Most of us are dreaming every night, although we are unlikely to remember any of our dreams. When we sleep, our brains repeatedly cross a boundary between unconsciousness and dreaming – a particular form of consciousness. Recently, researchers from the CIBM EEG HUG-UNIGE Section in collaboration with the Wisconsin Institute for Sleep and Consciousness questioned and elucidated which brain states determine whether dreams will occur and what prevents us from waking up during these conscious experiences.
The “EEG microstates of dreams” study (Bréchet et al., 2020, Scientific Reports) tackles these timely questions by parceling the brain network activity into meaningful brain states of stable and synchronous activity. This increasingly used EEG microstate approach is anchored in the CIBM EEG HUG-UNIGE Section led by Prof. Christoph Michel. So, why does it matter? Because dreams are a valuable model of consciousness, which represents everything that one may experience: the taste of summer BBQs, the warmth of home, the surviving memories of loved ones. The temporal dynamics of EEG microstates are highly sensitive to distinct levels of consciousness, different neuropsychiatric diseases, and cognitive contents.
In this collaborative study, the CIBM members of the EEG HUG-UNIGE Section, Dr. Lucie Bréchet, Dr. Denis Brunet and Prof. Christoph Michel together with Dr. Perogamvros from UNIGE/HUG and Prof. Giulio Tononi, from the Wisconsin Institute for Sleep and Consciousness, known in the field as the “Pope of Consciousness”, provide evidence that NREM sleep consists of alternating EEG microstates. These brain states’ transient temporal dynamics indicate temporary suppression of neural integration and communication within two distinct large-scale networks, one comprising the frontal and temporal brain regions, while the other was located in the occipital areas thalamus and extending to the brainstem.
Specifically, the researchers showed that “the awakening of the posterior hot zone” brain areas during dreaming is counterbalanced by a deeper local de-activation of prefrontal brain regions. The former may account for conscious experiences with rich perceptual content, while the latter may account for why the dreaming brain may undergo executive disconnection and remain asleep. Another exciting finding of this study is the demonstration that high-density EEG source imaging, rooted in the CIBM EEG HUG-UNIGE Section, can illuminate deep brain structures, the thalamus and the midbrain of the brainstem, that play a crucial role in the regulation of local sleep.
The study has already received international attention, being in the 91st percentile (ranked 1st) of tracked articles of the same category in Scientific Reports. The paper evoked a huge response in media such as Research Gate where it garnered 240 reads just three days after publication. The teamwork between researchers of CIBM EEG HUG-UNIGE and the University of Wisconsin is encouraging for future national and international collaborations. A better understanding of the brain signature in health and disease using the EEG microstate approach could help to diagnose and develop early treatments of distinct diseases.
And if you have not seen the Closer to Truth Series on Consciousness featuring Prof. Giulio Tononi, we highly recommend it.
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