Long-range synchrony in the gamma band: Role in music perception

Synchronization seems to be a central mechanism for neuronal information pr ocessing within and between multiple brain areas. Furthermore, synchronizat ion in the gamma band has been shown to play an important role in higher co gnitive functions, especially by binding the necessary spatial and temporal information in different cortical areas to build a coherent perception. Sp ecific task-induced (evoked) gamma oscillations have often been taken as an indication of synchrony, but the presence of long-range synchrony cannot b e inferred from spectral power in the gamma range. We studied the usefulnes s of a relatively new measure, called similarity index to detect asymmetric interdependency between two brain regions. Spontaneous EEG from two groups -musicians and non-musicians-were recorded during several states: listening to music, listening to text, and at rest (eyes closed and eyes open). Whil e listening to music, degrees of the gamma band synchrony over distributed cortical areas were found to be significantly higher in musicians than non- musicians. Yet no differences between these two groups were found at restin g conditions and while listening to a neutral text. In contrast to the degr ee of long-range synchrony, spectral power in the gamma band was higher in non-musicians. The degree of spatial synchrony, a measure of signal complex ity based on eigen-decomposition method, was also significantly increased i n musicians while listening to music. As compared with non-musicians, the f inding of increased long-range synchrony in musicians independent of spectr al power is interpreted as a manifestation of a more advanced musical memor y of musicians in binding together several features of the intrinsic comple xity of music in a dynamical way.