EEG Signal Diversity Varies With Sleep Stage and Aspects of Dream Experience
Published in Frontiers in Psychology, 2021
Several prominent theories of consciousness—including Integrated Information Theory and the Entropic Brain Hypothesis—predict that neural signal diversity should scale with the richness of conscious experience. Sleep, with its staged progression from wakefulness to deep slow-wave sleep and varying quality of dream experience, offers a tractable testing ground for these predictions.
Sleep-deprived participants underwent a repeated awakening protocol using polysomnography and high-density EEG; after each awakening, they immediately reported dream content and rated it along a thought–perceptual spectrum. Signal diversity was quantified using Lempel-Ziv complexity (LZC) and coalition-based entropy measures.
As predicted, signal diversity progressively decreased with sleep depth (wakefulness > light NREM > deep NREM). However, within NREM2, diversity did not significantly differ between dreaming and non-dreaming awakenings. A positive correlation was found between posterior LZC and more perceptual (as opposed to abstract or thought-like) dream reports, partially consistent with the hypothesis that complexity reflects phenomenal richness. The mixed results call for further investigation into which aspects of consciousness complexity measures can—and cannot—distinguish.
Recommended citation: Aamodt A, Sevenius Nilsen A, Thürer B, HasanzadehMoghadam F, Kauppi N, Juel BE, Storm JF. (2021). "EEG Signal Diversity Varies With Sleep Stage and Aspects of Dream Experience." Frontiers in Psychology. 12:655884. https://doi.org/10.3389/fpsyg.2021.655884
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