On a confusion about a function of consciousness

Cooperation of the basal ganglia, cerebellum, sensory cerebrum and hippocampus: possible implications for cognition, consciousness, intelligence and creativity

It is suggested that the anatomical structures which mediate consciousness evolved as decisive embellishments to a (non-conscious) design strategy present even in the simplest unicellular organisms. Consciousness is thus not the pinnacle of a hierarchy whose base is the primitive reflex, because reflexes require a nervous system, which the single-celled creature does not possess. By postulating that consciousness is intimately connected to self-paced probing of the environment, also prominent in prokaryotic behavior, one can make mammalian neuroanatomy amenable to dramatically straightforward rationalization. Muscular contraction is the nervous system's only externally directed product, and the signaling routes which pass through the various brain components must ultimately converge on the motor areas. The function of several components is still debatable, so it might seem premature to analyze the global operation of the circuit these routes constitute. But such analysis produces a remarkably simple picture, and it sheds new light on the roles of the individual components. The underlying principle is conditionally permitted movement, some components being able to veto muscular contraction by denying the motor areas sufficient activation. This is true of the basal ganglia (BG) and the cerebellum (Cb), which act in tandem with the sensory cerebrum, and which can prevent the latter's signals to the motor areas from exceeding the threshold for overt movement. It is also true of the anterior cingulate, which appears to play a major role in directing attention. In mammals, the result can be mere thought, provided that a second lower threshold is exceeded. The veto functions of the BG and the Cb stem from inhibition, but the countermanding disinhibition develops at markedly different rates in those two key components. It develops rapidly in the BG, control being exercised by the amygdala, which itself is governed by various other brain regions. It develops over time in the Cb, thereby permitting previously executed movements that have proved advantageous. If cognition is linked to overt or covert movement, intelligence becomes the ability to consolidate individual motor elements into more complex patterns, and creativity is the outcome of a race-to-threshold process which centers on the motor areas. Amongst the ramifications of these ideas are aspects of cortical oscillations, phantom limb sensations, amyotrophic lateral sclerosis (ALS) the difficulty of self-tickling and mirror neurons.

Paradox and cross purposes in recent work on consciousness

Functionalists about consciousness identify consciousness with a role; physicalists identify consciousness with an implementer of that role. The global workspace theory of consciousness fits the functionalist perspective, but the physicalist sees consciousness as a biological phenomenon that implements global accessibility.

Introspective physicalism as an approach to the science of consciousness

Most 'theories of consciousness' are based on vague speculations about the properties of conscious experience. We aim to provide a more solid basis for a science of consciousness. We argue that a theory of consciousness should provide an account of the very processes that allow us to acquire and use information about our own mental states - the processes underlying introspection. This can be achieved through the construction of information-processing models that can account for 'Type-C' processes. Type-C processes can be specified experimentally by identifying paradigms in which awareness of the stimulus is necessary for an intentional action. The Shallice (1988b) framework is put forward as providing an initial account of Type-C processes, which can relate perceptual consciousness to consciously performed actions. Further, we suggest that this framework may be refined through the investigation of the functions of prefrontal cortex. The formulation of our approach requires us to consider fundamental conceptual and methodological issues associated with consciousness. The most significant of these issues concerns the scientific use of introspective evidence. We outline and justify a conservative methodological approach to the use of introspective evidence, with attention to the difficulties historically associated with its use in psychology.

There are no Known Differences in Brain Mechanisms of Consciousness Between Humans and Other Mammals

Recent scientific findings indicate that consciousness is a fundamental biological adaptation. The known brain correlates of consciousness appear to be phylogenetically ancient, going back at least to early mammals. In all mammals, alertness and sensory consciousness are required for the goal-directed behaviours that make species survival and reproduction possible. In all mammals, the anatomy, neurochemistry and electrical activity of the brain in alert states show striking similarities.

After more than seven decades of cumulative discoveries about waking and sensory consciousness, we have not yet found any fundamental differences between humans and other mammals. Species differences such as the size of neocortex seem to be irrelevant to the existence of alertness and sensory consciousness, though different mammals obviously specialize in different kinds of sensory, cognitive and motor abilities.

