Distinct neuronal entrainment to beat and meter: Revealed by simultaneous EEG-fMRI

Rhythm perception refers to the mental interpretation of rhythm by a listener. Musical rhythm perception typically involves two steps: beat extraction and metrical structure assignment (meter perception). The entrainment theories propose that different neuronal oscillations entrain to different levels of metrical structure in the rhythm (e.g., beat and meter) and thereby form a representation of the rhythm in the mind. Thus, neuronal populations that entrain to beat and meter should theoretically be different. However, although entrainment theories have been supported by many studies, the neuronal populations that entrain to beat and meter remain largely unknown. In this study, we used a paradigm to induce neuronal entrainment to beat and meter and obtained images of the neuronal populations with an electroencephalogram functional magnetic resonance imaging (EEG-fMRI) fusion method. We observed that some neuronal populations, including the bilateral putamen, bilateral caudate, left thalamus, and supplementary motor area (SMA), entrain to both beat and meter. We also observed that the bilateral putamen entrains more to meter and the SMA entrains more to beat. Our results suggest that the bilateral putamen plays an important role in meter perception.