Frontiers in Psychology
January 1, 2013
Enzo Tagliazucchi, Marion Behrens, Helmut Laufs
42 citations
Deep sleep, marked by reduced sensory activity and loss of conscious awareness, offers a natural setting for testing theories of consciousness. This review examines recent fMRI studies of spontaneous brain activity during sleep, linking findings to the global workspace theory, information integration theory, and the dynamical core hypothesis. The authors highlight a shift from studying evoked responses to resting-state activity and emphasize the need for dynamic analysis of functional interactions over time. They also stress the importance of experimentally verifying reduced or absent conscious content during the deepest sleep stages.
Interface Focus
April 14, 2023
Elvira G-Guzmán, Yonatan Sanz Perl, Jakub Vohryzek et al.
34 citations
Living systems must constantly work against equilibrium to survive, a property that can be measured through temporal asymmetry in brain signals. Using statistical physics, researchers analyzed reversibility in functional magnetic resonance imaging data from patients with disorders of consciousness. They found that decreased asymmetry and reduced non-stationarity in brain signals characterize impaired consciousness states, consistent with previous findings in sleep and anesthesia. The work aims to identify biomarkers for patient improvement and classification, and to deepen mechanistic understanding of consciousness disorders.
Conscious Cogn
December 8, 2020
Camila Sanz, Carla Pallavicini, Facundo Carrillo et al.
34 citations
Language produced under the influence of LSD shows increased entropy and reduced semantic coherence, consistent with a state of heightened neural entropy. Non-semantic analysis of speech organization revealed increased verbosity and a reduced lexicon, changes more similar to manic psychoses than to schizophrenia, as confirmed by direct comparison with reference samples. Features related to language organization allowed machine learning classifiers to identify speech under LSD with accuracy comparable to that obtained by examining semantic content. These results provide a quantitative characterization of disorganized natural speech as a landmark feature of the psychedelic state.
J Affect Disord
February 27, 2024
Debora Copa, David Erritzøe, Bruna Giribaldi et al.
31 citations
Brain connectivity patterns measured before psilocybin treatment can predict how much depression symptoms will improve. In people with treatment-resistant depression given two doses of psilocybin (25 mg each, one week apart), baseline resting-state functional MRI scans showed that connectivity within visual, default mode, and executive networks predicted early symptom improvement, while salience network connectivity predicted who would respond up to 24 weeks later, with about 90% accuracy. Similar patterns appeared in a separate trial comparing psilocybin to escitalopram. Fronto-occipital and fronto-temporal connections predicted early and late symptom reduction, respectively. Small sample sizes and differences between datasets limit generalizability, and the lack of a placebo arm limits specificity.
Journal of Psychedelic Studies
May 6, 2021
Federico Cavanna, Carla Pallavicini, Virginia Milano et al.
31 citations
During the COVID-19 pandemic, people who had used psychedelic drugs at least once in their lives reported higher positive affect and personality traits linked to resilience, such as greater openness and lower conscientiousness, compared to those who had not. Among 5,618 participants (average age 29, 72% female), 32% reported lifetime psychedelic use. The number of past psychedelic experiences predicted higher scores on a measure of plasticity. No evidence linked lifetime psychedelic use to impaired mental health indicators. Other psychoactive drugs showed opposite associations with mental health.
Journal of Cannabis Research
July 17, 2020
Laura Alethia de la Fuente, Federico Zamberlán, Andrés Sánchez Ferrán et al.
30 citations
Machine learning classifiers distinguished between Cannabis sativa and Cannabis indica cultivars based on user-reported flavours and subjective effects with high accuracy. Analysis of a large dataset from Leafly.com and chemical composition data from Psilabs.org revealed significant correlations between terpene and cannabinoid content and subjective effect and flavour tags. Reported effects clustered into three groups: unpleasant, stimulant, and soothing. Terpene profiles matched user perceptual characterizations, particularly for terpene-flavours associations. The findings suggest that flavour perception could serve as a reliable marker to indirectly characterize cannabis psychoactive effects, as terpene content is robustly inherited and less influenced by environmental factors.
