Effects of Optic Flow on Electrocortical Dynamics During Walking and Stepping Over Virtual Obstacles

Abstract

Successful obstacle avoidance relies on complex visuomotor processes. Although optic flow provides critical information about self-motion and object motion, the neural mechanisms underlying its role during obstacle avoidance remain largely unexplored. To address this gap, we developed a treadmill-based virtual reality paradigm to investigate cortical dynamics during obstacle avoidance performed with and without optic flow. Accordingly, 24 healthy adults walked on a treadmill and stepped over virtual obstacles in two environments: one with optic flow (textured walls/ceiling) and one without. Electroencephalography data were recorded, decomposed with independent component analysis, and clustered within the sensorimotor, parietal, and occipital regions. Time-frequency power was compared across conditions in the theta, alpha, and beta bands. Results revealed transient theta synchronizations shortly after obstacle presentation and before obstacle clearance were observed in all regions and conditions, together with sustained alpha/beta desynchronizations throughout the planning phase. Optic flow enhanced pre-obstacle alpha desynchronizations and uniquely induced sustained occipital theta synchronization in the same period. These modulations in electrocortical activity in the optic flow condition before obstacle presentation likely reflect responses associated with self-motion, whereas its persistence after obstacle presentation suggests a shared contribution of self- and object-motion processing. Sensorimotor alpha power decreased after obstacle presentation, indicating increased engagement in motor planning. Together, these findings demonstrate that optic flow shapes electrocortical dynamics during obstacle avoidance by eliciting distinct neural signatures associated with visual motion processing and motor planning.