Theories of consciousness

Bridging the gap of brain and experience - Converging Neurophenomenology with Spatiotemporal Neuroscience

Neuroscience faces the challenge of connecting brain and mind, with the mind manifesting in first-person experience while the brain's neural activity can only be investigated in third-person perspective. To connect neural and mental states, Neurophenomenology provides a methodological toolkit for systematically linking first-person subjective experience with third-person objective observations of the brain's neural activity. However, beyond providing a systematic methodological strategy ('disciplined circularity'), it leaves open how neural activity and subjective experience are related among themselves, independent of our methodological strategy. The recently introduced Spatiotemporal Neuroscience suggests that neural activity and subjective experience share a commonly underlying feature as their "common currency", notably analogous spatiotemporal dynamics. Can Spatiotemporal Neuroscience inform Neurophenomenology to allow for a deeper and more substantiative connection of first-person experience and third-person neural activity? The goal of our paper is to show how Spatiotemporal Neuroscience and Neurophenomenology can be converged and integrated with each other to gain better understanding of the brain-mind connection. We describe their convergence on theoretical grounds which, subsequently, is illustrated by empirical examples like self, meditation, and depression. In conclusion, we propose that the integration of Neurophenomenology and Spatiotemporal Neuroscience can provide complementary insights, enrich both fields, allows for deeper understanding of brain-mind connection, and opens the door for developing novel methodological approaches in their empirical investigation.

Large-scale functional networks underlying visual attention

Attention networks are loosely defined as the regions of the brain which interact to control behaviour during attentional tasks, but the specific definition of attention networks varies between research programs based on task demands and modalities. The Attention Network Task was designed to exemplify three aspects of attention, alerting, orienting, and executive control, using a visual cueing paradigm. Its proponents propose a system of networks which underlies these aspects. It is debated whether there exists a unified system of networks which underlies attention independently of other cognitive and sensory processing systems. We review the evidence for an attention system within the domain of visual attention. Neuroimaging research using fMRI, EEG, MEG, and others across a variety of tasks attributed to attention, visual cueing, visual search, and divided attention, is compared. This concludes with a discussion on the limitations of an independent "attention system" for describing how the brain flexibly controls many abilities attributed to visual attention.

Quantum information as the scientific basis for the explanation of human consciousness and its evolution

A scientific explanation of consciousness and its evolution has become possible by a generalized quantum information concept. Crucial to this is a new understanding of matter and energy. Our consciousness, being an information structure, processes the information that we absorb from our bodies and our environment. This information reaches us as properties of material objects and the massless quanta of light, the photons. One of the properties of matter is motion - physically, kinetic energy. Einstein's E = mc2 shows that motion can be converted into matter. Matter is thus equivalent to one of its properties. The mathematical-physical structure of quantum theory has opened up a comprehensive view of the construction of complex systems from simple structures. Such a construction can and should begin with the simplest quantum structure, a quantum bit. Matter and also photons can thereby ultimately be understood as manifestations of abstract quantum information. Abstract, i.e. still meaning-free, and absolute, i.e. cosmically based, bits of quantum information, AQIs, provide the common basis for consciousness, energy and matter. This explains the mutual influences between matter, energy and the information that is meaningful for a living being.

Subcortical correlates of consciousness with human single neuron recordings

Subcortical brain structures such as the subthalamic nucleus or the thalamus are involved in regulating motor and cognitive behavior. However, their contribution to perceptual consciousness remains unclear, due to the inherent difficulties of recording subcortical neuronal activity in humans. Here, we asked neurological patients undergoing surgery for deep brain stimulation to detect weak vibrotactile stimuli applied on their hand while recording single neuron activity from the tip of a microelectrode. We isolated putative single neurons in the subthalamic nucleus and thalamus. A significant proportion of neurons modulated their activity while participants were expecting a stimulus. We found that the firing rate of 23% of these neurons differed between detected and undetected stimuli. Our results provide direct neurophysiological evidence of the involvement of the subthalamic nucleus and the thalamus for the detection of vibrotactile stimuli, thereby calling for a less cortico-centric view of the neural correlates of consciousness.

The Administration of Ketamine Is Associated with Dose-Dependent Stabilization of Cortical Dynamics in Humans

During wakefulness, external stimuli elicit conscious experiences. In contrast, dreams and drug-induced dissociated states are characterized by vivid internally generated conscious experiences and reduced ability to perceive external stimuli. Understanding the physiological distinctions between normal wakefulness and dissociated states may therefore disambiguate signatures of responsiveness to external stimuli from those that underlie conscious experience. The hypothesis that conscious experiences are associated with brain criticality has received considerable theoretical and experimental support. Consistent with this hypothesis, statistical signatures of criticality are similar in normal wakefulness and dissociative states but are abolished in dreamless sleep and under anesthesia. Thus, while statistical measures of criticality are associated with the ability to have conscious experience, they do not readily distinguish between perception of the external world from internally generated percepts. Here, we investigate distinct, dynamical, signatures of criticality during escalating ketamine doses in high-density EEG in human male volunteers. We show that during normal wakefulness, EEG is found at a critical point between damped and exploding oscillations. With increasing doses of ketamine, as dissociative symptoms intensify, activity is progressively stabilized-most prominently at higher frequencies. We also show that stabilization is a more reliable marker of the effects of ketamine than conventional measures such as power spectra. These findings suggest that stabilization of cortical dynamics correlates with decreased ability to respond to and perceive external stimuli rather than the ability to have conscious experiences per se. Altogether, these results suggest that combining statistical and dynamical criticality measures may distinguish wakefulness, dissociation, and unconsciousness.

Cognitive control and consciousness in open biological systems

Thermodynamically open biological systems not only sustain a life-supporting mutual relationship with their environment by exchanging matter and energy but also constantly seek information to navigate probabilistic changes in their surroundings. This work argues that cognition and conscious thought should not be viewed in isolation but rather as parts of an integral control of biological systems to identify and act upon meaningful, semantic information to sustain viability. Under this framework, the development of key cognitive control capacities in centralized nervous systems and the resulting behavior are categorized into distinct Markov decision processes: decision-making with partially observable sensory exteroceptive and interoceptive information, learning and memory, and symbolic communication. It is proposed that the state of conscious thought arises from a control mechanism for speech production resembling actuator control in engineered systems. Also known as the phonological loop, this feedback from the motor to the sensory cortex provides a third type of information flowing into the sensory cortex. The continuous, dissipative loop updates the fleeting working memory and provides humans with an advanced layer of control through a sense of self, agency and perception of flow in time. These capacities define distinct degrees of information fitness in the evolution of information-powered organisms.