Network Neuroscience
January 1, 2022
Josephine Cruzat, Yonatan Sanz Perl, Anira Escrichs et al.
28 citations
Psychedelic drugs like LSD and psilocybin may treat neuropsychiatric disorders by dose-dependently altering the brain's functional hierarchy—the organization of neural activity across regions. Using a turbulence framework that measures local synchronization (vorticity) in both space and time, researchers found that both drugs produce consistent and distinct effects, particularly compressing the default mode network, a higher-level network. These findings support the hypothesis that psychedelics modulate the functional hierarchy and provide a quantitative comparison of how LSD and psilocybin change brain dynamics, with implications for therapeutic use.
Cerebral cortex (New York, N.Y. : 1991)
August 1, 2024
Evan Lewis-Healey, Enzo Tagliazucchi, Andrés Canales-Johnson et al.
27 citations
Intentional breathing techniques (breathwork) can induce altered states of consciousness similar to those produced by psychedelics. By tracking subjective experiences moment-by-moment alongside portable EEG recordings across 301 sessions from 14 novice participants, researchers found that psychedelic-like experiences—especially intense bliss—corresponded with increased neural complexity (Lempel-Ziv complexity) and changes in the aperiodic exponent of brain activity, but not with alpha brainwave power. These non-linear neural features map onto both broad positive experiences and specific psychedelic-like states, suggesting breathwork alters consciousness through mechanisms distinct from simple relaxation or meditation.
Neuroscience of Consciousness
January 1, 2019
Andrew Peterson, Enzo Tagliazucchi, Charles Weijer
25 citations
An ethical analysis of proposed psychedelic research with patients who have disorders of consciousness, using the Value-Validity Framework and Component Analysis, finds that the approach by Scott and Carhart-Harris is ethically permissible under certain conditions. The frameworks applied are also relevant for evaluating other novel consciousness research protocols.
Frontiers in Psychiatry
November 5, 2021
Enzo Tagliazucchi, Federico Zamberlán, Federico Cavanna et al.
23 citations
Inhaled DMT, a classic psychedelic, produces short but profound shifts in consciousness. In 35 healthy volunteers, electroencephalography recorded before and during the drug's acute effects in a natural setting showed marked reductions in alpha and beta brain oscillations and increases in delta, theta, and gamma power, particularly in posterior regions. The power of fronto-temporal theta oscillations inversely correlated with feelings of unity and transcendence—core features of mystical-type experiences. These findings suggest that baseline brain activity prior to psychedelic use may help predict the likelihood of such experiences, which are linked to lasting well-being and improved therapeutic outcomes.
Communications Biology
September 30, 2024
Pablo Castro, Andrea I. Luppi, Enzo Tagliazucchi et al.
21 citations
Brain activity during unconsciousness, whether from general anaesthesia or slow wave sleep, is dominated by a recurrent functional connectivity pattern primarily mediated by structural connectivity and with a reduced capacity to transition to other patterns. Conscious awareness is characterized by richer brain dynamics measured by entropy and a greater repertoire of connectivity states. These findings suggest that the dynamic exploration of functional connectivity states provides robust and generalizable markers for the state of consciousness across different conditions.
Frontiers in Pharmacology
March 22, 2022
Enzo Tagliazucchi
20 citations
Psychedelics profoundly alter subjective experience, sometimes with lasting effects, yet how they affect language production is understudied. This review examines two aspects: how acute psychedelic effects impact speech organization regardless of semantic content, and how analyzing semantic content of written retrospective reports can characterize subjective effects. Computational analysis of language production can partially predict therapeutic outcomes, relate psychedelic effects to other altered states and psychiatric disorder symptoms, and investigate neurochemical profiles and mechanisms of action. The authors conclude that analyzing brief interviews before, during, and after acute effects can expand scientific conclusions, and they list open questions for future research.
bioRxiv (Cold Spring Harbor Laboratory)
August 20, 2020
Carla Pallavicini, Federico Cavanna, Federico Zamberlán et al.
