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PubMed1999

A concept of consciousness.

The term "consciousness", so widely used in clinical settings, is considered extremely complex and practically undefinable. Historically, consciousness was ignored by the great classical philosophers, and was regarded as a basic condition of "being". This changed with Descartes and during the ensuing centuries. A simplified, reductionistic and easily definable concept of consciousness is proposed; consciousness is proposed to consist of three main components: vigilance, mental contents, and selective attention. These three components can be investigated with modern neuroscientific methods--vigilance being the most readily explorable function. The striking differences between sleep and coma are pointed out (along with some observations on sleep initiation). Special attention is paid to epileptic impairment of consciousness and, in particular, to the spike-wave absence which is thought to be due to a temporary suspension of the "working memory circuits" within the frontal lobe.

Arousal↗
PubMed2005

Characteristics of interhemisphere interactions at different levels of consciousness.

The relationship between the level of consciousness and the level of brain activation was studied. A model for a gradual decrease in the level of consciousness was provided by the transition from waking to drowsiness. Measures of the level of consciousness, assessed by the subjects themselves, consisted of changes in the content of consciousness, i.e., the intensity and quality of involuntarily arising mental processes. In each subject, the level of consciousness was found to correspond to a pert EEG profile. The results obtained from these studies showed that the lowest level of activation corresponded to the state in which the subject noted inhibition of "inner speech," a "lapse of thoughts," and in this state the interhemisphere associations involving the major mechanism of transmission of cognitive information, i.e., the high-frequency EEG rhythm, was weakened.

Adolescent↗
PubMed2006

Frequency-amplitude characteristics of the EEG at different levels of consciousness.

The relationship between the level of consciousness and the level of brain activation was studied. The model providing gradual decreases in the level of consciousness consisted of states in the transition from waking to drowsiness. The measure of the level of consciousness, measured from subjects' self-assessments, was the change in the content of consciousness, i.e., the intensity and quality of involuntarily arising mental processes. Each of the levels of consciousness was found to correspond to a defined EEG profile. The results showed that the lowest level of activation corresponded to the state in which the subjects noted inhibition of "inner speech" and "cessation of thoughts," this being associated with a change in the dynamics of the high-frequency EEG rhythm associated with the mechanism of transmission of cognitive information.

Adolescent↗
PubMed1995

An introduction to the biology of consciousness.

This paper summarizes the main steps in a scientific study of consciousness. From a survey of the recent literature, it appears that: (1) there is a clear tendency to consider consciousness as a scientific object; (2) consistent subjective and objective descriptions of consciousness are possible; an intentional-modeling structure accounts for its main features; (3) from the evolutionary biology standpoint, conscious cognitive activities, as based on models of the self, the world and the alter-ego, have a functional value; (4) the material basis of consciousness can be clarified without recourse to new properties of the matter or to quantum physics. Current neurobiology, based on classical macrophysics, appears able to handle the problem. In this scope, the neurobiology of sleep-wakefulness and attention, and neuropsychology, have already achieved substantial advances.

Animals↗
PubMed1995

Consciousness: perspectives from symbolic and connectionist AI.

While consciousness has not been a major concern of most AI researchers, some theorists have tried to explore how computational models might explain consciousness. I explore how far computational models might go in explaining consciousness, focusing on three aspects of conscious mental states: their intrinsic intentionality, the awareness a subject has of the contents of these intentional states, and the distinctive qualitative character of these states. I describe and evaluate strategies for developing connectionist systems that satisfy these aspects of consciousness.

Animals↗
PubMed1996

On the origin of consciousness, a postulate and its corollary.

A hypothesis is presented according to which structure of consciousness is quadri-dimensional. The four dimensions are duration, quality, intensity, and affectivity. One may reach this conclusion by introspection alone, or by deduction along the following steps: (1) consciousness should be examined from the point of view of evolutionary psychology; (2) this leads to the following postulate--consciousness evolved from sensation; (3) the postulate entails a corollary-- consciousness has kept the quadri-dimensional structure of sensation. The above postulate could explain the phylogenetic origin of pleasure as the common currency, and in turn the tradeoffs for access to the behavioral final common path. It would also entail that joy is the transient sign of a useful conscious event, whereas happiness is the indifferent experience of a satisfied mind.

Consciousness↗
PubMed1993

Consciousness: criteria and possible mechanisms.

