Neurobiological Theories and Models of Consciousness

1.1 Bilateral damage to the thalamus abolishes waking consciousness. The critical site of this damage is believed to be a relatively small cluster of neurons, about the size of a pencil eraser on either side of the brain's midline, called the Intra-Laminar Nuclei (ILN) because they are located inside the white layers (laminae) that divide the two thalami into their major groupings of nuclei. The fact that bilateral damage to the ILNs abolishes consciousness is very unusual. There is no other (...) site in the brain that has this property, except the reticular formation in the brain stem. In contrast, huge chunks of cortex can be damaged without abolishing the STATE of consciousness. (Cortical damage does change the CONTENTS of consciousness, of course). (shrink)

This paper explores a remarkable convergence of ideas and evidence, previously presented in separate places by its authors. That convergence has now become so persuasive that we believe we are working within substantially the same broad framework. Taylor's mathematical papers on neuronal systems involved in consciousness dovetail well with work by Newman and Baars on the thalamocortical system, suggesting a brain mechanism much like the global workspace architecture developed by Baars (see references below). This architecture is relational, in the sense (...) that it continuously mediates the interaction of input with memory. While our approaches overlap in a number of ways, each of us tends to focus on different areas of detail. What is most striking, and we believe significant, is the extent of consensus, which we believe to be consistent with other contemporary approaches by Weiskrantz, Gray, Crick and Koch, Edelman, Gazzaniga, Newell and colleagues, Posner, Baddeley, and a number of others. We suggest that cognitive neuroscience is moving toward a shared understanding of consciousness in the brain. (shrink)

The paper outlines an analysis of two types of information - ordinary and subjective, consideration is given to the difference between the concepts of intelligence and perceiving mind. It also provides description of some logical functional features of consciousness. A technical approach is proposed to technical obtaining of subjective information by changing the signal’s time degree of freedom to the spatial one in order to obtain the "observer" function in the system and information signals appearing in relation to it, that (...) serve as subjective sensations. The solution to this problem may give a new approach to designing a strong artificial intelligence and shed light on the difficult problem of the mind. (shrink)

In this paper we present theoretical and experimental evidence for a set of mechanisms by which intention is understood. We propose that three basic aspects are involved in the understanding of intention. The first aspect to consider is intention recognition, i.e., the process by which we recognize other people’s intentions, distinguishing among different types. The second aspect concerns the attribution of intention to its author: the existence of shared neural representations provides a parsimonious explanation of how we recognize other people’s (...) intentions , but in and of itself, is not sufficient to determine who the agent is. Once the intention has been recognized and attributed to an agent, the reasons for, and the aim of, the intention are to be considered. Hence, the third aspect concerns the aim-intention motivating the execution of a certain action. We discuss the neural basis of these three theoretical aspects suggesting a conceptual synthesis. (shrink)

The Global Workspace Theory (GWT) proposed by Bernard Baars (1988) along with Daniel Dennett’s (1991) Multiple Drafts Model (MDM) of consciousness are renowned cognitive theories of consciousness bearing similarities and differences. Although Dennett displays sympathy for GWT, his own MDM does not seem to be fully compatible with it. This work discusses this compatibility, by asking if GWT suffers from Daniel Dennett’s criticism of what he calls a “Cartesian Theater”. We identified in Dennett 10 requirements for avoiding the Cartesian Theater. (...) We believe that some of these requirements are violated by GWT, but not all, hence there is partial incompatibility with MDM, and it is nonsense to answer if GWT is or is not a Cartesian Theater. However, by asking such question we conclude that the issues around this discussion involve fuzzy claims about degrees of consciousness and we show how the Neuro-Astroglial Interaction Model (NAIM) is fit for solving such conceptual issues. (shrink)

Can we consciously see more items at once than can be held in visual working memory? This question has elud- ed resolution because the ultimate evidence is subjects’ reports in which phenomenal consciousness is filtered through working memory. However, a new technique makes use of the fact that unattended ‘ensemble prop- erties’ can be detected ‘for free’ without decreasing working memory capacity.

One of the most important issues concerning the foundations ofconscious perception centerson thequestion of whether perceptual consciousness is rich or sparse. The overflow argument uses a form of ‘iconic memory’ toarguethatperceptual consciousnessisricher (i.e.,has a higher capacity) than cognitive access: when observing a complex scene we are conscious of more than we can report or think about. Recently, the overflow argumenthas been challenged both empirically and conceptually. This paper reviews the controversy, arguing that proponents of sparse perception are committed to the (...) postulation of (i) a peculiar kind of generic conscious representation that has no independent rationale and (ii) an unmotivated form of unconscious representation that in some cases conflicts with what we know about unconscious representation. (shrink)

The main idea in this series of essays is that subjective awareness depends upon the intralaminar nuclei of each thalmus. This implies that the internal structure and external relations of ILN make subjective awareness possible. An array of material relevant to this proposal was briefly reviewed in Part I. This Part II considers in more detail some semantic aspects and a bit of philosophic background as these pertain to propositions 0, 1, and 2 of Part I. Part II should be (...) read in conjunction with Part I. (shrink)

