Beta-Band Oscillations Represent Auditory Beat and Its Metrical Hierarchy in Perception and Imagery

Dancing to music involves synchronized movements, which can be at the basic beat level or higher hierarchical metrical levels, as in a march (groups of two basic beats, one–two– one–two . . .) or waltz (groups of three basic beats, one–two–three– one–two–three . . .). Our previous human magnetoencephalography studies revealed that the subjective sense of meter influences auditory evoked responses phase locked to the stimulus. Moreover, the timing of metronome clicks was represented in periodic modulation of induced (non-phase locked) 􏰀-band (13–30 Hz) oscillation in bilateral auditory and sensorimotor cortices. Here, we further examine whether acoustically accented and subjectively imagined metric processing in march and waltz contexts during listening to isochronous beats were reflected in neuromagnetic 􏰀-band activity recorded from young adult musicians. First, we replicated previous findings of beat-related 􏰀-power decrease at 200 ms after the beat followed by a predictive increase toward the onset of the next beat. Second, we showed that the 􏰀 decrease was significantly influenced by the metrical structure, as reflected by differences across beat type for both perception and imagery conditions. Specifically, the 􏰀-power decrease associated with imagined downbeats (the count “one”) was larger than that for both the upbeat (preceding the count “one”) in the march, and for the middle beat in the waltz. Moreover, beamformer source analysis for the whole brain volume revealed that the metric contrasts involved auditory and sensorimotor cortices; frontal, parietal, and inferior temporal lobes; and cerebellum. We suggest that the observed 􏰀-band activities reflect a translation of timing information to auditory–motor coordination.