BMC Neuroscience
November 2, 2004
Giulio Tononi
1,703 citations
Consciousness corresponds to a system's capacity to integrate information, measurable as Phi—the amount of causally effective information integrated across a complex of elements. This theory explains why consciousness arises from the thalamocortical system but not the cerebellum, why it diminishes during dreamless sleep and generalized seizures, and why neural processes underlying consciousness can influence or be influenced by unconscious ones. It also accounts for the unity and differentiation of conscious experiences. The theory implies that consciousness is a graded, fundamental quantity present in infants and animals, and that conscious artifacts could be built.
Nature reviews. Neuroscience
April 20, 2016
Christof Koch, Marcello Massimini, Mélanie Boly et al.
1,654 citations
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Annals of the New York Academy of Sciences
March 1, 2008
Giulio Tononi, Christof Koch
615 citations
This review synthesizes recent findings on the neural correlates of consciousness, distinguishing consciousness from other brain functions. It examines global changes in consciousness during sleep, anesthesia, and seizures, then explores paradigms for studying neural correlates of specific conscious percepts, highlighting the roles of different brain regions. Dynamic aspects of neural activity—sustained versus phasic, feedforward versus reentrant, and neural synchronization—are discussed. The review also considers how theoretical analysis of consciousness's fundamental properties can complement neurobiological research.
Nature Communications
February 25, 2022
Minji Lee, Leandro Sanz, Alice Barra et al.
120 citations
A deep-learning-based explainable consciousness indicator (ECI) uses EEG responses to transcranial magnetic stimulation and resting-state EEG to separately quantify arousal and awareness. Tested during sleep (n=6), general anesthesia (n=16), and severe brain injury (n=34), ECI distinguishes states such as ketamine-induced anesthesia and rapid eye movement sleep, which combine low arousal with high awareness. Parietal brain regions are most relevant for these measurements. The indicator offers a way to disentangle the two components of consciousness across physiological, pharmacological, and pathological conditions.
Scientific Reports
December 6, 2018
Benjamin Baird, Anna Castelnovo, Olivia Gosseries et al.
74 citations
People who have frequent lucid dreams—three or more per week—show stronger functional connections between the left anterior prefrontal cortex and several brain regions, including the angular gyrus, middle temporal gyrus, and inferior frontal gyrus, compared to people who rarely or never lucid dream. These connections involve areas that are normally less active during sleep. No differences in brain structure were found. The findings suggest that frequent lucid dreaming is linked to how certain brain networks communicate, not to structural differences.
Neuroscience of consciousness
January 1, 2021
Francesco Ellia, Jeremiah Hendren, Matteo Grasso et al.
61 citations
Subjective experience can be objectively explained in physical terms by moving beyond cognitive functions and understanding how experience is structured. Integrated information theory provides a framework to account for both the essential properties of every experience and the specific properties that make particular experiences feel the way they do, avoiding the fallacy that only objective properties should be explained by science.
bioRxiv Preprint Server
March 19, 2017
Melanie Boly, Marcello Massimini, Naotsugu Tsychiya et al.
56 citations
preprint
The role of the frontal cortex in consciousness is debated. This perspective critically reviews clinical and neuroimaging evidence on whether the front or back of the cortex specifies conscious contents, and discusses promising research avenues. The authors argue that current evidence does not clearly support a primary role for the frontal cortex in generating conscious experience, pointing instead to posterior regions as more directly involved. They suggest that future research should focus on distinguishing neural correlates of consciousness from prerequisites and consequences.
iScience
May 19, 2023
Andres Ort, John W Smallridge, Simone Sarasso et al.
47 citations
Classical psychedelic drugs like psilocybin induce profound changes in consciousness, including heightened sensory-emotional awareness and arousal, accompanied by increased spontaneous EEG signal diversity. By combining Transcranial Magnetic Stimulation (TMS) with EEG, this work shows that psilocybin creates a state of increased chaotic brain activity, which is not due to altered complexity in causal interactions between brain regions. The study also maps regional effects of psilocybin on TMS-evoked activity, identifying changes in frontal brain structures that may relate to the phenomenology of psychedelic experiences.
