Beat perception – the ability to detect a regular pulse in rhythmic sounds – is innate, emerges in early childhood, and is present across all cultures. However, understanding how the brain processes this ability remains a scientific challenge. A team led by Carlotta Lega used transcranial magnetic stimulation (TMS) to investigate the role of motor areas in musical beat perception. TMS was applied to regions of the premotor cortex (PMC) and the supplementary motor area (SMA) in both hemispheres while participants performed rhythm detection tasks. The results showed that only inhibitory stimulation of the caudal portion of the right dorsal PMC (dPMC) interfered with beat perception, reducing participants’ ability to detect subtle variations in rhythm. Stimulation of other areas had no significant effect. These findings suggest that the brain relies on motor circuits, originally involved in movement planning, to anticipate musical beats, supporting the “neuronal recycling” hypothesis, which proposes that cultural functions reuse ancient brain structures. This study reinforces the idea that music, although culturally rich and diverse, is grounded in mechanisms deeply rooted in our biology. And perhaps that’s why dancing to music feels so natural because our brain is already, silently, keeping the beat. This study was published in the scientific journal Human Brain Mapping, in the article Topography of functional organization of beat perception in human premotor cortex: Causal evidence from a transcranial magnetic stimulation (TMS) study, as a part of research project 241/20 - The premotor roots of musical beat perception and imagery: A neurophysiological investigation, supported by the BIAL Foundation.
ABSTRACT
Humans can flexibly extract a regular beat from complex rhythmic auditory patterns, as often occurs in music. Contemporary models of beat perception suggest that the premotor cortex (PMC) and the supplementary motor area (SMA) are integral to this process. However, how these motor planning regions actively contribute to beat perception, along with any potential hemispheric specialization, remains open questions. Therefore, following the validation of stimuli in a behavioral experiment (Experiment I, N = 29, 12 males, mean age = 23.8 ± 0.7 years), we employed transcranial magnetic stimulation (TMS) to test the causal contribution of these regions to beat perception. In Experiment II (N = 40, 16 males, mean age = 23.2 ± 2.37 years), we applied online repetitive TMS (rTMS) over a defined grid encompassing the right rostral and caudal dPMC, SMA, and pre-SMA, and a sham control location. Results showed that stimulation of the caudal portion of right dPMC selectively affected beat perception compared to all other regions. In Experiment III (preregistered, N = 42, 17 males, mean age = 23.5 ± 2.61 years), we tested the lateralization of this contribution by applying rTMS over right and left caudal dPMC. Our results showed that only stimulation over right, but not left, dPMC modulated beat perception. Finally, across all three experiments, individual differences in musical reward predicted beat perception sensitivity. Together, these results support the causal role of the right dPMC in generating internal action predictions and perceptual expectations regarding ongoing sequential events, in line with recent models emphasizing the role of the dorsal auditory stream in beat-based temporal perception. These findings offer valuable insights into the functional organization of the premotor cortex, contributing to a deeper understanding of the neural mechanisms involved in human rhythm perception.
