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PubMed1996

[The anatomy of consciousness in domestic animals. Opening address of the 20th Congress of the EVVA in Zürich in memory of Eugen Seiferle].

All living organisms have a consciousness, not only humans. To seek to find humans' consciousness in animals is to seek wrongly. The question must be: "To what extent are prehuman and human consciousness comparable.' Animals have an instinctive sensational consciousness with a partial learning consciousness. It is a purely self-sustaining consciousness. In addition, humans have a spiritual-thinking consciousness, which is predominantly a learning consciousness and is not a pure self-sustaining consciousness. Since human consciousness arose from animals' consciousness, that behaviour in animals which is similar to the thought process in human beings can only be based on sensations. Sensations of pain and fear are not very different in man and animal, because they also belong to the sensation consciousness in humans, but humans have the additional advantage of being able to think about them and to understand their cause and meaning. That is not possible in animals, therefore, animals have to be anaesthetized to protect them from pain. Seiferle recognized this clearly, and my consciousness theory reinforces Seiferle's view, i.e. that consciousness is the central force of the soul. Its afferent forces are perception and sensation; its efferent forces are will, feeling, and deed.

Animals↗
PubMed2005

Consciousness, information integration, and the brain.

Clinical observations have established that certain parts of the brain are essential for consciousness whereas other parts are not. For example, different areas of the cerebral cortex contribute different modalities and submodalities of consciousness, whereas the cerebellum does not, despite having even more neurons. It is also well established that consciousness depends on the way the brain functions. For example, consciousness is much reduced during slow wave sleep and generalized seizures, even though the levels of neural activity are comparable or higher than in wakefulness. To understand why this is so, empirical observations on the neural correlates of consciousness need to be complemented by a principled theoretical approach. Otherwise, it is unlikely that we could ever establish to what extent consciousness is present in neurological conditions such as akinetic mutism, psychomotor seizures, or sleepwalking, and to what extent it is present in newborn babies and animals. A principled approach is provided by the information integration theory of consciousness. This theory claims that consciousness corresponds to a system's capacity to integrate information, and proposes a way to measure such capacity. The information integration theory can account for several neurobiological observations concerning consciousness, including: (i) the association of consciousness with certain neural systems rather than with others; (ii) the fact that neural processes underlying consciousness can influence or be influenced by neural processes that remain unconscious; (iii) the reduction of consciousness during dreamless sleep and generalized seizures; and (iv) the time requirements on neural interactions that support consciousness.

Brain↗
PubMed2001

Consciousness, the brain, and spacetime geometry.

What is consciousness? Conventional approaches see it as an emergent property of complex interactions among individual neurons; however these approaches fail to address enigmatic features of consciousness. Accordingly, some philosophers have contended that "qualia," or an experiential medium from which consciousness is derived, exists as a fundamental component of reality. Whitehead, for example, described the universe as being composed of "occasions of experience." To examine this possibility scientifically, the very nature of physical reality must be re-examined. We must come to terms with the physics of spacetime--as described by Einstein's general theory of relativity, and its relation to the fundamental theory of matter--as described by quantum theory. Roger Penrose has proposed a new physics of objective reduction: "OR," which appeals to a form of quantum gravity to provide a useful description of fundamental processes at the quantum/classical borderline. Within the OR scheme, we consider that consciousness occurs if an appropriately organized system is able to develop and maintain quantum coherent superposition until a specific "objective" criterion (a threshold related to quantum gravity) is reached; the coherent system then self-reduces (objective reduction: OR). We contend that this type of objective self-collapse introduces non-computability, an essential feature of consciousness which distinguishes our minds from classical computers. Each OR is taken as an instantaneous event--the climax of a self-organizing process in fundamental spacetime--and a candidate for a conscious Whitehead "occasion of experience." How could an OR process occur in the brain, be coupled to neural activities, and account for other features of consciousness? We nominate a quantum computational OR process with the requisite characteristics to be occurring in cytoskeletal micro-tubules within the brain's neurons. In this model, quantum-superposed states develop in microtubule subunit proteins ("tubulins") within certain brain neurons, remain coherent, and recruit more superposed tubulins until a mass-time-energy threshold (related to quantum gravity) is reached. At that point, self-collapse, or objective reduction (OR), abruptly occurs. We equate the pre-reduction, coherent superposition ("quantum computing") phase with pre-conscious processes, and each instantaneous (and non-computable) OR, or self-collapse, with a discrete conscious event. Sequences of OR events give rise to a "stream" of consciousness. Microtubule-associated proteins can "tune" the quantum oscillations of the coherent superposed states; the OR is thus self-organized, or "orchestrated" ("Orch OR"). Each Orch OR event selects (non-computably) microtubule subunit states which regulate synaptic/neural functions using classical signaling. The quantum gravity threshold for self-collapse is relevant to consciousness, according to our arguments, because macroscopic superposed quantum states each have their own spacetime geometries. These geometries are also superposed, and in some way "separated," but when sufficiently separated, the superposition of spacetime geometries becomes significantly unstable and reduces to a single universe state. Quantum gravity determines the limits of the instability; we contend that the actual choice of state made by Nature is non-computable. Thus each Orch OR event is a self-selection of spacetime geometry, coupled to the brain through microtubules and other biomolecules. If conscious experience is intimately connected with the very physics underlying spacetime structure, then Orch OR in microtubules indeed provides us with a completely new and uniquely promising perspective on the difficult problems of consciousness.