The Awakening of the Newborn Human Infant and the Emergence of Consciousness

Consciousness develops gradually in the womb and after birth, rather than being an all or none phenomenon. A newborn infant is aroused and wakes up at birth, due to the enormous sensory stimulation and stress that it undergoes during the transition from an aquatic environment to air. Its first breaths activate the locus coeruleus, as indicated by the large pupils of the newborn. The infant seems to be aware of its body and can recognise its mother's facial expressions, voice and smell. A default mode network matures soon after birth which appears to keep the brain in a conscious state. Thus the newborn infant is probably conscious, albeit at a low level. The foetus also shows some signs of being conscious after about 24 weeks of gestation, although it is mainly asleep in the womb and less aware of its environment. Before that stage, the nerves from the primary somatosensory, visual and auditory areas are not yet connected with the site of consciousness in the cerebral cortex.

The changes in neural complexity and connectivity in thalamocortical and cortico-cortical systems after propofol-induced unconsciousness in different temporal scales

Existing studies have indicated neural activity across diverse temporal and spatial scales. However, the alterations in complexity, functional connectivity, and directional connectivity within the thalamocortical and corticocortical systems across various scales during propofol-induced unconsciousness remain uncertain. We analyzed the stereo-electroencephalography (SEEG) from wakefulness to unconsciousness among the brain regions of the prefrontal cortex, temporal lobe, and anterior nucleus of the thalamus. The complexity (examined by permutation entropy (PE)), functional connectivity (permutation mutual information (PMI)), and directional connectivity (symbolic conditional mutual information (SCMI) and directionality index (DI)) were calculated across various scales. In the lower-band frequency (0.1-45 Hz) SEEG, after the loss of consciousness, PE significantly decreased (p < 0.001) in all regions and scales, except for the thalamus, which remained relatively unchanged at large scales (τ=32 ms). Following the loss of consciousness, inter-regional PMI either significantly increased or remained stable across different scales (τ=4 ms to 32 ms). During the unconscious state, SCMI between brain regions exhibited inconsistent changes across scales. In the late unconscious stage, the inter-regional DI across all scales indicated a shift from a balanced state of information flow between brain regions to a pattern where the prefrontal cortex and thalamus drive the temporal lobe. Our findings demonstrate that propofol-induced unconsciousness is associated with reduced cortical complexity, diverse functional connectivity, and a disrupted balance of information integration among thalamocortical and cortico-cortical systems. This study enhances the theoretical understanding of anesthetic-induced loss of consciousness by elucidating the scale- and region-specific effects of propofol on thalamocortical and cortico-cortical systems.

The Mind-Matter Dichotomy: A Persistent Challenge for Neuroscientific and Philosophical Theories

Several areas of cognitive neuroscience tackle traditional philosophical questions. Among the range of problems, two closely related issues will be addressed in more detail from both neurobiological and philosophical perspectives: the relationship between mind and matter and the nature of perception. Neuropsychological and neurophysiological studies are reviewed that examine the connection between neuronal processes and consciousness. The most prominent theories on the neuronal correlates of consciousness (NCC) are then compared with philosophical attempts to address the epistemic gap between the material processes in the brain and mental phenomena. Before exploring whether neurobiological discoveries can help resolve philosophical problems, the epistemic challenges are discussed, stemming from the fact that perceptions are shaped by the brain's functional architecture. It is suggested that the 'hard problem of consciousness'-the challenge of explaining how the qualia of subjective experience can arise from neuronal processes-can be alleviated if two conditions are met: first, that perception depends on priors and, second, that some of these priors are formed through interactions with the immaterial realities of cultural concepts. Although this approach offers a coherent naturalistic explanation for the emergence of mental phenomena, it does not resolve the cognitive dissonance between our intuitions and scientific evidence regarding the relationship between matter and mind.

Adversarial testing of global neuronal workspace and integrated information theories of consciousness

Different theories explain how subjective experience arises from brain activity1,2. These theories have independently accrued evidence, but have not been directly compared3. Here we present an open science adversarial collaboration directly juxtaposing integrated information theory (IIT)4,5 and global neuronal workspace theory (GNWT)6-10 via a theory-neutral consortium11-13. The theory proponents and the consortium developed and preregistered the experimental design, divergent predictions, expected outcomes and interpretation thereof12. Human participants (n = 256) viewed suprathreshold stimuli for variable durations while neural activity was measured with functional magnetic resonance imaging, magnetoencephalography and intracranial electroencephalography. We found information about conscious content in visual, ventrotemporal and inferior frontal cortex, with sustained responses in occipital and lateral temporal cortex reflecting stimulus duration, and content-specific synchronization between frontal and early visual areas. These results align with some predictions of IIT and GNWT, while substantially challenging key tenets of both theories. For IIT, a lack of sustained synchronization within the posterior cortex contradicts the claim that network connectivity specifies consciousness. GNWT is challenged by the general lack of ignition at stimulus offset and limited representation of certain conscious dimensions in the prefrontal cortex. These challenges extend to other theories of consciousness that share some of the predictions tested here14-17. Beyond challenging the theories, we present an alternative approach to advance cognitive neuroscience through principled, theory-driven, collaborative research and highlight the need for a quantitative framework for systematic theory testing and building.

Classification Schemes of Altered States of Consciousness

In recent years, there has been a renewed interest in the conceptual and empirical study of altered states of consciousness (ASCs) induced pharmacologically or otherwise, driven by their potential clinical applications. To draw attention to the rich history of research in this domain, we review prominent classification schemes that have been proposed to introduce systematicity in the scientific study of ASCs. The reviewed ASC classification schemes fall into three groups according to the criteria they use for categorization: (1) based on the nature, variety, and intensity of subjective experiences (state-based), including conceptual descriptions and psychometric assessments, (2) based on the technique of induction (method-based), and (3) descriptions of neurophysiological mechanisms of ASCs (neuro/physio-based). By comparing and extending existing classification schemes, we can enhance efforts to identify neural correlates of consciousness, particularly when examining mechanisms of ASC induction and the resulting subjective experience. Furthermore, an overview of what defining ASC characteristics different authors have proposed can inform future research in the conceptualization and quantification of ASC subjective effects, including the identification of those that might be relevant in clinical research. This review concludes by clustering the concepts from the state-based schemes, which are suggested for classifying ASC experiences. The resulting clusters can inspire future approaches to formulate and quantify the core phenomenology of ASC experiences to assist in basic and clinical research.

