EEG COHERENCE AND MUSICAL THINKING

This study was performed to test the usefulness of the EEG as a resear ch instrument for music psychology in individuals. Measuring the degre e 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 th e 19 electrodes (i.e., 171 values) and to observe any significant chan ges in those values caused by different musical tasks. This report con cerns observations in a total of 49 healthy subjects (29 male and 20 f emale). The main goal of this study was to determine the degree of eng agement of either hemisphere in the processing of music. Two items wer e shown to indicate hemispheric involvement: (1) the topographic distr ibution 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 a s parameters for hemispheric engagement, the following principal obser vations were made: the beta bands (and particularly their uppermost ra nges) seem to play a major role in the processing of music; the hemisp heric engagement, however, need not be the same for each frequency ban d. No hemisphere seems to be preferred. When listening to music is shi fted between different styles, laterality may change. When the same ta sks are repeated at several weeks' intervals, a fairly large degree of consistency is found. Imagining music and composing clearly differs f rom 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 musi c is processed by an individual. The coherence changes observed may re present 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.