Human Brain Mapping
January 1, 1995
Karl Friston, Giulio Tononi, Olaf Sporns et al.
114 citations
Neuronal interactions in the brain balance two opposing organizational principles: functional segregation, where specialized cortical areas exhibit relatively high entropy (unpredictable dynamics), and functional integration, where distributed influence across areas produces lower entropy overall. A measure of complexity is highest when small brain regions have high entropy on average relative to the whole system's entropy, equivalent to the average mutual information between small regions and the rest of the system. Applied to nonlinear simulations and fMRI data during photic stimulation, complexity peaked between high-dimensional chaotic behavior and low-dimensional orderly behavior—between asynchronous oscillations and global synchrony—confirming the hypothesis.
PLoS ONE
February 10, 2023
Lucia Melloni, Liad Mudrik, Michael Pitts et al.
106 citations
An adversarial collaboration between proponents of Global Neuronal Workspace and Integrated Information Theory devised and preregistered two experiments that test contrasting predictions about the location and timing of correlates of visual consciousness. Six theory-impartial laboratories will follow the study protocol using fMRI, M-EEG, and intracranial EEG, with built-in replications between labs and within datasets. The project aims to provide decisive evidence for or against the two theories and clarify the neural footprints of conscious visual perception, while modeling large-scale, collaborative, and open science practice.
Cerebral Cortex
July 10, 2013
Gustavo Deco, P. Hagmann, Anthony G. Hudetz et al.
99 citations
The transition from wakefulness to sleep involves gradual neural changes rather than an abrupt shift. Local slow waves appear during wakefulness and increase as arousal-promoting neuromodulation decreases, while resting-state brain networks maintain their overall organization. Only when neuromodulation drops to very low levels do slow waves become global and resting-state networks merge into a single synchronized network.
Scientific Reports
March 26, 2019
Minji Lee, Benjamin Baird, Olivia Gosseries et al.
98 citations
During non-rapid eye movement sleep, conscious experiences are linked to reduced phase-locking at low frequencies (<4 Hz) and lower transitivity and clustering coefficient in delta and theta bands compared to unconsciousness, especially over parietal-occipital regions. No significant differences in Granger-causality patterns between frontal and parietal areas were found. These findings suggest that decreased local connectivity at low frequencies in posterior brain regions may indicate consciousness during sleep.
Neuroscience of Consciousness
January 1, 2017
Andrew Haun, Giulio Tononi, Christof Koch et al.
97 citations
Some researchers claim that perceptual experience is impoverished—that people perceive and remember very little visual information. However, the evidence indicates that this view is mistaken and that visual phenomenology is actually immensely rich. To accurately assess perceptual content, experiments should go beyond simple binary forced-choice tasks and instead analyze broader reports of experience. Adopting such methods will reveal the genuine richness of experience and its underlying neural basis.
Nature
June 1, 2025
Oscar Ferrante, Urszula Gorska-Klimowska, Simon Henin et al.
94 citations
Different theories explain how subjective experience arises from brain activity. An open science adversarial collaboration directly juxtaposed integrated information theory (IIT) and global neuronal workspace theory (GNWT). Human participants (n = 256) viewed suprathreshold stimuli for variable durations while neural activity was measured with fMRI, MEG, and intracranial EEG. Information about conscious content was found in visual, ventrotemporal, 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. These results align with some predictions of IIT and GNWT but substantially challenge key tenets of both theories, including a lack of sustained posterior cortex synchronization for IIT and a lack of ignition at stimulus offset and limited prefrontal representation for GNWT.
Scientific Reports
October 13, 2020
Lucie Bréchet, Denis Brunet, Lampros Perogamvros et al.
92 citations
During non-rapid eye movement (NREM) sleep, brief brain states lasting less than a second, called EEG microstates, determine whether a person will recall a dream upon waking. Two microstates (3 and 4) dominated NREM sleep compared to wakefulness. Within NREM sleep, microstate 3 was more present before dream recall, while microstate 4 was less present. Microstate 3 involved the medial frontal lobe, suggesting deeper local deactivation and executive disconnection that keeps the brain asleep. Microstate 4 involved the occipital cortex, thalamus, and brainstem, and its reduced presence may indicate local activation enabling rich perceptual dream content. The temporal dynamics of these alternating brain states determine whether conscious experience arises during NREM sleep.
Journal of Cognitive Neuroscience
May 31, 2017
Lampros Perogamvros, Benjamin Baird, Mitja Seibold et al.
76 citations
Spontaneous thoughts occur during wakefulness, NREM sleep, and REM sleep, and all share activation in the midcingulate cortex. Waking thoughts additionally involve a medial prefrontal region linked to metacognition and have more metacognitive content than sleep thoughts. REM sleep thoughts are more social in content. The findings suggest a core neural substrate for thoughts across behavioral states, with medial prefrontal regions contributing to metacognitive qualities during wake.
Entropy
March 18, 2021
Leonardo S. Barbosa, William Marshall, Larissa Albantakis et al.
74 citations
Integrated Information Theory (IIT) begins with essential properties of consciousness and translates them into postulates that any physical system must satisfy to specify the physical substrate of consciousness. A recently introduced information measure captures three of these postulates—existence, intrinsicality, and information—and is unique. This work shows that the measure also satisfies the remaining postulates of integration and exclusion, creating a framework that identifies maximally irreducible mechanisms. These mechanisms can form maximally irreducible systems, which then specify the physical substrate of conscious experience.
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.