Sceptics sometimes claim that objective evidence for consciousness tells us little about subjective experience, such as the experience of conscious pain. Scientifically, however, plausible inferences are routinely based on reliable and consistent patterns of evidence. In other humans, we invariably infer subjective experiences from objective behavioural and brain evidence - if someone yells ‘Ouch!’ after striking a finger with a hammer, we infer that they feel pain. The brain and behavioural evidence for subjective consciousness is essentially identical in humans and other mammals. On the weight of the objective evidence, therefore, subjective experience would seem to be equally plausible in all species with human-like brains and behaviour. Either we deny this experience to other humans (which is rarely done) or, to be consistent, we must also attribute it to other species that meet the same objective standards. It seems that the burden of proof for the absence of subjectivity in mammals should be placed on the sceptics.

Levels of self-awareness after acute brain injury: how patients' and rehabilitation specialists' perceptions compare

OBJECTIVE

To examine self-awareness regarding performance on 4 daily living tasks and to test theoretical predictions for a model of self-awareness in persons with acquired brain injury.

DESIGN

A comparative design examining the level of self-awareness recorded by patients and actual patient performance as judged by rehabilitation clinicians.

SETTING

A community-based residential center providing comprehensive rehabilitation services to persons with acquired brain injury.

PARTICIPANTS

Fifty-five persons with acquired brain injury and the identified potential to return to independent function in the community. Ten subjects without brain injury provided comparison data.

INTERVENTION

Information was collected by using patient self-report, clinician rating of patient performance, patient rating of non-brain-injured subjects, and clinician rating of non-brain-injured subjects.

MAIN OUTCOME MEASURES

Three self-awareness criteria were examined: intellectual, emergent, and anticipatory. Self-awareness was rated for 3 tasks: dressing, meal planning, and money management.

RESULTS

Statistically significant differences (p <.05) were found for all levels of self-awareness across the 3 tasks. Persons with brain injury judged their abilities higher than clinician ratings of actual performance. No statistical support was found for a hierarchy among intellectual, emergent, and anticipatory self-awareness.

CONCLUSIONS

No evidence was found supporting a hierarchy among levels of self-awareness as defined and measured in the present study. New methods for operationally defining intellectual, emergent, and anticipatory self-awareness are necessary to examine the relationship between self-awareness and performance.

The neural-cognitive basis of the Jamesian stream of thought

William James described the stream of thought as having two components: (1) a nucleus of highly conscious, often perceptual material; and (2) a fringe of dimly felt contextual information that controls the entry of information into the nucleus and guides the progression of internally directed thought. Here I examine the neural and cognitive correlates of this phenomenology. A survey of the cognitive neuroscience literature suggests that the nucleus corresponds to a dynamic global buffer formed by interactions between different regions of the brain, while the fringe corresponds to a set of mechanisms in the frontal and medial temporal lobes that control the contents of this global buffer. A consequence of this account is that there might be conscious imagistic representations that are not part of the nucleus. I argue that phenomenology can be linked to psychology and neuroscience and a meaningful way that illuminates both.

Consciousness: mapping the theoretical landscape

What makes us conscious? Many theories that attempt to answer this question have appeared recently in the context of widespread interest about consciousness in the cognitive neurosciences. Most of these proposals are formulated in terms of the information processing conducted by the brain. In this overview, we survey and contrast these models. We first delineate several notions of consciousness, addressing what it is that the various models are attempting to explain. Next, we describe a conceptual landscape that addresses how the theories attempt to explain consciousness. We then situate each of several representative models in this landscape and indicate which aspect of consciousness they try to explain. We conclude that the search for the neural correlates of consciousness should be usefully complemented by a search for the computational correlates of consciousness.

Neural representation and the cortical code

The principle function of the central nervous system is to represent and transform information and thereby mediate appropriate decisions and behaviors. The cerebral cortex is one of the primary seats of the internal representations maintained and used in perception, memory, decision making, motor control, and subjective experience, but the basic coding scheme by which this information is carried and transformed by neurons is not yet fully understood. This article defines and reviews how information is represented in the firing rates and temporal patterns of populations of cortical neurons, with a particular emphasis on how this information mediates behavior and experience.

