Infraslow EEG oscillations organize large-scale cortical-subcortical interactions during sleep: a combined EEG/fMRI...

Infraslow (<0.1 Hz) oscillations of brain activity, measured by EEG and other methods, have become a subject of increasing interest. While their prominence during sleep has been established, the functional significance of these oscillations for sleep physiology is unknown. To clarify this role, we examined correlations between infraslow EEG oscillations and BOLD fMRI during the course of natural sleep in healthy volunteers. Infraslow EEG oscillations appear to organize a broad dissociation of activity in cortical and subcortical regions: in general, correlations between power in the infraslow EEG band and BOLD were positive in subcortical regions and negative in the cortex. Robust negative correlations were found principally in paramedian heteromodal cortices whereas positive correlations were seen in cerebellum, thalamus, basal ganglia, lateral neocortices and hippocampus. This pattern of correlations suggests a mechanism by which infraslow oscillations may organize sleep-dependent neuroplastic processes including consolidation of episodic memory.