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George A. Mashour

University of Michigan, Michigan Medicine

74 papers in the library · 2,172 citations · publishing 2006-2026

Papers

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Subanesthetic nitrous oxide alters large-scale network organization and insula connectivity during visual stimulation

Communications Biology August 31, 2026 Niloufar Pouyan, Chelsea Kaplan, Tony E. Larkin et al.

Pharmacological agents that alter consciousness, including classic psychedelics and non-classic agents such as nitrous oxide, are known to affect multiple domains of conscious experience, including visual perception. While most neuroimaging studies rely on resting-state data to characterize altered states of consciousness, task-based approaches enable investigation of specific perceptual...

Opposite network patterns of integration-segregation in psychedelic and sedated states of consciousness.

Cell Reports August 1, 2026 Rui Dai, Hyunwoo Jang, A. Hudetz et al.

Understanding the relationship of conscious states to large-scale brain dynamics remains a central challenge in neuroscience. Here, diverse pharmacological and physiological perturbations-including psychedelics, sleep, and propofol sedation-are used to examine integration-segregation organization of brain networks across altered states of consciousness in humans using functional MRI. Across...

Sub-second fluctuations between top-down and bottom-up modes distinguish diverse human brain states.

Current biology : CB July 2, 2026 Youngjai Park, Younghwa Cha, Hyoungkyu Kim et al.

Information continuously flows between regions of the human brain, forming patterns that shift across states of consciousness, cognitive modes, and neuropsychiatric conditions. While functional magnetic resonance imaging (fMRI) reveals large-scale activity changes over seconds, the electrophysiological dynamics governing sub-second reconfiguration remain poorly understood. Here, relative phase...

General Anesthesia and Discrete Components of Ketamine Neurophysiology.

JAMA Psychiatry June 1, 2026 Ben Deverett, Duan Li, Theresa R. Lii et al. 1 citation

Ketamine has well-known dissociative, analgesic, and antidepressant properties, but it is unknown whether the neurophysiologic effects that are associated with these properties can be modulated separately from one another. Considering that specific cortical oscillations have been associated with specific therapeutic effects, modulating selective aspects of ketamine neurophysiology could inform...

Reorganization of Human Brain Waves Across Diverse States of Consciousness.

bioRxiv : the preprint server for biology June 1, 2026 Panagiotis Fotiadis, Hyunwoo Jang, Rui Dai et al.

Brain waves are ubiquitous phenomena of human brain activity. As they propagate, they coordinate neural communication, shaping conscious perception. Understanding how brain waves unfold across space and time is thus critical for uncovering the neural mechanisms that support and suppress consciousness. Here, we analyzed data from the Human Connectome Project alongside multiple independent human...

Acute effects of nitrous oxide on visual processing: a connectome study in healthy adults.

Research Square January 12, 2026 Niloufar Pouyan, Chelsea M Kaplan, Tony E. Larkin et al.

Nitrous oxide (N2O) produces perceptual alterations and changes in large-scale brain network organization, yet its effects on task-specific visual processing remain unclear. Given the prominence of visual alterations during psychedelic exposure, we investigated how subanesthetic N2O modulates functional connectivity during visual stimulation. Thirteen healthy adults completed a...

An open fMRI resource for studying human brain function and covert consciousness under anesthesia.

Scientific Data January 9, 2026 Zirui Huang, Vijay Tarnal, Panagiotis Fotiadis et al.

Anesthesia has revolutionized surgical practice and offers a controlled model to study the neurobiology of consciousness. Functional magnetic resonance imaging (fMRI) studies have shown that anesthesia primarily disrupts connectivity across association cortices, suggesting that impaired integration between higher-order brain regions underlies unconsciousness. However, traditional fMRI paradigms...

Neurochemical and Neurophysiological Effects of Intravenous Administration of N,N -Dimethyltryptamine in Rats

Journal of Neuroscience December 19, 2025 Nicolas G. Glynos, Emma R. Huels, Trent Groenhout et al. 11 citations

N,N-Dimethyltryptamine (DMT) is a serotonergic psychedelic that is being investigated for the treatment of psychiatric disorders. Although the neurophysiological effects of DMT in humans are well characterized, similar studies in animal models and data on the neurochemical effects of DMT are generally lacking, which are critical for a mechanistic understanding. Here, we combined behavioral...