Sleep
April 11, 2022
Benjamin Baird, Giulio Tononi, Stephen LaBerge
41 citations
Lucid dreaming is not a hybrid state mixing sleep and wakefulness, as previously claimed based on increased 40 Hz brain activity. The apparent rise in frontolateral 40 Hz power during lucid REM sleep is actually an artifact caused by saccadic spike potentials from heightened eye movement density. In a reanalysis of 14 signal-verified lucid dreams from six participants, lucid REM sleep showed higher REM density than baseline REM sleep, but no difference in 40 Hz power after removing the spike potential artifact. Lucid REM also showed small reductions in low-frequency and beta band power and increased signal complexity, all within normal REM sleep variation. Lucid dreams involve higher physiological activation, including subcortical and cortical measures.
Psychology of consciousness (Washington, D.C.)
March 1, 2019
Benjamin Baird, Brady A Riedner, Melanie Boly et al.
41 citations
Lucid dreaming occurs more often in long-term meditators than in people who do not meditate. Among non-meditators, lucid dream frequency is linked to the ability to put experience into words, while among meditators it is linked to observing and decentering aspects of mindfulness. However, an 8-week mindfulness course did not increase lucid dream frequency. The findings suggest a continuity between awareness during waking and sleeping states and connect meditation training with meta-awareness, but the precise nature of the link remains unclear.
Neuroscience of consciousness
January 1, 2021
Matteo Grasso, Andrew M Haun, Giulio Tononi
20 citations
A grid-like neural network representing posterior cortical areas can perform the same fixation function as a map-like pretectal circuit, but only the grid-like network's cause-effect structure, as analyzed by Integrated Information Theory, accounts for the subjective experience of space as extended. Standard functional analysis explains what the model does—encoding, decoding, and triggering eye movements—but cannot explain why a human fixating a stimulus would also see it at a location. The map-like network, lacking lateral connections, is functionally equivalent yet cannot account for the phenomenal properties of space.
Consciousness and cognition
January 1, 2022
Benjamin Baird, Mariel Kalkach Aparicio, Tariq Alauddin et al.
17 citations
Spontaneous episodic thoughts about the past and future are common during waking but rarely occur during N2 or REM sleep. Analysis of thought reports from 138 participants who underwent experience-sampling while awake and serial awakenings during sleep shows that waking spontaneous thought frequently includes autobiographical planning with a strong bias toward the future. In contrast, dreaming sleep states rarely feature such mental time travel. This suggests that human consciousness differs substantially across the sleep-wake cycle in how it typically engages with episodic past and future events.
Trends in cognitive sciences
June 1, 2021
Benjamin Baird, Stephen LaBerge, Giulio Tononi
13 citations
Lucid dreamers can use eye movements to report on their dream content in real time during REM sleep, challenging the long-held belief that dreamers are completely isolated from the outside world. Sensory input is not entirely suppressed during sleep. A recent study by Konkoly et al. demonstrates that experimenters can question lucid dreamers during ongoing dreams and explores the feasibility of more extended two-way communication during lucid REM sleep dreaming.
Trends in cognitive sciences
July 3, 2025
Andrew M. Haun, Giulio Tononi
5 citations
Visual experience is unfathomably rich, not sparse. Seeing involves three levels: high-level object and scene categorizations, mid-level feature groupings, and a fundamental spatial field of spots and their relations. Seeing objects requires seeing the groupings that compose them, and seeing groupings requires seeing the spatial field that grounds them. Even the basic feeling of spatial extendedness implies rich phenomenal structure. Much of what we see cannot be used, reported, or remembered, yet we see it.
bioRxiv Preprint Server
April 18, 2024
Melanie Boly, Richard Smith, Giulietta Vigueras Borrego et al.