Brain↗
PubMed2002

Pathophysiology of altered consciousness during seizures: Subtraction SPECT study.

BACKGROUND: The mechanisms underlying altered consciousness during seizures are poorly understood. Previous clinicopathologic studies suggest a role for the thalamus and upper brainstem in consciousness mechanisms. OBJECTIVE: To examine blood flow changes associated with altered consciousness during seizures. METHODS: Seventy-one patients with epilepsy who underwent video-EEG monitoring and ictal/interictal SPECT were studied. Patients were divided into three groups depending on their conscious state during seizures: 1) complete impairment of consciousness (CI), 2) no impairment of consciousness (NI), or 3) uncertain impairment of consciousness (UI). The distribution of blood flow changes during these seizures was assessed by subtraction (ictal - interictal) SPECT co-registered to MRI. Conscious state was assessed in relation to secondary ictal hyperperfusion in subcortical regions (i.e., thalamus and upper brainstem). RESULTS: Impairment of consciousness showed a strong association with secondary hyperperfusion in the thalamic/upper brainstem region (p = 0.01), occurring in 92% (45/49) of CI, 69% (9/13) of UI, and 11% (1/9) of NI. CONCLUSIONS: These findings are consistent with a role for the thalamus and upper brainstem in consciousness mechanisms. The authors suggest that the spread of epileptic discharges or a trans-synaptic activation (diaschisis) of these structures is an important mechanism in the alteration of consciousness during seizures. Variance in the results may be due to differences in timing of radioisotope injection, sensitivity of the subtraction SPECT technique, and the ability to clinically assess the conscious state.

Adolescent↗
PubMed2001

The sense of consciousness.

I propose that consciousness might be understood as the property of a system that functions as a sense in the biological meaning of that term. The theory assumes that, as a complex system, the sense of consciousness is not a fixed structure but implies structure with variations and that it evolved, as many new functions do, through the integration of simpler systems. The recognized exteroceptive and enteroceptive senses provide information about the organism's environment and about the organism itself that are important to adaptation. The sense of consciousness provides information about the brain and thus about the organism and its environment. It senses other senses and processes in the brain, selecting and relating components into a form that "makes sense"-where making sense is defined as being useful to the organism in its adaptation to the environment. The theory argues that this highly adaptive organizing function evolved with the growing complexity of the brain and that it might have helped resolve discrepancies created at earlier stages. Neural energies in the brain that are the input to the sense of consciousness, along with the processing subsystem of which they are a part, constitute the base of consciousness. Consciousness itself is an emergent effect of an organizing process achieved through the sense of consciousness. The sense of consciousness thus serves an organizing function although it is not the only means of organization in the brain. Its uniqueness lies in the character of the organization it creates with consciousness as a property of that organization. The paper relates the theory to several general conceptions-interactionism, epiphenomenalism and identity theory-and illustrates a number of testable hypotheses. Viewing consciousness as a property of a sense provides a degree of conceptual integration. Much of what we know about the evolution and role of the conventionally recognized senses should help us understand the evolution and role of the sense of consciousness, and of consciousness itself.