Reframing “Paradoxical” Excitation: Disentangling EEG Complexity and Entropy Reveals Resting State Dynamics Associated with Propofol Susceptibility

medRxiv Preprint Server December 16, 2025 Derek Newman, Charlotte Maschke, George A. Mashour et al. preprint

Background Propofol exposure can produce heterogenous neural responses, from the expected suppression to transient paradoxical excitation. EEG measures of signal complexity and entropy have emerged as reliable markers of consciousness, but different types of complexity and entropy measures are often conflated. We used Type I and II complexity measures on the Complexity–Entropy Causal Plane...

A Mesoscale Framework for Psychedelic Drug Action in the Human Brain

bioRxiv November 26, 2025 Rui Dai, Rodrigo Cofré, Christopher Timmermann et al. preprint

The mechanism of psychedelic drug action is a dynamic area of neuroscience, with two major lines of investigation: (1) laboratory studies at the molecular and cellular level, and (2) human neuroimaging studies of functional brain networks. Despite considerable progress, there remains insufficient understanding of the link between molecular/cellular substrates of psychedelics and the whole-brain...

General anesthesia dissociates discrete components of ketamine neurophysiology

medRxiv August 7, 2025 Ben Deverett, Duan Li, Theresa R. Lii et al. preprint

Structured Abstract Importance Ketamine has well known dissociative, analgesic, and antidepressant properties, but it is unknown whether the neurophysiologic effects that are associated with these properties can be modulated separately from one another. Given prior studies that link specific cortical oscillations with specific therapeutic effects, it is likely that modulating selective aspects...

Regulation of REM and NREM Sleep by Preoptic Glutamatergic Neurons.

Sleep May 26, 2025 Alejandra Mondino, Amir Jadidian, Brandon A Toth et al. 4 citations

The preoptic area of the hypothalamus is key for the control of sleep onset and sleep homeostasis. Although traditionally considered exclusively somnogenic, recent studies identified a group of preoptic glutamatergic neurons that promote wakefulness. Specifically, our previous investigations demonstrated that chemogenetic stimulation of glutamatergic neurons within the medial-lateral preoptic...

Pictorial representation of illness and self measure (PRISM): A putative transdiagnostic tool for evaluating therapeutic effects of psychedelic treatments.

Journal of psychopharmacology (Oxford, England) May 1, 2025 Niloufar Pouyan, Jacob S. Aday, Steven E. Harte et al. 1 citation

Patients with refractory conditions often identify themselves with their illness, which affects multiple aspects of their lives. The pictorial representation of illness and self measure (PRISM) is a tool used to assess the enmeshment of individuals' perception of self with a particular medical condition, broadly termed self-condition enmeshment. This study aimed to evaluate changes in PRISM...

Pictorial representation of illness and self measure (PRISM): A putative transdiagnostic tool for evaluating therapeutic effects of psychedelic treatments

Universität Zürich, ZORA May 1, 2025 Niloufar Pouyan, Jacob S. Aday, Steven E. Harte et al.

Background: Patients with refractory conditions often identify themselves with their illness, which affects multiple aspects of their lives. The pictorial representation of illness and self measure (PRISM) is a tool used to assess the enmeshment of individuals' perception of self with a particular medical condition, broadly termed self-condition enmeshment. Aims: This study aimed to evaluate...

Sub-Second Fluctuation between Top-Down and Bottom-Up Modes Distinguishes Diverse Human Brain States.

bioRxiv : the preprint server for biology March 28, 2025 Youngjai Park, Younghwa Cha, Hyoungkyu Kim et al. preprint

Information continuously flows between regions of the human brain, exhibiting distinct patterns that dynamically shift across states of consciousness, cognitive modes, and neuropsychiatric conditions. In this study, we introduce Relative Phase Analysis (RPA), a method that leverages phase-lead/lag relationships to reveal the real-time dynamics of dominant directional patterns and their rapid...

Intravenous psilocybin induces dose-dependent changes in functional network organization in rat cortex

Translational Psychiatry March 25, 2025 Brian H Silverstein, Nicholas Kolbman, Amanda Nelson et al. 8 citations

Psilocybin produces an altered state of consciousness in humans and is associated with complex spatiotemporal changes in cortical networks. Given the emphasis on rodent models for mechanistic studies, there is a need for characterization of the effect of psilocybin on cortex-wide network dynamics. Previous electroencephalographic studies of psychedelics in rodents have primarily used sparse...

Preliminary safety and effectiveness of psilocybin-assisted therapy in adults with fibromyalgia: an open-label pilot clinical trial

Frontiers in Pain Research March 18, 2025 Jenna McAfee, Avinash Hosanagar, Vijay Tarnal et al. 18 citations

Introduction Fibromyalgia (FM) is the prototypical nociplastic pain condition, characterized by widespread pain and issues with cognition, mood, and sleep. Currently, there are limited treatment options available that effectively treat FM symptoms. Psilocybin-assisted therapy (PAT) is an emerging combined drug-therapy intervention, but no studies to-date have investigated PAT for FM. Methods...

