Equity and EthicsLSDKetaminePsilocybin

Increased spontaneous MEG signal diversity for psychoactive doses of ketamine, LSD and psilocybin

Using magnetoencephalography, the authors show that spontaneous neural signal diversity (entropy and Lempel–Ziv complexity) increases reliably under psilocybin, ketamine and LSD—most strongly for single-channel (temporal) LZ—and that these changes correlate with reported intensity of the psychedelic experience. This first application of such measures to the psychedelic state suggests that sustained psychedelic phenomenology corresponds to an elevated level of consciousness as indexed by neural signal diversity.

Authors

  • Suresh Muthukumaraswamy
  • Robin Carhart-Harris

Published

Scientific Reports
meta Study

Abstract

What is the level of consciousness of the psychedelic state? Empirically, measures of neural signal diversity such as entropy and Lempel-Ziv (LZ) complexity score higher for wakeful rest than for states with lower conscious level like propofol-induced anesthesia. Here we compute these measures for spontaneous magnetoencephalographic (MEG) signals from humans during altered states of consciousness induced by three psychedelic substances: psilocybin, ketamine and LSD. For all three, we find reliably higher spontaneous signal diversity, even when controlling for spectral changes. This increase is most pronounced for the single-channel LZ complexity measure, and hence for temporal, as opposed to spatial, signal diversity. We also uncover selective correlations between changes in signal diversity and phenomenological reports of the intensity of psychedelic experience. This is the first time that these measures have been applied to the psychedelic state and, crucially, that they have yielded values exceeding those of normal waking consciousness. These findings suggest that the sustained occurrence of psychedelic phenomenology constitutes an elevated level of consciousness - as measured by neural signal diversity.

Available with Blossom Pro

Research Summary of 'Increased spontaneous MEG signal diversity for psychoactive doses of ketamine, LSD and psilocybin'

Introduction

Understanding how brain dynamics relate to conscious experience remains a central challenge. Earlier work has distinguished conscious level (how conscious one is) from conscious content (what one is conscious of), and empirical measures such as the perturbational complexity index (PCI), Lempel-Ziv complexity and entropy-based metrics have been shown to decrease with diminished conscious level (for example during anaesthesia and deep sleep). By contrast, relatively little is known about how these measures behave during states that alter conscious content without producing global loss of awareness, such as the psychedelic state. Schartner and colleagues set out to test whether spontaneous MEG signal diversity increases during psychedelic states induced by three different compounds—psilocybin, subanaesthetic ketamine and LSD—compared with placebo. The investigators re-analysed previously collected multidimensional MEG recordings using a suite of signal diversity measures (Lempel-Ziv-derived metrics and coalition entropies), controlled for spectral changes using phase-randomised surrogate data, and examined relations between neural measures and retrospective reports of subjective experience. The aim was to determine whether psychedelic phenomenology is accompanied by elevated neural signal diversity relative to normal wakefulness, and whether any changes map onto particular phenomenological dimensions.

Expert Research Summaries

Go Pro to access AI-powered section-by-section summaries, editorial takes, and the full research toolkit.

See Pro PlansAlready have an account? Sign in

Full Text PDF

Full Paper PDF

Create a free account to open full-text PDFs.

Create Free AccountAlready have an account? Sign in

Study Details

References (9)

Papers cited by this study that are also in Blossom

The entropic brain: a theory of conscious states informed by neuroimaging research with psychedelic drugs

Carhart-Harris, R. L., Leech, R., Shanahan, M. et al. · Frontiers in Human Neuroscience (2014)

The paradoxical psychological effects of lysergic acid diethylamide (LSD)

Carhart-Harris, R. L., Kaelen, M., Bolstridge, M. et al. · Psychological Medicine (2016)

253 cited
LSD-induced entropic brain activity predicts subsequent personality change

Lebedev, A. V., Kaelen, M., L€ Ovd En, M. et al. · Human Brain Mapping (2016)

292 cited
Neural correlates of the LSD experience revealed by multimodal neuroimaging

Carhart-Harris, R. L., Muthukumaraswamy, S., Roseman, L. et al. · PNAS (2016)

Broadband Cortical Desynchronization Underlies the Human Psychedelic State

Muthukumaraswamy, S. D., Carhart-Harris, R. L., Moran, R. J. et al. · Journal of Neuroscience (2013)

