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Microstate and Omega Complexity Analyses of the Resting-state Electroencephalography
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EEG Connectivity is an Objective Signature of Reduced Consciousness and Sleep Depth
Toedt Inken1,2, Gesine Hermann1, Enzo Tagliazucchi3,4
1Department of Neurology, Christian-Albrechts University, Arnold-Heller-Strasse 3, 24105, Kiel, Germany.
Brain Topography
|September 5, 2025
Summary
Functional connectivity (FC) in electroencephalography (EEG) changes across human sleep stages. Alpha band coupling decreases, while delta band coupling increases, correlating with altered consciousness during sleep.
Area of Science:
- Neuroscience
- Computational Neuroscience
- Sleep Science
Background:
- Sleep stages are behaviorally defined by reduced consciousness.
- Electroencephalography (EEG) identifies sleep stages using localized brain oscillations.
- Consciousness is theoretically linked to long-range brain information sharing (functional connectivity, FC).
Purpose of the Study:
- To test if EEG-FC reflects sleep stages and changes in consciousness.
- To investigate how FC metrics differ across non-rapid eye movement (NREM) sleep stages.
- To identify specific frequency bands and electrode pairs crucial for distinguishing sleep stages.
Main Methods:
- Retrospective analysis of sleep EEG recordings from 14 participants.
- Quantification of FC using six phase coupling metrics.
- Training a gradient boosting classifier on FC coefficients to differentiate sleep stages.
Main Results:
- Frequency-specific differences in FC were observed across sleep stages (except imaginary coherence).
- Alpha band coupling decreased from wakefulness to N1/N2 sleep; delta band coupling increased in N3 sleep.
- FC-based classifiers achieved 51-73% accuracy, with alpha band patterns being highly important features.
Conclusions:
- EEG-derived FC significantly changes across sleep stages.
- Phase coupling patterns, particularly in the alpha band, serve as electrophysiological correlates of consciousness during sleep.
- Distributed phase coupling supports the hypothesis of long-range information sharing being fundamental to consciousness.