Behavior↗
PubMed2006

Conscious sedation guidance.

SCOPE AND PURPOSE: This guidance is intended to promote good clinical practice for the provision in dentistry of conscious sedation that is both safe and effective. It is not a recipe book for sedation and therefore does not include details of drug dosages. The recommendations are applicable to all patients receiving conscious sedation, to facilitate the provision of any type of dental treatment whether it is delivered in a dental practice, a community dental service clinic or a hospital setting. It also covers the provision of conscious sedation for dental treatment provided on a domiciliary basis. Specifically excluded from this guidance, however, are patients who require assisted ventilation, intensive care sedation, premedication for general anaesthesia, postoperative analgesia, sedation in palliative care, night sedation and sedation in the home setting other than for the provision of dental treatment on a domiciliary basis. METHODS: Existing guidelines, relevant systematic reviews, policy documents, legislation or other recommendations were reviewed and appraised for their quality of development, evidence base and applicability to the remit of the guidance under development. To supplement this information, key questions were formulated by the Guidance Development Group and used as the basis for designing systematic literature search strategies to identify further research evidence that may address these questions, including unpublished work where relevant.The following internet sites were searched for guidelines: New Zealand Guidelines Group, Canadian Collaboration on Clinical Practice Guidelines in Dentistry, National Guidelines Clearinghouse, FDI World Dental Federation, National Electronic Library for Health Guideline Finder, and Medline. The Cochrane Library was searched for systematic reviews and Medline, Embase and the Cochrane Library for studies to address key questions. The searches were supplemented by material already known to members of the Guidance Development Group. Titles and abstracts of the identified references were screened for relevance independently by two researchers who were not members of the Guidance Development Group. Disagreement about the inclusion of specific individual references for further consideration was resolved by discussion and if necessary the opinion of a third researcher was sought. Included references were appraised and data was abstracted independently by two researchers using a specifically designed data-abstraction form. This information was then checked for inconsistencies, which were resolved by discussion, and used to construct evidence tables. The evidence tables were presented to the Guidance Development Group to inform their decision-making and their recommendations related to the key question under consideration. Levels of evidence were assigned by two researchers who were not members of the Guidance Development Group. Formulation of each recommendation was achieved by consensus reached through discussion, drawing on the broad range of interest and experience of sedation related to dentistry within the membership of the Guidance Development Group. Consultation and peer review were conducted prior to publication. A draft of the guidance was the subject of discussion at the Dental Sedation Teachers Group annual symposium in April 2004. Subsequently, approximately 100 copies were distributed throughout the UK to a range of professional organisations and individuals who have an interest in dental sedation, and comments were requested. In addition, all dentists in Scotland who recently claimed the National Health Service allowance for treatment with sedation were invited to comment. The consultation draft was also made available on the group's website (www.scottishdental.org/cep). All comments received through this consultation were considered and the guidance was amended accordingly prior to peer review. Further amendments were made in response to feedback from peer reviewers before publication. REVIEW AND UPDATING: The guidance will be reviewed in 2 years' time (2008) and if there have been significant changes it will be updated accordingly. RECOMMENDATIONS: The detailed guidance make 48 recommendations in a range of areas: REFERRAL: Discuss alternative methods of anxiety management with patient and ensure that dental care with sedation meets agreed definition of conscious sedation. ASSESSMENT AND RECORD KEEPING: As part of a thorough assessment, discuss with patient all aspects of their conscious sedation treatment and also provide written instructions. Obtain patient's written consent; maintain comprehensive and contemporaneous patient records. ENVIRONMENT AND FACILITIES: Ensure that environment for sedation is safe and that correct equipment and drugs are provided for each sedation technique used. Ensure that equipment and drugs for dealing with medical emergencies or complications related to sedation are immediately available. TRAINING: Ensure all members of dental team are correctly trained in sedation techniques used, including monitoring of patient during treatment and management of any sedation-related complications. For oral and transmucosal sedation, ensure that sedationist is trained in other titratable techniques and skilled in performing venous cannulation. Ensure that teams giving conscious sedation provide treatment for patient groups they are experienced in managing. CONSCIOUS SEDATION TECHNIQUES: For inhalation sedation, ensure that a titrated dose of nitrous oxide is administered using dedicated purpose-designed equipment. Oral, transmucosal and intravenous sedation require pulse oximetry and blood-pressure monitoring. A titrated dose of midazolam is recommended for intravenous sedation. AFTERCARE: Monitor patients throughout the recovery period until discharge by sedationist into the care of responsible adult escort who has also been given written postoperative instructions. An escort might not be required after nitrous oxide inhalation sedation. RESEARCH RECOMMENDATIONS: A number of recommendations were made regarding the future conduct and reporting of clinical trials. The following areas were highlighted as requiring further high-quality research: Fasting before conscious sedation. Conscious sedation of paediatric dental patients. Dental conscious sedation using combinations of drugs. Dental conscious sedation using continuous infusion. The choice of sedation method for dental patients. Cognitive and behavioural effects of conscious sedation. The interaction of pharmacological and nonpharmacological anxiety management techniques. The complete guidance is available for download at www.scottishdental.org/cep/guidance/dentalsedation.htm.

