

Results: Four patterns of structured FC 'states' were identified: a frequent and sparsely connected network (State I), a less frequent but highly synchronized network (State IV), and two states with opposite connecting directions between the visual network and the sensorimotor network (positively connected in State II, negatively connected in State III). Compared with the non-FOG group, patients with FOG spent significantly less time in State II and more time in State III. The longer dwell time in State III was correlated with more severe FOG symptoms. The fractional window of State III tended to correlate to visual-spatial and executive dysfunction in FOG. Moreover, fewer transitions between brain states and lower variability in local efficiency were observed in FOG, suggesting a relatively 'rigid' brain.

Conclusions: This study highlights how visuomotor network dynamics are related to the presence and severity of FOG in PD patients, which provides new insights into understanding the pathophysiological mechanisms that underly FOG. © 2025 International Parkinson and Movement Disorder Society.