Interactive Rhythmic Auditory Stimulation reinstates natural 1/f structure in gait of Parkinson’s patients

Parkinson’s disease (PD) and basal ganglia dysfunction impair movement timing, which leads to gait instability and falls. Parkinsonian gait consists of random, disconnected stride times— rather than the 1/f structure observed in healthy gait—and this low fractal scaling of stride times is a strong predictor of falling. Walking with fixed-tempo Rhythmic Auditory Stimulation (RAS) improves many aspects of gait timing; however it requires attention and lowers fractal scaling away from healthy 1/f structure. In this experiment, PD patients and healthy participants walked with a) no auditory stimulation; b) fixed-tempo RAS; and c) an interactive rhythmic auditory stimulation system that used foot sensors and nonlinear oscillators to track and interact with the human’s timing. Patients effortlessly synchronized with the interactive system, their gait felt more stable, and their fractal scaling returned to levels of healthy participants. With the fixed-tempo RAS, patients and healthy participants rarely synchronized, and when they did their fractal scaling declined away from healthy 1/f levels. After removing the interactive rhythmic stimulation, the PD patients’ boost in fractal scaling persisted, indicating that the interaction stabilized the internal rhythm generating system and reintegrated timing networks. Interactive rhythmic auditory stimulation offers a flexible, portable, low-cost, non-invasive rehabilitation system that can improve the mobility, safety, and quality of life of Parkinson’s Disease patients.