Anesthesia, Dental↗
PubMed2002

Evaluation of endoscopic retrograde cholangiopancreatography under conscious sedation and general anesthesia.

BACKGROUND AND STUDY AIMS: In adults, general anesthesia is usually only provided during endoscopic retrograde cholangiopancreatography (ERCP) when prior attempts using conscious sedation have failed. It was hypothesized that in our hospital, other factors might be associated with general anesthesia for ERCP. The aim of this study was therefore to assess the indications for ERCP under general anesthesia, and to evaluate the underlying diseases, type, and efficacy of ERCP under general anesthesia in comparison with conscious sedation. PATIENTS AND METHODS: We retrospectively analyzed 1,056 ERCPs that had been carried out with the patients under general anesthesia or conscious sedation. The indications for general anesthesia were recorded, and the underlying diseases, the type and success of the interventions, and the causes of premature ERCP termination in both groups were assessed. RESULTS: Eighteen percent of the ERCPs were performed under general anesthesia and 82% under conscious sedation. The indications for general anesthesia were related to the type of procedure planned (46%), premature termination of ERCP under conscious sedation (28%), and other reasons. Patients with primary sclerosing cholangitis and liver transplant recipients received general anesthesia more frequently (general anesthesia vs. conscious sedation, 36% vs. 16%, P < 0.0001 and 22% vs. 13%, P = 0.003). Conscious sedation was provided more frequently in patients with neoplasms and cholelithiasis (21% vs. 12%, P = 0.004 and 13% vs. 3%, P < 0.001). Painful dilations were performed more frequently with the patients under general anesthesia (60% vs. 19%, P < 0.001), whereas major papillotomies were preferably performed with conscious sedation (34% vs. 21%, P = 0.006). More interventions per ERCP were performed with the patient under general anesthesia compared to conscious sedation (P < 0.001), during the same time (51 +/- 28 min vs. 52 +/- 26 min, P = 0.39). With conscious sedation, the ERCP failure rate was double that with general anesthesia (7% vs. 14%, P = 0.012), mainly due to inadequate conscious sedation (61%). CONCLUSIONS: The frequent use of general anesthesia for ERCP at our institution is related to the underlying diseases, which are frequently treated with complex and painful ERCP procedures. The efficacy of ERCP with general anesthesia supports a continued preference for general anesthesia rather than conscious sedation when complex and painful interventional ERCP procedures are planned.

Anesthesia, General↗
PubMed2005

Computational correlates of consciousness.

