Scientific Reports
October 20, 2020
Rubén Herzog, Pedro A. M. Mediano, Fernando E. Rosas et al.
60 citations
Psychedelic drugs such as lysergic acid diethylamide, which activate the serotonin 2A receptor, produce profound changes in consciousness and increase entropy in spontaneous neural activity. This study provides the first model-based explanation for that entropy increase by extending a whole-brain model of serotonergic neuromodulation. The model reproduced the overall entropy rise seen in previous experiments. Entropy changes were not uniform: some brain regions showed increased entropy while others showed decreases, indicating a topographical reconfiguration driven by receptor activation. At the whole-brain level, this reconfiguration was not well explained by receptor density but was closely related to the brain's anatomical connectivity topology.
Scientific reports
April 17, 2023
Rubén Herzog, Pedro A M Mediano, Fernando E Rosas et al.
51 citations
Psychedelic drugs such as LSD, which activate the serotonin 2A receptor, produce profound changes in consciousness and are linked to increased entropy in spontaneous brain activity. This study provides the first model-based explanation for that entropy increase by extending a whole-brain model of serotonin neuromodulation. The model reproduced the overall rise in neural entropy seen in prior experiments. Entropy increased across all brain regions, with the largest effects in visuo-occipital areas. At the whole-brain level, this reconfiguration was not well explained by the density of serotonin 2A receptors but was closely related to the topological properties of the brain's anatomical connectivity.
May 16, 2023
William Wong, Kátia C. Andrade, Thomas Andrillon et al.
21 citations
preprint
A new open-access database, DREAM, combines sleep magneto/electroencephalography (M/EEG) recordings with standardized dream reports to enable large-scale neurocognitive research on dreaming. The initial release includes 20 datasets from 561 participants and 2649 awakenings, each with at least 20 seconds of high-frequency M/EEG data and a classification of the subject's experience. Analyses demonstrate that features extracted from EEG can predict whether a person reports having had a conscious experience during both REM and NREM sleep. The database aims to overcome the limitations of small sample sizes and methodological variability in dream research, allowing new questions to be addressed at a scale unattainable by individual labs.
Translational psychiatry
July 27, 2024
Rubén Herzog, Florentine Marie Barbey, Md Nurul Islam et al.
13 citations
Ketamine increases redundancy in brain dynamics—copies of the same information retrievable from three or more electrodes—most notably in the alpha frequency band, as measured by portable low-density EEG. In a double-blind crossover trial with 30 male adults, racemic ketamine compared to saline infusion produced greater redundancy during resting state, linked to dissociative shifts in consciousness. During an auditory oddball task, the effect was stronger for predictable standard stimuli than for deviant ones. Associations between ketamine's high-order interactions and experiences of derealization were observed, suggesting these measures capture pharmacological alterations in consciousness.
Nature communications
August 13, 2025
William Wong, Rubén Herzog, Kátia Cristine Andrade et al.
10 citations
A new open database, the DREAM database, combines standardized sleep magneto/electroencephalography (M/EEG) recordings with dream reports from 505 participants across 20 datasets, totaling 2,643 awakenings. Each awakening includes at least 20 seconds of high-resolution sleep EEG (≥100 Hz, ≥2 electrodes) and a classification of the sleeper's reported experience. Analyses showed that reports of conscious experiences during sleep can be predicted from objective EEG features in both REM and NREM sleep. The database aims to overcome limitations of small sample sizes and methodological variability in dream research, enabling larger-scale investigations of the neurocognitive basis of dreaming.
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.
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.
Research square
March 21, 2024
Agustin Ibanez, Rubén Herzog, Florentine Barbey et al.
