Science
September 7, 2006
Adrian M. Owen, Martin R. Coleman, Melanie Boly et al.
1,974 citations
A patient who met the clinical criteria for a vegetative state showed brain activity indistinguishable from healthy volunteers when asked to imagine playing tennis or moving around her home. Using functional magnetic resonance imaging, the patient activated the same predicted cortical areas as conscious individuals, indicating preserved conscious awareness despite appearing unresponsive. This finding suggests that some patients diagnosed as vegetative may retain covert consciousness that standard behavioral assessments cannot detect.
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.
Trends in Cognitive Sciences
April 22, 2016
Tim Bayne, Jakob Hohwy, Adrian M. Owen
443 citations
The concept of a level of consciousness is central to the science of consciousness, used to describe global states in post-comatose disorders, epileptic absence seizures, anesthesia, and sleep. However, what a level of consciousness actually means remains unclear. This paper argues that the levels-based framework for understanding global states of consciousness is untenable and instead proposes a multidimensional account of global states.
PLoS Computational Biology
October 16, 2014
Srivas Chennu, Paola Finoia, Evelyn Kamau et al.
249 citations
Consciousness is thought to require balanced integration and differentiation of brain activity, supported by efficient networks. Analyzing high-density EEG from 32 patients with chronic disorders of consciousness and healthy controls, the authors found that patient networks showed reduced local and global efficiency and fewer hubs in the alpha frequency band. A new metric, modular span, revealed that alpha network modules in patients were spatially limited, lacking the long-distance interactions seen in controls. However, delta and theta band networks were partially reversed and more similar to each other in patients. Alpha network efficiency correlated with behavioral awareness. Notably, some behaviorally unresponsive vegetative patients with covert awareness had well-preserved alpha networks resembling controls, suggesting network mechanisms that may support consciousness despite severe behavioral impairment.
Proceedings of the National Academy of Sciences
September 15, 2014
Lorina Naci, Rhodri Cusack, Mimma Anello et al.
239 citations
A common neural code underpins similar conscious experiences across people, allowing the decoding of experience without behavior. Brain activity synchronized across healthy participants' frontal and parietal cortices while watching an engaging movie, and the timing of this activity matched their shared qualitative experience of the movie's moment-to-moment executive demands. A neural index based on executive function reliably predicted each healthy individual's similar conscious experience. This approach provided strong evidence for the conscious experience of a brain-injured patient who had been entirely behaviorally nonresponsive for 16 years, showing highly similar executive engagement and moment-to-moment perception of the movie content.
Scientific Reports
January 23, 2020
Thomas F. Varley, Andrea I. Luppi, Ioannis Pappas et al.
86 citations
Measures of algorithmic and process complexity, applied to functional MRI BOLD signals from individuals under propofol sedation, vary in their ability to distinguish sedation levels. Temporal complexity measures are more sensitive than topological ones. All measures strongly relate to a single underlying construct—termed 'overall complexity'—which explains most variance in the data, as assessed by principal component analysis. This overall complexity discriminates between sedation levels and propofol serum concentrations, supporting the idea that consciousness is linked to complexity, regardless of how complexity is measured.
Science
March 2, 2007
Adrian M. Owen, Martin R. Coleman, Melanie Boly et al.
72 citations
Functional neuroimaging data indicate that brain activity patterns in a patient diagnosed as vegetative could not have occurred automatically without conscious awareness. The most straightforward explanation is that the patient was consciously aware despite the vegetative state diagnosis.
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.
bioRxiv
November 26, 2020
Andrea I. Luppi, Pedro A. M. Mediano, Fernando E. Rosas et al.
49 citations
preprint
The brain coordinates information from many sources to create a unified conscious experience. Combining network science and information theory, the authors identify a “synergistic global workspace” where gateway regions gather synergistic information from specialized brain modules, integrate it, and then broadcast it widely via broadcaster regions. Functional MRI shows that gateway regions correspond to the default mode network and broadcasters to the executive control network. Loss of consciousness from general anesthesia or disorders of consciousness reduces the workspace’s ability to integrate information, which is restored upon recovery. This work reconciles aspects of the Global Neuronal Workspace and Integrated Information Theory.
Frontiers in Psychology
August 6, 2018
Stuart Fogel, L. Bryan Ray, Valya Sergeeva et al.