5 citations
preprint
A state called pure presence, reported in meditative traditions as a vivid experience without thoughts, perceptions, or self, was examined in twenty-two long-term meditators using high-density EEG. During pure presence, brain activity showed widespread reductions in gamma and delta power compared to mind-wandering, watching a movie, active thinking, and dreamless sleep. The strongest gamma decreases occurred in the posteromedial cortex. These findings align with integrated information theory's prediction that vivid consciousness can arise when the brain's cortical substrate is largely quiet yet highly awake.
Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference
July 1, 2019
Minji Lee, Benjamin Baird, Olivia Gosseries et al.
4 citations
Cortical networks show differences in functional integration and segregation across states of consciousness, but not in overall connectivity. In the beta frequency band, functional integration during wakefulness exceeded that during NREM sleep. In the theta band, functional segregation (transitivity and clustering coefficient) was stronger in NREM sleep without conscious experience than in wakefulness or REM sleep, while the opposite pattern appeared in the beta band. No significant differences in the weighted phase lag index were found among wakefulness, REM sleep with conscious experience, NREM sleep with conscious experience, and NREM sleep without conscious experience. These findings may relate to cortical bistability and contribute to understanding neural correlates of consciousness.
PLoS ONE
December 4, 2025
Jonathan Robinson, Andrew W. Corcoran, Christopher J. Whyte et al.
1 citation
Active inference, a framework for modeling how sentient agents behave, is being tested as necessary for changes in conscious content. In an adversarial collaboration, active inference will be contrasted with two other theories that do not require it for consciousness. This study protocol describes an adaptation of the motion-induced blindness paradigm: an active condition where participants direct their gaze toward a target after it disappears from consciousness and report its reappearance, versus a passive condition where participants fixate centrally while the stimulus array moves in a replay of active eye-tracking data. Two experiments will compare target reappearance across conditions to evaluate active inference's contribution to conscious awareness.
Neuroscience and biobehavioral reviews
August 1, 2026
Andrew W Corcoran, Andrew M Haun, Reinder Dorman et al.
Three theories of consciousness—Integrated Information Theory, Neurorepresentationalism, and Active Inference—are compared and contrasted in a structured adversarial collaboration. The review presents each theory's core claims, the phenomena they explain, their explanatory approaches, and methodological strategies. It outlines key hypotheses to be tested across multi-site experiments, discusses observations that would support or challenge each theory, and describes how data from disparate experiments can be formally integrated to quantify evidential support. The work also provides meta-scientific insights into the mechanics of adversarial collaboration and theory-testing, including how theories may be evaluated by the scientific progress they deliver.
bioRxiv Preprint Server
June 23, 2023
Oscar Ferrante, Urszula Gorska-Klimowska, Simon Henin et al.
preprint
An open science adversarial collaboration directly juxtaposed Integrated Information Theory (IIT) and Global Neuronal Workspace Theory (GNWT) by investigating neural correlates of visual experience. 256 human subjects viewed suprathreshold stimuli for variable durations while neural activity was measured with fMRI, MEG, and ECoG. Information about conscious content was found in visual, ventro-temporal, and inferior frontal cortex, with sustained responses in occipital and lateral temporal cortex reflecting stimulus duration, and content-specific synchronization between frontal and early visual areas.
arXiv Preprint Archive
May 27, 2014
Giulio Tononi, Christof Koch
Integrated Information Theory (IIT) starts from five axioms about conscious experience—existence, composition, information, integration, and exclusion—to derive physical postulates that specify which systems can be conscious and what their experience is like. IIT provides a calculus to measure both the quantity and quality of experience, explains clinical and laboratory findings, and makes testable predictions. It holds that consciousness is graded, common among biological organisms, and present even in some simple systems, but not in everything: groups of individuals or feedforward networks lack it. Crucially, IIT implies that digital computers, even those that perfectly simulate human behavior or brain function, would experience next to nothing, contradicting functionalist views.