NeuroImage
June 30, 2020
Thomas F. Varley, Robin Carhart‐Harris, Leor Roseman et al.
91 citations
Psychedelic drugs like psilocybin and LSD increase the fractal dimension of brain activity, suggesting that the brain moves toward a critical state between order and disorder. Using fMRI data from volunteers, the study tested two fractal measures: one for functional connectivity networks and one for BOLD time-series. Both drugs significantly increased the fractal dimension of functional connectivity networks. LSD also significantly increased the fractal dimension of BOLD signals, while psilocybin showed a non-significant trend in the same direction. Changes in the fractal dimension of BOLD signals were localized to brain areas in the dorsal attention network. These results indicate that psychedelic-induced changes in consciousness are associated with evolution toward a critical zone.
NeuroImage
September 1, 2017
Remko Van Lutterveld, Edwin Van Dellen, Prasanta Pal et al.
85 citations
During meditation, experienced meditators show more integrated brain networks in the alpha frequency band (8-13 Hz) than novice meditators. EEG measures of network integration—maximum betweenness centrality and leaf fraction—were higher in experienced meditators, while diameter and average eccentricity were lower, indicating more efficient network topology. No differences were found in theta or beta bands. The findings suggest that long-term meditation practice is associated with greater functional integration of alpha-band brain networks.
NeuroImage
April 11, 2020
Ignacio Pérez Ipiña, Patricio Donnelly Kehoe, Morten L. Kringelbach et al.
81 citations
A semi-empirical model combining fMRI data, structural connectivity, and anatomically-informed priors shows that brain states during the wake-sleep cycle are better described by multiple dimensions rather than a single continuum. The best fit used priors based on functionally coherent networks, dividing the cortex into regions with opposite dynamics: frontoparietal regions approached a noise-driven bifurcation from fixed-point dynamics, while sensorimotor regions approached a bifurcation from oscillatory dynamics. Sleep onset involved subcortical deactivation with low correlation, reversed in deeper stages. Periodic forcing simulating external perturbations identified key regions for wakefulness recovery. The model characterizes sleep as having diminished perceptual gating but latent capacity for rapid arousal.
NeuroImage
April 4, 2019
Ottavia Dipasquale, Pierluigi Selvaggi, Mattia Veronese et al.
79 citations
A double-blind, placebo-controlled study combined resting-state fMRI with a molecular atlas of serotonin receptors to examine how MDMA alters functional connectivity. Using the REACT method, the researchers found that MDMA-induced connectivity changes were specifically linked to brain regions rich in the serotonin transporter (5-HTT) and the 5-HT1A receptor, the drug's primary targets. Changes in 5-HT1A-enriched maps correlated with MDMA blood levels, while changes in 5-HT2A-enriched maps correlated with spiritual experiences reported by participants. The approach shows that MDMA's effects on brain connectivity can be explained by the distribution of its serotonergic targets, offering a new way to characterize psychoactive compounds.
NeuroImage
May 1, 2020
Matthew I Banks, Bryan M Krause, Christopher M Endemann et al.
78 citations
Disruption of cortical connectivity likely contributes to loss of consciousness during sleep and general anesthesia, but the degree of overlap in mechanisms is unclear. Using intracranial recordings from five adult neurosurgical patients, alpha-band connectivity (measured by weighted phase lag index) was compared across natural sleep stages and propofol anesthesia. In wake states, alpha-band connectivity within the temporal lobe was dominant, a pattern largely unchanged in light sleep (N1, REM) and sedated states. Transitions into states of reduced consciousness (deep sleep N2/N3 and anesthesia-induced unresponsiveness) showed dramatic shifts, with dominant connections moving to prefrontal cortex. The findings suggest common mechanisms of loss of consciousness in sleep and anesthesia.
NeuroImage
November 1, 2020
Gerald J. Hahn, Gorka Zamora‐lópez, Lynn Uhrig et al.
55 citations
Brain-wide signal levels can reliably distinguish sleep and anesthesia from the awake state in human and monkey fMRI resting state data. A whole-brain computational model reproduces changes in global synchronization, functional connectivity, structure-function relationship, integration, and segregation across vigilance states. The awake brain operates near a Hopf bifurcation, which coincides with globally correlated fMRI signals. Simulated lesions of connectivity hubs in the posterior brain and subcortical nuclei disrupt the model's awake state, matching predictions from graph-theoretical analyses of structural data.
NeuroImage
May 1, 2021
Pengmin Qin, Xuehai Wu, Changwei Wu et al.
