Emergent Multiscale Organisation of Neural Dynamics Fragments in Anaesthesia

Brain dynamics exhibit scale-dependent reversibility during consciousness transitions

Hyper-Hierarchical Brain States Are Associated with Disorders of Consciousness

Background Consciousness is increasingly understood as an emergent property of large-scale brain dynamics that depend upon flexible interactions among distributed cortical and subcortical systems. Although disorders of consciousness (DOC) have traditionally been associated with impaired integration and reduced network complexity, the role of hierarchical brain organization in supporting conscious awareness remains poorly understood. Here, we investigated how hierarchical organization relates to behavioral responsiveness in DOC by combining trophic-level analysis, trophic coherence, and whole-brain dynamical metrics. Methods Resting-state functional MRI data were analyzed from healthy controls (CNT), minimally conscious state (MCS) patients, and unresponsive wakefulness syndrome (UWS) patients drawn from a previously published DOC cohort. Static global and regional measures of functional hierarchy were computed from directed effective-connectivity networks. Dynamic trophic states were identified using time-resolved phase-coupling analyses and clustering of recurrent coordination patterns. State occupancy, dwell time, metastability, synchrony, and behavioral associations with Coma Recovery Scale–Revised (CRS-R) scores were evaluated. Results Regional trophic levels were positively associated with behavioral responsiveness, with higher frontal and thalamic trophic levels and lower insular trophic levels predicting higher Coma Recovery Scale–Revised (CRS-R) scores. Dynamic trophic-state analysis identified a pathological hyper-hierarchical state, defined by elevated frontal, thalamic, and insular trophic levels, that exhibited progressively greater occupancy and longer dwell times from healthy controls to minimally conscious state and unresponsive wakefulness syndrome patients. In contrast, occupancy and dwell time of this state distinguished diagnostic groups but were not significantly associated with behavioral responsiveness. Independent analyses demonstrated significant reductions in metastability and global synchrony across disorders of consciousness. Anatomical mapping localized elevated trophic levels within the pathological state predominantly to fronto-thalamo-limbic systems. Conclusions Disorders of consciousness are characterized not simply by loss of hierarchical organization but by prolonged stabilization within recurrent hyper-hierarchical brain states. Conscious awareness appears to depend not only on hierarchical organization itself but also on the capacity to flexibly transition between distinct brain states. Severe disorders of consciousness are associated with persistent occupation of pathological hyper-hierarchical states, potentially restricting the dynamical repertoire available for conscious processing.

Identifying and investigating emergent behaviour in neural systems

This manuscript distil theoretical approaches to emergence into a practical framework for assessing system behaviour focussed on “novelty” as a necessary condition for emergence and identifies a range of ways in which novelty can arise.

Thermodynamics of consciousness: Non-equilibrium brain dynamics track conscious states

Summary The quest for reliable and objective measures of consciousness is critical in basic and clinical neuroscience. Across species, the perturbational complexity index (PCI) has emerged as a robust empirical marker by directly perturbing the brain, yet its relationship to broader physical principles remains unclear. Here, we address this gap by introducing a non-invasive framework based on generative whole-brain models of non-equilibrium brain dynamics. Using these models, we identify violations of the fluctuation-dissipation theorem (FDT) in humans and rodents across wakefulness, anesthesia, and disorders of consciousness (DoC). Mirroring PCI, FDT violations decrease in unresponsive DoC and anesthesia compared with conscious conditions. These findings reveal a robust empirical link between PCI and non-equilibrium dynamics in spontaneous brain signals, suggesting that non-equilibrium dynamics capture an important aspect of perturbational complexity. Overall, this framework opens non-invasive, model-based avenues for understanding consciousness and supports efforts to assess its loss and recovery in health and disease.

Human cortex organizes dynamic co-fluctuations along the sensorimotor-association axis

Human functional brain networks, originating from coherent fluctuations in brain activity, are organized along a hierarchical axis. However, how this stable hierarchical architecture emerges from time-varying co-fluctuations remains unknown. Existing dynamic analyses have primarily focused on high-amplitude co-fluctuations, largely overlooking the contribution of lower-amplitude activity. Here, we investigated the amplitude-dependent configurations of regional co-fluctuation. We found that these patterns were hierarchically aligned with the sensorimotor-association (SA) axis: sensorimotor networks are preferentially expressed during high-amplitude co-fluctuations, associative systems prevailed during intermediate amplitudes, and limbic system preferentially engaged in low-amplitude states. This amplitude-stratified hierarchy underwent developmental refinement from childhood to adulthood and adaptively reconfigured under naturalistic stimuli. Replicated across four independent datasets including 7 T fMRI, these findings uncover a fundamental principle whereby the brain’s hierarchical architecture is actively preserved through a structured, amplitude-dependent cascade of functional co-fluctuations. Our framework bridges dynamic coordination and stable architecture, demonstrating how the brain balances external processing with internal cognition through amplitude-stratified interactions. This study reveals that amplitude-stratified co-fluctuations in brain activity transit from sensorimotor to association dominance. These patterns matured between childhood to adulthood and reconfigured under naturalistic stimuli, linking dynamic activity to stable network organization.

Cellular and Microcircuit Mechanisms of Anesthetic Disruption of Conscious-State Organization

Highlights What are the main findings? Anesthesia usually disrupts neural coordination without globally silencing the brain. Local firing and sensory responses may persist even when dendritic integration, recurrent processing, cortical feedback, and thalamocortical communication are impaired. Propofol and volatile agents mainly restrict distributed processing. Ketamine reorganizes neural activity in a manner that changes with dose and may permit substantial activity and internally generated experience to persist. What are the implications of the main findings? Lack of behavioral response or postoperative recall cannot directly establish the absence of conscious experience, because responsiveness, connectedness, memory, reportability, and conscious content can become dissociated. Assessment of anesthetic states should be adapted to each agent and integrate cellular and circuit mechanisms with thalamocortical dynamics, glial regulation, memory function, and activity across the brain. Abstract The reversible effects of general anesthesia can be used to examine how brain activity changes during transitions into and out of altered conscious states. Such changes are commonly tracked using behavioral responses, electroencephalographic recordings, and measures of functional connectivity. These measures, however, reflect processes occurring at lower levels of organization, including the activity of pyramidal neurons, dendritic integration, interneuron function, thalamocortical signaling, and glial regulation of the extracellular environment. Anesthesia does not affect all neural processes equally. Propofol and volatile agents interfere with synaptic transmission and apical dendritic integration, as well as cortical feedback and thalamocortical signaling. The resulting activity is not necessarily absent or uniformly weaker. It is often more stereotyped, temporally restricted, and poorly coordinated between regions. Ketamine produces a different organization. Substantial neural activity and complex cortical responses may persist after behavioral responsiveness has been lost, although deeper anesthesia also produces slower and less complex activity. Responsiveness, environmental connectedness, memory, reportability, and conscious content may therefore become partly uncoupled. Ketamine produces a dissociative state that cannot be interpreted simply as another form of the predominantly restrictive state produced by propofol or volatile anesthetics. This narrative review synthesizes evidence identified through a structured PubMed search to examine how anesthesia reshapes conscious processing and why unresponsiveness or absent recall may not indicate absent experience.