Effects of delay and amplification of auditory feedback for walking: anticipation, variability, and frequency adaptation.

Abstract

When we walk, our footsteps generate rich acoustic information about foot timing, dragging, loading rate, etc. The role of self-generated or endogenous auditory feedback for gait control remains underexplored. We investigated how delay and amplification of self-produced footstep sounds modulate gait. Thirty healthy young adults walked overground while receiving real-time lateralized playback of the sound produced by their feet. Amplified auditory feedback (AAF) was delivered with no, shorter, or longer delay, and either at full or half amplification. Cortical hemodynamic responses were recorded concurrently in prefrontal and temporal regions of interest (ROI) with mobile functional near-infrared spectroscopy (fNIRS). Spatiotemporal gait parameters were analyzed as change relative to baseline. We found that amplification without delay reduced variability by almost 10%, consistent with strengthened sensorimotor coupling via enhanced perceptual access to foot-ground interaction dynamics. Delay increased cadence instead of reducing it. At the level of hemodynamic response, the ROI containing the superior temporal gyrus (STG) exhibited an increase during walking relative to quiet standing, especially in the condition with no delay and full amplification. To explain the effects of amplification and delay on gait timing, we offer two alternative models, one using anticipatory dynamic systems and the other Bayesian predictive processing.