Auditory cues modulate the short timescale dynamics of STN activity during stepping in Parkinson's disease

Background: Gait impairment has a major impact on motor performance and quality of life in patients with Parkinson's disease (PD). The neurophysiological mechanisms of gait impairment remain poorly understood, meaning that treatment options are currently limited. It is believed that basal ganglia oscillatory activity at beta frequencies (15-30 Hz) may be a contributor to gait impairment in PD, but the precise dynamics of this oscillatory activity during gait remain unclear. Auditory cues are known to lead to improvements in gait kinematics in PD. If the neurophysiological mechanisms of this cueing effect were better understood they could be leveraged to treat gait impairments using brain-computer interface (BCI) technologies. Objective: We aimed to characterize the dynamics of subthalamic nucleus (STN) oscillatory activity during stepping movements in PD and to establish the neurophysiological mechanisms by which auditory cues modulate gait. Methods: We used local field potentials (LFPs) to study STN oscillatory activity in eight PD patients while stepping in place with auditory cueing. Hidden Markov Models (HMMs) were used to discover dynamic brain states that occurred pre-sound, on-sound, and post-sound cues.Results: The occurrence of beta bursts was suppressed during and after auditory cues. This manifested as a decrease in their fractional occupancy and state lifetimes. Interestingly, alpha transients showed the opposite effect, with fractional occupancy and state lifetimes increasing during and after auditory cues. Conclusions: We found transient oscillatory states in the STN LFP during stepping and showed that alpha and beta oscillations are differentially modulated by auditory cues during stepping in PD. ### Competing Interest Statement The authors have declared no competing interest.