Neuromagnetic beta-band oscillation for rhythmic processing induced by subjectively accented structure

Musical rhythm facilitates synchronized body movements and schema-based, predictive timing perception. Our previous magnetoencephalography (MEG) study demonstrated that beta-band (~20 Hz) activity in bilateral auditory cortices shows synchronized modulation that predicts the time point of the next beat (Fujioka et al. 2009, 2012). Furthermore, after finger tapping to a different musical meter such as a march or waltz (every 2nd or 3rd beat), the broadband evoked response from auditory cortex differentiates the metric conditions (Fujioka et al., 2010). Here we examined how beta-band activity indexed subjective metrical perception during listening to unaccented beats (1) after listening to acoustically accented beats, and (2) after finger tapping with either the left or right index finger. The auditory cortices showed beat-synchronized modulation in line with the previous studies in both march and waltz conditions. However, distinction between down-beat and up-beat positions was stronger in march than in waltz condition, with symmetrical activities in the left and right auditory cortices. This contrast between the two metric conditions was stronger in the side contralateral to the tapping finger in the tapping condition. This suggests that contribution of auditory cortices to metric processing depends on both its timing structure and rhythmic movement in the contralateral hemisphere.