Cross Frequency Coupling during the resting state with and without visual input

Abstract

Brain oscillations can be classified into different frequency bands: delta (1-4Hz), theta (4-8Hz), alpha (8-14Hz), beta (14-30Hz), low (30-45Hz) and high gamma (55-80Hz). These oscillations are often studied in isolation, but the interactions between frequency bands may also serve to implement important functions in the brain: for example, integration of sensory information from multiple sources or modalities, consciousness, memory or attention. As a first step to characterize these interactions and their functional roles, we measured phase-amplitude cross-frequency coupling between all EEG scalp locations (64 electrodes) and all pairs of frequency bands, during awake rest with eyes opened or closed (15 participants in each condition). This type of coupling quantifies the dependence of a certain oscillation's amplitude (recorded at a given scalp location) onto the phase of a lower-frequency oscillation (potentially recorded at a different scalp location). When the subjects' eyes were closed, we found a highly significant coupling between the phase of occipital alpha oscillations and the amplitude of the lower-gamma frequency band across all scalp locations (compatible with findings by Osipova et al., PLOS One, 2008). When subjects opened their eyes, this effect vanished and was replaced by a weaker and more local coupling between occipito-temporal alpha phase and oscillatory amplitude, this time in the higher-gamma frequency band. Furthermore, we found significant coupling between oscillatory amplitude of the beta frequency band in occipito-temporal brain regions and the phase of theta-band activity in occipital and fronto-central regions; this effect did not depend much on whether the participants' eyes were opened or closed. These phase-amplitude cross-frequency coupling interactions might help to maintain a specific spatio-temporal excitability pattern in the brain during the resting state. Finally, the dependence of occipital alpha-gamma coupling on visual inputs suggests that these interactions may also contribute (possibly in an inhibitory manner) to normal visual processing. Meeting abstract presented at VSS 2012