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Global workspace theory of consciousness: Toward a cognitive neuroscience of human experience
Abstract
Global workspace (GW) theory emerged from the cognitive architecture tradition in cognitive science. Newell and co-workers were the first to show the utility of a GW or "blackboard" architecture in a distributed set of knowledge sources, which could cooperatively solve problems that no single constituent could solve alone. The empirical connection with conscious cognition was made by Baars (1988, 2002). GW theory generates explicit predictions for conscious aspects of perception, emotion, motivation, learning, working memory, voluntary control, and self systems in the brain. It has similarities to biological theories such as Neural Darwinism and dynamical theories of brain functioning. Functional brain imaging now shows that conscious cognition is distinctively associated with wide spread of cortical activity, notably toward frontoparietal and medial temporal regions. Unconscious comparison conditions tend to activate only local regions, such as visual projection areas. Frontoparietal hypometabolism is also implicated in unconscious states, including deep sleep, coma, vegetative states, epileptic loss of consciousness, and general anesthesia. These findings are consistent with the GW hypothesis, which is now favored by a number of scientists and philosophers.
... Assuming that brain dynamics are cast as information processing functions, we contend that the richness of conscious experience can be interpreted as the amount of information in conscious state, and ineffability as the amount of information lost in processing. (ii) Attractor dynamics are empirically ubiquitous in neural activity across cortical regions and have been proposed as a computational model for working memory (Khona and Fiete, 2022;Rolls, 2010), while prominent models of consciousness argue that conscious experience is a projection of working memory states (Baars, 2005;Dehaene and Naccache, 2001). We connect these theories by contending that significant information loss induced by attractor dynamics offers an account for the significant ineffability of conscious experience. ...
... The paper is structured as follows. We present our dynamical systems model of conscious experience in the "An information theoretical dynamical systems perspective on conscious experience" section, beginning with the "Motivating attractor dynamics as a model for conscious experience" section, which motivates the use of attractor dynamics for modeling conscious processing using prior arguments from the literature that are independent of our own, including evidence for the Global Workspace Theory (Baars, 1993;Baars, 2005;Dehaene et al., 1998). The "Richness and ineffability" section formalizes the notions of richness and ineffability using both Shannon information theory (Shannon, 1948) and Kolmogorov complexity (Kolmogorov, 1965), which play a central role in making our later arguments precise. ...
... A central claim in several leading theories of consciousness is that what we are consciously aware of is the contents of working memory. For example, the Global Workspace Theory (Baars, 1993;Baars, 2005) and its neuronal extension (Dehaene et al., 1998) state that information becomes conscious by gaining entry into a limited workspace that serves as a bottleneck for the distributed activity present across the brain. Pairs of brain regions are largely isolated from each other, and arbitrary point-to-point communication is only possible via the workspace, which itself can both receive and broadcast information globally. ...
Conscious states—state that there is something it is like to be in—seem both rich or full of detail and ineffable or hard to fully describe or recall. The problem of ineffability, in particular, is a longstanding issue in philosophy that partly motivates the explanatory gap: the belief that consciousness cannot be reduced to underlying physical processes. Here, we provide an information theoretic dynamical systems perspective on the richness and ineffability of consciousness. In our framework, the richness of conscious experience corresponds to the amount of information in a conscious state and ineffability corresponds to the amount of information lost at different stages of processing. We describe how attractor dynamics in working memory would induce impoverished recollections of our original experiences, how the discrete symbolic nature of language is insufficient for describing the rich and high-dimensional structure of experiences, and how similarity in the cognitive function of two individuals relates to improved communicability of their experiences to each other. While our model may not settle all questions relating to the explanatory gap, it makes progress toward a fully physicalist explanation of the richness and ineffability of conscious experience—two important aspects that seem to be part of what makes qualitative character so puzzling.
... Many regard the problem of consciousness as primarily in the phenomenological domain, concerned with what is experienced by a subject when he or she is conscious, e.g., properties such as qualia, intentionality, and self-awareness as opposed to physical or functional descriptions of the brain function. There are experimental and theoretical approaches tackling the cognitive implications of consciousness based on ideas, such as neural correlates of consciousness (NCC, Crick and Koch, 1998;Koch et al., 2016), global workspace theory (Baars, 1997(Baars, , 2005, integrated information theory , and free-energy principle (Friston, 2010). Wiese and Friston (2021) discussed the relevance of the freeenergy principle as a constraint for the computational correlates of consciousness (CCC), stressing the importance of neural dynamics, not states. ...
... Acquiring new skills or making decisions in novel contexts would typically require the involvement of conscious processing, while the execution of acquired skills would proceed largely unconsciously (Solomon, 1911;Lisman and Sternberg, 2013) in terms of the accompanying phenomenological properties, such as qualia, intentionality, and attention. Any cognitive task, when it needs to integrate information analyzed across many different regions in the brain, typically requires consciousness, reflecting the global nature of consciousness in terms of cortical regions involved (Baars, 2005). The autonomous execution of familiar tasks would involve a different set of neural networks compared to the minimum set of neural activities (neural correlates, Koch et al., 2016) required for the sustaining of consciousness. ...
The computational significance of consciousness is an important and potentially more tractable research theme than the hard problem of consciousness, as one could look at the correlation of consciousness and computational capacities through, e.g., algorithmic or complexity analyses. In the literature, consciousness is defined as what it is like to be an agent (i.e., a human or a bat), with phenomenal properties, such as qualia, intentionality, and self-awareness. The absence of these properties would be termed “unconscious.” The recent success of large language models (LLMs), such as ChatGPT, has raised new questions about the computational significance of human conscious processing. Although instances from biological systems would typically suggest a robust correlation between intelligence and consciousness, certain states of consciousness seem to exist without manifest existence of intelligence. On the other hand, AI systems seem to exhibit intelligence without consciousness. These instances seem to suggest possible dissociations between consciousness and intelligence in natural and artificial systems. Here, I review some salient ideas about the computational significance of human conscious processes and identify several cognitive domains potentially unique to consciousness, such as flexible attention modulation, robust handling of new contexts, choice and decision making, cognition reflecting a wide spectrum of sensory information in an integrated manner, and finally embodied cognition, which might involve unconscious processes as well. Compared to such cognitive tasks, characterized by flexible and ad hoc judgments and choices, adequately acquired knowledge and skills are typically processed unconsciously in humans, consistent with the view that computation exhibited by LLMs, which are pretrained on a large dataset, could in principle be processed without consciousness, although conversations in humans are typically done consciously, with awareness of auditory qualia as well as the semantics of what are being said. I discuss the theoretically and practically important issue of separating computations, which need to be conducted consciously from those which could be done unconsciously, in areas, such as perception, language, and driving. I propose conscious supremacy as a concept analogous to quantum supremacy, which would help identify computations possibly unique to consciousness in biologically practical time and resource limits. I explore possible mechanisms supporting the hypothetical conscious supremacy. Finally, I discuss the relevance of issues covered here for AI alignment, where computations of AI and humans need to be aligned.
... However, at some point, we must start asking how is it that so many explanations for the same thing are possible, so we can look for commonalities. contents (Baars, 2005;Baars et al., 2013;Dehaene & Changeux, 2011). Similarly, higher order theories (HOT) stress the requirement of re-representing our experiences for one to be aware of their contents (Brown et al., 2019). ...
... Theories of Consciousness GWT GWTs (Baars, 1997(Baars, , 2005 can be characterized by three fundamental tenets. (a) There exist quasiindependent local hubs of early sensory systems, (b) these hubs are connected to and compete for access to a large global workspace, and (c) access to the global workspace is granted by a fleeting "ignition" process that allows for the broadcasting of information across the modules. ...
A prevailing pessimism in the scientific study of consciousness is about it having too many theories. With theories of consciousness becoming increasingly isolated from each other, recently, several proposals have been put forth to cull the number of theories in contention. Here, building on a suggested minimal model approach, we try to unify six prominent theories of consciousness, namely, theories of global workspace, integrated information, predictive processing, higher order awareness, recurrent processing, and temporospatiality. To do this, we use a nested hierarchical framework of temporal phenomenology designed to combine findings from time consciousness, timing of cognition, and time perception literature. Extending the same framework to theories of consciousness themselves, we show how the framework can be instrumental in bringing these six divergent theories together. We show how each theory can uniquely contribute to explaining distinct temporal mechanisms within an experience of a conscious moment. Our larger contention is that each of these theories has been developed by keeping at its core a unique temporal phenomenological property. Thus, when stripped away from their larger baggage under a minimal model approach, they are congenial to each other. Our approach is a demonstration of how collective theorizing about consciousness can offer more than any of the theories on their own.
... Global Neuronal Workspace Theory (GNWT) is currently one of the most influential theories of consciousness, based on Bernard Baars's Global Workspace Theory (Baars, 1988(Baars, , 2005Dehaene, 1998). The theory rests on the theoretical perspective of a cortico-thalamic core in the brain, believed to underlie conscious aspects of higher cognitive processes such as thinking, learning, and executive control (Baars et al., 2013). ...
... GNWT suggests there are unconscious local peripheral processes represented by coalitions of neurons that compete for conscious access to a global workspace in a winner-takes-all fashion. The "winner" broadcasts information into the global workspace, which propagates the information throughout the whole brain (Baars, 2005). The global workspace is composed of mobilised excitatory neurons with longrange cortico-cortical and thalamo-cortical connections, consequently creating patterns of global activity. ...
Consciousness is often described as the final frontier in science, tackled from multiple disciplines including philosophy, neuroscience, and computer science. Consciousness is most commonly defined as what exists from a first-person perspective, as the feeling of what it is like to be something, as well as through neuronal mechanisms that generate and support this phenomenology. Countless theories on consciousness have emerged to try to elucidate this complicated phenomenon. In our review, we aim to examine the three dominant theories of consciousness - Global Neuronal Workspace Theory (GNWT), Recurrent Processing Theory (RPT), Higher-order Theory (HOT) - and the Dendritic Integration Theory (DIT) as a newer, less prominent, theory that focuses on the cellular basis of consciousness. We propose that DIT may complement the postulations of the other three theories through its cellular approach that bridges state and content consciousness. Finally, we discuss the future of consciousness research more generally.
... Continual learning in the brain is governed by the conscious processing of multiple knowledge bases anchored by a rich set of neurophysiological processes (Goyal & Bengio, 2020). Global Workspace Theory (GWT) (Baars, 1994;2005;Baars et al., 2021) provides a formal account of cognitive information access and posits that one such knowledge base is a common representation space of fixed capacity from which information is selected, maintained, and shared with the rest of the brain (Juliani et al., 2022). During information access, the attention mechanism creates a communication bottleneck between the representation space and the global workspace, and only behaviorally relevant information is admitted into the global workspace. ...