51 citations
Consciousness depends on a network of brain regions that integrate sensory and motor information. Analyzing fMRI data from people in preserved (awake, fully conscious brain-injury survivors), reduced (N1-sleep, minimally conscious), and lost (N3-sleep, anesthesia, unresponsive wakefulness) states, plus a unique rapid-eye-movement (REM) sleep group, researchers identified key hubs whose degree centrality—a measure of network importance—dropped significantly when consciousness was reduced or absent. These hubs included the supplementary motor area, bilateral supramarginal gyrus, supragenual/dorsal anterior cingulate cortex, and left middle temporal gyrus. A higher-order sensorimotor circuit connecting these regions showed functional connectivity that correlated with consciousness levels across groups and remained active in REM sleep, suggesting this circuit supports consciousness and offers new targets for treating disorders of consciousness.
NeuroImage
June 1, 2023
Rui Dai, Tony E Larkin, Zirui Huang et al.
49 citations
Three different psychedelics—nitrous oxide, ketamine, and lysergic acid diethylamide—produce a common pattern of brain network changes despite having distinct molecular mechanisms and delivery methods. Each drug reduced connectivity within brain networks and enhanced connectivity between networks. Specifically, all three increased connections between the right temporoparietal junction and bilateral intraparietal sulcus, and between the precuneus and left intraparietal sulcus. These regions lie within the posterior cortical "hot zone," an area thought to mediate the qualitative aspects of experience. The findings identify a biologically plausible candidate for the subjective effects of both classical and non-classical psychedelics.
NeuroImage
October 27, 2022
Anders Lykkebo-Valløe, Brice Ozenne, Sophia Armand et al.
44 citations
Psilocybin's acute perceptual psychedelic effects may arise from drug-level decreases in the occurrence and duration of lateral and medial frontoparietal connectivity motifs. The authors apply and argue for a modified approach to modeling eigenvectors from LEiDA that more fully acknowledges their underlying structure. These findings contribute to a more comprehensive neurobiological framework underlying acute effects of serotonergic psychedelics.
NeuroImage
July 1, 2022
Fran Hancock, Joana Cabral, Andrea I. Luppi et al.
40 citations
Dynamic functional connectivity (dFC) in resting-state fMRI is promising for clinical biomarkers, but its reliability and interpretability are debated. This study combined phase-based dFC metrics from dynamical systems, stochastic processes, and information dynamics to assess their interrelationships and reliability. Novel relationships between metrics allowed building a predictive model for integrated information. Global metastability, reflecting simultaneous coupling and decoupling tendencies, was the most representative and stable metric in brain parcellations including cerebellar regions. Spatiotemporal patterns of phase-locking changed slowly and continuously over time. The findings suggest that most resting-state fMRI dynamics reflect an interrelated complexity profile unique to each acquisition, challenging cross-sectional designs for neuromarker discovery and indicating individual life-trajectories may be more informative.
NeuroImage
May 11, 2022
David Smith, Annemarie Wolff, Angelika Wolman et al.
40 citations
The self is experienced as continuous across time, and this temporal continuity may be reflected in the brain's intrinsic neural timescales, measured by the autocorrelation window (ACW). In an EEG study, participants first recorded an autobiographical narrative, then listened to their own narrative and a stranger's narrative while their brain activity was recorded. They also continuously rated the emotional valence of each narrative by moving a cursor. Compared to the non-self narrative, the self-narrative elicited longer neural ACWs and greater spatial extent and speed of cursor movement. These results suggest that longer temporal windows of neural activity are important for self-specificity, and that temporal continuity may serve as a common currency linking brain and self.
NeuroImage
October 15, 2022
Andrew Gaddis, Daniel E Lidstone, Mary Beth Nebel et al.
38 citations
Psilocybin alters the functional organization of distinct thalamic subregions and their connections to cortical networks, particularly the mediodorsal and pulvinar nuclei. Using a novel ICA-based approach in 18 healthy meditators, psilocybin-induced changes in intrathalamic spatial organization correlated with subjective drug effects. Thalamocortical connectivity predominantly decreased with visual and default mode networks. In contrast, treating the thalamus as a single unit showed a non-significant numerical increase in connectivity, suggesting that whole-thalamus analyses may mask focal decreases in specific nuclei that express serotonin 2A receptors.
NeuroImage
July 1, 2015
Manish Saggar, Anthony P Zanesco, Brandon G King et al.