The evolution of human-type consciousness - a by-product of mammalian innovation mechanism - a preliminary hypothesis

Human consciousness is often viewed as one of the pinnacles of evolution, with most theories positioning it as an upgrade of pre-existing cognitive skills. However, conscious perception, memory, action, and in some situations even decision-making, are often inferior-less complex, slower, and less accurate-than their nonconscious (subliminal) counterparts. The interface hypothesis challenges this perspective, proposing that human-type consciousness is not an advanced version of earlier cognitive capacities but a novel function that entered the arena of cognitive and operational processes and fundamentally changed its rules. According to this hypothesis, the neocortex emerged as part of an advanced innovation mechanism, where its unpredictable, chaotic activity is used to generate alternative patterns. The process of cropping these alternatives from the chaotic neocortex and mediating them to the constrained, goal-oriented, linear control system requires a serially functioning interface. Consciousness, it is suggested, arose as a byproduct or a side effect of this interface, eventually expanding its influence to a wide range of cognitive and operational functions. This perspective has significant implications for our understanding of human cognition, creativity, and the distinctive capacities of human consciousness, potentially bridging the gap between neuroscientific findings and phenomenological experiences of consciousness.

Event-related potential correlates of consciousness in simple auditory hallucinations

Neural correlates of consciousness (NCC) have been proposed for perceptual awareness in various sensory modalities. To date, perceptual awareness negativity (PAN) and late positivity (LP) are considered the main NCC candidates, and the question remains which one is the NCC proper. Investigating states where the content of consciousness is independent of the physical stimulus, may provide additional theoretical and empirical value. We studied the event-related potential (ERP) markers of auditory awareness in simple auditory hallucinations using a Pavlovian conditioning paradigm, where participants listened to the near-threshold tones and stimulus-absent trials, rating subjective clarity with the perceptual awareness scale (PAS). The results showed auditory awareness negativity (AAN) - an early event-related potential difference between aware and unaware stimuli - in the hallucinatory condition, suggesting that AAN is an NCC proper in auditory consciousness. Late positivity was absent in simple auditory hallucinations.

Human high-order thalamic nuclei gate conscious perception through the thalamofrontal loop

Human high-order thalamic nuclei activity is known to closely correlate with conscious states. However, it is not clear how those thalamic nuclei and thalamocortical interactions directly contribute to the transient process of human conscious perception. We simultaneously recorded stereoelectroencephalography data from the thalamic nuclei and prefrontal cortex (PFC), while patients with implanted electrodes performed a visual consciousness task. Compared with the ventral nuclei and PFC, the intralaminar and medial nuclei presented earlier and stronger consciousness-related activity. Transient thalamofrontal neural synchrony and cross-frequency coupling were both driven by the θ phase of the intralaminar and medial nuclei during conscious perception. The intralaminar and medial thalamic nuclei thus play a gate role to drive the activity of the PFC during the emergence of conscious perception.

Quantum-like Qualia hypothesis: from quantum cognition to quantum perception

To arbitrate theories of consciousness, scientists need to understand mathematical structures of quality of consciousness, or qualia. The dominant view regards qualia as points in a dimensional space. This view implicitly assumes that qualia can be measured without any effect on them. This contrasts with intuitions and empirical findings to show that by means of internal attention qualia can change when they are measured. What is a proper mathematical structure for entities that are affected by the act of measurement? Here we propose the mathematical structure used in quantum theory, in which we consider qualia as "observables" (i.e., entities that can, in principle, be observed), sensory inputs and internal attention as "states" that specify the context that a measurement takes place, and "measurement outcomes" with probabilities that qualia observables take particular values. Based on this mathematical structure, the Quantum-like Qualia (QQ) hypothesis proposes that qualia observables interact with the world, as if through an interface of sensory inputs and internal attention. We argue that this qualia-interface-world scheme has the same mathematical structure as observables-states-environment in quantum theory. Moreover, within this structure, the concept of a "measurement instrument" in quantum theory can precisely model how measurements affect qualia observables and states. We argue that QQ naturally explains known properties of qualia and predicts that qualia are sometimes indeterminate. Such predictions can be empirically determined by the presence of order effects or violations of Bell inequalities. Confirmation of such predictions substantiates our overarching claim that the mathematical structure of QQ will offer novel insights into the nature of consciousness.

Chaotic recurrent neural networks for brain modelling: A review

Even in the absence of external stimuli, the brain is spontaneously active. Indeed, most cortical activity is internally generated by recurrence. Both theoretical and experimental studies suggest that chaotic dynamics characterize this spontaneous activity. While the precise function of brain chaotic activity is still puzzling, we know that chaos confers many advantages. From a computational perspective, chaos enhances the complexity of network dynamics. From a behavioural point of view, chaotic activity could generate the variability required for exploration. Furthermore, information storage and transfer are maximized at the critical border between order and chaos. Despite these benefits, many computational brain models avoid incorporating spontaneous chaotic activity due to the challenges it poses for learning algorithms. In recent years, however, multiple approaches have been proposed to overcome this limitation. As a result, many different algorithms have been developed, initially within the reservoir computing paradigm. Over time, the field has evolved to increase the biological plausibility and performance of the algorithms, sometimes going beyond the reservoir computing framework. In this review article, we examine the computational benefits of chaos and the unique properties of chaotic recurrent neural networks, with a particular focus on those typically utilized in reservoir computing. We also provide a detailed analysis of the algorithms designed to train chaotic RNNs, tracing their historical evolution and highlighting key milestones in their development. Finally, we explore the applications and limitations of chaotic RNNs for brain modelling, consider their potential broader impacts beyond neuroscience, and outline promising directions for future research.

A neuroscientific model of near-death experiences

Near-death experiences (NDEs) are episodes of disconnected consciousness that typically occur in situations that involve an actual or potential physical threat or are perceived as such, and the experiences are characterized by a rich content with prototypical mystical features. Several explanatory theories for NDEs have been proposed, ranging from psychological or neurophysiological to evolutionary models. However, these concepts were often formulated independently, and, owing to the fragmented nature of research in this domain, integration of these ideas has been limited. Lines of empirical evidence from different areas of neuroscience, including non-human studies, studies investigating psychedelic-induced mystical experiences in humans, and research on the dying brain, are now converging to provide a comprehensive explanation for NDEs. In this Review, we discuss processes that might underlie the rich conscious experience in NDEs, mostly focusing on prototypical examples and addressing both the potential psychological mechanisms and neurophysiological changes, including cellular and electrophysiological brain network modifications and alterations in neurotransmitter release. On the basis of this discussion, we propose a model for NDEs that encompasses a cascade of concomitant psychological and neurophysiological processes within an evolutionary framework. We also consider how NDE research can inform the debate on the emergence of consciousness in near-death conditions that arise before brain death.