There are two sorts of criteria of consciousness--objective and subjective ones. They are the ability for operating with the knowledge which could be addressed to other people in the abstract form and the feeling of 'ego' as a 'host' of these actions, respectively. These two signs of consciousness are provided with the mechanism based on the synthesis in the brain structures of different kinds of information: sensory information, the data extracted from the memory and the signals from the centers of emotions and motivation. As a result of this synthesis, the sense of 'ego' arises and the message designated for others is determined. A significant role in the informational synthesis is played by dynamic cortical structures--foci of interaction. In perception they are localized predominantly in the projectional cortex, in thinking and in the associative areas. Realization is closely connected with communication and appearance of the interaction foci in the verbal zones of the left hemisphere. Pavlov (1951), in his program lecture in Madrid early in the present century, said that he saw the final aim of his study in the revealing of the mechanism and the inner vital sense of human consciousness. It is important, that Pavlov placed the words 'mechanism' and 'vital sense' near each other, i.e., he considered that the sense of consciousness would be realized through revealing its mechanism. This insight attracts our attention now, when the problem on consciousness mechanism is in scientific plans and the search for the meaning of life by the end of the twentieth century, one full of dramatic events, acquires a special value.

Brain↗
PubMed2006

Frequency response characteristic of sympathetic mediated low-frequency blood pressure fluctuations in conscious rats.

A quantitative relationship between power densities of blood pressure (PBP) and sympathetic nerve activity (PSNA) in a low-frequency range (LF, 0.016-0.85 Hz), expressed as PSNA=PBPxax10bx(frequency) was proposed in pentobarbital-anesthetized rats. For evaluating the general applicability of this equation, the quantitative relationship of power density ratio Hf=PBP/PSNA across frequency was tested in a conscious state. Wistar rats were chronically instrumented with a femoral artery catheter and recording electrode around the renal sympathetic nerve. The blood pressure and renal sympathetic nerve activity were monitored both under pentobarbital anesthesia and in a conscious state. Linear regression analysis of the relationship between the frequency and logarithmic magnitude of the power density ratio in the LF range revealed excellent fit in both conditions (r=-0.96+/-0.01 and -0.93+/-0.01 for anesthetized and conscious rats, respectively). Comparing the regression lines, rats under pentobarbital anesthesia had significantly larger values for the y-intercept and slope compared to rats in a conscious state (y-intercepts: 0.80+/-0.09>0.53+/-0.08; slopes: -2.86+/-0.26>-1.62+/-0.21). Our results demonstrate that it is also feasible to use the weighted PBP in LF as a quantitative index of sympathetic variability in conscious rats, but the evaluation of possible complications controlling the regression parameters is called for.

Action Potentials↗
PubMed2005

Neural Darwinism and consciousness.

Neural Darwinism (ND) is a large scale selectionist theory of brain development and function that has been hypothesized to relate to consciousness. According to ND, consciousness is entailed by reentrant interactions among neuronal populations in the thalamocortical system (the 'dynamic core'). These interactions, which permit high-order discriminations among possible core states, confer selective advantages on organisms possessing them by linking current perceptual events to a past history of value-dependent learning. Here, we assess the consistency of ND with 16 widely recognized properties of consciousness, both physiological (for example, consciousness is associated with widespread, relatively fast, low amplitude interactions in the thalamocortical system), and phenomenal (for example, consciousness involves the existence of a private flow of events available only to the experiencing subject). While no theory accounts fully for all of these properties at present, we find that ND and its recent extensions fare well.

Biological Evolution↗
PubMed2005

Identifying hallmarks of consciousness in non-mammalian species.

Most early studies of consciousness have focused on human subjects. This is understandable, given that humans are capable of reporting accurately the events they experience through language or by way of other kinds of voluntary response. As researchers turn their attention to other animals, "accurate report" methodologies become increasingly difficult to apply. Alternative strategies for amassing evidence for consciousness in non-human species include searching for evolutionary homologies in anatomical substrates and measurement of physiological correlates of conscious states. In addition, creative means must be developed for eliciting behaviors consistent with consciousness. In this paper, we explore whether necessary conditions for consciousness can be established for species as disparate as birds and cephalopods. We conclude that a strong case can be made for avian species and that the case for cephalopods remains open. Nonetheless, a consistent effort should yield new means for interpreting animal behavior.

Animals↗
PubMed2005

Affective consciousness: Core emotional feelings in animals and humans.

