Decoding natural gait cycle in Parkinson's disease from cortico-subthalamic field potentials

Human bipedal walking is a complex motor behavior that requires precisely timed alternating activity across multiple nodes of the supraspinal network. However, understanding the neural dynamics that underlie walking is limited. We investigated the cortical-subthalamic circuit dynamics of overground walking from three patients with Parkinsons disease without major gait impairments. All patients were implanted with chronic bilateral deep brain stimulation leads in the subthalamic nucleus (STN) and electrocorticography paddles overlying the primary motor (M1) and sensory (S1) cortices. Local field potentials were wirelessly streamed through implanted bidirectional pulse generators during overground walking and synchronized to external gait kinematics sensors. We found that the STN displays increased low frequency (4-12 Hz) spectral power between ipsilateral heel strike to contralateral leg swing. Furthermore, the STN shows increased theta frequency (4-8 Hz) coherence with M1 through the initiation and early phase of contralateral leg swing. Our findings support the hypothesis that oscillations from the basal ganglia and cortex direct out-of-phase, between brain hemispheres in accordance with the gait cycle. In addition, we identified patient-specific, gait-related biomarkers in both STN and cortical areas at discrete frequency bands. These field potentials support classification of left and right gait events. These putative biomarkers of the gait cycle may eventually be used as control signals to drive adaptive DBS to further improve gait dysfunction in patients with Parkinsons disease.