Continual learning (CL) remains a significant challenge for deep neural networks, as it is prone to forgetting previously acquired knowledge. Several approaches have been proposed in the literature, such as experience rehearsal, regularization, and parameter isolation, to address this problem. Although almost zero forgetting can be achieved in task-incremental learning, class-incremental learning remains highly challenging due to the problem of inter-task class separation. Limited access to previous task data makes it difficult to discriminate between classes of current and previous tasks. To address this issue, we propose `Attention-Guided Incremental Learning' (AGILE), a novel rehearsal-based CL approach that incorporates compact task attention to effectively reduce interference between tasks. AGILE utilizes lightweight, learnable task projection vectors to transform the latent representations of a shared task attention module toward task distribution. Through extensive empirical evaluation, we show that AGILE significantly improves generalization performance by mitigating task interference and outperforming rehearsal-based approaches in several CL scenarios. Furthermore, AGILE can scale well to a large number of tasks with minimal overhead while remaining well-calibrated with reduced task-recency bias.
... This is done by analyzing the functional basis of consciousness (Juliani et al., 2022). Examples include three well-known contemporary theories of the functional basis of consciousness from the perspective of conscious access: (1) Global Workspace Theory (GWT) (Baars, 2005); (2) Information Generation Theory (IGT) (Kanaietal, 2019) and (3) Attention Schema Theory (AST) (Graziano & Webb, 2015). ...
Edmund Husserl, the founder of phenomenological philosophy, developed the concept of the so-called pure transcendental consciousness. The author of the article asks whether the concept of consciousness understood this way can constitute a model for AI consciousness. It should be remembered that transcendental consciousness is the result of the use of the phenomenological method, the essence of which is referring to experience (“back to things themselves”). Therefore, one can legitimately ask whether the consciousness that AI can achieve can possess the characteristics attributed by Husserl to pure transcendental consciousness. The answer to such questions seems to be negative because AI, as created by humans, can only operate in the field of phenomena. Human intelligence, however, is capable of operating at the ontological level. In the face of difficulties in understanding the phenomenon of consciousness on a scientific basis, the question arises about the possibility of using the phenomenological concept of consciousness developed by Husserl as a starting point in analyzes aimed at answering the question about AI consciousness (The aim of the article is not to discuss in detail the contemporary state of research on consciousness. Therefore, many results currently achieved mainly in the field of neuroscience are omitted. It is just about indicating the possible application of Husserl’s transcendental concept of consciousness in research on AI consciousness).
... This view leads to a common notion held by influential theories-consciousness is required for the integration of multiple sources of information. For instance, popular theories of consciousness postulate that consciousness plays a functional role in interconnecting distributed sets of specialized neural networks (global workspace theory, Baars, 2005;Mashour et al., 2020), and even that integrated information is equivalent to the content that is consciously accessible (integrated information theory, Tononi, 2004;Tononi et al., 2016). Nonetheless, the necessity of consciousness for information integration has been challenged by instances in which contents could be integrated in the absence of conscious experience (Brogaard et al., 2021). ...
One central question in the scientific and philosophical study of consciousness is regarding the scope of human consciousness. There is a lively debate as to whether high-level information integration is necessarily dependent on consciousness. This study presents a new form of unconscious integration based on the facingness between two individuals. Using a breaking continuous flash suppression paradigm, Experiments 1–3 found that two facing human heads got a privilege in breaking into awareness compared to nonfacing pairs. Experiments 4 and 5 demonstrated that the breakthrough difference between facing and nonfacing pairs could not be attributed to low-level or mid-level factors. Experiments 6, 7a, and 7b showed that the unconscious priority of facing pairs was significantly diminished when the holistic processing of the two agents was disrupted. Experiments 8–11 demonstrated that the advantage of facing pairs was only observable for human agents and not for daily objects, directional arrows, or nonhuman animals. These findings have critical implications for better understanding the scope of human consciousness and the origins of social vision.
... 310 y ss) han cuestionado desde distintas posiciones que exista este problema o que realmente sea un problema distinto de los llamados problemas fáciles que el tiempo y la financiación científica deberían acabar resolviendo. Parece ser esta la postura mayoritaria entre neurocientíficos y científicos cognitivos (Pinker, 2007), que junto con algunos filósofos siguen cercando la consciencia a través de distintas teorías como las teorías de la consciencia de orden superior (Higher Order group of theories) (Brown et al., 2019), las teorías del correlato neuronal de la consciencia (Neural Correlate of Consciousness group of theories) (Koch et al., 2016), la Teoría del espacio de trabajo global (Global Workspace Theory) (Baars, 2005), el Modelo de borradores múltiples (Multiple Draft Model) (Dennett, 2018), la Teoría de la información integrada (Integrated Information Theory) (Guerrero et al., 2023), las Teorías cuánticas de la consciencia (Quantum consciousness theories) (Sánchez-Cañizares, 2016), u otras que tienen a casi todas las anteriores por pseudocientíficas, como la teoría de la identidad mente-objeto (Mindobject identity theory) (Manzotti, 2019 y Manzotti, 2021). Para una revisión algo más profunda sobre estas teorías puede recurrirse a los trabajos de Seth y Bayne (Seth & Bayne, 2022) y de Butlin et al. (Butlin et al., 2023). ...
Muchas publicaciones están tratando de pinchar la burbuja de expectativas sobre el desarrollo reciente de la IA. Sin embargo, en ciertos círculos humanistas donde un escepticismo conservador con respecto a las novedades va de serie, es conveniente detener la reflexión en el exceso contrario: la complacencia de posturas que se contentan con argumentos débiles y conceptos periclitados ya superados en la literatura científica y filosófica. Estas perspectivas tienden a adoptar una postura reaccionaria ante la IA, aferrándose defensivamente a cualquier argumento que pueda preservar la singularidad humana a costa de renunciar a una cierta honestidad intelectual. Así afirma taxativamente que la IA nunca logrará alcanzarla. No obstante, es posible adoptar posturas humanistas receptivas a los desarrollos de la IA, abiertas a sus retos actuales y capaces de dialogar y refinar sus argumentos a través de algunas claves: dignificar la miserabilidad humana, tender puentes interdisciplinares, y mantener la prudencia, la cortesía y la suspensión del juicio cuando sea preciso.
... Representatives of class 1 attribute consciousness to complex dynamic interactions between neurons, with different branches of this class emphasizing different aspects of the dynamic interactions. One branch views the generation of activity patterns exceeding the threshold of consciousness as a collective phenomenon and underlines the necessity of a global workspace that coordinates the activity of a large number of neurons distributed across functionally specialized brain regions (Baars, 1988(Baars, , 2005Dehaene and Naccache, 2001;Dehaene et al., 2006). A second branch highlights the importance of the thalamocortical system, which is assumed to operate as a dynamic core that is capable of forming an enormous range of differentiated, transiently stable states (Tononi and Edelman, 1998;Edelman, 2003;Seth et al., 2006). ...
Empirical evidence indicates that conscious states, distinguished by the presence of phenomenal qualities, are closely linked to synchronized neural activity patterns whose dynamical characteristics can be attributed to self-organized criticality and phase transitions. These findings imply that insight into the mechanism by which the brain controls phase transitions will provide a deeper understanding of the fundamental mechanism by which the brain manages to transcend the threshold of consciousness. This article aims to show that the initiation of phase transitions and the formation of synchronized activity patterns is due to the coupling of the brain to the zero-point field (ZPF), which plays a central role in quantum electrodynamics (QED). The ZPF stands for the presence of ubiquitous vacuum fluctuations of the electromagnetic field, represented by a spectrum of normal modes. With reference to QED-based model calculations, the details of the coupling mechanism are revealed, suggesting that critical brain dynamics is governed by the resonant interaction of the ZPF with the most abundant neurotransmitter glutamate. The pyramidal neurons in the cortical microcolumns turn out to be ideally suited to control this interaction. A direct consequence of resonant glutamate-ZPF coupling is the amplification of specific ZPF modes, which leads us to conclude that the ZPF is the key to the understanding of consciousness and that the distinctive feature of neurophysiological processes associated with conscious experience consists in modulating the ZPF. Postulating that the ZPF is an inherently sentient field and assuming that the spectrum of phenomenal qualities is represented by the normal modes of the ZPF, the significance of resonant glutamate-ZPF interaction for the formation of conscious states becomes apparent in that the amplification of specific ZPF modes is inextricably linked with the excitation of specific phenomenal qualities. This theory of consciousness, according to which phenomenal states arise through resonant amplification of zero-point modes, is given the acronym TRAZE. An experimental setup is specified that can be used to test a corollary of the theory, namely, the prediction that normally occurring conscious perceptions are absent under experimental conditions in which resonant glutamate-ZPF coupling is disrupted.
... The Projective Consciousness Model proposed by David Rudrauf, Karl Friston, and colleagues (2017) builds upon a perspectival phenomenological structure supporting consciousness with a free energy minimization model of active inference describing the modulation of cognitive and affective dynamics to control the embodied agentic self. A global workspace model was proposed by Bernard Baars (2005) that attempts to account for both phenomenal and access forms of consciousness. Metzinger's PSM theory of subjectivity, Karl Friston's free energy principle theory, and Anil Seth's utilization of hierarchical Bayesian inference have all contributed to philosophical and computational understandings and ontologic claims about the nature of the self. ...
This chapter is intended to provide an overview of considerations
for what may be regarded as a translational science of self and its
relevance to psychiatry. Conceptual issues are discussed from both
historical and theoretical perspectives to inform our current understanding
of the self. Evolutionary, neurobiologic, and clinical perspectives
inform the phenomenology and function supporting the act
of being a self in the world. A single paradigm for research on “self”
does not exist, as it is not necessarily a unitary phenomenon. Diverse
disciplines inform the study of the individual (qua self) and its varied
representations and relevance uniquely. However, conceptual convergence
in this scientific enterprise addressing self “issues” continues
to emerge along with signs of where a more advanced program for a
science of self may be heading. Implications for a critical interdisciplinary
analysis of self on the field of psychiatry and into the nature
of consciousness are provided.
... experiences; distinguishing two neighboring points rather than not distinguishing them. In metaphorical terms, if on the inside of Chalmers' zombies all is dark because they have no experience, appearance is that thing that occurs when the "light" of consciousness comes on (Baars, 1997(Baars, , 2005. This idea is often associated with something magical and inexplicable. ...