37 citations
The extent to which newly learned material is incorporated into dreams is related to individual differences in cognitive abilities. Using a computational linguistic approach to measure semantic similarity between waking experiences and dream reports, the study found that the richness of incorporation of a spatial or motor memory task into early hypnagogic dreams correlated with reasoning abilities (r=0.41), while incorporation into later dreams correlated with verbal abilities (r=0.46). Memory performance improvements were related to dream incorporation (r=0.47) for early but not late dreams, but this relationship was not mediated by cognitive abilities, suggesting a direct link between reasoning and dream incorporation.
Communications Biology
September 30, 2024
Pablo Castro, Andrea I. Luppi, Enzo Tagliazucchi et al.
21 citations
Brain activity during unconsciousness, whether from general anaesthesia or slow wave sleep, is dominated by a recurrent functional connectivity pattern primarily mediated by structural connectivity and with a reduced capacity to transition to other patterns. Conscious awareness is characterized by richer brain dynamics measured by entropy and a greater repertoire of connectivity states. These findings suggest that the dynamic exploration of functional connectivity states provides robust and generalizable markers for the state of consciousness across different conditions.
Neuroscience of Consciousness
January 1, 2023
Sidath Rankaduwa, Adrian M. Owen
21 citations
The entropic brain theory (EBT) explains how psychedelics alter brain activity by increasing brain entropy, offering insights into both normal and altered states of consciousness. This theory has implications for debates about whether consciousness exists in levels or dimensions, whether the psychedelic state represents a higher level of consciousness, and whether psychedelics could treat disorders of consciousness such as minimally conscious or vegetative states. The article summarizes EBT's core principles and their relevance to a theoretical model of consciousness, emphasizing that the therapeutic value of psychedelics for such patients depends on set and setting.
Scientific Reports
June 7, 2021
Evan Houldin, Zhuo Fang, Laura B Ray et al.
17 citations
During sleep, functional connections between brain networks shift in a directional manner. In non-REM (NREM) sleep, positive wake-like correlations often become negative and strengthen in the opposite direction, while in REM sleep they trend back toward positive correlations. This pattern supports the idea that NREM sleep involves altered, not merely reduced, functional connectivity. Many of these connections involve higher-order networks linked to cognition and consciousness, such as the default mode network, suggesting possible accompanying changes in cognitive and conscious states.
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.
Elife
July 18, 2024
Andrea I. Luppi, Pedro A. M. Mediano, Fernando E. Rosas et al.
1 citation
Loss of consciousness significantly disrupts the brain's ability to integrate information. In a study involving functional MRI analysis, it was revealed that gateway regions in a 'synergistic global workspace' correspond to the default mode network, while broadcaster regions align with the executive control network. This integration breakdown occurs during general anaesthesia or disorders of consciousness, with recovery restoring functionality. The findings enhance understanding of consciousness by bridging Global Neuronal Workspace and Integrated Information Theory, highlighting the critical role of brain networks in maintaining conscious experience.
Annals of Clinical and Translational Neurology
May 25, 2025
Charlotte Maschke, Loretta Norton, Catherine Duclos et al.
In patients with severe brain injury, the neurological wake-up test—a brief interruption of sedation to check responsiveness—often yields ambiguous or absent behavioral responses, limiting its prognostic value. Recording 128-channel EEG from 41 such patients during propofol sedation interruption revealed that brain responses, measured by EEG power, spatial ratios, and the spectral exponent, can show signs of waking even when behavior does not. Combining EEG with behavioral assessment improved predictions of survival, recovery of consciousness, and long-term functional outcomes, outperforming the predictions of attending physicians. EEG can complement the wake-up test to better inform clinicians, families, and treatment planning.
bioRxiv
December 17, 2024
Dian Lyu, Ram Adapa, Robin Carhart-Harris et al.
preprint
The default mode network (DMN) and frontoparietal control network (FPCN), typically anticorrelated at rest in healthy brains, show continuous rather than absolute anatomical boundaries in the posterior precuneus. Connectivity differences along the dorsal-ventral axis follow linear slopes, forming functional gradients that exist only within each network's territory. These gradients flatten in altered states of consciousness (ASC), with the gradient magnitude similarly impaired across different ASC types, while spatial entropy differs between psychedelic and sedative states. The findings suggest the DMN and FPCN, though appearing distinct, may originate from a single integrated mechanism, and the loss of functional differentiation between them characterizes altered conscious states.