The feeling of knowing: some metatheoretical implications for consciousness and control

The study of the feeling of knowing may have implications for some of the metatheoretical issues concerning consciousness and control. Assuming a distinction between information-based and experience-based metacognitive judgments, it is argued that the sheer phenomenological experience of knowing ("noetic feeling") occupies a unique role in mediating between implicit-automatic processes, on the one hand, and explicit-controlled processes, on the other. Rather than reflecting direct access to memory traces, noetic feelings are based on inferential heuristics that operate implicitly and unintentionally. Once such heuristics give rise to a conscious feeling that feeling can then affect controlled action. Examination of the cues that affect noetic feelings suggest that not only do these feelings inform controlled action, but they are also informed by feedback from the outcome of that action.

Probing for relevance: what metacognition tells us about the power of consciousness

Metacognitive attitudes can affect behavior but do they do so, as Koriat claims, because they enhance voluntary control? This Commentary makes a case for saying that metacognitive consciousness may enhance not control but subjective predictability and may be best studied by examining not just healthy, well-integrated cognizers, but victims of multilevel mental disorders.

Conscious and unconscious metacognition: A rejoinder

In this rejoinder we clarify several issues raised by the commentators with the hope of resolving some disagreements. In particular, we address the distinction between information-based and experience-based metacognitive judgments and the idea that memory monitoring may be mediated by direct access to internal representations. We then examine the possibility of unconscious metacognitive processes and expand on the critical role that conscious metacognitive feelings play in mediating between unconscious activations and explicit-controlled action. Finally, several open questions are articulated for further scrutiny. Copyright 2000 Academic Press.

Phänomenales Erleben: Ein fundamentales Problem für die Psychologie und die Neurowissenschaften

Zusammenfassung. In diesem Artikel versuchen wir aufzuzeigen, in welchem speziellen Sinne Bewußtsein ein Problem darstellt, für das die Psychologie und die Neurowissenschaften derzeit keinerlei theoretische Erklärung und kein methodisches Konzept haben. In experimentellen Arbeiten wird Bewußtsein meist verstanden als ein aufmerksamkeitsgekoppelter Zustand oder Prozeß, der selbst-referentielle Metakognitionen und darauf aufbauende kognitive Operationen ermöglicht. Diese Konzeption reduziert Bewußtsein auf vergleichsweise “einfache” Probleme, die mit den bekannten naturwissenschaftlichen Ansätzen gelöst werden können. Sie läßt aber unserer Meinung nach einen wesentlichen, viel schwierigeren Aspekt außer acht: Die Frage nach der Entstehung und der Funktion des phänomenalen Erlebens, der “Qualia”. Wir zeigen auf, daß dieses Problem zur Zeit prinzipiell unlösbar erscheint und argumentieren, daß sich darin eine fundamentale Wissenslücke der Psychologie und der gesamten Naturwissenschaften widerspiegelt, die ernstgenommen werden muß.

Biophysical body-brain-mind unity: theory and practice

A novel substance-attributed biophysical theory of brain-mind unity is presented. We separate spiritualism and matters of the soul from the medical sphere. Biophysical principles are responsible for the body's operational regimen (BOR) in the homeostatic state which allows for materialization and emergence of the mind; Excitation and/or inhibition modulate 8 BOR stages. There is automatic (somatic) and non-automatic (biophysical and psychological) Circadian cycle control. Computer-analog input and output occurs in wired neuronal electric pathways. Biotechnological devices located in emotional neurons positively signal homeostatic and negatively signal deranged BOR and biophysical mind operations. Macro and/or micro cerebral lesions which affect homeostasis may cause psychopathology, which can be treated with 'instrumental psychotherapy' (IPT) which enables recovery from homeostatic disorder in Phase 1, refining EGO in Phase 2, and social competence in Phase 3. The theory of brain-mind unity and practice of IPT is geared to medical workers and biophysical psychologists.

Conscious Experience Depends on Multiple Brain Systems

Following brain damage, information processing and consciousness can break down. This phenomenon is termed dissociation between preserved implicit (nonconscious) knowledge and impaired explicit (conscious) knowledge. Examples of the implicit/explicit dissociation are provided based on neuropsychological deficits such as cortical blindness, prosopagnosia, neglect, and amnesia. Also, models of the dissociation are discussed. The explicit/implicit dissociations are domain specific, in the sense that they always occur in a single domain only. For that reason, it is argued that there is no unitary area in the brain on which the activity of conscious experience depends. It is proposed instead that the neural substrate of conscious experience is distributed, and that the contents of consciousness depend on activity in many independent cortical areas.