1 citation
Ketamine increases redundancy in brain dynamics, particularly in the alpha frequency band, and this effect is more pronounced during resting state and associated with dissociative experiences. In a double-blinded cross-over design with 30 male adults, racemic ketamine was compared to saline infusion. Higher-order interactions (HOI) computed from EEG data showed that ketamine boosted redundancy, especially for predictable stimuli in an auditory oddball task. These findings suggest that ketamine-induced shifts toward dissociation correlate with increased redundancy in neural signal interactions, highlighting the potential of complexity measures with portable EEG for monitoring pharmacological changes in consciousness.
Translational Psychiatry
July 4, 2026
Krisha Shah, Rubén Herzog, Alan C. Swann et al.
Ketamine rapidly reduces depression in some people with treatment-resistant depression, but the brain mechanisms are not fully understood. This analysis of a randomized, double-blind trial compared ketamine to midazolam in 30 older veterans with treatment-resistant depression. Using EEG data and a measure called O-information, which captures how brain regions interact in groups of three or more, the study found that ketamine caused dynamic changes in these interactions over time. The strongest effects occurred in alpha brain waves one hour after infusion, with changes shifting to theta waves by 24 hours and partially returning in beta and gamma waves by day 7.
bioRxiv (Cold Spring Harbor Laboratory)
January 13, 2026
Iván Mindlin, Carlos Coronel-Oliveros, Jacobo Sitt et al.
A biologically grounded inhibitory homeostatic plasticity rule embedded into the Dynamic Mean Field (DMF) model creates a Homeostatic Dynamic Mean Field (HDMF) model that dynamically tunes local excitation-inhibition balance. The HDMF reproduces statistical observables of brain activity as well as the original DMF, can sustain neuromodulatory perturbations without overhead computations, and generates unprecedented sleep-like slow-wave activity that can coexist with wake-like asynchronous dynamics, permitting modeling of dissociated states of consciousness such as parasomnias. A single homeostatic rule broadens the stability and expressiveness of the DMF, providing a unified platform for studying how local adaptive processes shape the diverse global dynamics of the human brain.
arXiv (Cornell University)
August 6, 2020
Rodrigo Cofré, Rubén Herzog, Pedro A. M. Mediano et al.
Altered states of consciousness provide a key opportunity to understand how global brain activity changes relate to different subjective experiences. This paper advocates a research program that bridges bottom-up generative models of whole-brain activity with top-down signatures proposed by theories of consciousness. It defines altered states, discusses relevant brain-activity signatures, and introduces whole-brain models to explore the mechanisms of altered consciousness from the bottom-up. The authors argue that systematic investigation of altered states via bottom-up modeling may help clarify the biophysical, informational, and dynamical foundations of consciousness.
Cell reports
April 7, 2026
Nicolas Decat, Arthur Le Coz, Jade Sénéchal et al.
Mental experiences during wakefulness and sleep are not as distinct as commonly thought. Analyzing electroencephalography (EEG) from 92 participants during daytime rest, researchers collected 375 reports of mental content scored on bizarreness, fluidity, spontaneity, and wake perception. Clustering these reports revealed four distinct types of mental states. Crucially, all four types occurred across wakefulness, N1 sleep, and N2 sleep. EEG measures of spectral power, complexity, and connectivity differentiated these mental states independently of whether participants were awake or asleep. The findings indicate that the waking and sleeping brain can produce the same mental state, and that fine-grained brain dynamics shape the content of mental experiences.
arXiv Preprint Archive
August 6, 2020
Rodrigo Cofré, Rubén Herzog, Pedro A. M. Mediano et al.
Altered states of consciousness, such as those experienced during dreaming or meditation, offer a way to study how large-scale brain activity relates to different subjective experiences. This paper advocates a research program that combines bottom-up generative models of whole-brain activity, based on known properties of neural tissue, with top-down signatures proposed by theories of consciousness. The authors define altered states, discuss relevant brain-activity signatures, and introduce whole-brain models to explore the mechanisms behind these states. They argue that systematically investigating altered states through bottom-up modeling can clarify the biophysical, informational, and dynamical foundations of consciousness.