Adapting Footfall Rhythmicity to Auditory Perturbations Affects Resilience of Locomotor Behavior: A Proof-of-Concept Study.

Deepak K Ravi,William R Taylor,Caroline C Heimhofer,Navrag B Singh

doi:10.3389/fnins.2021.678965

Abstract

For humans, the ability to effectively adapt footfall rhythm to perturbations is critical for stable locomotion. However, only limited information exists regarding how dynamic stability changes when individuals modify their footfall rhythm. In this study, we recorded 3D kinematic activity from 20 participants (13 males, 18–30 years old) during walking on a treadmill while synchronizing with an auditory metronome sequence individualized to their baseline walking characteristics. The sequence then included unexpected temporal perturbations in the beat intervals with the subjects required to adapt their footfall rhythm accordingly. Building on a novel approach to quantify resilience of locomotor behavior, this study found that, in response to auditory perturbation, the mean center of mass (COM) recovery time across all participants who showed deviation from steady state (N = 15) was 7.4 (8.9) s. Importantly, recovery of footfall synchronization with the metronome beats after perturbation was achieved prior (+3.4 [95.0% CI +0.1, +9.5] s) to the recovery of COM kinematics. These results highlight the scale of temporal adaptation to perturbations and provide implications for understanding regulation of rhythm and balance. Thus, our study extends the sensorimotor synchronization paradigm to include analysis of COM recovery time toward improving our understanding of an individual’s resilience to perturbations and potentially also their fall risk.

Highlights

The rhythmic alternation of the trunk and limbs is a distinctive, visibly apparent characteristic of human walking
To investigate and identify subtle impairments in rhythmicity and its regulation related to clinical symptomatology, it is necessary to move beyond experiments involving observations during steady state walking, in order to challenge the underlying neuromuscular mechanisms (Full et al, 2002)
There was no difference in τ and d between unfiltered and filtered data in any of the three walking trials, supporting the use of filtered data for state space reconstruction

Summary

Introduction

The rhythmic alternation of the trunk and limbs is a distinctive, visibly apparent characteristic of human walking. One proposed approach has been to exploit the sensorimotor synchronization paradigm (Repp, 2005; Torre et al, 2010), which evaluates a subject’s ability to match the rhythmic oscillations of a limb with an external (often auditory) stimulus, including infrequent temporal perturbations (where beats are presented earlier or later than expected) This paradigm challenges the individual’s inherent rhythmicity during walking and assesses the elicited adaptive motor responses (Chen et al, 2006; Roerdink et al, 2009; Pelton et al, 2010; Wagner et al, 2016; Forner-Cordero et al, 2019). Synchronizing walking to steady metronome beats (without perturbation) has been shown to increase overall balance ability, and be effective for functional locomotor recovery of individuals with stroke (Lee et al, 2018), Parkinson’s disease (Capato et al, 2020), and multiple sclerosis (Maggio et al, 2021)

Methods

Results

Conclusion