Where is my mind? A neurocognitive investigation of mind blanking

During wakefulness, our thoughts transition between different contents. However, there are moments that are seemingly devoid of reportable content, referred to as mind blanking (MB). It remains unclear what these blanks represent, highlighting the definitional and phenomenological ambiguities surrounding MB. We map out MB in terms of its reportable expressions, neurophysiology, and relationship to adjacent phenomenology, including meditative practices and sleep. We propose a mechanistic account linking MB to changes at the physiological, neural, and cognitive levels. We suggest that ongoing experiences are characterized by degrees of richness, and that contentless events represent distinct mental states with their own diversity. We encourage future research to acknowledge MB as a reportable mental category, leading to a comprehensive understanding of ongoing experience.

Predictive value of resting-state fMRI graph measures in hypoxic encephalopathy after cardiac arrest

INTRODUCTION

Current multimodal prediction models can determine the prognosis of about half of comatose cardiac arrest patients. We investigated whether whole-brain graph-theoretical measures from early resting-state functional magnetic resonance imaging (fMRI) three days after cardiac arrest discriminate between good and poor outcome and improve outcome prediction.

METHODS

We conducted a prospective cohort study on comatose cardiac arrest patients on intensive care units. Resting-state fMRI three days after cardiac arrest was used to quantify whole-brain functional connectivity, global efficiency, clustering coefficient, and modularity. Neurological outcome at six months was classified as good or poor (Cerebral Performance Category 1-2 vs 3-5). Logistic regression models were used to examine between-group differences and study the additional value of graph-theoretical measures to clinical and EEG-based prediction.

RESULTS

In seventy included patients (good outcome n = 44, poor n = 26), whole-brain functional connectivity and clustering coefficient (but not global efficiency and modularity) were significantly lower in patients with poor outcome. Connectivity of nodes in posterior brain areas most prominently correlated with outcome. Clustering coefficient showed strong correlation with whole-brain functional connectivity. Patients with continuous EEG patterns differed in whole-brain functional connectivity levels from those with suppressed or epileptiform patterns. Combining functional connectivity or graph measures with clinical and EEG-based predictors slightly improved outcome prediction.

CONCLUSION

fMRI-based whole-brain functional connectivity is a sensitive measure for encephalopathy severity after cardiac arrest, according to relations with established EEG categories and discrimination between good and poor outcome. Additional predictive values for outcome seem small. Graph measures do not provide complementary information.

Thalamocortical interactions reflecting the intensity of flicker light-induced visual hallucinatory phenomena

Aberrant thalamocortical connectivity occurs together with visual hallucinations in various pathologies and drug-induced states, highlighting the need to better understand how thalamocortical interactions may contribute to hallucinatory phenomena. Flicker light stimulation (FLS) at 10-Hz reliably and selectively induces transient visual hallucinations in healthy participants. Arrhythmic flicker elicits fewer hallucinatory effects while delivering equal amounts of visual stimulation, together facilitating a well-controlled experimental setup to investigate the neural correlates of visual hallucinations driven by flicker rhythmicity. Using rhythmic and arrhythmic FLS during fMRI scanning, we found that rhythmic FLS elicited stronger activation in higher order visual cortices compared with arrhythmic control. Consistently, we found that rhythmic flicker selectively increased connectivity between ventroanterior thalamic nuclei and higher order visual cortices, which was also positively associated with the subjective intensity of visual hallucinatory effects. As these thalamic and cortical areas do not receive primary visual inputs, it suggests that the thalamocortical connectivity changes relate to a higher order function of the thalamus, such as in the coordination of cortical activity. In sum, we present novel evidence for the role of specific thalamocortical interactions with ventroanterior nuclei within visual hallucinatory experiences. Importantly, this can inform future clinical research into the mechanistic underpinnings of pathologic hallucinations.

Connecting brain and mind through temporo-spatial dynamics: Towards a theory of common currency

Despite major progress in our understanding of the brain, the connection of neural and mental features, that is, brain and mind, remains yet elusive. In our 2020 target paper ("Is temporospatial dynamics the 'common currency' of brain and mind? Spatiotemporal Neuroscience") we proposed the "Common currency hypothesis": temporo-spatial dynamics are shared by neural and mental features, providing their connection. The current paper aims to further support and extend the original description of such common currency into a first outline of a "Common currency theory" (CCT) of neuro-mental relationship. First, we extend the range of examples to thoughts, meditation, depression and attention all lending support that temporal characteristics, (i.e. dynamics) are shared by both neural and mental features. Second, we now also show empirical examples of how spatial characteristics, i.e., topography, are shared by neural and mental features; this is illustrated by topographic reorganization of both neural and mental states in depression and meditation. Third, considering the neuro-mental connection in theoretical terms, we specify their relationship by distinct forms of temporospatial correspondences, ranging on a continuum from simple to complex. In conclusion, we extend our initial hypothesis about the key role of temporo-spatial dynamics in neuro-mental relationship into a first outline of an integrated mind-brain theory, the "Common currency theory" (CCT).

Individual differences in prioritization for consciousness and the conscious detection of changes

A recent discovery documented robust and reliable individual differences in how quickly people become aware of non-conscious visual stimuli (Sklar, Goldstein, et al., 2021). Given the seemingly large role that conscious experiences play in our lives, this trait is likely to be associated with later cognitive, emotional, and motivational processes. Here we examine the possible implications of this trait to perceptual conscious experiences. In two experiments we demonstrate that the speed of prioritization to awareness is correlated with the ability to notice changes in a change blindness paradigm. The first experiment (N = 97) found a correlation between prioritization speed and multiple parameters of change blindness performance. The second, preregistered, replication experiment (N = 99), further demonstrated that variability in other perceptual-decision making tasks cannot account for this correlation. The results of both experiments suggest that prioritization speed is tightly related with conscious experiences in other situations.

