Interdependencies in the spontaneous EEG while listening to music.

We studied the patterns of interdependency between different brain regions during the performance of higher cognitive functions. Our goal was to check the existence in these patterns of both task-related differences (e.g. listening to music vs. rest) and training-related differences (musicians vs. non-musicians). For this purpose, a non-linear measure, called similarity index (S.I.), was used to detect asymmetric interdependencies between different brain regions by means of EEG signals. Relatively active and passive regions of the brain were found where the degree of activity was represented by excited degrees of freedom. The S.I. obtained during listening to different kinds of music was compared statistically with the S.I. with eyes closed, and significant changes (P< or = 0.05) were entered into schematic brain maps. A topographical representation of the S.I. yielded differences in the interdependency while performing different cognitive tasks. The results demonstrate the occurrence of task-related differences in both groups of subjects. Furthermore, subjects with musical training possessed significantly higher degrees of interdependencies than such without musical training while listening to music but not to text. We conclude that the new measure can be successfully applied for studying the dynamical co-operation between cortical areas during higher cognitive functioning.