Naturalizing the Unity of Consciousness: can neuroscience explain a fundamental feature of subjectivity? Martin Vraný Abstract The aim of the dissertation is to analyze the concept of the unity of conscious- ness as an explanandum for natural sciences and assess how good an explanation do leading neuroscientific theories of consciousness provide. The motivation be- hind this project is the idea that it is the unity which poses the greatest challenge for the scientific quest for consciousness. I argue in the Introduction that the reason why some theories of consciousness lead to what Dennett calls Cartesian materialism is precisely because they fail to address the problem of the unity of consciousness. If we had a good understanding of the unity of consciousness and its place in nature, we could more easily avoid the tendency to devise accounts of consciousness that are homuncular in disguise. In chapter 2 I analyze various aspects in which consciousness is thought be unified and conclude that two such aspects are particularly challenging for natu- ralizing the unity and that they cannot be treated separately. They are the unity of conscious contents at a time and the unity in the sense of a single subject having conscious contents and being able to reflect on them. Chapter 3 describes main conceptual and...

In this dissertation, we investigate whether consciousness is graded or dichotomous. Based on previous work and a level of processing framework, we hypothesize that consciousness in general, and visual experience specifically, can be conceived of as both graded and dichotomous. We present a series of experimental studies that provide support for this reasoning. We outline a set of future projects which can follow up on this research, and discuss the limitations of the current approach. / Doctorat en Sciences Psychologiques et de l'éducation / info:eu-repo/semantics/nonPublished

Abstract In the 1990s researchers discovered task-deactivated regions in the human brain. Together, these areas make up the default mode network (DMN). It was originally proposed to act as a balancing mechanism between different brain systems, explaining the deactivations, but is now mostly studied with regards to internal awareness, such as daydreaming and mental imagery. The purpose of this thesis is to present a summary of DMN research, focusing on the network’s suggested role in internal awareness. This will be done by reviewing a wide variety of research that either explicitly or indirectly correlate default mode network features with aspects of consciousness and internal awareness. The subjective experience of being conscious have been a source of argument primarily among philosophers, but the qualities we feel are intimately linked to cognitive functions that are supported by the regions found in the DMN. Cognitive neuroscience may therefore be able to contribute to the concept of internal awareness and consciousness.

In previous work, we presented evidence suggesting that ordinary people do not conceive of subjective experiences as having phenomenal qualities. We then argued that these findings undermine a common justification given for the reality of the hard problem of consciousness. In a thought-provoking article, Talbot has challenged our argument. In this article, we respond to his criticism.

Brain-computer interfaces (BCIs) are very convenient tools to assess locked-in (LIS) and completely locked-in state (CLIS) patients' hidden states of consciousness. For the time being, there is no ground-truth data in respect to these states for above-mentioned patients. This lack of gold standard makes this problem particularly challenging. In addition to consciousness assessment, BCIs also provide them with a communication device that does not require the presence of motor responses, which they are lacking. Communication plays an important role in the patients' quality of life and prognosis. Significant progress have been made to provide them with EEG-based BCIs in particular. Nonetheless, the majority of existing studies directly dive into the communication part without assessing if the patient is even conscious. Additionally, the few studies that do essentially use evoked brain potentials, mostly the P300, that necessitates the patient's voluntary and active participation to be elicited. Patients are easily fatigued, and would consequently be less successful during the main communication task. Furthermore, when the consciousness states are determined using resting state data, only one or two features were used. In this thesis, different sets of EEG features are used to assess the consciousness level of CLIS patients using resting-state data. This is done as a preliminary step that needed to be succeeded in order to engage to the next step, communication with the patient. In other words, the 'conversation' is initiated only if the patient is sufficiently conscious. This variety of EEG features is utilised to increase the probability of correctly estimating the patients' consciousness states. Indeed, each of them captures a particular signal attribute, and combining them would allow the collection of different hidden characteristics that could have not been obtained from a single feature. Furthermore, the proposed method should allow to determine if communication shall be initiated at a specific time with the patient. The EEG features used are frequency-based, complexity related and connectivity metrics. Besides, instead of analysing results from individual channels or specific brain regions, the global activity of the brain is assessed. The estimated consciousness levels are then obtained by applying two different soft-clustering analysis methods, namely Fuzzy c-means (FCM) and Gaussian Mixture Models (GMM), to the individual features and ensembling their results using their average or their product. The proposed approach is first applied to EEG data recorded from patients with unresponsive wakefulness syndrome (UWS) and minimally conscious state (MCS) (patients with disorders of consciousness (DoC)) to evaluate its performance. It is subsequently applied to data from one CLIS patient that is unique in its kind because it contains a time frame during which the experimenters affirmed that he was conscious. Finally, it is used to estimate the levels of consciousness of nine other CLIS patients. The obtained results revealed that the presented approach was able to take into account the variations of the different features and deduce a unique output taking into consideration the individual features contributions. Some of them performed better than others, which is not surprising since each person is different. It was also able to draw very accurate estimations of the level of consciousness under specific conditions. The approach presented in this thesis provides an additional tool for diagnosis to the medical staff. Furthermore, when implemented online, it would enable to determine the optimal time to engage in communication with CLIS patients. Moreover, it could possibly be used to predict patients' cognitive decline and/or death.