31 citations
Intensive meditation training alters brain dynamics by increasing the delay between cortical and thalamic cells and reducing inhibitory connections within the thalamus. These changes, identified through computational modeling of EEG data from two 3-month meditation retreats, provide a neural mechanism for the previously observed slowing of individual alpha frequency. The reduced thalamic inhibition enhances dynamical stability in the model. This is the first computational approach incorporating anatomical and physiological constraints to formally model brain processes underlying intensive meditation, offering testable hypotheses for attention training and potential clinical applications.
NeuroImage
February 9, 2021
Riku Ihalainen, Olivia Gosseries, Frederik van de Steen et al.
30 citations
Using dynamic causal modelling of high-density EEG recordings from 10 people during propofol anaesthesia, the study evaluated how three resting state networks—the default mode network, the salience network, and the central executive network—contribute to consciousness. Loss of consciousness reduced inter-network connectivity in the parietal cortex, especially feed-forward frontoparietal and parietal connections at the precuneus node within the default mode network. Within the salience and central executive networks, unconsciousness generated small increases in bidirectional connectivity. The most consistent predictions of consciousness came from a key set of frontoparietal connections, supporting the importance of the posterior hot zone in explaining loss of consciousness.
NeuroImage
December 1, 2023
Stefano Delli Pizzi, Piero Chiacchiaretta, Carlo Sestieri et al.
27 citations
LSD selectively alters the functional connectivity between specific thalamic nuclei and sensory and associative cortical areas. Using structural and resting-state functional MRI in healthy volunteers under acute LSD administration, researchers found increased coupling of the ventral complex, pulvinar, and non-specific thalamic nuclei with somatosensory and auditory cortices, as well as with associative cortex regions rich in serotonin 2A receptors. At subcortical levels, LSD increased connectivity among these thalamic nuclei but decreased striatal-thalamic connectivity. These nucleus-specific changes help explain LSD's modulation of subcortical-cortical circuits and associated behavioral effects.
NeuroImage
January 7, 2022
Duan Li, Phillip E. Vlisides, George A. Mashour
24 citations
Spontaneous brain activity explores a repertoire of recurring spatial patterns, and the richness of this repertoire may reflect the capacity for consciousness. Ketamine, which has both psychedelic and anesthetic properties depending on dose, was used to examine brain dynamics across a continuum of consciousness. Analyzing EEG data from source-localized cortical activity, researchers identified frequency-specific spatial coactivation patterns. Ketamine anesthesia shifted brain states toward those with low spatial variability. Subanesthetic ketamine was associated with a richer repertoire of brain states, while anesthetic ketamine initially reduced repertoire richness, which then evolved to a level comparable to normal wakefulness before recovery of consciousness. These findings describe ketamine's modulation of cortical dynamics across spatial, temporal, and spectral dimensions.
NeuroImage
November 1, 2022
Hardik Rajpal, Pedro A M Mediano, Fernando E Rosas et al.
23 citations
Schizophrenia and drug-induced states from LSD and ketamine both increase neural signal diversity, but they differ in brain connectivity: schizophrenia shows increased information flow from front to back of the brain, while the drugs reduce it. These differences can be modeled by altering Bayesian inference in a predictive processing framework: drug effects correspond to reduced precision of prior beliefs, whereas schizophrenia involves increased precision of sensory information. The findings clarify similarities and differences between these altered states, with implications for understanding consciousness and developing mental health treatments.
NeuroImage
August 15, 2024
Bianca Ventura, Yasir Çatal, Angelika Wolman et al.
22 citations
Meditation practices with a wider attentional focus, such as Shoonya meditation, are associated with longer intrinsic neural timescales (INTs) in the brain, measured as the autocorrelation window (ACW) of EEG signals, compared to practices with a narrower focus like Mantra or Vipassana meditation. The study compared three groups of highly proficient practitioners from different traditions and a meditation-naïve control group. The results indicate a correspondence between the width of attentional scope and the duration of neural temporal windows, suggesting that subjective attentional width relates to objective neural activity patterns.
NeuroImage
June 1, 2024
Pradeep Kumar G, Rajanikant Panda, Kanishka Sharma et al.
20 citations
High-order interactions between brain regions, measured as synergistic and redundant information, change differently across three non-ordinary states of consciousness. During Rajyoga meditation, synergy increased across the whole brain in delta and theta brainwave bands, while redundancy decreased in frontal, central, and posterior electrodes in delta and beta bands. During hypnosis, synergy decreased in mid-frontal, temporal, and mid-centro-parietal electrodes in the delta band, and in left frontal and right parietal electrodes in the beta2 band. During auto-induced cognitive trance, synergy decreased in delta and theta bands in left-frontal, right-frontocentral, and posterior electrodes, and at the whole brain level in the alpha band. Redundancy changes during hypnosis and auto-induced cognitive trance were not significant. Subjective reports of absorption, dissociation, and mystical experience did not correlate with the high-order measures.
