NeuroImage
May 1, 2021
Pengmin Qin, Xuehai Wu, Changwei Wu et al.
51 citations
Consciousness depends on a network of brain regions that integrate sensory and motor information. Analyzing fMRI data from people in preserved (awake, fully conscious brain-injury survivors), reduced (N1-sleep, minimally conscious), and lost (N3-sleep, anesthesia, unresponsive wakefulness) states, plus a unique rapid-eye-movement (REM) sleep group, researchers identified key hubs whose degree centrality—a measure of network importance—dropped significantly when consciousness was reduced or absent. These hubs included the supplementary motor area, bilateral supramarginal gyrus, supragenual/dorsal anterior cingulate cortex, and left middle temporal gyrus. A higher-order sensorimotor circuit connecting these regions showed functional connectivity that correlated with consciousness levels across groups and remained active in REM sleep, suggesting this circuit supports consciousness and offers new targets for treating disorders of consciousness.
NeuroImage
June 1, 2023
Rui Dai, Tony E Larkin, Zirui Huang et al.
49 citations
Three different psychedelics—nitrous oxide, ketamine, and lysergic acid diethylamide—produce a common pattern of brain network changes despite having distinct molecular mechanisms and delivery methods. Each drug reduced connectivity within brain networks and enhanced connectivity between networks. Specifically, all three increased connections between the right temporoparietal junction and bilateral intraparietal sulcus, and between the precuneus and left intraparietal sulcus. These regions lie within the posterior cortical "hot zone," an area thought to mediate the qualitative aspects of experience. The findings identify a biologically plausible candidate for the subjective effects of both classical and non-classical psychedelics.
bioRxiv : the preprint server for biology
October 23, 2024
Rui Dai, Hyunwoo Jang, Anthony G Hudetz et al.
1 citation
preprint
Consciousness appears to depend on global interactions across multiple brain regions rather than on localized neural activity. Using fMRI data across psychedelic, sleep, and deep sedation states, the study found a mirror-image pattern: psychedelic states increased global functional connectivity and decreased local neural synchrony, while non-REM sleep and deep sedation showed the opposite pattern. This pattern was observed in anterior-posterior and posterior-posterior brain regions but not within the anterior brain alone. Anterior transmodal regions were key for anterior-posterior connectivity, while posterior transmodal and unimodal regions were critical for posterior-posterior connectivity. The findings support global theories of consciousness and bridge the Global Neuronal Workspace hypothesis and Integrated Information Theory by showing shared neural mechanisms.
bioRxiv : the preprint server for biology
June 1, 2026
Panagiotis Fotiadis, Hyunwoo Jang, Rui Dai et al.
Brain waves coordinate neural communication and shape conscious perception. Analyzing blood oxygen level-dependent activity from the Human Connectome Project and other datasets across sleep, propofol anesthesia, and psychedelic states (LSD, DMT, psilocybin, nitrous oxide, ketamine), four dominant wave propagation motifs were identified: a global synchronized wave, an anti-correlated unimodal-transmodal wave, an anti-correlated task-positive/task-negative wave, and an anti-correlated visual-somatomotor wave.
Cambridge quarterly of healthcare ethics : CQ : the international journal of healthcare ethics committees
January 3, 2025
Matthew Owen, Darren Hight, Anthony G Hudetz
Some brain-injured patients who appear unresponsive can covertly answer simple questions through neuronal responses, raising the possibility of including them in low-stakes medical decisions to protect their autonomy. The warrant for crediting these neuronal responses is analyzed from neurology, bioethics, law, and philosophy of mind. Nonreductive physicalism's causal exclusion problem casts doubt on interpreting neural activity as indicating a conscious response, while a hylomorphism-inspired mind-body powers model supports such interpretation.
Nature communications
October 24, 2024
Hyunwoo Jang, George A Mashour, Anthony G Hudetz et al.
A metric called the integration-segregation difference (ISD), derived from fMRI data, captures two key brain network properties: efficiency (integration) and clustering (segregation). During anesthesia with propofol, brain networks shift profoundly toward segregation as consciousness is lost. A common sequence of disintegration and reintegration occurs in unimodal and transmodal networks during loss and return of responsiveness. Machine learning models using these measures accurately identify awake versus unresponsive states. Metastability is more closely linked to integration, while complexity is linked to segregation. Similar patterns appear in sleep. The ISD reliably indexes states of consciousness.
Brain sciences
August 30, 2024
Hyunwoo Jang, Rui Dai, George A Mashour et al.
A machine learning model that combines functional connectivity, graph-theoretic metrics, and cortical gradient features can classify brain states—including unconsciousness (NREM2 sleep, propofol sedation and anesthesia), psychedelic states (ketamine, LSD, nitrous oxide), and neuropsychiatric disorders (ADHD, bipolar disorder, schizophrenia)—with an average balanced accuracy of 79% (range 62–98%). The ensemble model outperformed individual feature-based models (70–76%). Transferability across datasets varied, and feature importance analysis indicated that different brain states rely on distinct neural mechanisms, suggesting that tailored approaches are needed for accurate classification. The findings highlight the value of integrating multiple feature types for robust brain-state classification, though further work is needed for broader generalizability.
Frontiers in neuroscience
January 1, 2024
Anthony G Hudetz
Intracortical microstimulation in rat visual cortex reveals that anesthesia dramatically reduces the density and complexity of effective connectivity among neurons compared to wakefulness. Stimulation caused an early increase in spiking followed by a prolonged decrease. Excitatory neurons' early responses decayed rapidly with distance under all conditions. Network motifs, especially higher-order ones, increased substantially as anesthesia was withdrawn, indicating a large increase in network connectivity as animals woke up. The findings illuminate how anesthesia impacts the functional integrity of local cortical circuits, affecting the state of consciousness.
Frontiers in Psychology
September 16, 2014
Talis eBachmann, Anthony G Hudetz
Consciousness arises from the interaction of two distinct brain mechanisms: one that represents the specific contents of perception and cognition (the data) and another that regulates the level of activity of those contents. Neither mechanism alone is sufficient; without specific contents there is no conscious experience, and without sufficient activity those contents remain unconscious. When both are activated to the necessary degree, they jointly provide conditions sufficient for conscious experience to emerge. This theoretical integration combines two previously separate research traditions—one studying the contents of conscious experience and the other studying the level of consciousness—and emphasizes understanding the mechanisms of consciousness rather than mere correlates.
Rui Dai, Hyunwoo Jang, Anthony G Hudetz et al.
Across altered states of consciousness, psychedelics and sedatives produce opposite patterns of brain network organization. Psychedelics increase large-scale integration and reduce segregation of brain network interactions, while sleep and propofol sedation show the opposite pattern. These opposing integration-segregation patterns were consistently observed across multiple measures of functional connectivity, network topology, and interaction complexity, and reliably differentiated conscious states in an unbiased, data-driven manner. The findings demonstrate that psychedelic and sedated states are characterized by systematic and opposing shifts in large-scale brain organization.