The neural activity of auditory conscious perception

Although recent work has made headway in understanding the neural temporospatial dynamics of conscious perception, much of that work has focused on visual paradigms. To determine whether there are shared mechanisms for perceptual consciousness across sensory modalities, here we test within the auditory domain. Participants completed an auditory threshold task while undergoing intracranial electroencephalography. Recordings from >2,800 grey matter electrodes were analyzed for broadband gamma power (a range which reflects local neural activity). For perceived trials, we find nearly simultaneous activity in early auditory regions, the right caudal middle frontal gyrus, and the non-auditory thalamus; followed by a wave of activity that sweeps through auditory association regions into parietal and frontal cortices. For not perceived trials, significant activity is restricted to early auditory regions. These findings show the cortical and subcortical networks involved in auditory perception are similar to those observed with vision, suggesting shared mechanisms for conscious perception.

Reverse-breaking CFS (rev-bCFS): Disentangling conscious and unconscious effects by measuring suppression and dominance times during continuous flash suppression

Breaking continuous flash suppression (bCFS) is a widely used experimental paradigm that exploits detection tasks to measure the time an invisible stimulus requires to access awareness. Oneunresolved issue is whether differences in detection times reflect unconscious or conscious processing. To answer this question, here we introduce a novel approach (reverse-bCFS [rev-bCFS]) that measures the time an initially visible stimulus requires to be suppressed from awareness. Results from two experiments using face stimuli indicate that rev-bCFS can capture conscious effects, which indicates that contrasting standard bCFS with rev-bCFS can isolate unconscious processing occurring specifically during bCFS. For example, while face inversion impacted both bCFS and rev-bCFS, effects were larger in bCFS, suggesting a distinct contribution of unconscious processing to the advantage of upright over inverted faces in accessing awareness. Combining standard bCFS and rev-bCFS may offer a fruitful approach to disentangle conscious and unconscious effects occurring during interocular suppression.

Unpacking the complexities of consciousness: Theories and reflections

As the field of consciousness science matures, the research agenda has expanded from an initial focus on the neural correlates of consciousness, to developing and testing theories of consciousness. Several theories have been put forward, each aiming to elucidate the relationship between consciousness and brain function. However, there is an ongoing, intense debate regarding whether these theories examine the same phenomenon. And, despite ongoing research efforts, it seems like the field has so far failed to converge around any single theory, and instead exhibits significant polarization. To advance this discussion, proponents of five prominent theories of consciousness-Global Neuronal Workspace Theory (GNWT), Higher-Order Theories (HOT), Integrated Information Theory (IIT), Recurrent Processing Theory (RPT), and Predictive Processing (PP)-engaged in a public debate in 2022, as part of the annual meeting of the Association for the Scientific Study of Consciousness (ASSC). They were invited to clarify the explananda of their theories, articulate the core mechanisms underpinning the corresponding explanations, and outline their foundational premises. This was followed by an open discussion that delved into the testability of these theories, potential evidence that could refute them, and areas of consensus and disagreement. Most importantly, the debate demonstrated that at this stage, there is more controversy than agreement between the theories, pertaining to the most basic questions of what consciousness is, how to identify conscious states, and what is required from any theory of consciousness. Addressing these core questions is crucial for advancing the field towards a deeper understanding and comparison of competing theories.

Testing the role of spontaneous activity in visuospatial perception with patterned optogenetics

A major debate in the field of consciousness pertains to whether neuronal activity or rather the causal structure of neural circuits underlie the generation of conscious experience. The former position is held by theoretical accounts of consciousness based on the predictive processing framework (such as neurorepresentationalism and active inference), while the latter is posited by the integrated information theory. This protocol describes an experiment, part of a larger adversarial collaboration, that was designed to address this question through a combination of behavioral tests in mice, functional imaging, patterned optogenetics and electrophysiology. The experiment will directly test if optogenetic inactivation of a portion of the visual cortex not responding to behaviorally relevant stimuli will affect the perception of the spatial distribution of these stimuli, even when the neurons being inactivated display no or very low spiking activity, so low that it does not induce a significant effect on other cortical areas. The results of the experiment will be compared against theoretical predictions, and will provide a major contribution towards understanding what the neuronal substrate of consciousness is.

Evaluating animal consciousness

An emerging field shows how animal feelings can be studied scientifically.

Talking to sleepwalkers? Response to communication efforts in disorders of arousals

STUDY OBJECTIVES

Disorders of arousal (DoA) are diagnosed on the basis of clinical criteria, including inappropriate or absent responsiveness to communication attempts. Surprisingly, the ability of patients to interact with others during DoA episodes has not been systematically investigated. To address this gap, we conducted three studies.

METHODS

First, we used a retrospective questionnaire to assess verbal responsiveness during episodes in 61 adult patients with DoA (Study 1). Second, we used auditory stimulation during polysomnographically verified N3 sleep to trigger DoA episodes in 14 patients. We then asked questions to test the possibility of verbal interactions during the episodes (Study 2). Third, we assessed the presence and quality of conversations with a bed partner in 364 home video-recorded episodes from 19 patients (Study 3).

RESULTS

In Study 1, most patients (81%) reported occasional conversations during parasomnia episodes. Patients' ongoing mental content influenced both their responses to questions during episodes and their perception of the outside world (including their surroundings and the identity of their interlocutor ). In Study 2, auditory stimulation had a limited effect in inducing episodes (7/157 trials). One patient indirectly responded to our verbal prompts in a DoA episode. In Study 3, we found 37 video instances of discussion between patients and their partner.

CONCLUSIONS

Overall, our findings suggest that DoA episodes are not a uniform state but may instead encompass varying states of consciousness, characterized by different levels of responsiveness and a complex interplay between internal and external information processing. These results highlight the limitations of current diagnostic criteria for DoA.

Markers of consciousness in infants: Towards a 'cluster-based' approach

As recently as the 1980s, it was not uncommon for paediatric surgeons to operate on infants without anaesthesia. Today, the same omission would be considered criminal malpractice, and there is an increased concern with the possibility of consciousness in the earliest stage of human infancy. This concern reflects a more general trend that has characterised science since the early 1990s of taking consciousness seriously. While this attitude shift has opened minds towards the possibility that our earliest experiences predate our first memories, convincing demonstrations of infant consciousness remain challenging given that infants cannot report on their experiences. Furthermore, while many behavioural and neural markers of consciousness that do not rely on language have been validated in adults, no one specific marker can be confidently translated to infancy. For this reason, we have proposed the 'cluster-based' approach, in which a consensus of evidence across many markers, all pointing towards the same developmental period, could be used to argue convincingly for the presence of consciousness. CONCLUSION: We review the most promising markers for early consciousness, arguing that consciousness is likely to be in place by 5 months of age if not earlier.

