Investigating the causal role of motor brain areas in rhythm reproduction: a transcranial direct current stimulation study

Humans have an intrinsic tendency to move to the beat in music, yet the neural mechanisms behind the music-movement connection remain poorly understood. Most studies to date have been correlational. In this study, we used transcranial direct current stimulation (tDCS) to explore the causal role of four brain regions commonly involved in movement timing and beat perception: the supplementary motor area (SMA), the left and right premotor cortices (PMC), and the right cerebellum. Participants received anodal, cathodal, or sham stimulation in one of the four regions on three separate days while reproducing strong-beat, weak-beat, and non-beat rhythms via finger tapping. Because the SMA is thought to play a central role in beat perception, while the premotor cortex and cerebellum are involved in general timing processes, we predicted that SMA stimulation would influence the reproduction of beat-based rhythms, while premotor and cerebellar stimulation would affect the reproduction of non-beat rhythms. As expected, reproduction accuracy depended on beat strength; strong-beat rhythms were more accurately reproduced than weak and non-beat rhythms. Unexpectedly, tDCS had no effect on reproduction accuracy in any brain region. Thus, we found no evidence that modulating brain excitability in SMA, PMC, or cerebellum altered the accuracy of rhythm reproduction.