Perception of phrase structure in music
Neither music nor spoken language form uniform auditory streams, rather, they are structured into phrases. For the perception of such structures, the detection of phrase boundaries is crucial. We discovered electroencephalography (EEG) and magnetoencephalography (MEG) correlates for the perception of phrase boundaries in music. In EEG, this process was marked by a positive wave approximately between 500 and 600 ms after the offset of a phrase boundary with a centroparietal maximum. In MEG, we found major activity in an even broader time window (400-700 ms). Source localization revealed that likely candidates for the generation of the observed effects are structures in the limbic system, including anterior and posterior cingulate as well as posterior mediotemporal cortex. The timing and topography of the EEG effect bear some resemblance to a positive shift (closure positive shift, CPS) found for prosodic phrase boundaries during speech perception in an earlier study, suggesting that the underlying processes might be related. Because the brain structures, which possibly underlie the observed effects, are known to be involved in memory and attention processes, we suggest that the CPS may not reflect the detection of the phrase boundary as such, but those memory and attention related processes that are necessary to guide the attention focus from one phrase to the next, thereby closing the former and opening up the next phrase.