Isolating the effect of beat salience on rhythmic auditory stimulation outcomes

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 to it) improves gait relative to low-groove music, but how this effect occurs is unclear. Greater beat salience in high-groove music may improve gait because salient beats are easier to synchronize with. Here, 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). Here, we quantified gait synchronization in terms of period-matching (overall step rate to the cue pace) and phase-matching (individual step onsets to beat onsets). We tested a sample of healthy younger and older adults, with auditory cues matched to 10% faster than baseline. Low-groove music with embedded metronome, compared to without, elicited better period-matching; there were no differences between metronome conditions in high-groove music. These findings suggest gait improvements to high-groove music could be due to its high beat salience. On the other hand, embedded metronome did not improve phase-matching accuracy, but high-groove music did. This suggests that beat salience may not improve gait via easing step-to-beat synchronization, but rather through an overall increase in movement vigor.