427 cited
Recent advances in the neuropsychopharmacology of serotonergic hallucinogens

Halberstadt, A. L. · Behavioural Brain Research (2014)

Hallucinogens recruit specific cortical 5-HT(2A) receptor-mediated signaling pathways to affect behavior

Gonza ´lez-Maeso, J., Weisstaub, N. V., Zhou, M. et al. · Neuron (2007)

818 cited
Psilocybin-induced spiritual experiences and insightfulness are associated with synchronization of neuronal oscillations

Kometer, M., Pokorny, T., Seifritz, E. et al. · Psychopharmacology (2015)

Restructuring consciousness -the psychedelic state in light of integrated information theory

Gallimore, A. R. · Frontiers in Human Neuroscience (2015)

Cited By (85)

Papers in Blossom that reference this study

DMT-induced shifts in criticality correlate with self-dissolution

Irrmischer, M., Aqil, M., Luan, L. et al. · Journal of Neuroscience (2025)

Magnesium-ibogaine therapy effects on cortical oscillations and neural complexity in veterans with traumatic brain injury

Lissemore, J. I., Chaiken, A., Keller, C. J. et al. · Nature Mental Health (2025)

Molecular, haemodynamic, and functional effects of LSD in the human brain

McCulloch, D. E-W., Larsen, K., Johansen, A. et al. · MedRvix (2025)

Network control energy reductions under DMT relate to serotonin receptors, signal diversity, and subjective experience

Singleton, S. P., Timmermann, C., Luppi, A. I. et al. · Communications Biology (2025)

Transient destabilization of whole brain dynamics induced by N,N-Dimethyltryptamine (DMT)

Piccinini, J. I., Perl, Y. S., Pallavicini, C. et al. · Communications Biology (2025)

Psychedelics Align Brain Activity with Context

Stoliker, D., Novelli, L., Khajehnejad, M. et al. · Biorxiv (2025)

From relaxed beliefs under psychedelics (REBUS) to revised beliefs after psychedelics (REBAS)

Zeifman, R. J., Spriggs, M. J., Kettner, H. et al. · Scientific Reports (2025)

24 cited
An investigation of acute Physiological and Psychological Moderators of Psychedelic-induced Personality Change among Healthy Volunteers

Godfrey, K., Weiss, B., Zhang, X. et al. · Neuroscience Applied (2025)

Human brain changes after first psilocybin use

Lyons, T., Spriggs, M. J., Kerkelä, L. et al. · Biorxiv (2024)

LSD flattens the hierarchy of directed information flow in fast whole-brain dynamics

Shinozuka, K., Tewarie, P. K. B., Luppi, A. et al. · Biorxiv (2024)

Show all 85 papers
Exploring psychedelic-assisted therapy in the treatment of functional seizures: A review of underlying mechanisms and associated brain networks

Lewis, E. C., Jaeger, A., Girn, M. et al. · Journal of Psychopharmacology (2024)

Psychedelics and the 'inner healer': Myth or mechanism?

Peill, J. M., Marguilho, M., Erritzoe, D. et al. · Journal of Psychopharmacology (2024)

11 cited
Unique Psychological Mechanisms Underlying Psilocybin Therapy Versus Escitalopram Treatment in the Treatment of Major Depressive Disorder

Weiss, B., Leor Roseman, •., Giribaldi, B. et al. · International Journal of Mental Health and Addiction (2024)

Exploring mechanisms of psychedelic action using neuroimaging

Erritzoe, D., Timmermann, C., Godfrey, K. et al. · Nature Mental Health (2024)

28 cited
Neural complexity is increased after low doses of LSD, but not moderate to high doses of oral THC or methamphetamine

Murray, C., Frohlich, J, Haggarty, C. J., Tare, I. et al. · Neuropsychopharmacology (2024)

Effects of external stimulation on psychedelic state neurodynamics

Mediano, P. A. M., Rosas, F. E., Timmermann, C. et al. · ACS Chemical Neuroscience (2024)

Psychedelics for acquired brain injury: a review of molecular mechanisms and therapeutic potential

Allen, J., Dames, S., Foldi, C. J. et al. · Molecular Psychiatry (2024)