How certain neural mechanisms momentarily endow with the subjective awareness percepts and affects represented elsewhere is more likely to be clarified when structures essential to Mc are identified. The loss of C with bilateral thalmic lesions involving the intralaminar nuclei contrasts with retention of C after large cortical ablations depriving C of specific contents. A role of ILN in the perception of primitive sensations is suggested by their afference of directly ascending pathways. A role for ILN in awareness of cortical (...) activity is suggested by their widespread afference from cortex, a property shared with striatum. A role for ILN in volition is suggested by their heavy projection to striatum. Unlike striatum, ILN also project widely to almost all neocortex, enabling an effect on ideation; this last property is in common with other structures but none of them has the same direct cortical afference. And passage through the reticular nucleus of ILN efferents to cortex could impact the attention-selective action of nRt. It is suggested that the quickest route to a better understanding of C involves more intensive study of ILN. No other structure seems, in the light of our current knowledge, a more likely site for Mc. (shrink)

It is natural to assume that the fine-grained and highly accurate spatial information present in visual experience is often used to guide our bodily actions. Yet this assumption has been challenged by proponents of the Two Visual Systems Hypothesis , according to which visuomotor programming is the responsibility of a “zombie” processing stream whose sources of bottom-up spatial information are entirely non-conscious . In many formulations of TVSH, the role of conscious vision in action is limited to “recognizing objects, selecting (...) targets for action, and determining what kinds of action, broadly speaking, to perform” . Our aim in this study is to show that the available evidence not only fails to support this dichotomous view but actually reveals a significant role for conscious vision in motor programming, especially for actions that require deliberate attention. (shrink)

In recent times we have seen an explosion in the amount of attention paid to the conscious brain from scientists and philosophers alike. One message that has emerged loud and clear from scientific work is that the brain is a dynamical system whose operations unfold in time. Any theory of consciousness that is going to be physically realistic must take account of the intrinsic nature of neurons and brain activity. At the same time a long discussion on consciousness among philosophers (...) has resulted in our distinguishing several kinds of consciousness. So when we ask where the place of consciousness is in nature we may mean several different things. In this chapter I will argue that it is plausible that all of the kinds of consciousness turn out to be nothing but patterns of synchronized neural activity in various frequencies against a dynamically changing chemical background. (shrink)

This volume takes the first step toward building the necessary local bridges.

cal basis of consciousness. We continue by discussing the relation between spatiotem- One of the outstanding problems in the cog- poral patterns of brain activity and con- nitive sciences is to understand how ongo- sciousness, with particular attention to pro- ing conscious experience is related to the cesses in the gamma frequency band. We workings of the brain and nervous system. then adopt a critical perspective and high-.

This book is the integrated presentation of a large body of work on understanding the operation of biological brains as systems.

The legacy of René Descartes' notorious dualism of mind and body extends far beyond academia into everyday thinking: "These athletes are prepared both mentally and physically," and "There's nothing wrong with your body--it's all in your mind." Even among those of us who have battled Descartes' vision, there has been a powerful tendency to treat the mind (that is to say, the brain) as the body's boss, the pilot of the ship. Falling in with this standard way of thinking, we (...) ignore an important alternative: viewing the brain (and hence the mind) as one organ among many, a relatively recent usurper of control, whose functions cannot properly be understood until we see it not as the boss, but as just one more somewhat fractious servant, working to further the interests of the body that shelters and fuels it, and gives its activities meaning. This historical or evolutionary perspective reminds me of the change that has come over Oxford in the thirty years since I was a student there. It used to be that the dons were in charge, while the bursars and other bureaucrats, right up to the Vice Chancellor, acted under their guidance and at their behest. Nowadays the dons, like their counterparts on American university faculties, are more clearly in the role of employees hired by a central Administration, but from where, finally, does the University get its meaning? In evolutionary history, a similar change has crept over the administration of our bodies. Where resides the "I" who is in charge of my body? In his wonderfully written book, Antonio Damasio seeks to restore our appreciation for the perspective of the body, and the shared balance of powers from which we emerge as conscious persons. (shrink)

Having laid the groundwork in his critically acclaimed books Neural Darwinism (Basic Books, 1987) and Topobiology (Basic Books, 1988), Nobel laureate Gerald M. Edelman now proposes a comprehensive theory of consciousness in The Remembered ...

The chapters comprising this book represent a collective attempt on the part of their authors to redress this aberration.

[opening paragraph]: Nicholas Humphrey argues persuasively that consciousness results from active and efferent rather than passive and afferent functions. These arguments contribute to the mounting recent evidence that consciousness is inseparable from the motivated action planning of creatures that in some sense are organismic and agent-like rather than passively mechanical and reactive in the way that digital computers are. Newton calls this new approach the ‘action theory of understanding'; Varela et al. dubbed it the ‘enactive’ view of consciousness. It was (...) endorsed in passing by the early Dennett , although he never followed up on it in his later work. According to Dennett, ‘No afferent can be said to have a significance ‘A’ until it is ‘taken’ to have the significance ‘A’ by the efferent side of the brain’ . Luria also stressed the neurophysiology of efferent processes as correlated with consciousness . Further elaborations of the enactive approach are defended by Ellis , Newton , Ellis and Newton , Watt , Thelen and Smith , Jarvilehto and Gendlin . According to this view, conscious information processing can arise only as the self-regulated action of a self-organizing process that confronts the world as a system of action affordances. While information can be passively absorbed in the form of afferent input, only efferent nervous activity in the interest of a living organism's homeostatic balance can create consciousness of any information, whether perceptual, imagistic, emotional or intellectual. (shrink)