EEG Microstate Dynamics Associated with Dream-Like Experiences During the Transition to Sleep.
Sarah Diezig, Simone Denzer, Peter Achermann, Fred W Mast, Thomas Koenig
Brain topography March 1, 2024 Peer reviewed DOI: 10.1007/s10548-022-00923-y via PubMed
Summary
During the transition to sleep, reflective awareness decreases before phenomenal awareness, leading to dream-like experiences characterized by uncontrolled thinking and perceptual images. In a study with 45 healthy young subjects, an inverse relationship was found between cognitive effects and physiological activation; increased presence of a specific EEG microstate in frontal areas was linked to these experiences, while another microstate related to visual processing decreased. This suggests a disengagement of cognitive control systems during this transition.
Study at a glance
| Sample size | 45 |
|---|---|
| Population | healthy young subjects |
| Key finding | Dream-like experiences during the transition to sleep are associated with increased presence of a specific EEG microstate in frontal areas and decreased presence of another microstate related to higher-order visual areas. |
Abstract
Consciousness always requires some representational content; that is, one can only be conscious about something. However, the presence of conscious experience (awareness) alone does not determine whether its content is in line with the external and physical world. Dreams, apart from certain forms of hallucinations, typically consist of non-veridical percepts, which are not recognized as false, but rather considered real. This type of experiences have been described as a state of dissociation between phenomenal and reflective awareness. Interestingly, during the transition to sleep, reflective awareness seems to break down before phenomenal awareness as conscious experience does not immediately fade with reduced wakefulness but is rather characterized by the occurrence of uncontrolled thinking and perceptual images, together with a reduced ability to recognize the internal origin of the experience. Relative deactivation of the frontoparietal and preserved activity in parieto-occipital networks has been suggested to account for dream-like experiences during the transition to sleep. We tested this hypothesis by investigating subjective reports of conscious experience and large-scale brain networks using EEG microstates in 45 healthy young subjects during the transition to sleep. We observed an inverse relationship between cognitive effects and physiological activation; dream-like experiences were associated with an increased presence of a microstate with sources in the superior and middle frontal gyrus and precuneus. Additionally, the presence of a microstate associated with higher-order visual areas was decreased. The observed inverse relationship might therefore indicate a disengagement of cognitive control systems that is mediated by specific, inhibitory EEG microstates.