The entropic heart: Tracking the psychedelic state via heart rate dynamics

Rosas, F. E., Mediano, P. A. M., Timmermann, C. et al. · Biorxiv (2023)

Navigating the chaos of psychedelic neuroimaging: A multi-metric evaluation of acute psilocybin effects on brain entropy

McCulloch, D. E-W., Olsen, A. S., Ozenne, B. et al. · MedRvix (2023)

12 cited
Overcoming blinding confounds in psychedelic randomized controlled trials using biomarker driven causal mediation analysis

Muthukumaraswamy, S. · Psyarxiv (2023)

Classical and non-classical psychedelic drugs induce common network changes in human cortex

Dai, R., Larkin, T. E., Huang, Z. et al. · NeuroImage (2023)

41 cited
A complex systems perspective on psychedelic brain action

Girn, M., Rosas, F. E., Daws, R. E. et al. · Trends in Cognitive Sciences (2023)

TMS-EEG and resting-state EEG applied to Altered States of Consciousness: Oscillations, Complexity, and Phenomenology

Ort, A., Smallridge, J. W., Sarasso, S. et al. · iScience (2023)

Neural complexity EEG biomarkers of rapid and post-rapid ketamine effects in late-life treatment-resistant depression: a randomized control trial

Murphy, N., Tamman, A. J. F., Lijffijt, M. et al. · Neuropsychopharmacology (2023)

A whole-brain model of the neural entropy increase elicited by psychedelic drugs

Herzog, R., Mediano, P. A. M., Rosas, F. E. et al. · Scientific Reports (2023)

Human brain effects of DMT assessed via EEG-fMRI

Timmermann, C., Roseman, L., Haridas, S. et al. · PNAS (2023)

158 cited
Canalization and plasticity in psychopathology

Carhart-Harris, R. L., Chandaria, S., Erritzoe, D. E. et al. · Neuropharmacology (2023)

N,N-dimethyltryptamine affects EEG response in a concentration dependent manner - a pharmacokinetic/pharmacodynamic analysis

Eckernäs, E., Timmermann, C., Carhart-Harris, R. et al. · Philosophy and the Mind Sciences (2023)

LSD-induced increase of Ising temperature and algorithmic complexity of brain dynamics

Ruffini, G., Damiani, G., Lozano-Soldevilla, D. et al. · PLOS ONE (2023)

Distributed harmonic patterns of structure-function dependence orchestrate human consciousness

Luppi, A. I., Vohryzek, J., Kringelbach, M. L. et al. · Communications Biology (2023)

32 cited
Psychedelics and schizophrenia: Distinct alterations to Bayesian inference

Rajpal, H., Mediano, P. A. M., Rosas, F. E. et al. · NeuroImage (2022)

The neural basis of psychedelic action

Kwan, A. C., Olson, D. E., Preller, K. H. et al. · Nature Medicine (2022)

Receptor-informed network control theory links LSD and psilocybin to a flattening of the brain’s control energy landscape

Singleton, S. P., Luppi, A. I., Carhart-Harris, R. L. et al. · Nature Communications (2022)

Neural Mechanisms and Psychology of Psychedelic Ego Dissolution

Stoliker, D., Egan, G. F., Friston, K. J. et al. · Pharmacological Reviews (2022)

Microdosing with psilocybin mushrooms: a double-blind placebo-controlled study

Cavanna, F., Muller, S., de la Fuente, L. A. et al. · Translational Psychiatry (2022)

90 cited
Serotonergic psychedelic drugs LSD and psilocybin reduce the hierarchical differentiation of unimodal and transmodal cortex

Girn, M., Roseman, L., Bernhardt, B. et al. · NeuroImage (2022)

Pharmacological, Neural, and Psychological Mechanisms underlying Psychedelics: A Critical Review

van Elk, M., Yaden, D. B. · Neuroscience and Biobehavioral Reviews (2022)

Mapping Pharmacologically-induced Functional Reorganisation onto the Brain’s Neurotransmitter Landscape

Luppi, A. I., Hansen, J. Y., Adapa, R. et al. · Biorxiv (2022)

4 cited
Pattern Breaking: A Complex Systems Approach to Psychedelic Medicine

Hipólito, I., Mago, J., Rosas, F. E. et al. · Psyarxiv (2022)

Dynamic reconfiguration of frequency-specific cortical coactivation patterns during psychedelic and anesthetized states induced by ketamine

Li, D., Vlisides, P. E., Mashour, G. A. · NeuroImage (2022)

18 cited
Beating Pain with Psychedelics: Matter over Mind?