Over the past few years numerous proposals have appeared that attempt to characterize consciousness in terms of what could be called its computational correlates: Principles of information processing with which to characterize the differences between conscious and unconscious processing. Proposed computational correlates include architectural specialization (such as the involvement of specific regions of the brain in conscious processing), properties of representations (such as their stability in time or their strength), and properties of specific processes (such as resonance, synchrony, interactivity, or information integration). In exactly the same way as one can engage in a search for the neural correlates of consciousness, one can thus search for the computational correlates of consciousness. The most direct way of doing is to contrast models of conscious versus unconscious information processing. In this paper, I review these developments and illustrate how computational modeling of specific cognitive processes can be useful in exploring and in formulating putative computational principles through which to capture the differences between conscious and unconscious cognition. What can be gained from such approaches to the problem of consciousness is an understanding of the function it plays in information processing and of the mechanisms that subtend it. Here, I suggest that the central function of consciousness is to make it possible for cognitive agents to exert flexible, adaptive control over behavior. From this perspective, consciousness is best characterized as involving (1) a graded continuum defined over quality of representation, such that availability to consciousness and to cognitive control correlates with properties of representation, and (2) the implication of systems of meta-representations.

Cognition↗
PubMed2006

What do we mean by "conscious" and "aware"?

The concepts of consciousness and awareness are multifaceted, and steeped in cultural and intellectual history. This paper explores their complexities by way of a series of contrasts: (1) states of consciousness, such as wakefulness and sleep are contrasted with awareness, a term that picks out the contents of consciousness: these range across all our psychological capacities; the scientific background of the two concepts is briefly outlined; (2) consciousness is contrasted to self-consciousness, itself a complex term embracing self-detection, self-monitoring, self-recognition, theory of mind and self-knowledge; (3) "narrow" and "broad" senses of consciousness are contrasted, the former requiring mature human awareness capable of guiding action and self-report, the latter involving the much broader capacity to acquire and exploit knowledge; (4) an "inner" conception of consciousness, by which awareness is essentially private and beyond the reach of scientific scrutiny, is contrasted with an "outer" conception which allows that consciousness is intrinsically linked with capacities for intelligent behaviour; (5) finally "easy" and "hard" questions of consciousness are distinguished, the former involving the underlying neurobiology of wakefulness and awareness, the latter the allegedly more mysterious process by which biological processes generate experience: Whether this final distinction is valid is a focus of current debate. Varied interests converge on the study of consciousness from the sciences and the humanities, creating scope for interdisciplinary misunderstandings, but also for a fruitful dialogue. Health professionals treating disorders of consciousness should be aware both of its scientific complexities and of its broad cultural background, which influences the public understanding of these conditions.

Animals↗
PubMed1998

How to study consciousness scientifically.

The neurosciences have advanced to the point that we can now treat consciousness as a scientific problem like any other. The problem is to explain how brain processes cause consciousness and how consciousness is realized in the brain. Progress is impeded by a number of philosophical mistakes, and the aim of this paper is to remove nine of those mistakes: (i) consciousness cannot be defined; (ii) consciousness is subjective but science is objective; (iii) brain processes cannot explain consciousness; (iv) the problem of 'qualia' should be set aside; (v) consciousness is epiphenomenal; (vi) consciousness has no evolutionary function; (vii) a causal account of consciousness is necessarily dualistic; (viii) science is reductionistic, so a scientific account of consciousness would show it reducible to something else; and (ix) an account of consciousness must be an information processing account.

Biological Evolution↗
PubMed2000

Consciousness.

Until recently, most neuroscientists did not regard consciousness as a suitable topic for scientific investigation. This reluctance was based on certain philosophical mistakes, primarily the mistake of supposing that the subjectivity of consciousness made it beyond the reach of an objective science. Once we see that consciousness is a biological phenomenon like any other, then it can be investigated neurobiologically. Consciousness is entirely caused by neurobiological processes and is realized in brain structures. The essential trait of consciousness that we need to explain is unified qualitative subjectivity. Consciousness thus differs from other biological phenomena in that it has a subjective or first-person ontology, but this subjective ontology does not prevent us from having an epistemically objective science of consciousness. We need to overcome the philosophical tradition that treats the mental and the physical as two distinct metaphysical realms. Two common approaches to consciousness are those that adopt the building block model, according to which any conscious field is made of its various parts, and the unified field model, according to which we should try to explain the unified character of subjective states of consciousness. These two approaches are discussed and reasons are given for preferring the unified field theory to the building block model. Some relevant research on consciousness involves the subjects of blindsight, the split-brain experiments, binocular rivalry, and gestalt switching.