According to Loorits, if we want consciousness to be explained in terms of natural sciences, we should be able to analyze its seemingly non-structural aspects, like qualia, in structural terms. However, the studies conducted over the last three decades do not seem to be able to bridge the explanatory gap between physical phenomena and phenomenal experience. One possible way to bridge the explanatory gap is to seek the structure of consciousness within consciousness itself, through a phenomenal analysis of the qualitative aspects of experience. First, this analysis leads us to identify the explanandum concerning the simplest forms of experience not in qualia but in the unitary set of qualities found in early vision. Second, it leads us to hypothesize that consciousness is also made up of non-apparent parts, and that there exists a hidden structure of consciousness. This structure, corresponding to a simple early visual experience, is constituted by a Hierarchy of Spatial Belongings nested within each other. Each individual Spatial Belonging is formed by a primary content and a primary space. The primary content can be traced in the perceptibility of the contents we can distinguish in the phenomenal field. The primary space is responsible for the perceptibility of the content and is not perceptible in itself. However, the phenomenon I refer to as subtraction of visibility allows us to characterize it as phenomenally negative. The hierarchical relationships between Spatial Belongings can ensure the qualitative nature of components of perceptual organization, such as object, background, and detail. The hidden structure of consciousness presents aspects that are decidedly counterintuitive compared to our idea of phenomenal experience. However, on the one hand, the Hierarchy of Spatial Belongings can explain the qualities of early vision and their appearance as a unitary whole, while on the other hand, it might be more easily explicable in terms of brain organization. In other words, the hidden structure of consciousness can be considered a bridge structure which, placing itself at an intermediate level between experience and physical properties, can contribute to bridging the explanatory gap.
... Definitions of consciousness vary across different academic fields, such as philosophy and psychology. In neurosciences, consciousness is generally defined as a wakeful state characterized by the ability to perceive, interact, and communicate with the environment and others in the integrated manner that wakefulness normally implies (Gloor 1986, Dennett 1995, Searle 2000, Baars 2005, Monaco et al. 2005, Ali et al. 2012, Beniczky et al. 2016. Although much has been written about consciousness, it continues to be a topic of ongoing discussion (Searle 2000, Tononi 2005, Ali et al. 2012, Campora and Kochen 2016. ...
The loss of consciousness (LOC) during seizures is one of the most striking features that significantly impact the quality of life, even though the neuronal network involved is not fully comprehended. We analyzed the intracerebral patterns in patients with focal drug-resistant epilepsy, both with and without LOC. We assessed the localization, lateralization, stereo electroencephalography (SEEG) patterns, seizure duration, and the quantification of contacts exhibiting electrical discharge. The degree of LOC was quantified using the Consciousness Seizure Scale. Thirteen patients (40 seizures) with focal drug-resistant epilepsy underwent SEEG. In cases of temporal lobe epilepsy (TLE, 6 patients and 15 seizures), LOC occurred more frequently in seizures with mesial rather than lateral temporal lobe onset. On the other hand, in cases of frontal lobe epilepsy (7 patients; 25 seizures), LOC was associated with pre-frontal onset, a higher number of contacts with epileptic discharge compared to the onset count and longer seizure durations. Our study revealed distinct characteristics during LOC depending on the epileptogenic zone. For temporal lobe seizures, LOC was associated with mesial seizure onset, whereas in frontal lobe epilepsy, seizure with LOC has a significant increase in contact showing epileptiform discharge and a pre-frontal onset. This phenomenon may be correlated with the broad neural network required to maintain consciousness, which can be affected in different ways, resulting in LOC
... Several models of consciousness, to more or less extent, also claim core structures. Some examples are the global workspace (GW) (Baars, 2005), the global neuronal workspace (GNW) (Dehaene and Changeux, 2011), the dynamical core (Tononi and Edelman, 1998), and the memory evolutive neural systems (MENS) (Ehresmann and Vanbremeersch, 2009), among many others. All these models treat conscious experience as emerging and reduced to the core structure, while this structure is postulated as a key initial assumption. ...
An algebraic interpretation of multigraph networks is introduced in relation to conscious experience, brain and body. These multigraphs have the ability to merge by an associative binary operator , accounting for biological composition. We also study a mathematical formulation of splitting layers, resulting in a formal analysis of the transition from conscious to non-conscious activity. From this construction, we recover core structures for conscious experience, dynamical content and causal constraints that conscious interactions may impose. An important result is the prediction of structural topological changes after conscious interactions. These results may inspire further use of formal mathematics to describe and predict new features of conscious experience while aligning well with formal tries to mathematize phenomenology, phenomenological tradition and applications to artificial consciousness.
... Regardless of one's approach, whether and how to consider animals' welfare has been based on whether the species in question is sentient [27,29] and thus aware of its present condition and choices for the future. Carruthers [33] evaluates possible explanations for whether animals have Qualia, defined as "instances of subjective conscious experience", and concludes that no theory explains this very well, though the Global Workspace Theory of Baars [34] comes closest for him. Dawkins [35] takes a more practical approach in our search for phenomenal consciousness in animals as a basis for welfare activity. ...
Ethical behaviour tends to lead to the welfare consideration of animals, but much less so for invertebrates. Indigenous tradition often valued all animals as having an important role in life on the planet, a practical application of modern ecology. The Judaeo–Christian–Islamic tradition postulated ‘man’ as having dominion over all of Earth, resulting in anthropocentrism and careless practices. In contrast, the Buddhist/Hindu belief in rebirth leads to ahisma, or doing no harm. In the face of capitalist systems, practice does not necessarily follow these beliefs, especially in the ‘shepherding’ of domestic animals. Only Jainist beliefs value the lives of all invertebrates. Philosophers are often divorced from the physiological reality of the animals they muse about, and science’s traditions of objectivity and the simplest possible explanation of behaviour led to ignorance of invertebrates’ abilities. Ninety-seven percent of animals on the planet are invertebrates. We have a long way to go to provide moral standing and welfare consideration, which is consistent with the new information about the sentience of some of these animals.
... Contentspecific NCCs are defined as the minimal neuronal mechanisms jointly sufficient for a specific conscious experience, for instance, of colors, oriented lines, faces, and buildings (e.g., Boly et al., 2017). One way to isolate the NCC is to use the contrastive method (Baars, 2005; see also Dehaene et al., 2014), i.e., by subtracting the neural activity elicited by the stimulus/feature of interest in a condition where the participant lacks awareness (on the basis of their report) from the neural activity elicited by the same stimulus/feature in a condition of awareness (i.e., aware-minus-unaware). The assumption behind this approach is that this subtraction cancels out the neural activity commonly elicited in the two conditions, unveiling the neural activity that is uniquely related to the awareness of the stimulus of interest (but see Aru et al. 2012;Lepauvre & Melloni, 2021;Miller, 2007;de Graaf et al. 2012;Tsuchiya et al. 2015). ...
... Если рассмотреть это явление шире, то речь идет о природе сознания человека. В нейробиологии существует ряд самостоятельных подходов к пониманию сознания [7,14]. Для нас важны два из них. ...
Нейронные сети призваны смоделировать процессы работы человеческого мозга. Поэтому в исследованиях, посвященных нейробиологическим основам работы мозга, все чаще возникает проблема понимания сути человеческого сознания. Глобальный переход к цифровой эпохе радикальным образом изменил характер повседневной жизни человека. В настоящее время переход к специфической цифровой деятельности и смешанной реальности усиливает функции мозга по бессознательной обработке информации и по-новому ставит задачу рассмотрения функции сознания. Чтобы понять это явление, необходимо более детально разобрать процесс работы мозга при погружении в цифровую среду. Такой средой может быть как свободный поиск в Интернете, так и работа с конкретной платформой или программой, когда автоматизированные когнитивные нейропаттерны продолжают переработку избыточной информации в режиме «внутреннего диалога». Внешне и по внутренним субьективным ощущениям человека индикатором такого состояния является избыточное напряжение височно-нижнечелюстного сустава (ВНЧС) и корня языка, которые как для внешней, так и для внутренней речи являются артикуляционным аппаратом. Для того чтобы включить осознанное восприятие новой учебной и/или рабочей информации, необходимо отключить автоматизированные когнитивные нейропаттерны естественного интеллекта. В статье представляются результаты исследования участников в возрасте от 20 до 76 лет, занимающихся интеллектуальным или офисным трудом в рамках учебно-исследовательских программ ООО «Нейроцентр развития профессиональной надежности «Ресурс».
... Although some vegetative people with relatively intact brains can have the same intelligence as ordinary people, due to the small scale of brain activities, they only have very small level of consciousness. The scale and time in the formula can be considered to be similar to the idea in global workspace theory (GNWT) [19], and the information conversion coefficient can be considered to be similar to idea in the integrated information theory (IIT) [20]. ...
An algorithm for brain processing of sequence information is proposed. For short sequence information, the neural circuit and neuron morphology required by the theory are perfectly consistent with the characteristics of the cerebellum, and it can be inferred that this structure requires a large number of neurons and can achieve a time accuracy of at least 1 ms. When trying to optimize the circuit to reduce the number of neurons required, a structure very similar to the hippocampus will be obtained, and the correspondence between the CA3 area of the hippocampus and the multi-head attention structure of the Transformer algorithm is specifically analyzed. The neocortex, on the other hand, can be thought of as a conveniently manufactured hippocampus. Because the brain can enhance the processing of sequence information by creating time delays, the fold structure in the brain and the geometry of the neocortex may enhance the processing of long-term sequence information. And the intelligence of the brain can be attributed to the ability to process information in sequences of different lengths. Starting from this theory, it can be concluded that memory is not stored in a single neuron, but different patterns of oscillations in neural circuits. Therefore, different memories may interfere with each other. The brain can clear useless oscillations through mechanisms such as sleep, thus retaining normal functionality. Human consciousness can be considered to be related to the intensity and frequency of oscillations in neural circuits.
... The agent assigns new long-term tasks to sailors who have finished their current ones. A notable feature of the architecture is its working memory, based on the global workspace theory [66]. In comparison to Virtual Mattie, IDA possesses more enhanced cognitive abilities. ...
Software bots have attracted increasing interest and popularity in both research and society. Their contributions span automation, digital twins, game characters with conscious-like behavior, and social media. However, there is still a lack of intelligent bots that can adapt to the variability and dynamic nature of digital web environments. Unlike human users, they have difficulty understanding and exploiting the affordances across multiple virtual environments.
Despite the hype, bots with human user-like cognition do not currently exist. Chatbots, for instance, lack situational awareness on the digital platforms where they operate, preventing them from enacting meaningful and autonomous intelligent behavior similar to human users.
In this survey, we aim to explore the role of cognitive architectures in supporting efforts towards engineering software bots with advanced general intelligence. We discuss how cognitive architectures can contribute to creating intelligent software bots. Furthermore, we highlight key architectural recommendations for the future development of autonomous, user-like cognitive bots.
... Given these findings, one can cautiously conclude that valuing as a process based on first-person affective attitudes is an activity in which cerebral hemispheres play an essential role. First-person affective experience in adult humans is probably impossible without cerebral hemispheres [83][84][85][86]. The endocrine system also plays an integral part in one's valuations since it produces and releases hormones like testosterone, adrenaline, progesterone, and many others, significantly impacting the subjective quality of one's affective experience [87]. ...