Elman, I., Borsook, D., Pustilink, A. · Neuroscience and Biobehavioral Reviews (2022)

Classic Psychedelic Drugs: Update on Biological Mechanisms

Vollenweider, F. X., Smallridge, J. W. · Pharmacopsychiatry (2022)

71 cited
Models of psychedelic drug action: modulation of cortical-subcortical circuits

Doss, M. K., Madden, M. B., Gaddis, A. et al. · Brain (2021)

Microevidence for microdosing with psilocybin mushrooms: a double-blind placebo-controlled study of subjective effects, behavior, creativity, perception, cognition, and brain activity

Cavanna, F., Muller, S., de la Fuente, L. A. et al. · Translational Psychiatry (2021)

5 cited
Low doses of LSD reduce broadband oscillatory power and modulate event-related potentials in healthy adults

Perry, C. M., Malina, M. · Psychopharmacology (2021)

Prefrontal contributions to the stability and variability of thought and conscious experience

Zamani, A., Carhart-Harris, R. L., Christoff, K. · Neuropsychopharmacology (2021)

Psychedelics for Brain Injury: A Mini-Review

Khan, S. I., Carter, G. T., Aggarwal, S. K. et al. · Frontiers in Neuroscience (2021)

Transcriptomics-informed large-scale cortical model captures topography of pharmacological neuroimaging effects of LSD

Burt, J. B., Preller, K. H., Demirtaş, M. et al. · eLife (2021)

Does psychedelic therapy have a transdiagnostic action and prophylactic potential?

Kočárová, C., Horacek, J., Carhart-Harris, R. L. · Frontiers in Psychiatry (2021)

73 cited
Increased Entropic Brain Dynamics during DeepDream-Induced Altered Perceptual Phenomenology

Greco, A., Gallitto, G., Rastelli, C. · Entropy (2021)

LSD induces increased signalling entropy in rats' prefrontal cortex

Savino, A., Nichols, C. D. · Biorxiv (2021)

Psychedelics and health behaviour change

Teixeira, P. J., Johnson, M. W., Timmermann, C. et al. · Journal of Psychopharmacology (2021)

Increased sensitivity to strong perturbations in a whole-brain model of LSD

Jobst, B. M., Atasoy, S., Ponce-Alvarez, A. et al. · NeuroImage (2021)

Neural Correlates of the Shamanic State of Consciousness

Pasquini, L., Luke, D., Harris, R. E. et al. · Frontiers in Human Neuroscience (2021)

Neural and subjective effects of inhaled N,N-dimethyltryptamine in natural settings

Pallavicini, C., Cavanna, F., Zamberlan, F. et al. · Journal of Psychopharmacology (2021)

The entropic tongue: Disorganization of natural language under LSD

Sanz, C., Pallavicini, C., Carrillo, F. et al. · Consciousness and Cognition (2021)

24 cited
Ketamine and Serotonergic Psychedelics: Common Mechanisms Underlying the Effects of Rapid-Acting Antidepressants

Kadriu, B., Greenwald, M., Ba et al. · International Journal of Neuropsychopharmacology (2020)

DMT alters cortical travelling waves

Alamia, A., Timmermann, C., Carhart-Harris, R. L. · eLife (2020)

Serotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatial and temporal domains

Varley, T. F., Carhart-Harris, R., Roseman, L. et al. · NeuroImage (2020)

Psychedelic drugs: neurobiology and potential for treatment of psychiatric disorders

Vollenweider, F. X., Preller, K. H. · Nature Reviews Neuroscience (2020)

Updating the dynamic framework of thought: Creativity and psychedelics

Girn, M., Mills, C., Roseman, L. et al. · NeuroImage (2020)

LSD flattens the functional hierarchy of the human brain

Girn, M., Roseman, L., Bernhardt, B. et al. · Biorxiv (2020)