17 citations
preprint
Inhaled DMT, a short-acting psychedelic found in plants and animals, was studied in 35 experienced participants in natural settings using wireless EEG and questionnaires. DMT reduced alpha brain waves (8-12 Hz) across the scalp while increasing delta (1-4 Hz) and gamma (30-40 Hz) waves. Increases in gamma power correlated with reports of mystical-type experiences. DMT also altered global synchrony and metastability in gamma and alpha bands and increased signal complexity. These findings align with prior psychedelic research and suggest EEG markers for mystical experiences in natural contexts, underscoring the value of studying these compounds in real-world settings.
bioRxiv (Cold Spring Harbor Laboratory)
July 4, 2021
Gustavo Deco, Yonatan Sanz Perl, Jacobo Sitt et al.
16 citations
preprint
The brain operates far from equilibrium due to forces from the body and environment. Using a deep learning framework called Temporal Evolution NETwork (TENET) applied to large-scale neuroimaging data from over a thousand participants, researchers show that the arrow of time—a thermodynamic measure of non-reversibility—varies with cognitive state. Non-equilibrium levels are higher during tasks than at rest and differ across seven distinct cognitive tasks. In a separate dataset of 265 participants, the framework distinguishes resting-state brain activity in healthy controls from that in schizophrenia, bipolar disorder, and ADHD, with higher non-equilibrium levels in health. This thermodynamics-based approach offers new insights into how brain dynamics orchestrate behavior-environment interactions.
Chaos An Interdisciplinary Journal of Nonlinear Science
September 1, 2021
Sofía Morena del Pozo, Helmut Laufs, Vincent Bonhomme et al.
13 citations
Consciousness is linked to brain regions that synchronize transiently in ways that are both integrated and differentiated. Using dynamic brain networks from fMRI data collected during deep sleep and propofol anesthesia, this study found that unconsciousness reduced the size and flexibility of the largest spatiotemporal module, identified as the dynamic core. These results support the dynamic core hypothesis of consciousness.
Psychology of Consciousness Theory Research and Practice
June 12, 2025
Etzel Cardeña, Aviva Berkovich‐ohana, Katja Valli et al.
11 citations
A multidisciplinary, international group used taxonomic principles and a modified Delphi method to create a taxonomy of altered states of consciousness based on central phenomenological features. They identified eight distinct states, some with subcategories: proto and transitional, delirium, minimal to no awareness, experiential detachment, enhanced physicality, altered identity, imaginary/fantasy/visionary, and unity/mystical. The authors hope this taxonomy will foster conceptual clarity and stimulate research across specializations, helping reveal what is common and different across triggers and antecedents of altered states, and encouraging phenomenological, psychological, cultural, and neuroscientific understanding.
bioRxiv (Cold Spring Harbor Laboratory)
December 7, 2021
Federico Cavanna, Stephanie Müller, Laura Alethia de la Fuente et al.
8 citations
preprint
A double-blind placebo-controlled trial tested the effects of a low (0.5 g) sub-hallucinogenic dose of dried psilocybin mushrooms in 34 individuals planning to microdose. Acute subjective effects were significantly stronger with the active dose than with placebo, possibly due to unblinding. For other measures—including creativity, perception, cognition, and brain activity—the results were null or showed a trend toward cognitive impairment and, in electroencephalography, reduced theta band spectral power. These findings suggest that expectation effects may account for some of the anecdotal benefits people report from microdosing psilocybin.
Communications biology
March 11, 2025
Juan Ignacio Piccinini, Yonatan Sanz Perl, Carla Pallavicini et al.
6 citations
The transition into a psychedelic brain state is often overlooked in favor of static descriptions of acute effects. Using a time-dependent whole-brain model and fMRI data from 15 volunteers given intravenous DMT, the work shows that a transient of heightened reactivity in fronto-parietal regions and visual cortices correlates with serotonin 5HT2a receptor density. Simulated perturbations suggest that minimal disturbances can achieve maximal effects during this brief period, and the temporal evolution of these features aligns with pharmacokinetics. These findings indicate a mechanism for how short psychedelic episodes may exert a lasting influence over time.
