Science Advances
February 1, 2019
Athena Demertzi, Enzo Tagliazucchi, Stanislas Dehaene et al.
545 citations
Consciousness depends on the brain's ability to sustain rich, dynamic patterns of signal coordination. Using functional magnetic resonance imaging, a complex pattern of coordinated and anticoordinated signals characterized healthy individuals and minimally conscious patients. Unresponsive patients showed low interareal phase coherence mainly mediated by structural connectivity, with fewer transitions between patterns. This complex pattern was also seen in patients with covert cognition who could perform mental imagery tasks, validating its link to consciousness. Anesthesia increased the probability of the less complex pattern to levels seen in unresponsive patients, confirming its role in unconsciousness. These results establish generalizable fingerprints of conscious and unconscious states after brain damage.
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.
Anesthesiology
August 9, 2016
Vincent Bonhomme, Audrey Vanhaudenhuyse, Athena Demertzi et al.
206 citations
Ketamine alters consciousness by disrupting connectivity within and between specific resting-state brain networks, particularly the default mode network (DMn) and salience network (SALn), while leaving sensory and motor networks largely intact. In healthy volunteers given stepwise ketamine infusions until they lost responsiveness, DMn connectivity between the medial prefrontal cortex and other network regions decreased (from 0.20 to 0.07), and the normal anticorrelated activity between the DMn and sensory regions reversed (e.g., right sensory cortex shifted from -0.07 to 0.04). SALn connectivity was also suppressed but nonuniformly. These specific changes, including preserved sensory network connectivity, are shared with propofol-induced unconsciousness.
Annals of the New York Academy of Sciences
March 1, 2009
Athena Demertzi, Charlene Liew, Didier Ledoux et al.
125 citations
Attitudes about whether mind and brain are separate or the same thing vary by age, gender, and religious belief. Two surveys—one of university students in Edinburgh (250 people) and another of health-care workers and the public in Liège (1,858 people)—found that dualistic views (seeing mind and brain as distinct) were common. In the Liège survey, younger participants, women, and those with religious beliefs were more likely to endorse separation of mind and brain, survival of a spiritual part after death, and the existence of a soul distinct from the body. Religious belief was the strongest predictor of dualism. Over a third of medical and paramedical professionals also regarded mind and brain as separate, even though most health-care workers rejected that distinction.
Frontiers in Systems Neuroscience
August 14, 2019
Vincent Bonhomme, Cécile Staquet, Javier Montupil et al.
109 citations
General anesthesia reversibly alters consciousness without globally shutting down the brain. Depending on the agent and dose, it can produce a complete absence of subjective experience (unconsciousness), a conscious experience without environmental perception (disconnected consciousness, like during dreaming), or oriented consciousness with environmental awareness (connected consciousness). Each state may be followed by explicit or implicit memories. Progress in brain function exploration has improved understanding of neural correlates of consciousness and their alterations during anesthesia, including changes in functional and effective brain connectivity, consciousness network topology, and spatio-temporal dynamics.
Science Advances
June 14, 2023
Leor Roseman, Christopher Timmermann, Daniel Golkowski et al.
65 citations
The effects of mind-altering drugs on brain function arise from complex interactions with multiple neurotransmitter systems, not just one. By linking the distribution of 19 neurotransmitter receptors and transporters (measured with PET) to changes in functional connectivity (measured with fMRI) caused by 10 drugs—anesthetics (propofol, sevoflurane, ketamine), psychedelics (LSD, psilocybin, DMT, ayahuasca), and others (MDMA, modafinil, methylphenidate)—the work shows a many-to-many mapping between drug effects and neurotransmitter systems. The drugs' impacts follow hierarchical gradients of brain structure and function, and regional susceptibility to drug-induced changes mirrors susceptibility to structural alterations from brain disorders.
Trends in Neurosciences
May 31, 2024
Andrea I. Luppi, Fernando E. Rosas, Pedro A. M. Mediano et al.
23 citations
Unconsciousness increases the coupling between brain structure and function across scales, while psychedelics may decouple brain function from structure. Anaesthetics, psychedelics, and disorders of consciousness can produce similar reconfigurations along the brain's unimodal-transmodal functional axis. Decomposing brain function into fundamental constituents of time, space, and information has driven recent advances in understanding consciousness and the brain's functional organisation. Computational modelling offers a path toward mechanistic integration, and decomposition approaches may help translate discoveries across species.
Biological psychiatry. Cognitive neuroscience and neuroimaging
July 1, 2024
Sepehr Mortaheb, Larry D Fort, Natasha L Mason et al.