bioRxiv Preprint Server
October 20, 2024
Peter Coppola, Adrian M. Owen, David K. Menon et al.
preprint
A new method captures the brain dynamics unique to each person's subjective experience. Using fMRI while people listened to a story awake and under different levels of anaesthesia, the approach tracks moment-to-moment changes in functional connectivity without assuming common brain states across individuals. The default mode network's dynamics were more dissimilar between conscious participants, reflecting personal engagement with the story. In contrast, the auditory and posterior dorsal attention networks showed higher similarity across conscious individuals, supporting more generalizable experiences. Conscious brain dynamics were more complex for individual-specific patterns but less complex for shared patterns.
bioRxiv Preprint Server
April 12, 2021
Peter Coppola, Lennart R.b. Spindler, Andrea I. Luppi et al.
preprint
The diversity of brain dynamics within small-world network topology, measured as sample entropy (dSW-E), consistently predicts levels of awareness across sedation and disorders of consciousness, even after accounting for underlying functional connectivity dynamics. Both subcortical and cortical areas show predictive value, but subcortical regions exhibit higher and more robust effect sizes. The dynamic reorganization of the functional information architecture, especially in the subcortex, emerges with awareness and offers explanatory power beyond the complexity of dynamic functional connectivity alone.
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.
Brain Communications
January 1, 2026
Dorottya Szocs, Dian Lyu, Andrea I. Luppi et al.
The pulvinar nucleus of the thalamus shows the strongest functional connectivity change with loss of consciousness under anesthesia in healthy volunteers, while the ventral-latero-ventral nucleus shows the strongest change in patients with disorders of consciousness. These nuclei exhibit distinct connectivity patterns with higher-order brain networks such as the default mode and executive control networks. In patients, the neural connectivity biomarker mirrored behavioral changes, suggesting potential clinical relevance for targeted deep brain stimulation therapy.
Trends in Cognitive Sciences
March 1, 2024
Tim Bayne, Anil K. Seth, Marcello Massimini et al.
New tests for consciousness (C-tests) are urgently needed to resolve uncertainty about when consciousness arises in human development, when it is lost due to neurological disorders and brain injury, and how it is distributed in nonhuman species. This need is amplified by recent developments in AI, neural organoids, and xenobot technology. Existing C-tests are of limited use, and no tests exist for many critical populations. The paper identifies challenges facing any attempt to develop C-tests, proposes a multidimensional classification of such tests, and identifies strategies for validating them.
Communications Biology
July 5, 2023
Idan E Nemirovsky, Nicholas J M Popiel, Jorge Rudas et al.
Integrated Information Theory aims to explain and measure consciousness by quantifying how integrated a system's causal properties are. This work implemented version 3.0 of the theory on functional MRI data from 17 healthy volunteers sedated with propofol. Using the PyPhi software, the measure Φmax was computed and compared with other proposed consciousness metrics: an earlier integrated information version, Granger causality, and correlation-based functional connectivity. Φmax showed varied responses to sedation across different brain networks. Changes in Φmax closely tracked changes in conscious level within the frontoparietal and dorsal attention networks, which support higher-order cognition. The findings offer guidance for future use of these measures in neuroimaging.
Communications Biology
November 3, 2022
Peter Coppola, Judith Allanson, Lorina Naci et al.
Consciousness is associated with short-term brain connectivity transitions that are less predictable, quicker, but on average more constant than those in unconscious states. By combining modern consciousness theories with phenomenology and dynamical systems theory, the authors created an individual-specific landscape of brain connectivity dynamics as a proxy for the stream of consciousness. They found that temporally-specific connectivity states are less easily describable by network patterns distant in time, suggesting a richer space of possible states. The cortex, cerebellum, and subcortex all display consciousness-relevant dynamics.
Alzheimer's & dementia (New York, N. Y.)
January 1, 2021
Jonathan Huntley, Stephen M Fleming, Daniel C Mograbi et al.
People with Alzheimer's disease show a range of changes in consciousness, including reduced awareness of cognitive deficits, diminished self-awareness, and impaired introspection, which appear early and worsen as the disease progresses. These awareness impairments are linked to brain damage in areas that overlap with proposed neural correlates of consciousness. The authors argue that recognizing Alzheimer's disease as a disorder of consciousness is overdue and important for understanding patients' lived experience and improving care.