In 2017, Michael Nair-Collins formulated his Transitivity Argument which claimed that brain-dead patients are alive according to a concept that defines death in terms of the loss of moral status. This article challenges Nair-Collins’ view in three steps. First, I elaborate on the concept of moral status, claiming that to understand this notion appropriately, one must grasp the distinction between direct and indirect duties. Second, I argue that his understanding of moral status implicit in the Transitivity Argument is faulty since it is not based on a distinction between direct and indirect duties. Third, I show how this flaw in Nair-Collins’ argument is grounded in the more general problems between preference utilitarianism and desire fulfillment theory. Finally, I present the constructivist theory of moral status and the associated moral concept of death and explain how this concept challenges the Transitivity Argument. According to my view, brain death constitutes a valid criterion of death since brain death is incompatible with the preserved capacity to have affective attitudes and to value anything.
... In cognitive and brain science there are basically four theories. The Global Workspace Theory (GWS), proposed by Bernard Baars (2005), claims that consciousness arises from the brain's ability to integrate and broadcast information from various specialized brain areas to a central "workspace." This integrated information is what is experienced consciously. ...
This commentary discusses the papers included in this special issue which focuses on the role of consciousness in various aspects of behavior. The commentary first outlines dominant theories of consciousness and awareness. It then focuses on the papers included in the special issue, outlining the main findings or claims of each and embedding them in the general frame of the current study of consciousness. Finally, we conclude by outlining some general premises a general theory of consciousness would have to satisfy.
... The GWT is a prominent cognitive science theory that explains how distributed modules communicate to achieve higher-order cognitive states, including consciousness [93]. In this theory, a fleeting memory enables the system to access shared brain functions, and long-range connections between modules facilitate large-scale network operations [94] The GWT posits that sensory brain structures provide network inputs, with modules filtering out irrelevant information to share relevant activity. ...
The pulvinar nucleus of the thalamus is a crucial component of the visual system and plays significant roles in sensory processing and cognitive integration. The pulvinar’s extensive connectivity with cortical regions allows for bidirectional communication, contributing to the integration of sensory information across the visual hierarchy. Recent findings underscore the pulvinar’s involvement in attentional modulation, feature binding, and predictive coding. In this review, we highlight recent advances in clarifying the pulvinar’s circuitry and function. We discuss the contributions of the pulvinar to signal modulation across the global cortical network and place these findings within theoretical frameworks of cortical processing, particularly the global neuronal workspace (GNW) theory and predictive coding.
... En neurociencia la posición cartesiana se le atribuye a Baars (2005), por su tesis de que existe una estructura de mando unificada donde se integran y coordinan subsistemas expertos, redes semánticas, sistemas de memoria y sensaciones: un conjunto masivo de procesos especializados que pueden así intercambiar e integrar información. Hay que anotar, por ende, que la discusión especializada dista mucho de haber dicho la última palabra sobre el asunto y que, por ello, alguna publicación divulgativa reciente (Hoel, 2023) afirma que la neurociencia está todavía en un estado preparadigmático debido a que en el cerebro todo está interconectado y no es posible -aún-rastrear la red causal. ...
Anil Seth, en su libro Being I (La creación del yo), recientemente traducido, pretende suministrar una explicación neuorocientífica de la conciencia y la “yoidad”, prosiguiendo el enfoque de Daniel Dennett y, en último término, la crítica empirista de la metafísica que arranca de Hume. Para Seth, la yoidad es una percepción compleja, trabada con distintos ingredientes (corporal, perceptivo, volitivo, narrativo y social) que el autor no llega a explicar por qué o cómo se enlazan entre sí. Para Dennett, es una abstracción que postula un centro de gravedad narrativo, pero no se corresponde con ningún centro unitario de la experiencia humana. Al cuestionamiento de Dennett y Seth de la identidad y constancia del yo, le objetamos tres cosas: primera, las teorizaciones neurocientíficas no capturan en modo alguno la manera en que nos experimentamos ordinariamente y de forma unitaria como sujetos. Segundo, no logran articular entre sí las distintas capas de la yoidad, es decir, del por qué el yo narrativo, que se hace cargo del pasado, podría o debería sentirse culpable. Tercero, tampoco alcanzan a explicar (por lo dicho) ni la posibilidad de un progreso moral de la propia persona ni, respecto de los demás, experiencias tan cruciales como el amor.
... A global workspace: Some theorists hold that a global workspace, that is, a mechanism for broadcasting representations for global access throughout an information system, is necessary for consciousness [87]. In humans, for example, a visual state is conscious when the brain broadcasts it for global access. ...
This paper makes a simple case for extending moral consideration to some AI systems by 2030. It involves a normative premise and a descriptive premise. The normative premise is that humans have a duty to extend moral consideration to beings that have a non-negligible chance, given the evidence, of being conscious. The descriptive premise is that some AI systems do in fact have a non-negligible chance, given the evidence, of being conscious by 2030. The upshot is that humans have a duty to extend moral consideration to some AI systems by 2030. And if we have a duty to do that, then we plausibly also have a duty to start preparing now, so that we can be ready to treat AI systems with respect and compassion when the time comes.
A central goal of neuroscience is to understand how the brain orchestrates information from multiple input streams into a unified conscious experience. Here, we address two fundamental questions: how is the human information-processing architecture functionally organised, and how does its organisation support consciousness? We combine network science and a rigorous information-theoretic notion of synergy to delineate a “synergistic global workspace”, comprising gateway regions that gather synergistic information from specialised modules across the brain. This information is then integrated within the workspace and widely distributed via broadcaster regions. Through functional MRI analysis, we show that gateway regions of the synergistic workspace correspond to the brain’s default mode network, whereas broadcasters coincide with the executive control network. Demonstrating the empirical relevance of our proposed architecture for neural information processing, we show that loss of consciousness due to general anaesthesia or disorders of consciousness corresponds to a diminished ability of the synergistic workspace to integrate information, which is restored upon recovery. Thus, loss of consciousness coincides with a breakdown of information integration within the synergistic workspace of the human brain. This work contributes to conceptual and empirical reconciliation between two prominent scientific theories of consciousness, the Global Neuronal Workspace and Integrated Information Theory. Taken together, this work provides a new perspective on the role of prominent resting-state networks within the human information-processing architecture, while also advancing our understanding of how the human brain supports consciousness through the synergistic integration of information.
The evolutionary foundations of brain development represent point of departure. It delves into the depths of evolutionary history, unveiling the intricate journey that has shaped the human brain. Comparative neuroanatomy and phylogeny provide the canvas upon which we paint the portrait of our cognitive evolution. It contemplates the constraints, both genetic and epigenetic, that have sculpted the human brain's architecture. These insights serve as the bedrock upon which Evolutionary Global Neuroscience stands. In the quest to unlock the enigmatic complexities of the human brain, Evolutionary Global Neuroscience emerges as a transformative paradigm that transcends disciplinary boundaries. This expansive field explores the profound interplay between our evolutionary heritage and contemporary challenges in cognition, brain health, and the ever-evolving landscape of neurotechnology. Cognition, that quintessential hallmark of human existence, is next to claim our attention. It interrogate the adaptive value of cognition across epochs, deciphering its role in survival and prosperity. Yet, in this age of rapid societal transformation, the concept of “evolutionary mismatch” comes to the fore. It explore how this mismatch underlies a burgeoning epidemic of brain disorders, underscoring the urgent need for a new paradigm in addressing cognitive health. This paper illuminates the grim landscape of modernity's brain disorders. Alzheimer's disease and autism spectrum disorders serve as poignant exemplars of the evolutionary puzzle that engulfs us. From genetic predispositions to environmental influences, it contemplates the multifaceted origins of these disorders, ever mindful of the shadows cast by evolutionary history. The promise of Evolutionary Global Neuroscience, however, is not confined to diagnosis and treatment. It extends to innovative approaches that safeguard cognitive well-being. Drawing inspiration from our evolutionary past, it uncovers preventive strategies, therapeutic interventions, and personalized medicine approaches. Lifestyle modifications and environmental adaptations emerge as potent tools in preserving cognitive resilience. Amidst this transformative journey, neurotechnology emerges as the catalyst of innovation. Neuroimaging, brain-machine interfaces, neuromodulation, and artificial intelligence converge to redefine the boundaries of human brain exploration. The fusion of biology and technology holds the key to unlocking new frontiers in brain science, offering hope to individuals grappling with brain disorders. Yet, as it propels ourselve toward these novel discoveries, it confront an array of ethical challenges. Questions of cognitive enhancement, informed consent, privacy, and equitable access to neurotechnological advancements loom large. Our abstract engages with these ethical considerations, advocating for responsible innovation that harmonizes with our ethical and societal values. Evolutionary Global Neuroscience is not merely a scientific endeavor; it is a call to action. It beckons us to unite disciplines, fostering interdisciplinary collaboration that transcends borders and cultures. It urges us to invest in longitudinal and cross-cultural research that expands our understanding of the human brain's exquisite diversity. It demands a commitment to brain health literacy and thoughtful policy recommendations to ensure that the fruits of neurotechnological advancement are accessible to all. This paper journeyed through the realm of Evolutionary Global Neuroscience, a journey that begins in our evolutionary past and charts a course toward an enlightened, innovative, and equitable future for brain science, brain health, and the human mind.
The chapter digs into the confluence of digital and human consciousness, a frontier where neuroscience, psychology, philosophy, and AI studies come together. The chapter demonstrates the varied nature of consciousness by exploring several perspectives, including subjective experience, cognitive processes, and ethical implications. Ethical quandaries regarding merging AI and human consciousness are examined, emphasizing the significance of responsibility, transparency, and ethical innovation in AI research. The chapter emphasises the importance of multidisciplinary collaboration in navigating the complexity and seizing the opportunities AI technology offers. Finally, it argues for continued debate and collaboration in AI discourse to foster a unified approach to understanding consciousness and building a future that emphasises human well-being and ethical integrity.
A central goal of neuroscience is to understand how the brain orchestrates information from multiple input streams into a unified conscious experience. Here, we address two fundamental questions: how is the human information-processing architecture functionally organised, and how does its organisation support consciousness? We combine network science and a rigorous information-theoretic notion of synergy to delineate a “synergistic global workspace”, comprising gateway regions that gather synergistic information from specialised modules across the brain. This information is then integrated within the workspace and widely distributed via broadcaster regions. Through functional MRI analysis, we show that gateway regions of the synergistic workspace correspond to the brain’s default mode network, whereas broadcasters coincide with the executive control network. Demonstrating the empirical relevance of our proposed architecture for neural information processing, we show that loss of consciousness due to general anaesthesia or disorders of consciousness corresponds to a diminished ability of the synergistic workspace to integrate information, which is restored upon recovery. Thus, loss of consciousness coincides with a breakdown of information integration within the synergistic workspace of the human brain. This work contributes to conceptual and empirical reconciliation between two prominent scientific theories of consciousness, the Global Neuronal Workspace and Integrated Information Theory. Taken together, this work provides a new perspective on the role of prominent resting-state networks within the human information-processing architecture, while also advancing our understanding of how the human brain supports consciousness through the synergistic integration of information.