The position advanced in this paper is that the bedrock of emotional feelings is contained within the evolved emotional action apparatus of mammalian brains. This dual-aspect monism approach to brain-mind functions, which asserts that emotional feelings may reflect the neurodynamics of brain systems that generate instinctual emotional behaviors, saves us from various conceptual conundrums. In coarse form, primary process affective consciousness seems to be fundamentally an unconditional "gift of nature" rather than an acquired skill, even though those systems facilitate skill acquisition via various felt reinforcements. Affective consciousness, being a comparatively intrinsic function of the brain, shared homologously by all mammalian species, should be the easiest variant of consciousness to study in animals. This is not to deny that some secondary processes (e.g., awareness of feelings in the generation of behavioral choices) cannot be evaluated in animals with sufficiently clever behavioral learning procedures, as with place-preference procedures and the analysis of changes in learned behaviors after one has induced re-valuation of incentives. Rather, the claim is that a direct neuroscientific study of primary process emotional/affective states is best achieved through the study of the intrinsic ("instinctual"), albeit experientially refined, emotional action tendencies of other animals. In this view, core emotional feelings may reflect the neurodynamic attractor landscapes of a variety of extended trans-diencephalic, limbic emotional action systems-including SEEKING, FEAR, RAGE, LUST, CARE, PANIC, and PLAY. Through a study of these brain systems, the neural infrastructure of human and animal affective consciousness may be revealed. Emotional feelings are instantiated in large-scale neurodynamics that can be most effectively monitored via the ethological analysis of emotional action tendencies and the accompanying brain neurochemical/electrical changes. The intrinsic coherence of such emotional responses is demonstrated by the fact that they can be provoked by electrical and chemical stimulation of specific brain zones-effects that are affectively laden. For substantive progress in this emerging research arena, animal brain researchers need to discuss affective brain functions more openly. Secondary awareness processes, because of their more conditional, contextually situated nature, are more difficult to understand in any neuroscientific detail. In other words, the information-processing brain functions, critical for cognitive consciousness, are harder to study in other animals than the more homologous emotional/motivational affective state functions of the brain.

Affect↗
PubMed2005

Levels of consciousness and self-awareness: A comparison and integration of various neurocognitive views.

Quite a few recent models are rapidly introducing new concepts describing different levels of consciousness. This situation is getting confusing because some theorists formulate their models without making reference to existing views, redundantly adding complexity to an already difficult problem. In this paper, I present and compare nine neurocognitive models to highlight points of convergence and divergence. Two aspects of consciousness seem especially important: perception of self in time and complexity of self-representations. To this I add frequency of self-focus, amount of self-related information, and accuracy of self-knowledge. Overall, I conclude that many novel concepts (e.g., reflective, primary, core, extended, recursive, and minimal consciousness) are useful in helping us distinguish between delicate variations in consciousness and in clarifying theoretical issues that have been intensely debated in the scientific literature--e.g., consciousness in relation to mirror self-recognition and language.

Awareness↗
PubMed2005

Seizure anticipation, states of consciousness and marginal predictability in temporal lobe epilepsy.

PURPOSE: It has recently been shown that differences between the marginal predictability associated with scalp electrodes adjacent to and remote from the site of a seizure focus are able to distinguish between epochs temporally distant from and just prior to (within about 20 min) the onset of a seizure in patients with temporal lobe epilepsy. The purpose of this paper is to show that these differences of marginal predictability intervals are independent of the state of consciousness of the patient. METHODS: We have studied a data set encompassing 33 preictal epochs (within 1 h prior to a seizure) and 61 interictal epochs (defined as at least 1 h away from any seizure) from 14 patients. Each 30 s interval of each epoch was categorized into one of seven different states of consciousness. Statistical models were used to search for relationships (in aggregated data) between the values of differences of marginal predictabilities and state of consciousness. RESULTS: It was not possible to reject the null hypothesis of no relationship between differences of marginal predictabilities and state of consciousness. CONCLUSIONS: The values of the differences between marginal predictabilities on aggregated data are apparently insensitive to the state of consciousness. This conclusion, coupled with the fact that the differences between marginal predictabilities do depend on time to seizure, suggests the potential utility of these measures as the basis for ambulatory, non-invasive methods of seizure anticipation. However, the development of a practical non-invasive method for seizure anticipation requires further extensive study on disaggregated data from individual patients.

Adolescent↗
PubMed2005

The blind protocol and its place in consciousness research.