Animals↗
PubMed1993

Spatial attention and two modes of visual consciousness.

The relationship between spatial attention and visual consciousness was critically examined in an attempt to show the operation of two simultaneously available modes of visual consciousness (i.e., object consciousness, which concerns the conscious identification of objects, and background consciousness, which deals with conscious monitoring of the background scene). The traditional view seems to pay attention only to object consciousness, which is a product of spatial attention. To substantiate the hypothesis, five topics from varied fields of human experimental psychology were chosen: iconic storage, stabilized retinal image disappearance, stable perception of external space, texture segregation and attention, and spatial frequency sensitivity in a figure-ground reversal figure. The findings of these studies suggest that there may be visual consciousness outside of focal attention and that background consciousness operates as a default mode for global scene analysis and early warning of anomalies. Finally, neural substrata for these two modes of consciousness are suggested.

Attention↗
PubMed1995

Visual perception and phenomenal consciousness.

In the (re-)animated debate on consciousness we focus on three questions: Who has consciousness? What is its neuronal basis? What is its function? Regarding the first, we suggest that consciousness is exclusive to living organisms able to distinguish self from non-self. It may be restricted further to organisms who possess a repertoire of overt and covert behaviour which can be voluntarily modified and suppressed. This requires an intermediary neuronal net mediating between sensory input and behavioural output. What are the properties of this net which distinguish unalloyed information processing per se from conscious representation? To tackle this second question, we use the visual system and the functional losses that result from lesions at its different levels, and differentiate a reflexive, a phenomenal, and a consciously accessible stage of visual processing. We suggest that the latter two represent two distinct aspects of consciousness. Blindsight, a neurological example of visual processing in the absence of phenomenal vision, could help to elucidate the neuronal basis of phenomenality, and the special role of striate cortex. Like the patients, our monkeys with unilateral striate cortical removal show evidence not just of residual visual processing, but of the same absence of phenomenal vision, opening routes to further exploring the details of its neuronal implementation. The second aspect, conscious access to presently or previously processed information, is likely to require higher cortical structures, and may depend on the stage of phenomenal representations. In patients with blindsight, both aspects are lost, and it is conceivable that a loss of phenomenality generally causes a loss of conscious accessibility. One important function of phenomenal representations, our third question, would then be to allow conscious retrieval and manipulation of currently processed or formerly stored information, enabling organisms to consciously think and plan.

Animals↗
PubMed2001

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

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 'workspace neurons' 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.

Brain↗
PubMed2001

Are we explaining consciousness yet?

Theorists are converging from quite different quarters on a version of the global neuronal workspace model of consciousness, but there are residual confusions to be dissolved. In particular, theorists must resist the temptation to see global accessibility as the cause of consciousness (as if consciousness were some other, further condition); rather, it is consciousness. A useful metaphor for keeping this elusive idea in focus is that consciousness is rather like fame in the brain. It is not a privileged medium of representation, or an added property some states have; it is the very mutual accessibility that gives some informational states the powers that come with a subject's consciousness of that information. Like fame, consciousness is not a momentary condition, or a purely dispositional state, but rather a matter of actual influence over time. Theorists who take on the task of accounting for the aftermath that is critical for consciousness often appear to be leaving out the Subject of consciousness, when in fact they are providing an analysis of the Subject, a necessary component in any serious theory of consciousness.

Brain↗
PubMed2005

What in the world is consciousness?