Research Square
October 26, 2022
Rubén Herzog, Pedro A.M Mediano, Fernando E. Rosas et al.
6 citations
Psychedelic drugs like LSD, which activate serotonin 2A receptors, dramatically alter subjective experience and offer a window into the neurobiology of consciousness. A key signature of these drugs is increased entropy—or randomness—in spontaneous brain activity, but why this occurs was unclear. Using a computational model of serotonin's effects on the whole brain, researchers reproduced the entropy increase seen in living brains, providing the first model-based explanation. Entropy rose across all brain regions but was most pronounced in visual and occipital areas. Surprisingly, this pattern was not tied to the density of serotonin receptors but instead linked to the brain's structural connectivity network. The findings clarify how psychedelics reconfigure brain activity.
Preprints.org
November 10, 2021
Enzo Tagliazucchi
5 citations
preprint
Psychedelics profoundly alter subjective experience, often with lasting effects, yet their impact on language production is underexplored. This review examines how acute psychedelic effects disrupt speech organization regardless of semantic content, and how analyzing the semantic content of written retrospective reports can characterize subjective effects. Computational analysis of language production is an emerging tool to predict therapeutic outcomes, relate psychedelic effects to other altered states, compare them to psychiatric disorder symptoms, and investigate neurochemical profiles and mechanisms of different psychedelics. Researchers can expand scientific conclusions by analyzing brief interviews before, during, and after acute effects. Several open questions remain to consolidate this approach.
Journal of Cognitive Neuroscience
December 30, 2025
Evan Lewis-Healey, Carla Pallavicini, Federico Cavanna et al.
4 citations
The psychedelic drug DMT rapidly reorganizes conscious experience and brain activity, but the link between brain dynamics and subjective effects remains unclear. In a blinded, dose-dependent study, 19 participants received 20 mg or 40 mg of DMT. The higher dose produced more intense visual hallucinations and emotional experiences. Electroencephalography data showed that alpha power and permutation entropy best tracked moment-to-moment changes in subjective experience, while Lempel-Ziv complexity—previously thought to be a strong correlate—showed the weakest association. The findings indicate that the relationship between neural complexity and psychedelic phenomenology is less straightforward than hypothesized.
bioRxiv (Cold Spring Harbor Laboratory)
November 1, 2023
Stephanie Müller, Federico Cavanna, L. de la Fuente et al.
3 citations
preprint
High doses of psilocybin mushrooms cause people to explore paintings with more local, less random eye movements, making their gaze patterns less entropic. Participants also reported stronger emotional responses and a greater state of flow under the high dose. These effects are consistent with psilocybin altering the perception of low-level visual features like textures, shapes, and colors. The findings demonstrate that eye-tracking under naturalistic conditions can objectively measure psychedelic-induced perceptual changes, supporting greater ecological validity.
Sci Rep
September 15, 2022
Rubén Herzog, Pedro A. M. Mediano, Fernando E. Rosas et al.
3 citations
A scientific paper was retracted because a typo in the script used to calculate differential entropy made the reported entropy estimations invalid. The corrected calculations no longer show the expected increase in brain signal diversity or complexity that the original analysis had claimed.
bioRxiv Preprint Server
March 11, 2021
Enzo Tagliazucchi, Federico Zamberlán, Federico Cavanna et al.
3 citations
preprint
Inhaled DMT, a classic psychedelic, produces brief but profound changes in consciousness that vary with context. Using wireless EEG and source imaging, researchers mapped changes in neural oscillations. Frontal and temporal theta power inversely correlated with feelings of unity and transcendence—hallmarks of mystical-type experiences. A machine learning model confirmed the robustness of these results. The findings align with the idea that pre-drug mindset influences subjective experience. Priming individuals to lower theta power before taking a serotonergic psychedelic might increase the likelihood of mystical-type experiences, potentially enhancing well-being and therapeutic outcomes.
Frontiers in neuroscience
January 1, 2018
Camila Sanz, Federico Zamberlán, Earth Erowid et al.
3 citations
correction
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