Elsevier

Cognition

Volume 79, Issues 1ā€“2, April 2001, Pages 1-37
Cognition

Towards a cognitive neuroscience of consciousness: basic evidence and a workspace framework

https://doi.org/10.1016/S0010-0277(00)00123-2Get rights and content

Abstract

This introductory chapter attempts to clarify the philosophical, empirical, and theoretical bases on which a cognitive neuroscience approach to consciousness can be founded. We isolate three major empirical observations that any theory of consciousness should incorporate, namely (1) a considerable amount of processing is possible without consciousness, (2) attention is a prerequisite of consciousness, and (3) consciousness is required for some specific cognitive tasks, including those that require durable information maintenance, novel combinations of operations, or the spontaneous generation of intentional behavior. We then propose a theoretical framework that synthesizes those facts: the hypothesis of a global neuronal workspace. This framework postulates that, at any given time, many modular cerebral networks are active in parallel and process information in an unconscious manner. An information becomes conscious, however, if the neural population that represents it is mobilized by top-down attentional amplification into a brain-scale state of coherent activity that involves many neurons distributed throughout the brain. The long-distance connectivity of these ā€˜workspace neuronsā€™ can, when they are active for a minimal duration, make the information available to a variety of processes including perceptual categorization, long-term memorization, evaluation, and intentional action. We postulate that this global availability of information through the workspace is what we subjectively experience as a conscious state. A complete theory of consciousness should explain why some cognitive and cerebral representations can be permanently or temporarily inaccessible to consciousness, what is the range of possible conscious contents, how they map onto specific cerebral circuits, and whether a generic neuronal mechanism underlies all of them. We confront the workspace model with those issues and identify novel experimental predictions. Neurophysiological, anatomical, and brain-imaging data strongly argue for a major role of prefrontal cortex, anterior cingulate, and the areas that connect to them, in creating the postulated brain-scale workspace.

Introduction

The goal of this volume is to provide readers with a perspective on the latest contributions of cognitive psychology, neuropsychology, and brain imaging to our understanding of consciousness. For a long time, the word ā€˜consciousnessā€™ was used only reluctantly by most psychologists and neuroscientists. This reluctance is now largely overturned, and consciousness has become an exciting and quickly moving field of research. Thanks largely to advances in neuropsychology and brain imaging, but also to a new reading of the psychological and neuropsychological research of the last decades in domains such as attention, working memory, novelty detection, or the body schema, a new comprehension of the neural underpinnings of consciousness is emerging. In parallel, a variety of models, pitched at various levels in neural and/or cognitive science, are now available for some of its key elements.

Within this fresh perspective, firmly grounded in empirical research, the problem of consciousness no longer seems intractable. Yet no convincing synthesis of the recent literature is available to date. Nor do we know yet whether the elements of a solution that we currently have will suffice to solve the problem, or whether key ingredients are still missing. By grouping some of the most innovative approaches together in a single volume, this special issue aims at providing the readers with a new opportunity to see for themselves whether a synthesis is now possible.

In this introduction, we set the grounds for subsequent papers by first clarifying what we think should be the aim of a cognitive neuroscience approach to consciousness. We isolate three major findings that are explored in greater detail in several chapters of this volume. Finally, we propose a synthesis that integrates them into what we view as a promising theoretical framework: the hypothesis of a global neuronal workspace. With this framework in mind, we look back at some of the remaining empirical and conceptual difficulties of consciousness research, and examine whether a clarification is in sight.

Section snippets

Nature of the problem and range of possible solutions

Let us begin by clarifying the nature of the problem that a cognitive neuroscience of consciousness should address. In our opinion, this problem, though empirically challenging, is conceptually simple. Human subjects routinely refer to a variety of conscious states. In various daily life and psychophysical testing situations, they use phrases such as ā€˜I was not conscious of Xā€™, ā€˜I suddenly realized that Yā€™, or ā€˜I knew that Z, therefore I decided to do Xā€™. In other words, they use a vocabulary

Three fundamental empirical findings on consciousness

In this section, we begin by providing a short review of empirical observations that we consider as particularly relevant to the cognitive neuroscience of consciousness. We focus on three findings: the depth of unconscious processing; the attention-dependence of conscious perception; and the necessity of consciousness for some integrative mental operations.

A theoretical framework for consciousness

Once those three basic empirical properties of conscious processing have been identified, can a theoretical framework be proposed for them? Current accounts of consciousness are founded on extraordinarily diverse and seemingly incommensurate principles, ranging from cellular properties such as thalamocortical rhythms to purely cognitive constructions such as the concept of a ā€˜central executiveā€™. Instead of attempting a synthesis of those diverse proposals, we isolate in this section three

Empirical consequences, reinterpretations, and predictions

The remainder of this paper is devoted to an exploration of the empirical consequences of this theoretical framework. We first examine the predicted structural and dynamical conditions under which information may become conscious. We then consider the consequences of our views for the exploration of the neural substrates of consciousness and its clinical or experimental disruption.

Final remarks

The present chapter was aimed at introducing the cognitive neuroscience of consciousness and proposing a few testable hypotheses about its cerebral substrates. While we think that a promising synthesis is now emerging, based on the concepts of global workspace, dynamic mobilization, attentional amplification, and frontal circuitry, some readers may feel that those ideas hardly scratch the surface. What about the so-called ā€˜hard problemsā€™ posed by concepts such as voluntary action, free will,

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