In the face of the stupefying complexity of the human brain, network analysis is a most useful tool that allows one to greatly simplify the problem, typically by approximating the billions of neurons making up the brain by means of a coarse-grained picture with a practicable number of nodes. But even such relatively small and coarse networks, such as the human connectome with its 100–1000 nodes, may present challenges for some computationally demanding analyses that are incapable of handling networks with more than a handful of nodes. With such applications in mind, we set out to study the extent to which dynamical behavior and critical phenomena in the brain may be preserved following a severe coarse-graining procedure. Thus we proceeded to further coarse grain the human connectome by taking a modularity-based approach, the goal being to produce a network of a relatively small number of modules. After finding that the qualitative dynamical behavior of the coarse-grained networks reflected that of the original networks, albeit to a less pronounced extent, we then formulated a hypothesis based on the coarse-grained networks in the context of criticality in the Wilson-Cowan and Ising models, and we verified the hypothesis, which connected a transition value of the former with the critical temperature of the latter, using the original networks. This preservation of dynamical and critical behavior following a severe coarse-graining procedure, in principle, allows for the drawing of similar qualitative conclusions by analyzing much smaller networks, which opens the door for studying the human connectome in contexts typically regarded as computationally intractable, such as Integrated Information Theory and quantum models of the human brain.
The article examines the history of the development of artificial intelligence (AI), starting from its first theoretical and practical steps and tracing the evolution to modern achievements. The article provides an overview of the key milestones, scientific discoveries and technological breakthroughs made in the field of AI. The most important figures, ideas and principles that influenced its development are also discussed. In the context of this development, various definitions of artificial intelligence are given. There are several key stages in the history of AI: the early stages, the quiet period, the AI renaissance, and the era of AI in the new millennium. Each of these stages made its own unique contribution to the progress of AI. The modern period is characterized by rapid development, especially in the field of machine learning and deep learning. These methods allow artificial intelligence to learn from data and identify complex patterns. Advances in natural language processing, such as models GPT and its modifications, have shown outstanding results. However, despite linguistic advances, GPT remains limited in aspects important to creating strong AI. The article discusses the limitations of modern language models, as well as the prerequisites and prospects for the development of strong artificial intelligence. Special attention is paid to the project of Elon Musk, who, having launched the company X.AI, is engaged in research in the field of creating strong AI with the goal of “knowledge of reality.” The article also proposes an alternative approach to creating strong artificial intelligence - the development of an artificial brain based on a multidimensional multi-connected receptor-effector neuron-like growing network. Some aspects of the emergence of artificial consciousness are also considered.
There exist no FDA- or CE-approved pharmacological treatments for tinnitus. Based on network science, tinnitus is proposed to be an emergent property of dynamically changing interacting networks. It is related to a balance between three cardinal networks: the lateral “loudness” pathway, the medial “suffering” pathway, and the noise canceling pathway. Invasive and non-invasive neuromodulation are an option for tinnitus management. Invasive neuromodulation consists of implanting electrodes in or on the brain or nerves. Implants have been performed in all three cardinal pathways: auditory cortex (lateral pathway), dorsal anterior cingulate cortex and caudate (medial pathway), dorsolateral prefrontal cortex, parahippocampal area (noise canceling pathway), as well as in the thalamus and subthalamus. Despite the theoretical science network suggestions, no multitarget implants have been performed. Vagus nerve stimulation, with or without paired sound stimulation, has also been performed with some success. However, invasive neuromodulation requires further research before it can become a routine part of tinnitus management.
Foremost in our experience is the intuition that we possess a unified conscious experience. However, many observations run counter to this intuition: we experience paralyzing indecision when faced with two appealing behavioral choices, we simultaneously hold contradictory beliefs, and the content of our thought is often characterized by an internal debate. Here, we propose the Nested Observer Windows (NOW) Model, a framework for hierarchical consciousness wherein information processed across many spatiotemporal scales of the brain feeds into subjective experience. The model likens the mind to a hierarchy of nested mosaic tiles—where an image is composed of mosaic tiles, and each of these tiles is itself an image composed of mosaic tiles. Unitary consciousness exists at the apex of this nested hierarchy where perceptual constructs become fully integrated and complex behaviors are initiated via abstract commands. We define an observer window as a spatially and temporally constrained system within which information is integrated, e.g. in functional brain regions and neurons. Three principles from the signal analysis of electrical activity describe the nested hierarchy and generate testable predictions. First, nested observer windows disseminate information across spatiotemporal scales with cross-frequency coupling. Second, observer windows are characterized by a high degree of internal synchrony (with zero phase lag). Third, observer windows at the same spatiotemporal level share information with each other through coherence (with non-zero phase lag). The theoretical framework of the NOW Model accounts for a wide range of subjective experiences and a novel approach for integrating prominent theories of consciousness.
SOMU is a theory of artificial general intelligence, AGI, that proposes a system with a universal code embedded in it, allowing it to interact with the environment and adapt to new situations without programming. So far, the whole universe and human brain have been modelled using SOMU. Each brain element forms a cell of a fractal tape, a cell possessing three qualities: obtaining feedback from the entire tape (S), transforming multiple states simultaneously (R), and bonding with any cell-states within-and-above the network of brain components. The undefined and non-finite nature of the cells rejects the tuples of a Turing machine. SRT triplets extend the brain’s ability to perceive natural events beyond the spatio-temporal structure, using a cyclic sequence or loop of changes in geometric shapes. This topology factor, becomes an inseparable entity of space–time, i.e. space–time-topology (STt). The fourth factor, prime numbers, can be used to rewrite spatio-temporal events by counting singularity regions in loops of various sizes. The pattern of primes is called a phase prime metric, PPM that links all the symmetry breaking rules, or every single phenomenon of the universe. SOMU postulates space–time-topology-prime (STtp) quatret as an invariant that forms the basic structure of information in the brain and the universe, STtp is a bias free, attribution free, significance free and definition free entity. SOMU reads recurring events in nature, creates 3D assembly of clocks, namely polyatomic time crystal, PTC and feeds those to PPM to create STtps. Each layer in a within-and-above brain circuit behaves like an imaginary the world, generating PTCs. These PTCs of different imaginary worlds interact through a new STtp tensor decomposition mathematics. Unlike string theory, SOMU proposes that the fundamental elements of the universe are helical or vortex phases, not strings. It dismisses string theory's approach of using sum of 4 × 4 and 8 × 8 tensors to create a 12 × 12 tensor for explaining universe. Instead, SOMU advocates a network of multinion tensors ranging from 2 × 2 to 108 × 108 in size. With just 108 elements, a system can replicate ~90 of all symmetry breaking rules in the universe, allowing a small systemic part to mirror majority events of the whole, that is human level consciousness G. Under the SOMU model, for a part to be conscious, it must mirror a significant portion of the whole and should act as a whole for the abundance of similar mirroring parts within itself.
Miguel Bombarda: um visionário da consciência 1 Resumo Miguel Bombarda foi um médico psiquiatra português que viveu na transição do século XIX para o século XX. Mas foi, também, um filósofo da mente-por ventura o primeiro filósofo da consciência português. Os seus inúmeros trabalhos sobre o cérebro, a mente e a consciência merecem um olhar atento pois muitas das suas ideias, apesar de muitas vezes ignoradas e desprezadas pelos seus contemporâneos, acabaram por se mostrar válidas aos olhos da filosofia da mente e neurociência atuais. Neste artigo pretende-se desvendar algumas das contribuições pioneiras de Miguel Bombarda para o estudo e compreensão da consciência sob um olhar materialista-reducionista, confrontando algumas dessas ideias com filósofos, psicólogos e neurocientistas contemporâneos. Palavras-chave: Miguel Bombarda; consciência; livre-arbítrio; materialismo-reducionista Miguel Bombarda: a visionary of consciousness Abstract Miguel Bombarda was a Portuguese psychiatrist who lived in the transition from the 19th to the 20th century. But he was also a philosopher of mind-perhaps the first Portuguese philosopher of consciousness. His numerous works on the brain, mind and consciousness deserve a closer look because many of his ideas, despite being often ignored and despised by his contemporaries, have turned out to be valid in the eyes of contemporary philosophy of mind and neuroscience. This article intends to unveil some of Miguel Bombarda's pioneering contributions to the study and understanding of consciousness from a materialist-reductionist perspective, confronting some of these ideas with contemporary philosophers, psychologists and neuroscientists.
Consciousness is one of the most complex aspects of human experience. Studying the mechanisms involved in the transitions among different levels of consciousness remains as one of the greatest challenges in neuroscience. In this study we use a measure of integrated information (ΦAR) to evaluate dynamic changes during consciousness transitions. We applied the measure to intracranial electroencephalography (SEEG) recordings collected from 6 patients that suffer from refractory epilepsy, taking into account inter-ictal, pre-ictal and ictal periods. We analyzed the dynamical evolution of ΦAR in groups of electrode contacts outside the epileptogenic region and compared it with the Consciousness Seizure Scale (CCS). We show that changes on ΦAR are significantly correlated with changes in the reported states of consciousness.
There is still controversy surrounding the definition and mechanisms of consciousness. The constrained disorder principle (CDP) defines complex systems by their dynamic borders, limiting their inherent disorder. In line with the CDP, the brain exhibits a disorder bounded by dynamic borders essential for proper function, efficient energy use, and life support under continuous perturbations. The brain’s inherent variability contributes to its adaptability and flexibility. Neuronal signal variability challenges the association of brain structures with consciousness and methods for assessing consciousness. The present paper discusses some theories about consciousness, emphasizing their failure to explain the brain’s variability. This paper describes how the CDP accounts for consciousness’s variability, complexity, entropy, and uncertainty. Using newly developed second-generation artificial intelligence systems, we describe how CDP-based platforms may improve disorders of consciousness (DoC) by accounting for consciousness variability, complexity, entropy, and uncertainty. This platform could be used to improve response to current interventions and develop new therapeutic regimens for patients with DoC in future studies.
The handheld diagnosis and analysis are highly dependent on the physiological data in the clinical sector. Detection of the defect in the neuronal-assisted activity raises the challenge to the prevailing treatment that benefits from machine learning approaches. The congregated EEG data is then utilized in design of learning applications to develop a model that classifies intricate EEG patterns into active and inactive segments. During arithmetic problem-solving EEG signal acquired from frontal lobe contributes for intelligence detection. The low intricate statistical parameters help in understanding the objective. The mean of the segmented samples and standard deviation are the features extracted for model building. The feature selection is handled using correlation and Fisher score between {Fp1 and F8} and priority ranking of the regions with enhanced activity are selected for the classifier models to the training net. The R-studio platform is used to classify the data based on active and inactive liability. The radial basis function kernel for support vector machine (SVM) is deployed to substantiate the proposed methodology. The vulnerable regions F1 and F8 for arithmetic activity can be visualized from the correlation fit performed between regions. Using SVM classifier sensitivity of 92.5% is obtained for the selected features. A wide range of clinical problems can be diagnosed using this model and used for brain-computer interface.
