Figure 2.

A, Example of the timings of the heel strikes (triangles) relative to the cues (rectangles) presented in the video of one participant (P5; red, right heel strike; blue, left heel strike). We call the difference between rectangles and the corresponding heel strike step-to-cue difference and the variability of these differences step timing variability. When the sound was off (top row), heel strikes were less rhythmic and less well synchronized with the video than when it was on (bottom row), which was expressed as a larger step timing variability. B, Correlation between step timing variability and the FOG-Q scores. Correlations with the behavioral data from the soundOn condition are to the left (n = 9) and correlations with the data from the soundOff condition are to the right (n = 13). The titles show Spearman's ρ with the 95% bootstrapped CIs. The line denotes the robust linear regression fit with 95% CIs.