15 citations
Psilocybin produces profound alterations in both brain connectivity and subjective experience. In a randomized study, healthy volunteers received psilocybin or placebo and underwent ultrahigh field 7T fMRI scanning during the peak drug effect. Psilocybin caused widespread increases in averaged brain functional connectivity and a recurrent hyperconnected brain pattern with low blood oxygen level-dependent signal amplitude, suggesting heightened cortical arousal. This hyperconnected pattern was linked to feelings of oceanic boundlessness and visionary restructuralization. The brain's tendency to enter this hyperconnected-hyperarousal state may underlie the variant mental associations characteristic of the psychedelic experience.
Journal of Cognitive Neuroscience
January 1, 2023
Rajanikant Panda, Audrey Vanhaudenhuyse, Andrea Piarulli et al.
15 citations
During hypnosis, brain connectivity changes in ways that suggest more efficient cognitive processing and less mind-wandering. In nine healthy participants, hypnosis increased delta-wave connections between frontal brain regions and between frontal and parietal regions. It decreased alpha and beta-2 connections among frontal, parietal, and midline areas. Network analysis showed greater segregation of short-range connections in delta and alpha bands and greater integration of long-range connections in beta-2 bands. Frontal and right parietal electrodes became central hubs. These altered dynamics may reflect a modified balance between internal and external awareness networks.
Neuroscience and biobehavioral reviews
August 1, 2025
Larry Douglas Fort, Cyril Costines, Marc Wittmann et al.
14 citations
A review of classification schemes for altered states of consciousness (ASCs) groups them into three types: those based on subjective experiences (state-based), those based on induction methods (method-based), and those based on neurophysiological mechanisms (neuro/physio-based). Comparing and extending these schemes can improve identification of neural correlates of consciousness and inform clinical research. The authors cluster concepts from state-based schemes to help quantify core ASC phenomenology for basic and clinical studies.
Trends in cognitive sciences
March 12, 2025
Thomas Andrillon, Antoine Lutz, Jennifer Windt et al.
14 citations
Moments during wakefulness that seem empty of any reportable thought, called mind blanking (MB), are not simply gaps in experience but distinct mental states with their own characteristics. This review maps MB by examining how people report it, its brain activity, and its links to related phenomena such as meditation and sleep. The authors propose that ongoing experience varies in richness, and contentless events represent a diverse category of mental states. They argue that recognizing MB as a reportable mental category is essential for a full understanding of how the mind works during wakefulness.
bioRxiv (Cold Spring Harbor Laboratory)
September 18, 2023
Sepehr Mortaheb, Larry D. Fort, Natasha L. Mason et al.
7 citations
preprint
Psilocybin increases functional connectivity across the brain and induces a recurrent hyperconnected pattern with low BOLD signal amplitude, suggesting heightened cortical arousal. These brain dynamics are linked to feelings of oceanic boundlessness and visionary restructuralization, as measured by the 5-Dimensional Altered States of Consciousness Rating Scale. The brain's tendency to enter this hyperconnected-hyperarousal pattern under psilocybin may enable variant mental associations. For the first time, these findings connect brain dynamics with phenomenological alterations, offering new insights into the neurophenomenology and neurophysiology of the psychedelic state.
bioRxiv (Cold Spring Harbor Laboratory)
July 13, 2022
Andrea I. Luppi, Justine Y. Hansen, R. Adapa et al.
5 citations
preprint
Psychoactive drugs reshape brain function by engaging multiple neurotransmitter systems simultaneously. By mapping the distribution of 19 neurotransmitter receptors and transporters (via PET) and the connectivity changes caused by 10 drugs (anesthetics, psychedelics, and stimulants), the study shows that drug effects are organized along hierarchical gradients of brain structure and function. Additionally, brain regions susceptible to drug-induced changes are also vulnerable to structural alterations from brain disorders. These findings reveal systematic links between molecular neurochemistry and large-scale functional reorganization.
October 17, 2024
Thomas Andrillon, Antoine Lutz, Jennifer Windt et al.
4 citations
preprint
Mind blanking (MB) refers to moments during wakefulness when people report no specific thoughts. This review maps MB by examining its reportable expressions, brain signatures, and links to meditative practices and sleep (white dreams). The authors propose a mechanistic account linking MB to changes at physiological, neural, and cognitive levels. They argue that ongoing experience varies in richness and that seemingly contentless events are distinct mental states with their own diversity, challenging the view of the mind as primarily content-oriented.
British journal of anaesthesia
April 1, 2025
Milan Van Maldegem, Jakub Vohryzek, Selen Atasoy et al.
