Cortico-striatal network architecture shapes rhythmic biases in music.

Why is human music rhythmically structured the way it is? One hypothesis is that the human brain is intrinsically wired to favor specific rhythmic organizations. To test this, we collected diffusion and resting-state functional MRI (fMRI) data from musically untrained participants and, weeks later, asked them to imitate randomly generated drumming sequences using finger taps. These imitations exhibited systematic biases toward temporal structures widespread in human music: predictable patterns characterized by isochronous organization (1:1) and other small integer ratios (2:1 and 3:1). Functional connectome analyses linked the increased rhythmic predictability of reproduced rhythms to intrinsic interactions between networks implicated in auditory timing (auditory basal ganglia) and executive control (task-positive and task-negative networks). Notably, the tendency toward isochrony-a feature highly conserved across species-was selectively associated with increased fiber density within a cortico-basal ganglia-thalamo-cortical network previously implicated in the perception and production of a metronomic pulse from music (the "beat"). Our findings reveal how stable neural architecture predisposes humans to produce rhythmically structured patterns. This evidence links intrinsic brain circuitry to individual cultural expressions, supporting the account of human symbolic systems, including music, as biocultural hybrids.