States of consciousness and interoceptive hypersensibility: A study in patients with insomnia disorder

This exploratory study aimed to investigate the relationship between interoceptive sensibility and quality of consciousness in individuals with insomnia disorder, in order to understand how the modulation of internal states may contribute to modifying the experience of consciousness during sleep difficulties. A total of 37 patients with insomnia disorder (mean age = 46.05 ± 18.16) and 41 healthy good sleepers (mean age = 50.2 ± 12.99) underwent a psychometric sleep and interoceptive sensibility assessment, using Insomnia Severity Index (ISI), Pittsburgh Sleep Quality Index (PSQI), and Multidimensional Assessment of Interoceptive Awareness (MAIA). Moreover, patients with insomnia disorder also completed a quality of consciousness evaluation, using the Phenomenology of Consciousness Inventory (PCI). Patients with insomnia disorder exhibited heightened interoceptive sensibility, particularly in noticing body sensations (p < 0.0001) and emotional awareness (p = 0.032), along with diminished abilities in attention regulation (p = 0.040), not-worrying (p = 0.001), and trusting (p = 0.002). Furthermore, correlations between interoceptive sensibility and multiple aspects of the consciousness state during the insomnia night were identified. Specifically, higher emotional awareness was linked to a 2.49-fold increase in the likelihood of subjectively experiencing altered consciousness states during insomnia. The study sheds light on the relationship between interoceptive sensibility and the subjective state of consciousness during insomnia, emphasising the importance of exploring and considering interoception as part of the therapeutic process for insomnia disorder. Given the exploratory nature of the study and the increased risk of type-I error from numerous correlations, the results should be interpreted with caution. Further research is needed to validate and confirm their robustness.

Why Uncertainty Is Essential for Consciousness: Local Prospect Theory vs. Predictive Processing

We present and develop local prospect theory (LPT), a novel framework for understanding consciousness, and, in particular, subjective experience and free will. While predictive processing (PP) theories model the brain as trying to optimize the accuracy of predictions, LPT sees uncertainty as an essential feature of conscious decision-making. This is achieved by creating a "local prospect"-a range of potential developments colored by subjective experience from which an agent can freely choose how to react. Drawing on global workspace theory, LPT conceptualizes consciousness as a self-maintaining process of circulating neural activation, creating a temporary working memory where thoughts and feelings coming from different brain modules enter into an asynchronous, non-linear interaction. This contrasts with unconscious processes, which operate automatically and deterministically. LPT proposes entropy-based measures, including the determination of actions by conditions and the breadth of prospect, to quantify the range of potential developments considered. This framework allows us to understand Buddhist practices and concepts, such as mindfulness, liberation from attachments, and meditation, which broaden consciousness and de-automatize reactions by reducing the influence of conditioning. The proposed prospect measure may be operationalized by indicators such as the variety of action, breadth of perception, and unpredictability of behavior, thus allowing for the empirical testing of the theory.

The UnconTrust Database for Studies of Unconscious Semantic Processing and Attentional Allocation

The question of what processes can take place without conscious awareness has generated extensive research. Yet there is still no consensus regarding the extent and scope of unconscious processing, and past research abounds with conflicting results. A possible reason for this lack of consensus is the diversity of methods in the field, as the methodological choices might influence the results. Thus far, such possible influence of methods, measures, and analyses has not been systematically investigated and mapped. Here, we present the UnconTrust database for studies of unconscious processing focusing on two major domains - semantic and attentional processing. The database allows researchers to explore potential influences and obtain a bird's eye view on the field with respect to these domains. Currently, the database includes information about the methods and findings of 426 experiments (though notably, the data collected in these experiments is not included). The database is also presented as an interactive website.

In Search of an Integrative Method to Study Unconscious Processing: An Application of Bayesian and General Recognition Theory Models to the Processing of Hierarchical Patterns in the Absence of Awareness

The dissociation between conscious and unconscious perception is one of the most relevant issues in the study of human cognition. While there is evidence suggesting that some stimuli might be unconsciously processed up to its meaning (e.g., high-level stimulus processing), some authors claim that most results on the processing of subliminal stimuli can be explained by a mixture of methodological artefacts and questionable assumptions about what can be considered non-conscious. Particularly, one of the most controversial topics involves the method by which the awareness of the stimuli is assessed. To address this question, we introduced an integrative approach to assess the extent to which masked hierarchical stimuli (i.e., global shapes composed of local elements) can be processed in the absence of awareness. We combined a priming task where participants had to report global or local shapes, with the use of subjective and objective awareness measures collected either in a separate block (offline), or trial-by-trial during the main task (online). The unconscious processing of the masked primes was then evaluated through two different novel model-based methods: a Bayesian and a General Recognition Theory modeling approach. Despite the high correlation between awareness measures, our results show that the use of alternative approaches based on different theoretical assumptions leads to diverging conclusions about the extent of the unconscious processing of the masked primes.

Frontal engagement in perceptual integration under low subjective visibility

We investigated how spatiotemporal neural dynamics underlying perceptual integration changed with the degree of conscious access to a set of backward-masked pacman-shaped inducers that generated the percept of an illusory triangle. We kept the stimulus parameters at a fixed near-threshold level throughout the experiment and recorded electroencephalography from participants who reported the orientation and subjective visibility of the illusory triangle on each trial. Our multivariate pattern analysis revealed that posterior and central areas initially used dynamic neural code and later switched to stable neural code. The transition from dynamic to stable neural code in posterior area occurred increasingly later and eventually disappeared with decreasing conscious access. Anterior area primarily used stable neural code which waned with decreasing conscious access, but increased at below-median visibility and remained even when stimulus awareness was minimal. These results demonstrate differential spatiotemporal neural dynamics underlying perceptual integration depending on conscious access and emphasize a unique role of anterior area in processing integrated shape information especially under low subjective visibility.

Biological mechanisms contradict AI consciousness: The spaces between the notes

The presumption that experiential consciousness requires a nervous system and brain has been central to the debate on the possibility of developing a conscious form of artificial intelligence (AI). The likelihood of future AI consciousness or devising tools to assess its presence has focused on how AI might mimic brain-centered activities. Currently, dual general assumptions prevail: AI consciousness is primarily an issue of functional information density and integration, and no substantive technical barriers exist to prevent its achievement. When the cognitive process that underpins consciousness is stipulated as a cellular attribute, these premises are directly contradicted. The innate characteristics of biological information and how that information is managed by individual cells have no parallels within machine-based AI systems. Any assertion of computer-based AI consciousness represents a fundamental misapprehension of these crucial differences.