This chapter deals with consciousness and its relation with identity, or with what we perceive as identity. To explore this topic from a broad perspective, we will first take a tour of the different explanations with which philosophy, throughout history, has tried to explain the phenomenon of consciousness. Secondly, we will go into the neurofunctional and neuroanatomical perspective, to set the precedents on which we will expose the current theories with which neuroscience tries to explain consciousness. Finally, we will recapitulate on what has been seen so far and try to reconstruct, with it, a possible explanation of the relationship between consciousness and identity, and the relationship that it has not only with ourselves but with our environment – we will try to explore whether consciousness and identity are individual phenomena or also dependent on others; If our identity is something that relies on us, or that also relies on what others think about us.
Objective. Deep Brain Stimulation (DBS) is a potential treatment that promotes the recovery of patients with disorders of consciousness (DOC). This study quantified the changes in consciousness and the neuromodulation effect of DBS on patients with DOC. Approach. Eleven patients were recruited for this study which consists of three conditions: ’Pre’ (two days before DBS surgery), ’Post-On’ (one month after surgery with stimulation), and ’Post-Off’ (one month after surgery without stimulation). Functional near-infrared spectroscopy (fNIRS) was recorded from the frontal lobe, parietal lobe, and occipital lobe of patients during the experiment of auditory stimuli paradigm, in parallel with the Coma Recovery Scale-Revised (CRS-R) assessment. The brain hemodynamic states were defined and state transition acceleration was taken to quantify the information transmission strength of the brain network. Linear regression analysis was conducted between the changes in regional and global indicators and the changes in the CRS-R index. Main Results. Significant correlation was observed between the changes in the global transition acceleration indicator and the changes in the CRS-R index (slope=55.910, p < 0.001, R2 = 0.732). For the regional indicators, similar correlations were found between the changes in the frontal lobe and parietal lobe indicators and the changes in the CRS-R index (slope=46.612, p < 0.01, R2 = 0.694; slope=47.491, p < 0.01, R2 = 0.676). Significance. Our study suggests that fNIRS-based brain hemodynamics transition analysis can signify the neuromodulation effect of DBS treatment on patients with DOC, and the transition acceleration indicator is a promising brain functional marker for DOC.
Reviews the book, Human brain function by R. S. J. Frackowiak, K. J. Friston, C. D. Frith, R. J. Dolan, and J. C. Mazziotta (1997). A significant recent development in the rapidly evolving field of imaging technology has been the relative shift of emphasis from positron emission tomography (PET) activation studies to functional magnetic resonance imaging (MRI). Not only is MRI technology more widely available than PET, it is less invasive and can benefit from improved temporal and spatial resolution. It seems timely, therefore, to take stock and ask what has been learned from human brain imaging so far. This volume, by Frackowiak and colleagues from the Functional Imaging Laboratory in London, seeks to do that through a comprehensive overview of the group's own work in the field to date; that is, mainly through the use of PET. Physiologists, in particular, may find the title somewhat misleading; "Human Brain Function" focuses almost exclusively on the results of PET activation studies, while relevant electrophysiological studies are only given detailed consideration in one chapter on the visual system. In spite of this, the book does demonstrate, unequivocally, that functional neuroimaging has had a dramatic impact on the study of human brain function. What also continues to be clear, however, is that the gulf between technological know how and depth of understanding has never been wider. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
The study of conscious experience has seen remarkable strides in the last ten years, reflecting important technological breakthroughs and the enormous efforts of researchers. Although still embroiled in debate, scientists are now beginning to find common ground in their understanding of consciousness, which may pave the way for a unified explanation of how and why we experience and understand the world around us. This book brings the subject to life with a metaphor that has been used to understand consciousness since the time of Aristotle-the mind as theater. Here consciousness is seen as a "stage" on which our sensations, perceptions, thoughts, and feelings play to a vast, silent audience (the immensely complicated inner-workings of the brain's unconscious processes). Behind the scenes, silent context operators shape conscious experience; they include implicit expectations, self systems, and scene setters. Using this framework, the book presents compelling evidence that human consciousness rides on top of biologically ancient mechanisms. In humans it manifests itself in inner speech, imagery, perception, and voluntary control of thought and action. Topics like hypnosis, absorbed states of mind, adaptation to trauma, and the human propensity to project expectations on uncertainty, all fit into the expanded theater metaphor.
1 Human Information Agents Human information agents include insurance agents, travel agents, voter registrars, mail-order service clerks, telephone information operators, employment agents, AAA route planners, customer service agents, bank loan officers, and many, many others. Such human agents must typically possess a common set of skills. These would often include most of the following: • Communicating with clients in their natural language; • Reading from and writing to databases of various sorts (insurance rates, airline schedules, voter roles, company catalogs, etc.); • Knowing, understanding and adhering to company or agency policies; • Planning and decision making (coverage to suggest, routes and carriers to offer, loan to authorize, etc); • Negotiating with clients about the issues involved; • Generating a tangible product (insurance policy, airline tickets, customer order, etc.). I suspect that millions of people, mostly in developed countries, earn their livings as such human information agents. Each of these, in addition to salary and benefits, is typically provided with office space and furniture, and with computing facilities. The total yearly cost of each such agent in a developed country must conservatively be on the order of $100,000. Thus the total yearly cost of human information agents around the world must push a trillion dollars.
People often are unable to report the content of ignored information, but it is unknown whether this reflects a complete failure
to perceive it (inattentional blindness) or merely that it is rapidly forgotten (inattentional amnesia). Here functional imaging
is used to address this issue by measuring brain activity for unattended words. When attention is fully engaged with other
material, the brain no longer differentiates between meaningful words and random letters, even when they are looked at directly.
These results demonstrate true inattentional blindness for words and show that visual recognition wholly depends on attention
even for highly familiar and meaningful stimuli at the center of gaze.
Why should conscious recollection be associated with recovery of some memories and not others? A hypothesis is proposed and defended that the medial temporal lobe/hippocampal complex (MTL/H) and related limbic structures comprise a memory module that receives as its input only information that is consciously apprehended. The module then binds or conjoins into memory traces those neural elements that mediated the conscious experience so that effectively "consciousness" is as intergral a part of the memory traces as it was during the experience of the event. When memory traces are retrieved, what is recovered are the phenomenological records (Conway, 1992) of experienced events which are integrated content-consciousness packets. Evidence is presented which suggests that the MTL/H module satisfies Fodorian criteria of modularity. The MTL/H module is compared to perceptual modules in nonfrontal neocortex that mediate performance on tests of memory without awareness and to prefrontal neocortex that acts as a central working-with-memory system that operates on the input to MTL/H and the shallow output from it.
By repeating words 'in our head', verbal material (such as telephone numbers) can be kept in working memory almost indefinitely. This 'articulatory loop' includes a subvocal rehearsal system and a phonological store. Little is known about neural correlates of this model of verbal short-term memory. We therefore measured regional cerebral blood flow, an index of neuronal activity, in volunteers performing a task engaging both components of the articulatory loop (short-term memory for letters) and a task which engages only the subvocal rehearsal system (rhyming judgement for letters). Stimuli were presented visually and the subjects did not speak. We report here that comparisons of distribution of cerebral blood flow in these conditions localized the phonological store to the left supramarginal gyrus whereas the subvocal rehearsal system was associated with Broca's area. This is, to our knowledge, the first demonstration of the normal anatomy of the components of the 'articulatory loop'.
Conventional approaches to understanding consciousness are generally concerned with the contribution of specific brain areas or groups of neurons. By contrast, it is considered here what kinds of neural processes can account for key properties of conscious experience. Applying measures of neural integration and complexity, together with an analysis of extensive neurological data, leads to a testable proposal-the dynamic core hypothesis-about the properties of the neural substrate of consciousness.
In the present study, we used positron emission tomography to investigate changes in regional cerebral blood flow (rCBF) during a general anesthetic infusion set to produce a gradual transition from the awake state to unconsciousness. Five right-handed human volunteers participated in the study. They were given propofol with a computer-controlled infusion pump to achieve three stable levels of plasma concentrations corresponding to mild sedation, deep sedation, and unconsciousness, the latter defined as unresponsiveness to verbal commands. During awake baseline and each of the three levels of sedation, two scans were acquired after injection of an H 2 ¹⁵ O bolus. Global as well as regional CBF were determined and correlated with propofol concentrations. In addition, blood flow changes in the thalamus were correlated with those of the entire scanned volume to determine areas of coordinated changes.
In addition to a generalized decrease in global CBF, large regional decreases in CBF occurred bilaterally in the medial thalamus, the cuneus and precuneus, and the posterior cingulate, orbitofrontal, and right angular gyri. Furthermore, a significant covariation between the thalamic and midbrain blood flow changes was observed, suggesting a close functional relationship between the two structures.
We suggest that, at the concentrations attained, propofol preferentially decreases rCBF in brain regions previously implicated in the regulation of arousal, performance of associative functions, and autonomic control. Our data support the hypothesis that anesthetics induce behavioral changes via a preferential, concentration-dependent effect on specific neuronal networks rather than through a nonspecific, generalized effect on the brain.
One way to approach the study of consciousness is to explore lesional cases in which impairment of consciousness is the prominent clinical sign. Vegetative state is such a condition wherein awareness is abolished whereas arousal persists. It can be diagnosed clinically soon after a brain injury and may be reversible (as in the following case report) or progress to a persistent vegetative state or death. The distinction between vegetative state and persistent vegetative state is that the second is defined as a vegetative state that has continued or endured for at least 1 month.1 We present a patient who developed a vegetative state after carbon monoxide poisoning and in whom we had the opportunity to measure brain glucose metabolism distribution during the vegetative state and after recovery to consciousness. Using [18F]fluorodeoxyglucose (FDG) PET and statistical parametric mapping (SPM) we compared both patient’s sets to a normal control population. Our findings offer an insight into the neural correlates of “awareness”, pointing to a critical role for posterior associative cortices in consciousness.