Simulating consciousness in a bilateral neural network: "nuclear" and "fringe" awareness

A technique for the bilateral activation of neural nets that leads to a functional asymmetry of two simulated "cerebral hemispheres" is described. The simulation is designed to perform object recognition, while exhibiting characteristics typical of human consciousness-specifically, the unitary nature of conscious attention, together with a dual awareness corresponding to the "nucleus" and "fringe" described by William James (1890). Sensory neural nets self-organize on the basis of five sensory features. The system is then taught arbitrary symbolic labels for a small number of similar stimuli. Finally, the trained network is exposed to nonverbal stimuli for object recognition, leading to Gaussian activation of the "sensory" maps-with a peak at the location most closely related to the features of the external stimulus. "Verbal" maps are activated most strongly at the labeled location that lies closest to the peak on homologous sensory maps. On the verbal maps activation is characterized by both excitatory and inhibitory Gaussians (a Mexican hat), the parameters of which are determined by the relative locations of the verbal labels. Mutual homotopic inhibition across the "corpus callosum" then produces functional cerebral asymmetries, i.e., complementary activation of homologous "association" and "frontal" maps within a common focus of attention-a nucleus in the left hemisphere and a fringe in the right hemisphere. An object is recognized as corresponding to a known label when the total activation of both hemispheres (nucleus plus fringe) is strongest for that label. The functional dualities of the cerebral hemispheres are discussed in light of the nucleus/fringe asymmetry.

Attention, self-regulation and consciousness

Consciousness has many aspects. These include awareness of the world, feelings of control over one's behaviour and mental state (volition), and the notion of continuing self. Focal (executive) attention is used to control details of our awareness and is thus closely related to volition. Experiments suggest an integrated network of neural areas involved in executive attention. This network is associated with our voluntary ability to select among competing items, to correct error and to regulate our emotions. Recent neuroimaging studies suggest that these various functions involve separate areas of the anterior cingulate. We have adopted a strategy of using marker tasks, shown to activate the brain area by imaging studies, as a means of tracing the development of attentional networks. Executive attention appears to develop first to regulate distress during the first year of life. During later childhood the ability to regulate conflict among competing stimuli builds upon the earlier cingulate anatomy to provide a means of cognitive control. During childhood the activation of cingulate structures relates both to the child's success on laboratory tasks involving conflict and to parental reports of self-regulation and emotional control. These studies indicate a start in understanding the anatomy, circuitry and development of executive attention networks that serve to regulate both cognition and emotion.

Investigating form and colour perception in blindsight using an interference task

Patients with striate cortical damage causing a hemianopic field defect can nevertheless demonstrate residual visual capacities in their blind field. Previous research investigating blindsight required patients to respond explicitly to stimuli appearing in the blind field by making forced choice judgements. We present data from a patient with a left occipital lesion resulting in a homonymous hemianopia, using the flanker task. This patient displayed a significant flanker congruency effect (FCE) for colour and letter stimuli even when they appeared in the blind field. A control patient with a lesion of the right thalamus showed no FCE in the blind field. This suggests that thalamo-extrastriate neural pathways are necessary for residual functioning in blindsight.

Implicit short-lived motor representations of space in brain damaged and healthy subjects

This article reviews experimental evidence for a specific sensorimotor function which can be dissociated from higher level representations of space. It attempts to delineate this function on the basis of results obtained by psychophysical experiments performed with brain damaged and healthy subjects. Eye and hand movement control exhibit automatic features, such that they are incompatible with conscious control. In addition, they rely on a reference frame different from the one used by conscious perception. Neuropsychological cases provide a strong support for this specific motor representation of space, which can be spared in patients with lesions of primary sensory systems who have lost conscious perception of visual, tactile or proprioceptive stimuli. Observation of these patients also showed that their motor behavior can be "attracted" by a goal only under specific conditions, that is, when the response is immediate and when no cognitive representation of this goal is elaborated at the same time. Beyond the issue of the dissociation between an implicit motor representation and more cognitive processing of spatial information, the issue of the interaction between these two systems is thus a matter of interest. It is suggested that the conscious, cognitive representation of a stimulus can contaminate or override the short-lived motor representation, but no reciprocal influence seem to occur. The interaction observed in patients can also be investigated in normals. The literature provides examples of interaction between sensorimotor and cognitive framing of space, which confirm that immediate action is not mediated by the same system as delayed action, and that elaborating a categorial representation of the action goal prevents the expression of the short-lived sensorimotor representation. It is concluded that action can be controlled by a sensory system which is specialized for on-line processing of relevant goal characteristics. The temporal constraints of this system are such that it can affect the action before a full sensory analysis of this goal has been completed. The performance obtained on the basis of this spatial sensory processing suggests that short-lived motor representations may rather be considered as real "presentation" of the action world, which share its metric properties.