Psychedelic-mediated Reversal of General Anesthesia and Restoration of Brain Dynamics in Rat

bioRxiv Preprint Server January 22, 2025 Emma R. Huels, Nicholas Kolbman, Christopher W Fields et al. 4 citations preprint

Serotonergic psychedelics enhance neurophysiological complexity and the repertoire of brain states, whereas general anesthetics produce opposite effects. Serotonergic psychedelics are also known to increase wakefulness and reduce sleep time in rodents. Therefore, we hypothesized that 2,5-dimethoxy-4-iodopamphetamine (DOI), a serotonergic psychedelic, will reverse general anesthesia and restore...

Measuring the dynamic balance of integration and segregation underlying consciousness, anesthesia, and sleep in humans.

Nature Communications October 24, 2024 Hyunwoo Jang, George A. Mashour, Anthony G. Hudetz et al.

Consciousness requires a dynamic balance of integration and segregation in brain networks. We report an fMRI-based metric, the integration-segregation difference (ISD), which captures two key network properties: network efficiency (integration) and clustering (segregation). With this metric, we quantify brain state transitions from conscious wakefulness to unresponsiveness induced by the...

Neural Correlates of Psychedelic, Sleep, and Sedated States Support Global Theories of Consciousness.

bioRxiv : the preprint server for biology October 23, 2024 Rui Dai, Hyunwoo Jang, Anthony G. Hudetz et al. 1 citation preprint

Understanding neural mechanisms of consciousness remains a challenging question in neuroscience. A central debate in the field concerns whether consciousness arises from global interactions that involve multiple brain regions or focal neural activity, such as in sensory cortex. Additionally, global theories diverge between the Global Neuronal Workspace (GNW) hypothesis, which emphasizes frontal...

Propofol disrupts the functional core-matrix architecture of the thalamus in humans

Nature Communications September 9, 2024 Zirui Huang, George A. Mashour, Anthony G. Hudetz 23 citations

Research into the role of thalamocortical circuits in anesthesia-induced unconsciousness is difficult due to anatomical and functional complexity. Prior neuroimaging studies have examined either the thalamus as a whole or focused on specific subregions, overlooking the distinct neuronal subtypes like core and matrix cells. We conducted a study of heathy volunteers and functional magnetic...

Classifying Unconscious, Psychedelic, and Neuropsychiatric Brain States with Functional Connectivity, Graph Theory, and Cortical Gradient Analysis.

Brain Sciences August 30, 2024 Hyunwoo Jang, Rui Dai, George A. Mashour et al.

Accurate and generalizable classification of brain states is essential for understanding their neural underpinnings and improving clinical diagnostics. Traditionally, functional connectivity patterns and graph-theoretic metrics have been utilized. However, cortical gradient features, which reflect global brain organization, offer a complementary approach. We hypothesized that a machine learning...

Consciousness and the Dying Brain.

Anesthesiology June 1, 2024 George A. Mashour, UnCheol Lee, Dinesh Pal et al. 8 citations

The near-death experience has been reported since antiquity and is often characterized by the perception of light, interactions with other entities, and life recall. Near-death experiences can occur in a variety of situations, but they have been studied systematically after in-hospital cardiac arrest, with an incidence of 10 to 20%. Long attributed to metaphysical or supernatural causes, there...

Effect of Intravenous Delivery of N,N Dimethyltryptamine on Sleep-Wake States in Rat

Physiology May 1, 2024 Rachel Summerfield, Trent Groenhout, Tiecheng Liu et al.

Psychedelics, including N, N, Dimethyltryptamine (DMT), are being increasingly explored for therapeutic potential to treat psychiatric disorders such as depression, anxiety, and post-traumatic stress disorder. These and other psychiatric conditions have a bidirectional relationship with sleep patterns but the impact of psychedelics, particularly DMT, on sleep architecture is incompletely...

Measuring the dynamic balance of integration and segregation underlying consciousness, anesthesia, and sleep

bioRxiv April 15, 2024 Hyunwoo Jang, George A. Mashour, Anthony G. Hudetz et al. preprint

Consciousness requires a dynamic balance of integration and segregation in functional brain networks. An optimal integration-segregation balance depends on two key aspects of functional connectivity: global efficiency (i.e., integration) and clustering (i.e., segregation). We developed a new fMRI-based measure, termed the integration-segregation difference (ISD), which captures both aspects. We...