NeuroImage
November 29, 2019
David T. J. Liley, Suresh Muthukumaraswamy
18 citations
The reduction in alpha-band brain wave power when people open their eyes is explained by increased damping of oscillatory activity, not by changes in neuronal population synchrony as commonly believed. Using time series modeling of EEG data, the authors found that the NMDA antagonist ketamine modifies these damping changes through glutamatergic neurotransmission. The results challenge the prevailing view that thalamus and neuronal population synchronization drive alpha rhythm generation and modulation, suggesting instead that physiological damping dynamics play a key role.
NeuroImage
January 1, 2024
Pablo Mallaroni, Natasha L Mason, Lilian Kloft et al.
17 citations
Brain functional connectomes are unique fingerprints that persist across mental states, but their stability under altered states is unknown. After collective ayahuasca intake in 21 Santo Daime members, 7T fMRI showed reduced idiosyncrasy in static and dynamic functional connectivity, with a spatiotemporal reallocation of keypoint edges. Interindividual differences in higher-order connectivity motifs predicted perceptual drug effects, demonstrating that individualized connectivity markers can trace a subject's functional connectome across altered states of consciousness.
NeuroImage
January 1, 2025
Winson F Z Yang, Avijit Chowdhury, Terje Sparby et al.
12 citations
The stages of insight (SoI) are a series of psychological realizations experienced during advanced investigative insight meditation (AIIM). In a case study of one adept meditator who underwent 4 hours of 7T functional magnetic resonance imaging (fMRI) across 26 runs with concurrent phenomenological reports, distinct whole-brain activity patterns were identified for specific SoI, differing from non-meditative control states. SoI consistently deactivated brain regions involved in self-related processing, such as the medial prefrontal cortex and temporal poles, while activating areas linked to awareness and perception, including parietal and visual cortices, caudate, brainstem nuclei, and cerebellum. Patterns of brain activity related to affective processing and SoI phenomenology were also observed. This provides the first neurophenomenological evidence that SoI shifts and deconstructs self-related perception and conceptualization, increasing general awareness and perceptual sensitivity.
NeuroImage
September 1, 2024
Charlotte Martial, Andrea Piarulli, Olivia Gosseries et al.
10 citations
During fainting, some people have dream-like experiences with extraordinary, mystical features similar to near-death experiences. In 22 healthy volunteers who fainted under controlled conditions, eight reported such near-death-like features. Their brain activity showed higher electrical activity in delta, theta, and beta2 frequency bands in temporal and frontal regions, including the insula, right temporoparietal junction, and cingulate cortex. The richer the experience, the stronger the activity in these areas. The brains of those with near-death-like experiences also showed more complex, more connected, and more integrated neural networks compared to those without such experiences. These surges of neural activity may mark disconnected consciousness during fainting.
NeuroImage
August 15, 2024
Marta Lapo Pais, Marta Teixeira, Carla Soares et al.
8 citations
Inhaled DMT, a psychedelic acting on 5-HT2A serotonin receptors, increases the size of neural population receptive fields (pRFs) in the peripheral visual field of the primary visual cortex (V1). This change, measured with MRI and pRF mapping in a within-subject design, occurred during visual effects documented by the Hallucinogen Rating Scale and was not explained by differences in eye or head movements. The enlarged pRFs may underlie perceptual distortions such as field blurring, tunnel vision, and enlargement of nearby visual space. The findings suggest that 5-HT2A receptor activation controls gain in visual cortex, linking neural population responses to psychedelic visual phenomena.
NeuroImage
July 1, 2025
Hang Yang, Bruno Herbelin, Chuong Ngo et al.
6 citations
Experienced meditators often report feeling detached from their body and current concerns. This study used virtual reality to manipulate perspective during meditation in 23 participants, comparing a third-person perspective (3PP) with a first-person perspective (1PP). The 3PP condition produced stronger feelings of detachment and disconnection, reduced awareness of body boundaries, and less identification with the body. Neural recordings showed a more negative heartbeat-evoked potential in the 3PP condition, linked to activity in the posterior cingulate cortex and medial prefrontal cortex. These results connect changes in the sense of self during meditation to brain processes underlying bodily self-awareness, suggesting VR could help cultivate self-transcendent experiences.