CATEGORHYTHM · Neural basis of rhythm categorization: how does the brain make sense of musical rhythm?

When we listen to music, recognizing a well-known rhythmic pattern and moving our body along seems like a natural and effortless task. Yet, these widespread human abilities are far from trivial, due to the sheer diversity and variability of possible rhythmic inputs that may stimulate our sensory organs. How does the brain categorize a particular sensory input as an instance of a particular rhythmic pattern? One view, which dates back to Darwin, is that rhythm categorization is driven by fixed mechanisms anchored in the ancient subcortical parts of the brain. However, recent behavioral research argues that categorical perception of rhythm is a complex flexible function, possibly relying on evolutionarily newer plastic cortical networks. The current project scrutinizes these views by combining an innovative methodological approach with high-resolution neuroimaging techniques (electroencephalography and magnetoencephalography). This novel approach will be used to unravel how different brain regions contribute to the transformation from faithful encoding of stimulus’ physical properties towards internal rhythmic categories. Moreover, neural categorization processes will be probed in participants with developmental dyslexia to assess their contribution to generalized rhythmic abilities, which are impaired in this population. The results are expected to provide key insights into the neurobiological mechanisms underlying perceptual categorization of rhythm, and their role in driving the universality, yet remarkable diversity of musical rhythms observed across cultures. Likewise, the outcomes of this project are expected to improve our understanding of the role of rhythm categorization processes in language development and its disorders, such as developmental dyslexia, with implications for the improvement of diagnostic and therapeutic tools.