The processing of violations in nested musical structures

Music and language are complex means of communication that embody hierarchically-organised sequences. Processing hierarchical sequences require the resolution of both local and non-local dependencies. That is, one must be able to relate elements beyond its immediate temporal order. A type of non-local dependency that is frequently encountered arises from nested or centre-embedded structures. It was recently shown that both musicians and non-musicians perceive nested non-local dependencies in tonal harmony. However, its neuroanatomical basis is unknown, and it is unclear if the perception of nested non-local dependencies is specific to harmony. Original musical sequences composed by concatenating three-note motifs in a nested matter were presented alongside modified counterparts to musicians in a two-alternative forced choice task. Using functional MRI (fMRI), the present experiment demonstrates that processing nested motific structures in music recruits the right homologue of Broca’s area, and for the first time, that musical structures with at least two levels of embedding can be perceived. This finding establishes the functional neuroanatomy of processing nested non-local dependencies in music and provides striking evidence that the functional neuroanatomical network of musical syntax is a mirror image of that in human language