The concept of consciousness is multifaceted, and steeped in cultural and intellectual history. This paper explores its complexities by way of a series of contrasts: (i) states of consciousness, such as wakefulness and sleep, are contrasted with awareness, a term that picks out the contents of consciousness, which range across all our psychological capacities; (ii) consciousness is contrasted to self-consciousness, which is itself a complex term embracing self-detection, self-monitoring, self-recognition theory of mind and self-knowledge; (iii) "narrow" and "broad" senses of consciousness are contrasted, the former requiring mature human awareness capable of guiding action and self-report, the latter involving the much broader capacity to acquire and exploit knowledge; (iv) an "inner" conception of consciousness, by which awareness is essentially private and beyond the reach of scientific scrutiny, is contrasted with an "outer" conception which allows that consciousness is intrinsically linked with capacities for intelligent behavior; and finally (v) "easy" and "hard" questions of consciousness are distinguished, the former involving the underlying neurobiology of wakefulness and awareness, and the latter the allegedly more mysterious process by which biological processes generate experience - the question of whether this final distinction is valid is a focus of current debate. Varied interests converge on the study of consciousness, from the sciences and the humanities, creating scope for interdisciplinary misunderstandings, but also for a fruitful dialog.

Awareness↗
PubMed2002

How many kinds of consciousness?

Ned Block's influential distinction between phenomenal and access consciousness has become a staple of current discussions of consciousness. It is not often noted, however, that his distinction tacitly embodies unargued theoretical assumptions that favor some theoretical treatments at the expense of others. This is equally so for his less widely discussed distinction between phenomenal consciousness and what he calls reflexive consciousness. I argue that the distinction between phenomenal and access consciousness, as Block draws it, is untenable. Though mental states that have qualitative character plainly differ from those with no mental qualities, a mental state's being conscious is the same property for both kinds of mental state. For one thing, as Block describes access consciousness, that notion does not pick out any property that we intuitively count as a mental state's being conscious. But the deeper problem is that Block's notion of phenomenal consciousness, or phenomenality, is ambiguous as between two very different mental properties. The failure to distinguish these results in the begging of important theoretical questions. Once the two kinds of phenomenality have been distinguished, the way is clear to explain qualitative consciousness by appeal to a model such as the higher-order-thought hypothesis.

Consciousness↗
PubMed2001

Consciousness.

Consciousness is topical, for reasons including its renewed respectability among psychologists, rapid progress in the neuroscience of perception, memory and action, advances in artificial intelligence and dissatisfaction with the dualistic separation of mind and body. Consciousness is an ambiguous term. It can refer to (i) the waking state; (ii) experience; and (iii) the possession of any mental state. Self-consciousness is equally ambiguous, with senses including (i) proneness to embarrassment in social settings; (ii) the ability to detect our own sensations and recall our recent actions; (iii) self-recognition; (iv) the awareness of awareness; and (v) self-knowledge in the broadest sense. The understanding of states of consciousness has been transformed by the delineation of their electrical correlates, of structures in brainstem and diencephalon which regulate the sleep-wake cycle, and of these structures' cellular physiology and regional pharmacology. Clinical studies have defined pathologies of wakefulness: coma, the persistent vegetative state, the 'locked-in' syndrome, akinetic mutism and brain death. Interest in the neural basis of perceptual awareness has focused on vision. Increasingly detailed neuronal correlates of real and illusory visual experience are being defined. Experiments exploiting circumstances in which visual experience changes while external stimulation is held constant are tightening the experimental link between consciousness and its neural correlates. Work on unconscious neural processes provides a complementary approach. 'Unperceived' stimuli have detectable effects on neural events and subsequent action in a range of circumstances: blindsight provides the classical example. Other areas of cognitive neuroscience also promise experimental insights into consciousness, in particular the distinctions between implicit and explicit memory and deliberate and automatic action. Overarching scientific theories of consciousness include neurobiological accounts which specify anatomical or physiological mechanisms for awareness, theories focusing on the role played by conscious processes in information processing and theories envisaging the functions of consciousness in a social context. Whether scientific observation and theory will yield a complete account of consciousness remains a live issue. Physicalism, functionalism, property dualism and dual aspect theories attempt to do justice to three central, but controversial, intuitions about experience: that it is a robust phenomenon which calls for explanation, that it is intimately related to the activity of the brain and that it has an important influence on behaviour.

Animals↗