EEG Coherence and Musical Thinking

Abstract

This study was performed to test the usefulness of the EEG as a research instrument for music psychology in individuals. Measuring the degree of functional interrelatedness of brain areas by coherence estimates has turned out to be more efficient than amplitude mapping. Therefore, the method, based on the analysis of EEG periods of at least 1 min, has been expanded to estimate all possible coherence values between the 19 electrodes (i.e., 171 values) and to observe any significant changes in those values caused by different musical tasks. This report concerns observations in a total of 49 healthy subjects (29 male and 20 female). The main goal of this study was to determine the degree of engagement of either hemisphere in the processing of music. Two items were shown to indicate hemispheric involvement: (1) the topographic distribution of "focal points of coherence" (brain areas participating in coherence changes with respect to a great number of other brain areas) and (2) the number of intrahemispheric coherence increases. In most cases, both items seem to focus on the same hemisphere. Taking these as parameters for hemispheric engagement, the following principal observations were made: the beta bands (and particularly their uppermost ranges) seem to play a major role in the processing of music; the hemispheric engagement, however, need not be the same for each frequency band. No hemisphere seems to be preferred. When listening to music is shifted between different styles, laterality may change. When the same tasks are repeated at several weeks' intervals, a fairly large degree of consistency is found. Imagining music and composing clearly differs from listening by activating many more coherence increases in the beta band and by an increasing percentage of hemispheric interaction. This kind of analysis may also provide some clues as to how a piece of music is processed by an individual. The coherence changes observed may represent events taking place in a system of differential attention that selects and orders the sensory inputs before the musical material is further processed at higher order hierarchical levels.