This paper describes the development of the blind protocol, and its place in this history of consciousness research. It was first devised by Croesus, King of the Lydians (BCE 560-547) and reported by Herodotus ( approximately BCE 484 - approximately 424), and was created to protect against fraud in assessing an Anomalous Perception (AP) event; a Remote Viewing (RV) experiment little different from those conducted today. Its next use in the 17th century was to study a peasant farmer, Jacques Aymar, who solved crimes with Anomalous Perception, using dowsing. Not only was a blind protocol employed, but the rudiments of controls were introduced to assess Aymar. The next documented use of a blind protocol in consciousness research occurred in 1784, when it was explicitly employed in the interest of science, and its history as a research technique can be said to have formally begun. King Louis the XVIth created a commission to evaluate Franz Anton Mesmer's claims concerning healing through "animal magnetism," administered while people were in a trance, and asked Benjamin Franklin to be the commission's head. The paper proposes that Franklin be considered the first parapsychologist. He created the blind protocol to answer the king's question as to whether "animal magnetism" was real, and he not only introduced demographic variables and controls, but literally blindfolded people, which is why today we call it the blind protocol. Franklin's observations also present the first recorded Western description of psychosomatic illness. An unintended consequence of Franklin's Mesmer study was the loss of the idea of psychophysical self-regulation (PPSR) as a research vector, although the English surgeon John Eliotson (1791-1868) apparently saw through the failure of Mesmer's explanatory model to the deeper insight in the form of hypnosis that was Mesmer's real discovery. He seems to have avoided all attempts at explaining how it worked but conducted a considerable number of surgeries using hypnosis as the anesthetic, anticipating its usage in this capacity a century later. So great was the disapproval of Mesmer, however, that no one seems to have gotten Eliotson's point. Franklin's protocol, though, rapidly became the gold standard of science. Rupert Sheldrake, however, carried out a survey of the leading scientific journals and discovered that the main use of the blind protocol is not in medicine per se, but parapsychology and consciousness research, in which it is used for the same purposes it was originally conceived: to winnow out fraud in anomalous consciousness events and to avoid introducing experimenter effects. Ultimately, though, the protocol may be based on a false assumption, because increasingly research in areas such as therapeutic intent/healing and remote viewing suggest that all consciousness from single-celled organisms to human beings may be interlinked through a nonlocal aspect of awareness they all share.

Autosuggestion↗
PubMed2006

Autonoetic consciousness in Alzheimer's disease: neuropsychological and PET findings using an episodic learning and recognition task.

OBJECTIVE: This study aims to map in patients with mild Alzheimer's disease (AD) the correlations between resting-state brain glucose utilization measured by FDG-PET and scores reflecting autonoetic consciousness in an episodic learning and recognition task. METHODS: Autonoetic consciousness, that gives a subject the conscious feeling to mentally travelling back in time to relive an event, was assessed using the Remember/Know (R/K) paradigm. RESULTS: AD patients provided less R responses (reflecting autonoetic consciousness) and more K ones (indicating the involvement of noetic consciousness) than healthy controls. Correct recognitions associated with a R response correlated with the metabolism of frontal areas bilaterally whereas those associated with a K response mainly correlated with the metabolism of left parahippocampal gyrus and lateral temporal cortex. CONCLUSIONS: These data show that recollection is impaired in AD and recognition is more based on a feeling of familiarity than in controls. In addition, the findings of our correlative approach indicate that the impairment of episodic memory is mainly subserved by the dysfunction of frontal areas and of the hippocampal region.

Aged↗
PubMed2003

Dissecting out conscious and unconscious memory (sub)processes within the human medial temporal lobe.

The human medial temporal lobe (MTL) system mediates memories that can be consciously recollected. However, the specific natures of the individual contributions of its various subregions to conscious memory processes remain equivocal. Here we show a functional dissociation between the hippocampus proper and the parahippocampal region in conscious and unconscious memory as revealed by invasive recordings of limbic event-related brain potentials recorded during explicit and implicit word recognition: Only hippocampal and not parahippocampal neural activity exhibits a sensitivity to the implicit versus explicit nature of the recognition memory task. Moreover, only within the hippocampus proper do the neural responses to repeated words differ not only from those to new words but also from each other as a function of recognition success. By contrast parahippocampal (rhinal) responses are sensitive to repetition independent of conscious recognition. These findings thus demonstrate that it is the hippocampus proper among the MTL structures that is specifically engaged during conscious memory processes.

Brain Mapping↗
PubMed2004

The development of conscious control in childhood.

Developmental data suggest that the growth of executive function in childhood can be understood in terms of the development of consciousness. According to the "levels of consciousness" (LOC) model, there are age-related increases in the highest degree of self-reflection or LOC that children are able to muster in response to situational demands. These increases in LOC with age have consequences for the quality of experience, the potential for recall, the complexity of children's explicit knowledge structures, and the possibility of the conscious control of thought, emotion, and action. The hierarchical LOCs identified by this analysis are also useful for understanding the complex structure of conscious experience in adults, and they provide a metric for measuring the level at which consciousness is operating in specific situations.

Adult↗
PubMed2006

Attention and consciousness: two distinct brain processes.

The close relationship between attention and consciousness has led many scholars to conflate these processes. This article summarizes psychophysical evidence, arguing that top-down attention and consciousness are distinct phenomena that need not occur together and that can be manipulated using distinct paradigms. Subjects can become conscious of an isolated object or the gist of a scene despite the near absence of top-down attention; conversely, subjects can attend to perceptually invisible objects. Furthermore, top-down attention and consciousness can have opposing effects. Such dissociations are easier to understand when the different functions of these two processes are considered. Untangling their tight relationship is necessary for the scientific elucidation of consciousness and its material substrate.

Attention↗