3 citations
Ketamine, at anesthetic doses, produces a state where people are unresponsive yet often report vivid inner experiences, separating conscious awareness from behavioral responsiveness. Using connectome harmonic decomposition on fMRI data, researchers found that brain signals during ketamine-induced unresponsiveness show increased fine-grained spatial patterns, indicating higher neural granularity. This harmonic signature aligned with those of LSD-induced and ketamine-induced psychedelic states, but misaligned with signatures from unconscious individuals due to propofol sedation or brain injury. The method can track changes in conscious awareness even when behavior is absent, offering a tool for consciousness and anesthesia research.
bioRxiv (Cold Spring Harbor Laboratory)
June 25, 2024
Milan van Maldegem, Jakub Vohryzek, Selen Atasoy et al.
2 citations
preprint
Ketamine, a dissociative anesthetic, produces different brain dynamics at anesthetic versus sub-anesthetic doses. Using connectome harmonic decomposition (CHD) to analyze resting-state fMRI data from volunteers during ketamine-induced unresponsiveness, the study found increased prevalence of localized harmonics, similar to patterns seen in psychedelic states induced by LSD or psilocybin. This contrasts with traditional GABAergic sedation (e.g., propofol), where global harmonics increase with higher doses. The results indicate that ketamine-induced unresponsiveness does not necessarily suppress conscious experience and influences connectome harmonics oppositely to GABAergic hypnotics. CHD may track alterations in conscious awareness rather than behavioral responsiveness.
Frontiers in Neuroscience
January 1, 2018
Rajanikant Panda, Olivia Gosseries, Audrey Vanhaudenhuyse et al.
2 citations
No Summary
Biological Psychiatry
October 21, 2025
Katharina S Lege, Pablo Mallaroni, Sepehr Mortaheb et al.
1 citation
Acute cannabis intoxication alters brain network dynamics, reducing the occurrence of a hyperconnected brain state in both occasional and chronic users. Chronic users show persisting neuroadaptations, including decreased brain network segregation, independent of intoxication. Attentional performance is most impaired in occasional users, suggesting tolerance develops in chronic users. Both acute and persistent effects on brain dynamics correlate with spatial CB1 receptor density. The findings indicate that cannabis-induced cognitive impairment depends on individual neuroadaptations and receptor density, relevant for therapeutic, legal, and societal contexts.
September 3, 2025
Paradeisios Alexandros Boulakis, Athena Demertzi, Jaco Sitt et al.
preprint
Consciousness research typically separates the study of states of consciousness (e.g., wakefulness, sleep, drug-induced states) from the study of contents of consciousness (what we are aware of). This chapter emphasizes the dynamic nature of both aspects. Life alternates between conscious and unconscious states like sleep and wakefulness, and within each state, conscious experience ranges from content-full to content-less. Similarities in reported contents across wakefulness and sleep are highlighted. The possibility of conscious experiences without specific content challenges the notion that being conscious always involves being conscious of something. Reviewing neural correlates of consciousness, the authors propose a potential convergence in studying conscious states and contents.
bioRxiv Preprint Server
June 7, 2026
Andrea I. Luppi, Dragana Manasova, Justine Y. Hansen et al.
preprint
Functional connectivity in the awake human brain is shaped primarily by cognitive co-activation—the tendency of brain regions to work together during mental tasks—more than by structural or molecular constraints. This predominance is systematically lost across five datasets involving pharmacological and pathological perturbations of consciousness (chronic disorders of consciousness; anesthesia with sevoflurane, propofol, or ketamine), when cognition is disconnected from the environment or abolished. During such states, the predictors of functional architecture shift away from cognitive co-activation and toward anatomical and molecular constraints.
bioRxiv Preprint Server
September 28, 2022
Yonatan Sanz Perl, Carla Pallavicini, Juan Piccinini et al.
preprint
Brain states are often described on a single scale from full consciousness to unconsciousness, but this ignores the complex, high-dimensional nature of brain activity. By combining whole-brain modeling, data augmentation, and deep learning, researchers mapped states of consciousness into a low-dimensional space where distances reflect similarities between states. They found an orderly trajectory from wakefulness to brain-injured patients, with coordinates related to functional modularity and structure-function coupling, both increasing as consciousness is lost. Model perturbations provided a geometric interpretation of state stability and reversibility. The work suggests conscious awareness depends on functional patterns encoded as a low-dimensional trajectory within the vast space of brain configurations.
bioRxiv Preprint Server
July 2, 2020
Yonatan Sanz Perl, Carla Pallavicini, Ignacio Pérez Ipiña et al.
preprint
The level of consciousness—how conscious someone is—is often measured by how similar their brain activity is to normal wakefulness. However, this approach misses important information about how stable that state is. Using computer models of the whole brain, the authors show that the stability of a conscious state—how easily it can be disrupted—provides additional, complementary information. They propose a new framework that sorts brain states by both their similarity to wakefulness and their stability, which helps distinguish between different types of unconsciousness: natural sleep, anesthesia, and brain injury. This framework offers a more complete way to characterize and differentiate states of consciousness.