PLoS ONE
May 13, 2015
Melanie Boly, Shuntaro Sasai, Olivia Gosseries et al.
69 citations
A meaningful sequence of stimuli, like movie frames, triggers varied experiences, while meaningless stimuli, like TV noise, produce a uniform experience despite physical differences. The differentiation of cortical responses, measured by Lempel-Ziv complexity of functional MRI images, reflects the overall meaningfulness of a stimulus set rather than differences among stimuli. Brain activity patterns showed highest differentiation during a movie, intermediate for a temporally scrambled movie, and minimal for spatially scrambled TV noise, even though overall cortical activation was strong and widespread in all conditions. Meaningfulness also correlated with higher information integration among cortical regions. This approach can assess stimulus meaningfulness without identifying relevant features or neural locations.
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.
Scientific Reports
August 5, 2016
Jaakko O. Nieminen, Olivia Gosseries, Marcello Massimini et al.
60 citations
During non-rapid eye movement (NREM) sleep, the brain's response to transcranial magnetic stimulation (TMS) differs depending on whether the person is conscious (dreaming) or not. When subjects reported no conscious experience upon awakening, TMS evoked a larger negative deflection and a shorter phase-locked response compared to when they reported a dream. The amplitude of the negative deflection—a hallmark of neuronal bistability—was inversely correlated with the length of the dream report. These findings suggest that variations in the level of consciousness within the same physiological state are associated with changes in underlying cortical bistability.
March 17, 2017
Giulio Tononi
57 citations
Integrated information theory (IIT) begins with the essential properties of experience (axioms) and translates them into requirements that any physical system must satisfy to be conscious (postulates). The postulates can be seen as a list of requirements for something to exist 'for itself', as an intrinsic entity, and thus have relevance for ontology and metaphysics. Some implications of the theory include the divide between intrinsic and extrinsic entities, the incoherence of ontological reductionism, and the intrinsic nature of meaning.
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.
Progress in brain research
January 1, 2009
Melanie Boly, Marcello Massimini, Giulio Tononi
50 citations
Assessing consciousness in noncommunicative brain-damaged patients is challenging because behavioral responses are limited by motor impairment and cognitive dysfunctions. Recent studies have compared brain activity in comatose, vegetative state, sleep, anesthesia, and epileptic seizure conditions, but no consensus on the brain mechanisms generating consciousness has emerged. The authors argue that combining theoretical approaches with experimental procedures is necessary for a coherent explanation of consciousness loss across these conditions. They review current theories, emphasizing the Integrated Information Theory of Consciousness (IITC), which predicts reduced consciousness in certain states. While technical and conceptual issues limit its clinical applicability, some predictions are testable with available imaging techniques.
Scientific Reports
November 5, 2018
Matthieu Darracq, Chadd M. Funk, Daniel Polyakov et al.
49 citations
Sleep and anesthesia alter conscious experience, which can be absent (unconsciousness) or take the form of dreaming where sensory stimuli are not incorporated (disconnected consciousness). Using transcranial magnetic stimulation-electroencephalography over parietal regions, evoked alpha power (8-12 Hz) decreased during disconnected consciousness in rapid eye movement sleep and ketamine anesthesia compared to wakefulness. In unconscious states of propofol anesthesia and non-rapid eye movement sleep, evoked low-gamma power (30-40 Hz) decreased compared to wakefulness or disconnected consciousness. These findings, confirmed with dream reports from serial awakenings, suggest suppression of evoked alpha activity may mark sensory disconnection.
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.
PLoS ONE
February 22, 2016
Daniela Dentico, Fabio Ferrarelli, Brady A. Riedner et al.
43 citations
After two intensive days of mindfulness or compassion meditation, long-term meditators showed increased low-frequency brain activity (1-12 Hz, peaking around 7-8 Hz) over prefrontal and left parietal areas during non-rapid eye movement sleep. This increase was strongest early in the night and extended to higher frequencies (25-40 Hz) during the third sleep cycle. The changes depended on meditation experience and did not differ between the two meditation styles. No such changes occurred in meditation-naive individuals. The findings suggest that intensive meditation practice acutely alters brain activity in regions linked to top-down regulation, complementing chronic changes seen in posterior areas.
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.
Entropy
February 11, 2023
William Marshall, Matteo Grasso, William G. P. Mayner et al.
19 citations
Integrated information theory (IIT) proposes that consciousness is identical to the cause-effect structure generated by a maximally irreducible substrate (a Φ-structure). This work introduces a definition for system-integrated information (φs) grounded in IIT's postulates of existence, intrinsicality, information, and integration. It examines how determinism, degeneracy, and connectivity fault lines affect system-integrated information. The proposed measure identifies complexes as systems whose φs exceeds that of any overlapping candidate systems.
European Journal of Neuroscience
August 24, 2018
Daniela Dentico, David R. W. Bachhuber, Brady A. Riedner et al.
18 citations
Long-term meditators showed increased low- and fast-frequency brain oscillations during wakefulness after two 8-hour sessions of mindfulness or compassion-and-loving-kindness meditation, peaking at 8 and 15 Hz over prefrontal and left centro-parietal electrodes. These waking changes correlated with previously observed meditation-related increases in low-frequency NREM sleep EEG activity (4-12 Hz), particularly in the theta-alpha range. The findings suggest that sleep homeostatic response alone cannot explain the post-meditation sleep changes; instead, a reverberation of meditation-related processes during subsequent sleep may be involved. No differences emerged between meditation styles or in meditation-naïve participants.
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.