Modulation of Motor Excitability by Metricality of Tone Sequences

When listening to music, humans tend to synchronize their movements with the perceived beat (e.g., foot-tapping). Brain areas associated with motor function have been closely linked to the perception of beat and rhythm, but the mechanism of this temporal auditory–motor coupling is not fully understood. To investigate how auditory rhythms affect movement, we applied single-pulse transcranial magnetic stimulation (TMS) to primary motor cortex, eliciting motor-evoked potentials (MEPs) in ankle-driving muscles of the lower leg, while participants (N 4) listened to metrically strong or weak tone sequences or music. When TMS pulses were delivered synchronously with perceptible beats in the metrically strong tone sequences, MEPs had greater amplitude than for metrically weak sequences. In contrast, for music that gave a strong or weak sense of the underlying beat, there were no differences in MEP amplitude. These results demonstrate that the pure metrical structure of an auditory rhythm presented as generic parametrically varied tone sequences can influence motor excitability but that the picture may be more complex for real recordings of musical pieces.