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Cette thèse, qui relève de la philosophie de l'esprit, consiste en la défense d'une version de la théorie auto-représentationnelle de la conscience. En acceptant d'une part la notion d'état mental possédant un certain contenu qui peut être conscient ou inconscient, et d'autre part l'hypothèse plausible que le contenu de tout état mental consiste en une représentation, alors le problème de la manifestation de la conscience s'appliquant au contenu de CERTAINS états mentaux acquiert intelligibilité dans ce cadre. Il peut être compris comme la recherche d'une structure de représentation qui donne lieu à cette manifestation. Pour certains auteurs (Fred Dretske, Michael Tye et dautres), des conditions particulières dans la représentation directe de l'objet y suffisent, pour d'autres (en particulier David Rosenthal) il y faut une méta-représentation de l'objet sous certaines conditions. Ni l'une ni l'autre de ces structures ne s'avère cependant suffisante pour justifier la démarcation entre états mentaux conscients et inconscients, et pour caractériser la phénoménalité de la conscience. En prenant alors au sérieux l'intuition forte d'auto-référentialité de la conscience (présente déjà chez Aristote - suivant certaines interprétations -, reprise par Brentano, Sartre, et ces dernières années, par Uriah Kriegel et plusieurs autres), on est conduit à proposer, pour les états mentaux conscients, une structure d'auto-représentation (de la représentation) de l'objet qui sous-tend une intentionnalité consciente duale dirigée vers l'objet et en même temps vers elle-même. on résout ainsi les problèmes de la théorie méta-représentationnelle, mais il faut monter que ce schéma est intelligible, que le risque de régression à l'infini dans les capacités repésentationnelles de la conscience n'existe pas, et que de robustes intuitions sont ainsi éclairées, telles que la structuration du champ conscient entre premier plan et arrière-plan, et le lien entre conscience d'arrière plan, ou marginale, et conscience de soi. Ce lien dérive du fait que la conscience marginale, dans la perspective de l'auto-représentation, est la conscience de la conscience d'objet, et se qualifie aussi comme conscience subjective, c'est à dire conscience "pour moi" de l'objet. Et la conscience de soi se construit à partir des épisodes de conscience subjective. L'étude du rapport entre structures de représentation mentale consciente et configurations neuronales spatio-temporelles qui les produisent dans le cerveau est hors du domaine du présent travail, mais la présence nécessaire de ces relations demeure à l'arrière-plan, et affleure dans la réflexion quand cela peut être éclairant. / This work illustrates a version of the self-representational theory of consciousness. If one accepts on the one hand the notion of mental states that have a given content - conscious or unconscious - and on the other hand the plausible hypothesis that the content of all mental states consists in a representation, then the problem of the manifestation of consciousness for (the content of) SOME states becomes intelligible within this frame. This problem can be understood as the research of the representational structure which gives rise to this manifestation. For some authors ( Fred Dretske, Michael Tye, and others) certain particular conditions in the direct representation of the object are sufficient, for others (particularly David Rosenthal) a meta-representation is necessary, under given conditions. However neither of those structures results sufficient to justify the demarcation between conscious and unconscious states and to characterize the phenomenality of consciousness. If one then takes seriously into account the strong intuition of self-referentiality of consciousness (already present in Aristotle - following some interpretations -, taken up again by Brentano, Sartre, and lately by Uriah Kriegel and several others) one is conducted to propose a self-representational structure for conscious mental states which involves a dual conscious intentionality targeting the object and itself at the same time. The problems of the meta-representational theory are thus resolved, but it remains to be shown that this scheme is intelligible, that the risk of infinite regress of the representing capacity of consciousness does not exist, and that strong intuitions are thus acknowledged : such as the distinction in the conscious field between foreground and background, and the link between background, or marginal consciousness, and self consciousness. Within the self-representational view, this link originates from the fact that marginal consciousness is the consciousness of the consciousness of the object, and qualifies itself as subjective consciousness, that is to say, consciousness "for me" of the object. Self consciousness is then constructed from the episodes of subjective consciousness. The relationship between conscious mental representational structures and the spatio-temporal neuronal configurations which produce them in the brain, is outside the domain of the present work, but it is necessarily present in the background, and it is considered when useful for the argument.

Two influential theories of consciousness disagree about if consciousness initially arises along the occipitotemporal cortex to later engage frontoparietal regions and attentional mechanisms, or if it necessarily requires the latter. Consequently, different predictions are made about the temporal emergence of consciousness. The event-related potential (ERP) technique can be used to resolve the issue. It can temporally track neural activity of consciously perceived stimuli relative to stimuli bypassing consciousness. This essay describes the two theories and reviews ERP studies on visual consciousness and its relationship to attention. Three ERP correlates of consciousness have been proposed. The question is if they should be interpreted as supporting the one or the other theory. Most plausibly, visual consciousness arises along occipitotemporal regions and later incorporates frontal areas engaging higher cognitive functions. Importantly it seems that consciousness cannot arise without spatial attention/parietal regions.