Neuroimage
January 18, 2017
Hannah Scheibner, Carsten Bogler, Tobias Gleich et al.
136 citations
Focused attention meditation is linked to reduced activity in the default mode network (DMN) compared to mind-wandering, regardless of whether attention is directed internally or externally. In twenty meditation-naïve adults who practiced mindfulness of sound and breathing for four days, brain scans showed that during mindful attention, regions like the medial prefrontal cortex, posterior cingulate cortex, and left temporoparietal junction were less active than during mind-wandering. Deactivation in the posterior cingulate cortex was stronger during internal attention than external attention. Refocusing after mind-wandering engaged the left inferior frontal gyrus. These findings suggest that mindful attention, not the focus of attention, drives DMN reduction.
Neuroimage
April 25, 2022
Manesh Girn, Leor Roseman, Boris C. Bernhardt et al.
112 citations
LSD and psilocybin flatten the brain's normal hierarchical organization, reducing the functional separation between sensory and higher-order networks and increasing cross-talk between them. Analyzing two resting-state fMRI datasets, the principal gradient of cortical connectivity—which normally runs from basic sensory areas to complex association regions—was significantly compressed under both drugs compared to placebo. This flattening was driven by decreased specialization at both ends of the hierarchy: default mode and frontoparietal networks at the top, and somatomotor networks at the bottom. The findings support a proposed mechanistic model of the psychedelic state and demonstrate that macroscale connectivity gradients can be acutely altered by a pharmacological intervention.
Neuroimage
July 1, 2008
Jacob M Hooker, Youwen Xu, Wynne Schiffer et al.
106 citations
Salvinorin A, the psychoactive component of the mint plant Salvia divinorum, is a uniquely potent agonist at kappa-opioid receptors. Positron emission tomography (PET) studies in 6 adult female baboons showed extremely rapid brain uptake, reaching a peak of 3.3% of the total administered dose within 40 seconds and clearing with a half-life of 8 minutes. The compound distributed throughout the brain, with highest concentration in the cerebellum and notable concentration in the visual cortex, which may account for visual hallucinations when smoked. Naloxone did not reduce overall concentration or alter regional distribution. The rapid brain kinetics match the brief time-course of visual hallucinations, and effects may occur at less than 10 micrograms in the human brain, emphasizing its remarkable potency.
Neuroimage
July 12, 2017
Candace R. Lewis, Katrin H. Preller, Rainer Kraehenmann et al.
105 citations
Psilocybin, the active compound in psychedelic mushrooms, acts on serotonin receptors. In a placebo-controlled, double-blind study with 58 healthy participants, two oral doses of psilocybin (0.160 mg/kg and 0.215 mg/kg) were given. After adjusting for global brain perfusion, psilocybin increased relative perfusion in right frontal and temporal regions and the anterior insula, while decreasing it in left parietal and temporal cortices and left subcortical regions. However, absolute perfusion was reduced across frontal, temporal, parietal, and occipital lobes, and in bilateral amygdalae, anterior cingulate, insula, striatal regions, and hippocampi. The findings show consistency with both the hyperfrontal hypothesis and recent studies showing decreased perfusion, depending on analysis method.
Neuroimage
April 5, 2019
Duan Li, George A. Mashour
103 citations
Ketamine produces dose-dependent effects on the brain's spatiotemporal complexity. At a subanesthetic dose, ketamine elevates complexity relative to baseline, while an anesthetic dose initially causes alternating low and high complexity levels before stabilizing at a high level comparable to baseline. These findings reveal that ketamine-induced state transitions blend features of general anesthesia, normal consciousness, and altered states, advancing understanding of its pharmacological and neurophysiological properties.
Neuroimage
June 22, 2020
Brontë Mckeown, Will Strawson, Hao-ting Wang et al.
102 citations
People whose brain connectivity patterns make the sensorimotor system most distinct from the visual system are more likely to report thoughts about solving problems or goals and less likely to report thoughts about the past. This finding comes from a study where participants underwent resting-state fMRI and then completed a questionnaire about their thoughts during the scan. A non-linear dimension reduction algorithm identified components explaining the greatest variance in whole-brain connectivity patterns. The results suggest that unique patterns of experience are linked to distinct neurocognitive profiles, with unimodal systems playing an important role.
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
December 17, 2019
Lionel Barnett, Suresh Muthukumaraswamy, Robin Carhart-Harris et al.
88 citations
The psychedelic state involves a breakdown in patterns of information flow in the brain. Using MEG recordings, researchers measured functional connectivity after administration of LSD, psilocybin, and low-dose ketamine, and compared them with the non-psychedelic drug tiagabine. All three psychedelics decreased directed functional connectivity (information flow) throughout the brain, as measured by Granger causality. For LSD, this decrease was coupled with an increase in undirected functional connectivity (correlation and coherence), a surprising opposite movement that highlights the importance of comparing multiple measures of functional connectivity in neuroimaging data.
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 Perez-Ipina, 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
June 24, 2019
Carla Pallavicini, Martina G. Vilas, Mirta Villarreal et al.
66 citations
Classic serotonergic psychedelics and dissociative drugs like ketamine produce overlapping subjective effects despite different pharmacological mechanisms. Using source-localized magnetoencephalography, researchers found that LSD, psilocybin, and ketamine all caused widespread broadband reductions in spectral power. Machine learning classifiers trained on one pair of drugs could identify the third, confirming similarity. Functional connectivity analysis revealed decreases in low alpha and theta bands specific to LSD and psilocybin, linked to 5-HT2A agonism, while low beta band decreases were common to all three drugs. These findings quantify shared large-scale brain activity patterns across drug classes and suggest that beta band decoupling is an effect shared between NMDA antagonists and 5-HT2A agonists.
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 W 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
January 29, 2021
Beatrice M. Jobst, Selen Atasoy, Adrián Ponce-Alvarez et al.
37 citations
After taking LSD, the brain's dynamics become less stable and more diverse in response to perturbations. Using a whole-brain computational model fitted to fMRI data from individuals under LSD or placebo, researchers simulated external disruptions to different brain regions. They measured recovery time with the Perturbational Integration Latency Index (PILI). Globally, LSD caused consistently higher PILI values, indicating a shift further from stable equilibrium. Locally, the largest differences appeared in the limbic, visual, and default mode networks. LSD also increased variability of PILI across brain regions, suggesting greater response diversity. These findings reveal brain-wide dynamical changes underlying the psychedelic state and suggest potential clinical applications for psychiatric disorders.
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.