Decreased directed functional connectivity in the psychedelic state

Barnett, L., Muthukumaraswamy, S., Carhart-Harris, R. L. · NeuroImage (2020)

Therapeutic Use of LSD in Psychiatry: A Systematic Review of Randomized-Controlled Clinical Trials

Fuentes, J. J., Fonseca, F., Elices, M. et al. · Frontiers in Psychiatry (2020)

Neural correlates of the DMT experience assessed with multivariate EEG

Timmermann, C., Roseman, L., Schartner, M. et al. · Scientific Reports (2019)

Dynamical exploration of the repertoire of brain networks at rest is modulated by psilocybin

Lord, L. D., Expert, P., Atasoy, S. et al. · NeuroImage (2019)

183 cited
Spectral signatures of serotonergic psychedelics and glutamatergic dissociatives

Pallavicini, C., Vilas, M. G., Villarreal, M. et al. · NeuroImage (2019)

51 cited
REBUS and the Anarchic Brain: Toward a Unified Model of the Brain Action of Psychedelics

Carhart-Harris, R. L., Friston, K. J. · Pharmacological Reviews (2019)

Classic psychedelics: An integrative review of epidemiology, therapeutics, mystical experience, and brain network function

Johnson, M. W., Hendricks, P. S., Barrett, F. S. et al. · Pharmacology and Therapeutics (2019)

Psychedelics as a treatment for disorders of consciousness

Scott, G., Carhart-Harris, R. L. · Neuroscience of Consciousness (2019)

How do psychedelics work?

Carhart-Harris, R. L. · Current Opinion in Psychiatry (2019)

LSD modulates effective connectivity and neural adaptation mechanisms in an auditory oddball paradigm

Timmermann, C., Spriggs, M. J., Kaelen, M. et al. · Neuropharmacology (2018)

The Varieties of the Psychedelic Experience: A Preliminary Study of the Association Between the Reported Subjective Effects and the Binding Affinity Profiles of Substituted Phenethylamines and Tryptamines

Zamberlan, F., Sanz, C., Pallavicini, C. et al. · Frontiers in Integrative Neuroscience (2018)

Dimensions of consciousness and the psychedelic state

Bayne, T., Carter, O. · Neuroscience of Consciousness (2018)

106 cited
Psychedelics, meditation, and self-consciousness

Milliere, R., Carhart-Harris, R. L., Roseman, L. et al. · Frontiers in Psychology (2018)

Double-blind comparison of the two hallucinogens psilocybin and dextromethorphan: effects on cognition

Barrett, F. S., Carbonaro, T. M., Hurwitz, E. et al. · Psychopharmacology (2018)

78 cited
Psychedelic-Assisted Psychotherapy: A Paradigm Shift in Psychiatric Research and Development

Schenberg, E. E. · Frontiers in Pharmacology (2018)

The abuse potential of medical psilocybin according to the 8 factors of the Controlled Substances Act

Johnson, M. W., Griffiths, R. R., Hendricks, P. S. et al. · Neuropharmacology (2018)

The entropic brain - revisited

Carhart-Harris, R. L. · Neuropharmacology (2018)

Unifying theories of psychedelic drug effects

Swanson, L. R. · Frontiers in Pharmacology (2018)

Quality of acute psychedelic experience predicts therapeutic efficacy of psilocybin for treatment-resistant depression

Roseman, L., Nutt, D. J., Carhart-Harris, R. L. · Frontiers in Pharmacology (2018)

Connectome-harmonic decomposition of human brain activity reveals dynamical repertoire re-organization under LSD

Atasoy, S., Leor, R., Kaelen, M. et al. · Scientific Reports (2017)

Serotonin and brain function: a tale of two receptors

Carhart-Harris, R. L., Nutt, D. J. · Journal of Psychopharmacology (2017)

Shannon entropy of brain functional complex networks under the influence of the psychedelic Ayahuasca

Viol, A., Palhano-Fontes, F., Onias, H. et al. · Scientific Reports (2017)

Psychedelic drug use in healthy individuals: A review of benefits, costs, and implications for drug policy

Elsey, J. W. B. · Drug Science Policy and Law (2017)

Your Personal Research Library

Go Pro to save papers, add notes, rate studies, and organize your research into custom shelves.

See Pro PlansSign in