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...
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...
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...
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...
bioRxiv (Cold Spring Harbor Laboratory)
February 12, 2024
Brian H Silverstein, Nicholas Kolbman, Amanda Nelson et al.
3 citations
preprint
Abstract Psilocybin produces an altered state of consciousness in humans and is associated with complex spatiotemporal changes in brain networks. Given the emphasis on rodent models for mechanistic studies, there is a need for characterization of the effect of psilocybin on brain-wide network dynamics. Previous rodent studies of psychedelics, using electroencephalogram, have primarily been done...
Frontiers in Systems Neuroscience
May 25, 2023
Charles Gervais, Louis-Philippe Boucher, Guillermo Martinez Villar et al.
25 citations
The healthy conscious brain is thought to operate near a critical state, reflecting optimal information processing and high susceptibility to external stimuli. Conversely, deviations from the critical state are hypothesized to give rise to altered states of consciousness (ASC). Measures of criticality could therefore be an effective way of establishing the conscious state of an individual....
Frontiers in Systems Neuroscience
December 1, 2021
Minkyung Kim, Hyoungkyu Kim, Zirui Huang et al.
Continuous switching between internal and external modes in the brain appears important for generating models of the self and the world. However, how the brain transitions between these two modes remains unknown. We propose that a large synchronization fluctuation of brain networks, emerging only near criticality (i.e., a balanced state between order and disorder), spontaneously creates...
Frontiers in Human Neuroscience
March 18, 2021
Emma R. Huels, Hyoungkyu Kim, UnCheol Lee et al.
51 citations
Psychedelics have been recognized as model interventions for studying altered states of consciousness. However, few empirical studies of the shamanic state of consciousness, which is anecdotally similar to the psychedelic state, exist. We investigated the neural correlates of shamanic trance using high-density electroencephalography (EEG) in 24 shamanic practitioners and 24 healthy controls...
Entropy
October 11, 2019
Hyoungkyu Kim, UnCheol Lee
Integrated information theory (IIT) describes consciousness as information integrated across highly differentiated but irreducible constituent parts in a system. However, in a complex dynamic system such as the brain, the optimal conditions for large integrated information systems have not been elucidated. In this study, we hypothesized that network criticality, a balanced state between a large...
Neuroimage
March 1, 2019
Heonsoo Lee, Daniel Golkowski, Denis Jordan et al.
ABSTRACT Recent modeling and empirical studies support the hypothesis that large‐scale brain networks function near a critical state. Similar functional connectivity patterns derived from resting state empirical data and brain network models at criticality provide further support. However, despite the strong implication of a relationship, there has been no principled explanation of how...
PLoS Computational Biology
August 30, 2018
Hyoungkyu Kim, Joon-Young Moon, George A. Mashour et al.
79 citations
Hysteresis, the discrepancy in forward and reverse pathways of state transitions, is observed during changing levels of consciousness. Identifying the underlying mechanism of hysteresis phenomena in the brain will enhance the ability to understand, monitor, and control state transitions related to consciousness. We hypothesized that hysteresis in brain networks shares the same underlying...
Entropy
July 10, 2018
Heonsoo Lee, Zirui Huang, Xiaolin Liu et al.
Theoretical consideration predicts that the alteration of local and shared information in the brain is a key element in the mechanism of anesthetic-induced unconsciousness. Ordinal pattern analysis, such as permutation entropy (PE) and symbolic mutual information (SMI), have been successful in quantifying local and shared information in neurophysiological data; however, they have been rarely...
Frontiers in Human Neuroscience
February 16, 2018
Hyoungkyu Kim, Anthony G. Hudetz, Joseph W Y Lee et al.
The integrated information theory (IIT) proposes a quantitative measure, denoted as Φ, of the amount of integrated information in a physical system, which is postulated to have an identity relationship with consciousness. IIT predicts that the value of Φ estimated from brain activities represents the level of consciousness across phylogeny and functional states. Practical limitations, such as...
PLoS Computational Biology
April 14, 2015
Joon-Young Moon, UnCheol Lee, Stefanie Blain-Moraes et al.
143 citations
The balance of global integration and functional specialization is a critical feature of efficient brain networks, but the relationship of global topology, local node dynamics and information flow across networks has yet to be identified. One critical step in elucidating this relationship is the identification of governing principles underlying the directionality of interactions between nodes....
Anesthesiology
September 7, 2013
Heonsoo Lee, George A. Mashour, Gyu‐jeong Noh et al.
153 citations
INTRODUCTION: General anesthesia induces unconsciousness along with functional changes in brain networks. Considering the essential role of hub structures for efficient information transmission, the authors hypothesized that anesthetics have an effect on the hub structure of functional brain networks. METHODS: Graph theoretical network analysis was carried out to study the network properties of...
Proceedings of the National Academy of Sciences of the United States of America
August 27, 2013
Jimo Borjigin, UnCheol Lee, Tiecheng Liu et al.
The brain is assumed to be hypoactive during cardiac arrest. However, the neurophysiological state of the brain immediately following cardiac arrest has not been systematically investigated. In this study, we performed continuous electroencephalography in rats undergoing experimental cardiac arrest and analyzed changes in power density, coherence, directed connectivity, and cross-frequency...
PLoS One
August 15, 2013
Jeongkyu Shin, George A. Mashour, Seungwoo Ku et al.
16 citations
General anesthesia significantly alters brain network connectivity. Graph-theoretical analysis has been used extensively to study static brain networks but may be limited in the study of rapidly changing brain connectivity during induction of or recovery from general anesthesia. Here we introduce a novel method to study the temporal evolution of network modules in the brain. We recorded...
Anesthesiology
May 22, 2013
UnCheol Lee, Seungwoo Ku, Gyu‐jeong Noh et al.
436 citations
INTRODUCTION: Directional connectivity from anterior to posterior brain regions (or "feedback" connectivity) has been shown to be inhibited by propofol and sevoflurane. In this study the authors tested the hypothesis that ketamine would also inhibit cortical feedback connectivity in frontoparietal networks. METHODS: Surgical patients (n = 30) were recruited for induction of anesthesia with...
Nature Precedings
November 20, 2008
UnCheol Lee, Seunghwan Kim, Gyu‐jeong Noh et al.
33 citations
Abstract The cognitive unbinding paradigm suggests that the synthesis of cognitive information is attenuated by general anesthesia. Here, we investigated the functional organization of brain activities in the conscious and anesthetized states, based on characteristic functional segregation and integration of electroencephalography (EEG). EEG recordings were obtained from 14 subjects undergoing...
Athokpam Langlen Chanu, Youngjai Park, Jaesung Choi et al.
We analyze electroencephalography (EEG) signals using the ordinal pattern framework to investigate whether different human brain states can be distinguished based on the disorder of EEG dynamics. Rather than analyzing raw EEG signals, we focus on the principal mode of EEG phase dynamics, reflecting anterior–posterior information flow, and quantify disorder using permutation entropy. We apply...