Long-Range Synchrony in the γ Band: Role in Music Perception

Abstract

Synchronization seems to be a central mechanism for neuronal information processing within and between multiple brain areas. Furthermore, synchronization in the ␥ band has been shown to play an important role in higher cognitive functions, especially by binding the necessary spatial and temporal information in different cortical areas to build a coherent perception. Specific task-induced (evoked) ␥ oscillations have often been taken as an indication of synchrony, but the presence of longrange synchrony cannot be inferred from spectral power in the ␥ range. We studied the usefulness 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). While listening to music, degrees of the ␥ band synchrony over distributed cortical areas were found to be significantly higher in musicians than nonmusicians. Yet no differences between these two groups were found at resting conditions and while listening to a neutral text. In contrast to the degree of long-range synchrony, spectral power in the ␥ band was higher in non-musicians. The degree of spatial synchrony, a measure of signal complexity based on eigen-decomposition method, was also significantly increased in musicians while listening to music. As compared with nonmusicians, the finding of increased long-range synchrony in musicians independent of spectral power is interpreted as a manifestation of a more advanced musical memory of musicians in binding together several features of the intrinsic complexity of music in a dynamical way. Key words: EEG; synchronization; music; ␥ band; cognitive task; binding; similarity indexWidespread oscillatory activity, particularly in the ␥ range (Ͼ30 Hz) has attracted the attention of researchers studying different cognitive phenomena in human and mammalian species (for review, see Basar-Eroglu et al., 1996;Tallon-Baudry and Bertrand, 1999). Synchronous 40 Hz oscillations, found in the olfactory system of the rabbit (Freeman, 1978), were supposed to play a key role in the detection of different odors (Freeman and Skarda, 1985). Furthermore, spatially distributed cells in the visual cortex of both the anesthetized (Gray et al., 1989) and the alert cat (Gray and DiPrisco, 1997) produced oscillations in the ␥ band in response to visual stimuli. Evidence of precise phase locking across different cortical areas with zero phase lag in this frequency range was also reported in alert cats during visual discrimination task (Roelfsema et al., 1997). In humans, transient phase locking at ϳ40 Hz generated in the contralateral and parietal cortical areas was found during selective attention (Desmedt and Tomberg, 1994). It has been postulated (Bressler et al., 1993;Tallon-Baudry et al., 1998) that the ␥ band serves as a mechanism for the visual representation of objects and as a means of "binding" various intricate as...

EEG synchrony during a perceptual-cognitive task: Widespread phase synchrony at all frequencies

“…In fact the suggestion that theta/alpha or theta/apha/beta synchrony is global while gamma or beta/gamma-synchrony is local has already been negated by numerous reports of long-range gamma synchrony coinciding with various conscious experiences (Haig et al, 2000;Bhattacharya et al, 2001;Gruber et al, 2001;Lutz et al, 2002;Summerfield and Mangels, 2005). We confirm that long-range synchrony is widespread in theta, alpha, beta, gamma and epsilon bands -and in fact is sometimes more widespread in gamma and epsilon bands than at lower frequencies.…”

Intelligence and Cognitive Control

“…Alpha amplitude tends to decrease (desynchronization) with increases in mental effort, while theta band amplitude tends to increase (synchronization) (Klimesch, 1996(Klimesch, , 1997Nunez, Wingeier, & Silberstein, 2001). Recent research has revealed that the gamma band (>30 Hz) may be of particular relevance to cognition -e.g., attention and arousal, basic acoustic and visual perception, perception of gestalt and language, music perception (for a review, see Başar, Başar-Eroglu, Karakaş, & Schürmann, 2001;Bhattacharya, Petsche, & Pereda, 2001;Pulvermüller, Birbaumer, Lutzenberger, & Mohr, 1997;Tallon-Baudry & Bertrand, 1999). Of special relevance for high level cognitive processes is the induced gamma band activity.…”

Development of Auditory Phase-Locked Activity for Music Sounds

“…Theta band phase patterns can track the temporal envelope of spoken sentences (Ahissar et al 2001;Luo and Poeppel 2007). In contrast, enhanced phase-locking and power of oscillations in the gamma band have been associated with increased spectral complexity of sounds (Shahin et al 2008), memory matching in auditory (Lenz et al 2007;Shahin et al 2008) and visual (Herrmann et al 2004) modalities, selective attention (Fries et al 2001;Polley et al 2006;Snyder et al 2006), and long-range synchrony during music processing (Bhattacharya et al 2001).…”