Parametrization of the dying brain: A case report from ICU bed-side EEG monitoring

BACKGROUND

Cortical high-frequency activation immediately before death has been reported, raising questions about an enhanced conscious state at this critical time. Here, we analyzed an electroencephalogram (EEG) from a comatose patient during the dying process with a standard bedside monitor and spectral parameterization techniques.

METHODS

We report neurophysiologic features of a dying patient without major cortical injury. Sixty minutes of frontal EEG activity was recorded using the Sedline™ monitor. Quantitative metrics of the frequency spectrum, the non-oscillatory 1/f characteristic, and signal complexity with Lemple-Ziv-Welch and permutation entropy were calculated. In addition to comparing the EEG trajectories over time, we provide a comparison to EEG records obtained from other studies with well-known vigilance states (sleep, anesthesia, and wake).

RESULTS

Although we observed changes in high-frequency activation during the dying process, larger alterations of the aperiodic EEG components were also noted. These changes differed dramatically when compared to EEG records representative of wake, slow-wave sleep, or anesthesia. Although still fundamentally unique, the neuronal activity present in the dying brain is more similar to REM sleep than any other state we tested.

CONCLUSION

Even in patients with coma, temporal dynamics in quantitative EEG features (including the aperiodic components) can be observed in the final hour before death.

Revolutionizing treatment for disorders of consciousness: a multidisciplinary review of advancements in deep brain stimulation

Among the existing research on the treatment of disorders of consciousness (DOC), deep brain stimulation (DBS) offers a highly promising therapeutic approach. This comprehensive review documents the historical development of DBS and its role in the treatment of DOC, tracing its progression from an experimental therapy to a detailed modulation approach based on the mesocircuit model hypothesis. The mesocircuit model hypothesis suggests that DOC arises from disruptions in a critical network of brain regions, providing a framework for refining DBS targets. We also discuss the multimodal approaches for assessing patients with DOC, encompassing clinical behavioral scales, electrophysiological assessment, and neuroimaging techniques methods. During the evolution of DOC therapy, the segmentation of central nuclei, the recording of single-neurons, and the analysis of local field potentials have emerged as favorable technical factors that enhance the efficacy of DBS treatment. Advances in computational models have also facilitated a deeper exploration of the neural dynamics associated with DOC, linking neuron-level dynamics with macroscopic behavioral changes. Despite showing promising outcomes, challenges remain in patient selection, precise target localization, and the determination of optimal stimulation parameters. Future research should focus on conducting large-scale controlled studies to delve into the pathophysiological mechanisms of DOC. It is imperative to further elucidate the precise modulatory effects of DBS on thalamo-cortical and cortico-cortical functional connectivity networks. Ultimately, by optimizing neuromodulation strategies, we aim to substantially enhance therapeutic outcomes and greatly expedite the process of consciousness recovery in patients.

The Antagonism Hypothesis: A New View on the Emergence of Consciousness

PURPOSE

The generation of consciousness poses a complex scientific challenge. Neuroscience and biological sciences have extensively studied this phenomenon, yielding numerous theories and hypotheses. However, to date, no reliable evidence has emerged to exclude any hypothesis conclusively, nor has any theory garnered unanimous agreement. This study aims to offer novel insights for further in-depth study on consciousness.

METHOD

A new theoretical hypothesis was proposed based on reviews and comments from predictive processing theory, information theory, thermodynamics, and neuroscience.

FINDINGS

This study argues that, first, it is necessary to clarify that the core implication of the concept of consciousness is first-person perception. Accordingly, the study of consciousness is based on this premise. Second, on this basis, the antagonistic hypothesis of consciousness generation was proposed. This hypothesis holds that consciousness arises from the antagonism of mature individual experiences that cannot be seamlessly integrated with the function of addressing and navigating these conflicts.

CONCLUSION

The antagonism hypothesis is a new concept regarding the generation of consciousness that deserves further study.

The function(s) of consciousness: an evolutionary perspective

The functions of consciousness, viewed from an evolutionary standpoint, can be categorized as being either general or particular. There are two general functions, meaning those that do not depend on the particulars of how consciousness influences behavior or how and why it first evolved: of (1) expanding the behavioral repertoire of the individual through the gradual accumulation of neurocircuitry innovations incorporating consciousness that would not exist without it, and (2) reducing the time scale over which preprogrammed behaviors can be altered, from evolutionary time, across generations, to real-time. But neither answers Velmans' question, of why consciousness is adaptive in a proximate sense, and hence why it would have evolved, which depends on identifying the particular function it first performed. Memory arguably plays a role here, as a strong case can be made that consciousness first evolved to make motivational control more responsive, though memory, to the past life experiences of the individual. A control mechanism of this kind could, for example, have evolved to consciously inhibit appetitive behaviors, whether consciously instigated or not, that would otherwise expose the individual to harm. There is then the question of whether, for amniote vertebrates, a role in memory formation and access would have led directly to a wider role for consciousness in the way the brain operates, or if some other explanation is required. Velmans' question might then have two answers, the second having more to do with the advantages of global oversight for the control of behavior, as in a global workspace, or for conferring meaning on sensory experience in a way that non-conscious neural processes cannot. Meaning in this context refers specifically to the way valence is embodied in the genomic instructions for assembling the neurocircuitry responsible for phenomenal contents, so it constitutes an embodied form of species memory, and a way of thinking about the adaptive utility of consciousness that is less concerned with real-time mechanistic events than with information storage on an evolutionary time scale.

Neuroimaging biomarkers for the diagnosis and prognosis of patients with disorders of consciousness

The progress in neuroimaging and electrophysiological techniques has shown substantial promise in improving the clinical assessment of disorders of consciousness (DOC). Through the examination of both stimulus-induced and spontaneous brain activity, numerous comprehensive investigations have explored variations in brain activity patterns among patients with DOC, yielding valuable insights for clinical diagnosis and prognostic purposes. Nonetheless, reaching a consensus on precise neuroimaging biomarkers for patients with DOC remains a challenge. Therefore, in this review, we begin by summarizing the empirical evidence related to neuroimaging biomarkers for DOC using various paradigms, including active, passive, and resting-state approaches, by employing task-based fMRI, resting-state fMRI (rs-fMRI), electroencephalography (EEG), and positron emission tomography (PET) techniques. Subsequently, we conducted a review of studies examining the neural correlates of consciousness in patients with DOC, with the findings holding potential value for the clinical application of DOC. Notably, previous research indicates that neuroimaging techniques have the potential to unveil covert awareness that conventional behavioral assessments might overlook. Furthermore, when integrated with various task paradigms or analytical approaches, this combination has the potential to significantly enhance the accuracy of both diagnosis and prognosis in DOC patients. Nonetheless, the stability of these neural biomarkers still needs additional validation, and future directions may entail integrating diagnostic and prognostic methods with big data and deep learning approaches.

