Interpersonal synchrony-based dynamic stabilization in walking rhythm of Parkinson´s disease

Considerable research attention has been devoted to interpersonal synchrony and to locomotor control. However their intersection, the interpersonal synchronization of stepping rhythms which is widely observed in our daily life, remains relatively unexplored, despite being a common phenomenon that has considerable rehabilitation potential. Therefore, from the perspective of mutual entrainment of gait rhythms, we have constructed an interpersonal synchrony emulation system between a human subject and a virtual biped robot that generates pacing signals using nonlinear oscillators. This system synchronizes the gait cycles of a human and the robot in a cross-feedback manner, by presenting auditory stimuli that indicate the timing of the partner´s foot contacting the ground. Here, we evaluated the effectiveness of this mutual synchrony model in gait stabilization of two Parkinson´s disease patients, who display disturbances in rhythm formation and gait festination (accelerating steps). The results showed that the gait festination, as measured as stride time reduction rate, stabilized and accelerated less compared to unassisted walking (i.e., not exposed to the auditory stimuli). In addition, carry-over effects were observed. After termination of the auditory stimuli, the gait remained stabilized. This is the first study using mutual entrainment in dynamically stabilizing gait festination. These results seem to warrant future clinical application of this interpersonal synchrony emulation system for patients with a variety of motor disorders.