Expectations of beat-level rhythmic information are modulated by priming with hierarchical structure: an MMN study

When musical rhythms contain simple integer-ratio intervals, listeners extract the underlying beat while understanding the rhythm in a hierarchical structure. We hypothesized that encoding of beat-level information pre-attentively may be influenced by the depth of hierarchy and its integration demands. We examined the mismatch negativity (MMN) during passive listening to rhythms containing a prime part and a subsequent part. Four primes with varied levels of hierarchical information, and in standard trials, the subsequent rhythm ended on the beat position, while in deviant trials, the final note occurred earlier by either an 8 th or 16 th note (50% or 25% of the standard IOI). While larger MMN was found for a larger temporal displacement, the effect of prime variation was also significant. Consistent with our hypothesis, the prime with the four 8 th notes elicited larger MMNs compared to the two 8 th and one quarter notes, indicating that the latter prime likely required increased processing demands at the beginning despite having the same subdivision level. Primes with increased subdivisions also tended to reduce behavioral detection accuracy. These results point to an interplay between sequential and hierarchical processes for beat-level encoding and rhythmic grouping.