Sensory representations in primary visual cortex are not sufficient for subjective imagery

The contemporary definition of mental imagery is characterized by two aspects: a sensory representation that resembles, but does not result from, perception, and an associated subjective experience. Neuroimaging demonstrated imagery-related sensory representations in primary visual cortex (V1) that show striking parallels to perception. However, it remains unclear whether these representations always reflect subjective experience or if they can be dissociated from it. We addressed this question by comparing sensory representations and subjective imagery among visualizers and aphantasics, the latter with an impaired ability to experience imagery. Importantly, to test for the presence of sensory representations independently of the ability to generate imagery on demand, we examined both spontaneous and voluntary imagery forms. Using multivariate fMRI, we tested for decodable sensory representations in V1 and subjective visual imagery reports that occurred either spontaneously (during passive listening of evocative sounds) or in response to the instruction to voluntarily generate imagery of the sound content (always while blindfolded inside the scanner). Among aphantasics, V1 decoding of sound content was at chance during voluntary imagery, and lower than in visualizers, but it succeeded during passive listening, despite them reporting no imagery. In contrast, in visualizers, decoding accuracy in V1 was greater in voluntary than spontaneous imagery (while being positively associated with the reported vividness of both imagery types). Finally, for both conditions, decoding in precuneus was successful in visualizers but at chance for aphantasics. Together, our findings show that V1 representations can be dissociated from subjective imagery, while implicating a key role of precuneus in the latter.

Episodic memory without autonoetic consciousness

Ever since Tulving's influential 1985 article 'Memory and consciousness', it has become traditional to think of autonoetic consciousness as necessary for episodic memory. This paper questions this claim. Specifically, it argues that the construct of autonoetic consciousness lacks validity and that, even if it was valid, it would still not be necessary for episodic memory. The paper ends with a proposal to go back to a functional/computational characterization of episodic memory in which its characteristic phenomenology is a contingent feature of the retrieval process and, as a result, open to empirical scrutiny. The proposal also dovetails with recent taxonomies of memory that are independent of conscious awareness and suggests strategies to evaluate within- and between-individual variability in the conscious experience of episodic memories in human and non-human agents. This article is part of the theme issue 'Elements of episodic memory: lessons from 40 years of research'.

Unconscious temporal attention induced by invisible temporal association cues

Temporal attention is the ability to prioritize information based on timing. While conscious perception of temporally structured information is known to generate temporal attention, whether it occurs unconsciously remains uncertain. This study used a temporal cueing paradigm with masking techniques to explore the differences between conscious and unconscious temporal attention mechanisms. Experiment 1 found that both visible and invisible cues triggered temporal attention, with stronger effects for visible cues. Experiment 2, using electroencephalogram (EEG) recordings, showed that both visible and invisible cues evoked contingent negative variation (CNV) component, albeit smaller with invisible cues. The P300 component further supported this pattern. Hierarchical drift-diffusion modeling (HDDM) analysis demonstrated that both conscious and unconscious temporal attention effects involve non-perceptual decision-making processes. These findings both align and challenge the Global Workspace Theory, suggesting that while consciousness enhances conscious attention via global broadcasting, unconscious attention may rely on more localized neural networks.

Modulation of electroencephalogram brain activity dynamics by 10 Hz parietal repetitive transcranial magnetic stimulation: Implications for recovery of the minimally conscious state

BACKGROUND AND OBJECTIVES

Despite the fact that the parietal cortex is associated with consciousness, the underlying mechanisms of parietal repetitive transcranial magnetic stimulation (rTMS) have not yet been specifically investigated. The present study aims to examine the effects of parietal rTMS on patients with disorders of consciousness (DoC) and identify a novel potential target.

METHODS

Twenty minimally conscious state (MCS) patients were stochastically assigned to a real or sham rTMS group in a controlled trial. The real rTMS group was administered over the parietal cortex, with a frequency of 10 Hz and a rest motor threshold of 90 %. The sham rTMS group was identical to the real rTMS group without magnetic stimulation over the cortex. Pre- and post-treatment resting-state electrophysiological (EEG) data and coma recovery scale-revised (CRS-R) score were gathered. Microstate analyses were calculated to evaluate the brain activity dynamics.

RESULTS

The real rTMS treatment improved the CRS-R scores. There were notable alterations in the mean microstate duration (MMD) of microstate B in the real rTMS group. The sham rTMS group did not exhibit such changes in CRS-R score or EEG results, which were not statistically significant. Furthermore, the MMD and RTC of microstate E were found to be negatively correlated with baseline CRS-R scores.

CONCLUSION

Parietal rTMS can induce behavioral improvement and brain activity dynamics in patients with MCS. EEG microstates can be used as a valuable method to study neurophysiological mechanisms behind MCS. And the parietal cortex represents an alternative for rTMS therapy protocols.

Consciousness and Energy Processing in Neural Systems

BACKGROUND

Our understanding of the relationship between neural activity and psychological states has advanced greatly in recent decades. But we are still unable to explain conscious experience in terms of physical processes occurring in our brains.

METHODS

This paper introduces a conceptual framework that may contribute to an explanation. All physical processes entail the transfer, transduction, and transformation of energy between portions of matter as work is performed in material systems. If the production of consciousness in nervous systems is a physical process, then it must entail the same. Here the nervous system, and the brain in particular, is considered as a material system that transfers, transduces, and transforms energy as it performs biophysical work.

CONCLUSIONS

Evidence from neuroscience suggests that conscious experience is produced in the organic matter of nervous systems when they perform biophysical work at classical and quantum scales with a certain level of dynamic complexity or organization. An empirically grounded, falsifiable, and testable hypothesis is offered to explain how energy processing in nervous systems may produce conscious experience at a fundamental physical level.

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

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 anesthetic propofol. The observed changes in ISD suggest a profound shift towards the segregation of brain networks during anesthesia. A common unimodal-transmodal sequence of disintegration and reintegration occurs in brain networks during, respectively, loss and return of responsiveness. Machine learning models using integration and segregation data accurately identify awake vs. unresponsive states and their transitions. Metastability (dynamic recurrence of non-equilibrium transient states) is more effectively explained by integration, while complexity (diversity of neural activity) is more closely linked with segregation. A parallel analysis of sleep states produces similar findings. Our results demonstrate that the ISD reliably indexes states of consciousness.