Fig. 5

Amplitude sensitivity to synchronization. Motor amplitudes where subjects first synchronized with the external oscillations (\(A_{m}^{*}\)) are shown to indicate subject sensitivity as a function of motor frequency (Δf_m). The measured external impulse associated with amplitude sensitivity (\(J_{c}^{*}\)) is also shown in a second vertical axis. Each data point represents the observed sensitivity of a single subject during a single trial (N = 56). Interpolation from a linear regression model is shown. In this experiment, lower amplitudes are interpreted to mean that a subject has higher sensitivity to synchronization and vice versa. In this sense, subjects exhibited higher sensitivity to synchronization at motor frequencies below their preferred step frequency at baseline (i.e., Δf_m < 0).