Optimizing Gait Outcomes in Parkinson’s Disease Using Rhythmic Auditory Stimulation: The Effects of Groove & Beat Salience
Abstract
Rhythmic auditory stimulation (RAS) is an intervention for gait-disordered populations that involves synchronizing footsteps to regular auditory cues. Previous research has shown that high-groove music (music that induces the desire to move or dance) improves gait relative to low-groove music, but it is unclear why. One possibility is that the greater beat salience inherent in high-groove music may improve gait because salient beats are easier to synchronize with. To test this, we manipulated beat salience by embedding metronome tones to emphasize beat onsets in both high- and low-groove music. We expected that, if beat salience drives gait improvements to high-groove music, then embedding metronome in low-groove music would elicit similar gait improvements (e.g. increased stride velocity). We quantified gait synchronization in terms of period matching (step rate to the cue pace) and phase matching (individual step onsets to beat onsets). The studies in this thesis assess healthy younger and older adults and people with Parkinson’s disease (PwP), walking to auditory cues matched to 10% faster than baseline cadence. We found that high beat salience is an important contributor to the effects of groove on gait, especially when the embedded metronome is a low-pitch bass drum. However, beat salience does not fully explain gait changes, nor does it enhance synchronization: groove improves accuracy, but beat salience does not. Thus, other musical features present in high-groove music may drive additional gait parameter changes. We also manipulated whether participants synchronized or walked freely. Instructions to synchronize improved gait speed in all populations, but also increased variability. However, in PwP, free-walking to music (especially with an embedded metronome) increased gait speed and decreased or maintained variability. This supports previous research in which embedding a metronome emphasizes rhythmic structure and reduces the cognitive demand associated with perceiving and synchronizing with the beat. Finally, we found that good beat-producers were more likely to improve gait to RAS cues than poor beat-producers, but that effects of beat production ability were generally small and do not fully explain individual variability in RAS responses.