Journal of Cognitive Neuroscience
June 1, 2010
Audrey Vanhaudenhuyse, Athena Demertzi, Manuel Schabus et al.
460 citations
Resting brain activity reveals two anticorrelated cortical systems linked to conscious awareness: an extrinsic system (lateral fronto-parietal areas) associated with external awareness and an intrinsic system (medial brain areas) associated with internal awareness. In 31 healthy volunteers, external and internal awareness were significantly anticorrelated, with a mean switching frequency of 0.05 Hz, similar to BOLD fMRI slow oscillations. In 22 volunteers, fMRI showed that precuneus/posterior cingulate, anterior cingulate/mesiofrontal cortices, and parahippocampal areas (intrinsic system) correlated with internal awareness, while lateral fronto-parietal cortices (extrinsic system) correlated with external awareness.
Proceedings of the National Academy of Sciences
March 26, 2012
Melanie Boly, Vincent Perlbarg, Guillaume Marrelec et al.
201 citations
Consciousness is reduced during nonrapid eye movement (NREM) sleep due to changes in brain function that are still poorly understood. Here, we tested the hypothesis that impaired consciousness during NREM sleep is associated with an increased modularity of brain activity. Cerebral connectivity was quantified in resting-state functional magnetic resonance imaging times series acquired in 13 healthy volunteers during wakefulness and NREM sleep. The analysis revealed a modification of the hierarchical organization of large-scale networks into smaller independent modules during NREM sleep, independently from EEG markers of the slow oscillation. Such modifications in brain connectivity, possibly driven by sleep ultraslow oscillations, could hinder the brain's ability to integrate information and account for decreased consciousness during NREM sleep.
NeuroImage
October 17, 2022
Natália Bezerra Mota, Ernesto Soares, Edgar Altszyler et al.
5 citations
Visual and emotional aspects of waking memories follow different paths as people fall asleep. Healthy adults viewed an emotional image, then were awakened seconds to minutes later during wakefulness, N1, or N2 sleep stages. Semantic similarity between the image and subsequent hypnagogic imagery—the 'image residue'—persisted and even increased during N1 sleep, lasting longer with more time in that stage. In contrast, the emotional tone of the image—the 'affect residue'—gradually faded as sleep progressed, becoming neutralized and reaching its lowest point during N2. Brain theta power (4.5–6.5 Hz) during N1 was inversely related to image residue. These findings suggest that visual content and strong negative emotions may decouple at sleep onset, possibly aiding emotional processing.
Current biology : CB
May 5, 2025
Pavlos I Topalidis, Gianpaolo Demarchi, Lisa Reisinger et al.
1 citation
During sleep, the brain retains the ability to preactivate representations of specific sound features, such as tone frequency, but loses the capacity to track higher-order statistical associations between sounds. Using EEG and MEG with multivariate pattern analysis, the study compared brain responses to predictable and random tone sequences during wakefulness and sleep. Feature-specific responses to subtle tone changes were present in N1 and N2 sleep, though weaker than when awake. The brain preactivated feature-specific representations during sleep, but tracking of statistical associations between tones occurred only during wakefulness. This suggests that while some automatic predictive processing of low-level features persists, higher-order anticipation of patterns is disrupted when consciousness fades.