Revealing rhythm categorization in human brain activity

Humans across cultures show an outstanding capacity to perceive, learn, and produce musical rhythms. These skills rely on mapping the infinite space of possible rhythmic sensory inputs onto a finite set of internal rhythm categories. What is the nature of the brain processes underlying rhythm categorization? We used electroencephalography to measure brain activity as human participants listened to a continuum of rhythmic sequences characterized by repeating patterns of two interonset intervals. Using frequency and representational similarity analyses, we show that brain activity does not merely track the temporal structure of rhythmic inputs but, instead, produces categorical representation of rhythms. These neural rhythm categories arise automatically, independent of any motor- or timing-related tasks, yet exhibit strong similarity with categorization observed in overt behavior. Together, these results and methodological advances constitute a critical step toward understanding the biological roots and diversity of musical behaviors across cultures.