Localisation of voxels in which cerebral glucose metabolism was impaired during vegetative state (in yellow) and after …
With each eye fixation, we experience a richly detailed visual world. Yet recent work on visual integration and change direction reveals that we are surprisingly unaware of the details of our environment from one view to the next: we often do not detect large changes to objects and scenes ('change blindness'). Furthermore, without attention, we may not even perceive objects ('inattentional blindness'). Taken together, these findings suggest that we perceive and remember only those objects and details that receive focused attention. In this paper, we briefly review and discuss evidence for these cognitive forms of 'blindness'. We then present a new study that builds on classic studies of divided visual attention to examine inattentional blindness for complex objects and events in dynamic scenes. Our results suggest that the likelihood of noticing an unexpected object depends on the similarity of that object to other objects in the display and on how difficult the priming monitoring task is. Interestingly, spatial proximity of the critical unattended object to attended locations does not appear to affect detection, suggesting that observers attend to objects and events, not spatial positions. We discuss the implications of these results for visual representations and awareness of our visual environment.
A baseline or control state is fundamental to the understanding of most complex systems. Defining a baseline state in the human brain, arguably our most complex system, poses a particular challenge. Many suspect that left unconstrained, its activity will vary unpredictably. Despite this prediction we identify a baseline state of the normal adult human brain in terms of the brain oxygen extraction fraction or OEF. The OEF is defined as the ratio of oxygen used by the brain to oxygen delivered by flowing blood and is remarkably uniform in the awake but resting state (e.g., lying quietly with eyes closed). Local deviations in the OEF represent the physiological basis of signals of changes in neuronal activity obtained with functional MRI during a wide variety of human behaviors. We used quantitative metabolic and circulatory measurements from positron-emission tomography to obtain the OEF regionally throughout the brain. Areas of activation were conspicuous by their absence. All significant deviations from the mean hemisphere OEF were increases, signifying deactivations, and resided almost exclusively in the visual system. Defining the baseline state of an area in this manner attaches meaning to a group of areas that consistently exhibit decreases from this baseline, during a wide variety of goal-directed behaviors monitored with positron-emission tomography and functional MRI. These decreases suggest the existence of an organized, baseline default mode of brain function that is suspended during specific goal-directed behaviors.
The primate visual brain consists of many separate, functionally specialized processing systems, each consisting of several apparently hierarchical stages or nodes. The evidence reviewed here leads me to speculate (a) that the processing systems are autonomous with respect to one another, (b) that activity at each node reaches a perceptual end point at a different time, resulting in a perceptual asynchrony in vision, and (c) that, consequently, activity at each node generates a microconsciousness. Visual consciousness is therefore distributed in space and time, with the universal organizing principle of abstraction applied separately within each processing system. The consequence of spatially and temporally distributed microconsciousnesses is that their integration is a multistage, nonhierarchical process that may involve a neural "glue."
We used functional magnetic resonance imaging (fMRI) and event-related potentials (ERPs) to visualize the cerebral processing of unseen masked words. Within the areas associated with conscious reading, masked words activated left extrastriate, fusiform and precentral areas. Furthermore, masked words reduced the amount of activation evoked by a subsequent conscious presentation of the same word. In the left fusiform gyrus, this repetition suppression phenomenon was independent of whether the prime and target shared the same case, indicating that case-independent information about letter strings was extracted unconsciously. In comparison to an unmasked situation, however, the activation evoked by masked words was drastically reduced and was undetectable in prefrontal and parietal areas, correlating with participants' inability to report the masked words.
Mental imagery has, until recently, fallen within the purview of philosophy and cognitive psychology. Both enterprises have raised important questions about imagery, but have not made substantial progress in answering them. With the advent of cognitive neuroscience, these questions have become empirically tractable. Neuroimaging studies, combined with other methods (such as studies of brain-damaged patients and of the effects of transcranial magnetic stimulation), are revealing the ways in which imagery draws on mechanisms used in other activities, such as perception and motor control. Because of its close relation to these basic processes, imagery is now becoming one of the best understood 'higher' cognitive functions.
Brain areas activated by stimuli in the left visual field of a right parietal patient suffering from left visual extinction were identified using event-related functional magnetic resonance imaging. Left visual field stimuli that were extinguished from awareness still activated the ventral visual cortex, including areas in the damaged right hemisphere. An extinguished face stimulus on the left produced robust category-specific activation of the right fusiform face area. On trials where the left visual stimulus was consciously seen rather than extinguished, greater activity was found in the ventral visual cortex of the damaged hemisphere, and also in frontal and parietal areas of the intact hemisphere. These findings extend recent observations on visual extinction, suggesting distinct neural correlates for conscious and unconscious perception.
Here we summarize our present approach to the problem of consciousness. After an introduction outlining our general strategy, we describe what is meant by the term 'framework' and set it out under ten headings. This framework offers a coherent scheme for explaining the neural correlates of (visual) consciousness in terms of competing cellular assemblies. Most of the ideas we favor have been suggested before, but their combination is original. We also outline some general experimental approaches to the problem and, finally, acknowledge some relevant aspects of the brain that have been left out of the proposed framework.
The persistent vegetative state (PVS) is a devastating medical condition characterized by preserved wakefulness contrasting with absent voluntary interaction with the environment. We used positron emission tomography to assess the central processing of noxious somatosensory stimuli in the PVS. Changes in regional cerebral blood flow were measured during high-intensity electrical stimulation of the median nerve compared with rest in 15 nonsedated patients and in 15 healthy controls. Evoked potentials were recorded simultaneously. The stimuli were experienced as highly unpleasant to painful in controls. Brain glucose metabolism was also studied with [18F]fluorodeoxyglucose in resting conditions. In PVS patients, overall cerebral metabolism was 40% of normal values. Nevertheless, noxious somatosensory stimulation-activated midbrain, contralateral thalamus, and primary somatosensory cortex in each and every PVS patient, even in the absence of detectable cortical evoked potentials. Secondary somatosensory, bilateral insular, posterior parietal, and anterior cingulate cortices did not show activation in any patient. Moreover, in PVS patients, the activated primary somatosensory cortex was functionally disconnected from secondary somatosensory, bilateral posterior parietal, premotor, polysensory superior temporal, and prefrontal cortices. In conclusion, somatosensory stimulation of PVS patients, at intensities that elicited pain in controls, resulted in increased neuronal activity in primary somatosensory cortex, even if resting brain metabolism was severely impaired. However, this activation of primary cortex seems to be isolated and dissociated from higher-order associative cortices.
Summary H2 15 O-PET was used to investigate changes in regional cerebral blood flow in response to auditory stimulation in patients in the vegetative state. Five patients in a vegetative state of hypoxic origin were compared with 18 age-matched controls. In addition, the cerebral metabolism of these patients and 53 age-matched controls was studied using [ 18 F]fluorodeoxyglucose. In control subjects, auditory click stimuli activated bilateral auditory cortices [Brodmann areas (BA) 41 and 42] and the contralateral auditory association cortices (BA 22). In the patients, although resting metabolism was decreased to 61% of normal values, bilateral auditory areas 41 and 42 showed activation as seen in the controls, but the temporoparietal junction cortex (BA 22) failed to be activated. Moreover, the auditory
We combined fMRI and EEG recording to study the neurophysiological responses associated with auditory stimulation across the sleep-wake cycle. We found that presentation of auditory stimuli produces bilateral activation in auditory cortex, thalamus, and caudate during both wakefulness and nonrapid eye movement (NREM) sleep. However, the left parietal and, bilaterally, the prefrontal and cingulate cortices and the thalamus were less activated during NREM sleep compared to wakefulness. These areas may play a role in the further processing of sensory information required to achieve conscious perception during wakefulness. Finally, during NREM sleep, the left amygdala and the left prefrontal cortex were more activated by stimuli having special affective significance than by neutral stimuli. These data suggests that the sleeping brain can process auditory stimuli and detect meaningful events.
Here we describe briefly the architecture and mechanisms of a "conscious" software agent named IDA who is to act as a type of employment agent. We go on to show how this architecture and these mechanisms allow IDA to deliberate much as we humans do and to make voluntary choices of actions. The technology described, if successful, should allow the automation of the work of many human information agents. The IDA model also makes, hopefully testable, hypotheses about how human deliberation and volition.
Active components of classical working memory are conscious, but traditional theory does not account for this fact. Global Workspace theory suggests that consciousness is needed to recruit unconscious specialized networks that carry out detailed working memory functions. The IDA model provides a fine-grained analysis of this process, specifically of two classical working-memory tasks, verbal rehearsal and the utilization of a visual image. In the process, new light is shed on the interactions between conscious and unconscious aspects of working memory.
Regional cerebral glucose metabolic rate (GMR) quantified with positron emission tomography (PET) with 18-fluoro-2-deoxyglucose (FDG) was measured twice in 8 young men performing a complex visuospatial/motor task (the computer game Tetris), before and after practice. After 4-8 weeks of daily practice on Tetris, GMR in cortical surface regions decreased despite a more than 7-fold increase in performance. Subjects who improved their Tetris performance the most after practice showed the largest glucose metabolic decreases after practice in several areas. These results suggest that learning may result in decreased use of extraneous or inefficient brain areas. Changes in regional subcortical glucose metabolic rate with practice may reflect changes in cognitive strategy that are a part of the learning process.
Practice of a novel task leads to improved performance. The brain mechanisms associated with practice-induced improvement in performance are largely unknown. To address this question we have examined the functional anatomy of the human brain with positron emission tomography (PET) during the naive and practiced performance of a simple verbal response selection task (saying an appropriate verb for a visually presented noun). As a control state, subjects were asked to repeat the visually presented nouns. Areas of the brain most active during naive performance (anterior cingulate, left prefrontal and left posterior temporal cortices, and the right cerebellar hemisphere), compared to repeating the visually presented nouns, were all significantly less active during practiced performance. These changes were accompanied by changes in the opposite direction in sylvian-insular cortex bilaterally and left medial extrastriate cortex. In effect, brief practice made the cortical circuitry used for verbal response selection indistinguishable from simple word repetition. Introduction of a novel list of words reversed the learning-related effects. These results indicate that two distinct circuits can be used for verbal response selection and normal subjects can change the brain circuits used during task performance following less than 15 min of practice. One critical factor in determining the circuitry used appears to be the degree to which a task is learned or automatic.
To test whether the silence of painless myocardial ischemia is caused by abnormal handling by the central nervous system of afferent messages from the heart.
Nonrandomized study.
A tertiary referral center (postgraduate medical school).
2 matched groups of nondiabetic patients with coronary artery disease. Group A consisted of nine patients with reproducible stress-induced angina; group B consisted of nine patients with reproducible stress-induced myocardial ischemia but no angina.
Intravenous placebo infusion and low-dose (5 and 10 micrograms/ kg per minute) and high-dose (20 to 35 micrograms/kg per minute) dobutamine infusions.
Positron emission tomography was used to measure regional cerebral blood flow changes as an index of neuronal activation during painful and silent myocardial ischemia induced by intravenous dobutamine.
