Aamodt Arnfinn, Nilsen André Sevenius, Thürer Benjamin, Moghadam Fatemeh Hasanzadeh, Kauppi Nils, Juel Bjørn Erik, Storm Johan Frederik
Brain Signalling Lab, Division of Physiology, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Oslo, Norway.
Front Psychol. 2021 Apr 23;12:655884. doi: 10.3389/fpsyg.2021.655884. eCollection 2021.
Several theories link consciousness to complex cortical dynamics, as suggested by comparison of brain signal diversity between conscious states and states where consciousness is lost or reduced. In particular, Lempel-Ziv complexity, amplitude coalition entropy and synchrony coalition entropy distinguish wakefulness and REM sleep from deep sleep and anesthesia, and are elevated in psychedelic states, reported to increase the range and vividness of conscious contents. Some studies have even found correlations between complexity measures and facets of self-reported experience. As suggested by integrated information theory and the entropic brain hypothesis, measures of differentiation and signal diversity may therefore be measurable correlates of consciousness and phenomenological richness. Inspired by these ideas, we tested three hypotheses about EEG signal diversity related to sleep and dreaming. First, diversity should decrease with successively deeper stages of non-REM sleep. Second, signal diversity within the same sleep stage should be higher for periods of dreaming vs. non-dreaming. Third, specific aspects of dream contents should correlate with signal diversity in corresponding cortical regions. We employed a repeated awakening paradigm in sleep deprived healthy volunteers, with immediate dream report and rating of dream content along a thought-perceptual axis, from exclusively thought-like to exclusively perceptual. Generalized linear mixed models were used to assess how signal diversity varied with sleep stage, dreaming and thought-perceptual rating. Signal diversity decreased with sleep depth, but was not significantly different between dreaming and non-dreaming, even though there was a significant positive correlation between Lempel-Ziv complexity of EEG recorded over the posterior cortex and thought-perceptual ratings of dream contents.
几种理论将意识与复杂的皮层动力学联系起来，这是通过比较意识状态与意识丧失或减弱状态之间的脑信号多样性得出的结论。特别是，莱姆尔-齐夫复杂度、振幅联合熵和同步联合熵能够区分清醒和快速眼动睡眠与深度睡眠和麻醉状态，并且在迷幻状态下会升高，据报道迷幻状态会增加意识内容的范围和生动程度。一些研究甚至发现复杂度测量与自我报告体验的各个方面之间存在相关性。正如整合信息理论和熵脑假说所表明的那样，分化和信号多样性的测量可能因此是意识和现象学丰富度的可测量相关指标。受这些观点的启发，我们测试了关于与睡眠和梦境相关的脑电图信号多样性的三个假设。第一，随着非快速眼动睡眠阶段的不断加深，多样性应该会降低。第二，在相同睡眠阶段，做梦期间的信号多样性应该高于非做梦期间。第三，梦境内容的特定方面应该与相应皮层区域的信号多样性相关。我们在睡眠剥夺的健康志愿者中采用了重复唤醒范式，同时立即进行梦境报告，并沿着从完全像思维到完全像感知的思维-感知轴对梦境内容进行评分。使用广义线性混合模型来评估信号多样性如何随睡眠阶段（包括清醒、快速眼动睡眠和非快速眼动睡眠）、梦境以及思维-感知评分而变化。信号多样性随着睡眠深度的增加而降低，但做梦和非做梦之间没有显著差异，尽管在后皮层记录的脑电图的莱姆尔-齐夫复杂度与梦境内容的思维-感知评分之间存在显著的正相关。