Visibility of brief images: the dual-process approach

If successive, brief visual images are exposed for recognition or for psychophysical ratings, various effects and phenomena of fast dynamics of conscious perception such as mutual masking, metacontrast, proactive enhancement of contrast, proactive speed-up of the latency of subjective visual experience, the Fröhlich Effect, the Tandem Effect, attentional facilitation by visuospatial precuing, and some others have been found. The theory proposed to deal with these phenomena proceeds from the assumption that two types of brain processes are necessary in order to consciously recognize visual stimuli: (1) fast, specific processes of encoding that allocate and reactivate the stimulus representation which is based on the activity of selected cortical neurons and (2) relatively slower processes of facilitation of the activity of this specific representation that are mediated by the excitatory modulation of the EPSPs of those selected cortical neurons by the ascending input from nonspecific thalamus. The perceptual retouch construct is proposed in order to characterize and analyze the interaction of (1) and (2). The neurophysiological characteristics of this bifunctional system of afference help to put forward several predictions that are found to be consistent with the empirical regularities of the above-described perceptual-attentional phenomena. These data form a body of converging evidence that is consistent with the predictions of the perceptual retouch approach.

Attention, awareness, and the triangular circuit

It is proposed that attention to an object requires the simultaneous activity of three brain regions that are interconnected by a triangular circuit. The regions are the cortical site of attentional expression, the thalamic enhancement structure, and the prefrontal area of control. It is also proposed that awareness of an object requires the additional component of attention directed to a representation of the self. The expression of attention to a self-representation may involve activations of cortical sites corresponding to the body landscape and/or verbal-based memories of autobiographical episodes. As in the case of attention to objects, attention to the self is presumed to involve a triangular circuit. The proposed triangular circuit of attention is shown to be generally consistent with current knowledge of brain structures and with data from a broad range of experiments concerned with the functions of neurons in these structures.

Blindsight in hindsight

Philosophers concerned with issues of mind have been turning to the neurosciences, especially neuropsychology, for empirical guidance. While I endorse this emphasis, I find that one important neuropsychological phenomenon, blindsight appears to have been misused by some prominent philosophers. In this paper, I examine this alleged misuse by spelling out the accounts of blindsight given by Daniel Dennett and Ned Block. I attempt to show that both Dennett and Block have ignored many complications surrounding blindsight including subjects' reports of visual sensations. This neglect has serious ramifications for their respective models of human consciousness which I also try to explicate. Further, by misrepresenting blindsight, these accounts serve to hamper scientific and philosophical understanding of the phenomenon and of consciousness. I conclude by sketching a model of blindsight that acknowledges these neglected details.

The role of the prefrontal cortex in higher cognitive functions

The higher cognitive functions, working memory, mental imagery and willed action, are all intimately associated with consciousness. The common process underlying all these functions is that information is "held in mind" for a period of time. This information, which may be about stimuli or responses, can be derived from the past or generated for the future. Brain imaging studies show that "holding something in mind" is associated with activity in an extended system which involves both prefrontal cortex and more posterior areas whose location is determined by the nature of the information being held in mind. Automatic actions and perceptions which do not involve consciousness are associated with activity in the relevant posterior areas, but not in the prefrontal cortex. These studies demonstrate that activity occurs in the same posterior area whether the associated information comes from the outside world or is internally generated. This raises the problem of how we know whether our experience derives from mental imagery or from something happening in the outside world. There is evidence that patients with schizophrenia have precisely this problem since they perceive their own thoughts and even sub-vocal speech as coming from outside (hallucinations). Recent brain imaging studies suggest that there is a disconnection between prefrontal and posterior areas in these patients which could explain their characteristic misperceptions.

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.