Regional cerebral blood flow changes during myocardial ischemia were compared with those during baseline conditions and during placebo infusion. During myocardial ischemia, regional cerebral blood flow increased bilaterally in the thalami and prefrontal, basal frontal, and ventral cingulate corticles in patients in group A. Both thalami were activated in group B, but cortical activation was limited to the right frontal region. A formal comparison of groups A and B showed significant differences (P < 0.01) in activation of the basal frontal cortex, ventral cingulate cortex, and left temporal pole. In both groups, thalamic regional cerebral blood flow remained increased after the symptoms and signs of ischemia had ceased.
Bilateral activation of the thalamus can be shown in both angina and silent ischemia; thus, peripheral nerve dysfunction cannot completely explain silent ischemia. Frontal cortical activation appears to be necessary for the sensation of pain. Abnormal central processing of afferent pain messages from the heart may play a determining role in silent myocardial ischemia.
The visual areas of the temporal lobe of the primate are thought to be essential for the representation of visual objects. To examine the role of these areas in the visual awareness of a stimulus, we recorded the activity of single neurons in monkeys trained to report their percepts when viewing ambiguous stimuli. Visual ambiguity was induced by presenting incongruent images to the two eyes, a stimulation condition known to instigate binocular rivalry, during which one image is seen at a given time while the other is perceptually suppressed. Previous recordings in areas V1, V2, V4, and MT of monkeys experiencing binocular rivalry showed that only a small proportion of striate and early extrastriate neurons discharge exclusively when the driving stimulus is seen. In contrast, the activity of almost all neurons in the inferior temporal cortex and the visual areas of the cortex of superior temporal sulcus was found to be contingent upon the perceptual dominance of an effective visual stimulus. These areas thus appear to represent a stage of processing beyond the resolution of ambiguities--and thus beyond the processes of perceptual grouping and image segmentation--where neural activity reflects the brain's internal view of objects, rather than the effects of the retinal stimulus on cells encoding simple visual features or shape primitives.
Vegetative state (VS) is a condition of abolished awareness with persistence of arousal. Awareness is part of consciousness, which itself is thought to represent an emergent property of cerebral neural networks. Our hypothesis was that part of the neural correlate underlying VS is an altered connectivity, especially between the associative cortices. We assessed regional cerebral glucose metabolism (rCMRGlu) and effective cortical connectivity in four patients in VS by means of statistical parametric mapping and [18F]fluorodeoxyglucose-positron emission tomography. Our data showed a common pattern of impaired rCMRGlu in the prefrontal, premotor, and parietotemporal association areas and posterior cingulate cortex/precuneus in VS. In a next step, we demonstrated that in VS patients various prefrontal and premotor areas have in common that they are less tightly connected with the posterior cingulate cortex than in normal controls. These results provide a strong argument for an alteration of cortical connectivity in VS patients.
By use of H2(15)O positron emission tomography we have shown that functional connectivity between intralaminar thalamic nuclei and prefrontal and anterior cingulate cortices was altered during vegetative state but not after recovery of consciousness.
H(2)(15)O-PET was used to investigate changes in regional cerebral blood flow in response to auditory stimulation in patients in the vegetative state. Five patients in a vegetative state of hypoxic origin were compared with 18 age-matched controls. In addition, the cerebral metabolism of these patients and 53 age-matched controls was studied using [(18)F]fluorodeoxyglucose. In control subjects, auditory click stimuli activated bilateral auditory cortices [Brodmann areas (BA) 41 and 42] and the contralateral auditory association cortices (BA 22). In the patients, although resting metabolism was decreased to 61% of normal values, bilateral auditory areas 41 and 42 showed activation as seen in the controls, but the temporoparietal junction cortex (BA 22) failed to be activated. Moreover, the auditory association cortex was functionally disconnected from the posterior parietal association area (BA 40), the anterior cingulate cortex (BA 24) and the hippocampus, as revealed by psychophysiological interaction analysis. Thus, despite altered resting metabolism, the auditory primary cortices were still activated during external stimulation, whereas hierarchically higher-order multi- modal association areas were not. Such a cascade of functional disconnections along the auditory cortical pathways, from the primary auditory areas to multimodal and limbic areas, suggests that the residual cortical processing observed in the vegetative state cannot lead to the integrative processes that are thought to be necessary for the attainment of the normal level of awareness.
We combined fMRI and EEG recording to study the neurophysiological responses associated with auditory stimulation across the sleep-wake cycle. We found that presentation of auditory stimuli produces bilateral activation in auditory cortex, thalamus, and caudate during both wakefulness and nonrapid eye movement (NREM) sleep. However, the left parietal and, bilaterally, the prefrontal and cingulate cortices and the thalamus were less activated during NREM sleep compared to wakefulness. These areas may play a role in the further processing of sensory information required to achieve conscious perception during wakefulness. Finally, during NREM sleep, the left amygdala and the left prefrontal cortex were more activated by stimuli having special affective significance than by neutral stimuli. These data suggests that the sleeping brain can process auditory stimuli and detect meaningful events.
The neocortex and the thalamus constitute a unified oscillatory machine during different states of vigilance. The cortically generated slow sleep oscillation has the virtue of grouping other sleep rhythms, including those arising in the thalamus, within complex wave-sequences. Despite the coherent oscillatory activity in corticothalamic circuits, on the functional side there is dissociation between thalamus and neocortex during sleep. While dorsal thalamic neurons undergo inhibitory processes induced by prolonged spikebursts of GABAergic thalamic reticular neurons, the cortex displays, periodically, a rich spontaneous activity and preserves the capacity to process internally generated signals. Simultaneous intracellular recordings from thalamic and cortical neurons show that short-term plasticity processes occur after prolonged and rhythmic spike-bursts fired by thalamic and cortical neurons during slow-wave sleep oscillations. This may serve to support resonant phenomena and reorganize corticothalamic circuitry.
The cortical anatomy of the conscious resting state (REST) was investigated using a meta-analysis of nine positron emission tomography (PET) activation protocols that dealt with different cognitive tasks but shared REST as a common control state. During REST, subjects were in darkness and silence, and were instructed to relax, refrain from moving, and avoid systematic thoughts. Each protocol contrasted REST to a different cognitive task consisting either of language, mental imagery, mental calculation, reasoning, finger movement, or spatial working memory, using either auditory, visual or no stimulus delivery, and requiring either vocal, motor or no output. A total of 63 subjects and 370 spatially normalized PET scans were entered in the meta-analysis. Conjunction analysis revealed a network of brain areas jointly activated during conscious REST as compared to the nine cognitive tasks, including the bilateral angular gyrus, the left anterior precuneus and posterior cingulate cortex, the left medial frontal and anterior cingulate cortex, the left superior and medial frontal sulcus, and the left inferior frontal cortex. These results suggest that brain activity during conscious REST is sustained by a large scale network of heteromodal associative parietal and frontal cortical areas, that can be further hierarchically organized in an episodic working memory parieto-frontal network, driven in part by emotions, working under the supervision of an executive left prefrontal network.
Continuous recordings of brain electrical activity were obtained from a group of 176 patients throughout surgical procedures using general anesthesia. Artifact-free data from the 19 electrodes of the International 10/20 System were subjected to quantitative analysis of the electroencephalogram (QEEG). Induction was variously accomplished with etomidate, propofol or thiopental. Anesthesia was maintained throughout the procedures by isoflurane, desflurane or sevoflurane (N = 68), total intravenous anesthesia using propofol (N = 49), or nitrous oxide plus narcotics (N = 59). A set of QEEG measures were found which reversibly displayed high heterogeneity of variance between four states as follows: (1) during induction; (2) just after loss of consciousness (LOC); (3) just before return of consciousness (ROC); (4) just after ROC. Homogeneity of variance across all agents within states was found. Topographic statistical probability images were compared between states. At LOC, power increased in all frequency bands in the power spectrum with the exception of a decrease in gamma activity, and there was a marked anteriorization of power. Additionally, a significant change occurred in hemispheric relationships, with prefrontal and frontal regions of each hemisphere becoming more closely coupled, and anterior and posterior regions on each hemisphere, as well as homologous regions between the two hemispheres, uncoupling. All of these changes reversed upon ROC. Variable resolution electromagnetic tomography (VARETA) was performed to localize salient features of power anteriorization in three dimensions. A common set of neuroanatomical regions appeared to be the locus of the most probable generators of the observed EEG changes.
Consciousness might help to mobilize and integrate brain functions that are otherwise separate and independent. Evidence for this 'conscious access hypothesis' was described almost two decades ago, in a framework called global workspace theory. The theory had little impact at first, for three reasons: because consciousness was controversial; the evidence, though extensive, was indirect; and integrative theory was unfashionable. Recent neuroimaging evidence appears broadly to support the hypothesis, which has implications for perception, learning, working memory, voluntary control, attention and self systems in the brain.
The persistent vegetative state (PVS) is a devastating medical condition characterized by preserved wakefulness contrasting with absent voluntary interaction with the environment. We used positron emission tomography to assess the central processing of noxious somatosensory stimuli in the PVS. Changes in regional cerebral blood flow were measured during high-intensity electrical stimulation of the median nerve compared with rest in 15 nonsedated patients and in 15 healthy controls. Evoked potentials were recorded simultaneously. The stimuli were experienced as highly unpleasant to painful in controls. Brain glucose metabolism was also studied with [(18)F]fluorodeoxyglucose in resting conditions. In PVS patients, overall cerebral metabolism was 40% of normal values. Nevertheless, noxious somatosensory stimulation-activated midbrain, contralateral thalamus, and primary somatosensory cortex in each and every PVS patient, even in the absence of detectable cortical evoked potentials. Secondary somatosensory, bilateral insular, posterior parietal, and anterior cingulate cortices did not show activation in any patient. Moreover, in PVS patients, the activated primary somatosensory cortex was functionally disconnected from secondary somatosensory, bilateral posterior parietal, premotor, polysensory superior temporal, and prefrontal cortices. In conclusion, somatosensory stimulation of PVS patients, at intensities that elicited pain in controls, resulted in increased neuronal activity in primary somatosensory cortex, even if resting brain metabolism was severely impaired. However, this activation of primary cortex seems to be isolated and dissociated from higher-order associative cortices.
Human self-consciousness depends on the metarepresentation of mental and bodily states as one's own mental and bodily states. First-person-perspective taking is not sufficient, but necessary for human self-consciousness. To assign a first-person-perspective is to center one's own multimodal experiential space upon one's own body, thus operating in an egocentric reference frame. The brain regions involved in assigning first-person-perspective comprise medial prefrontal, medial parietal and lateral temporoparietal cortex. These empirical findings complement recent neurobiologically oriented theories of self-consciousness which focus on the relation between the subject and his/her environment by supplying a neural basis for its key components.
Consciousness has a number of apparently disparate properties, some of which seem to be highly complex and even inaccessible to outside observation. To place these properties within a biological framework requires a theory based on a set of evolutionary and developmental principles. This paper describes such a theory, which aims to provide a unifying account of conscious phenomena.