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PubMed2004

Consciousness is discontinuous: the perception of continuity requires conscious vectors and needs to be balanced with creativity.

Consciousness is not what it appears to be. While we are awake and alert, consciousness appears to be continuous, but actually is broken up into discrete intervals. The perception of continuity is critical for cognitive performance, linking together an otherwise disparate collection of thoughts. The perception requires an understanding of how information changes and evolves between conscious intervals. This understanding is analogous to the vectors used by the visual system to add motion to otherwise still images. Determining conscious vectors, however, is much more complex than determining motion vectors and presumably strains cognitive resources. This strain, in turn, limits the ability to bring in new information and ideas, creating a tradeoff between continuity and creativity. Optimizing this tradeoff may provide significant benefits both for common mental tasks and serious neurological conditions.

Attention↗
PubMed2005

Non-conscious prediction and a role for consciousness in correcting prediction errors.

As a result of the evolutionary pressure for survival, the brain relies on a number of non-conscious predictive neural mechanisms which allow for rapid, efficient behavioral responses to the environment. These predictive mechanisms enable the brain to recognize objects by sampling just a few sensory inputs, to anticipate what events are likely to occur and to prepare a response before events actually occur. Consciousness appears to play a role in the detection and correction of prediction errors. The author, a psychotherapist and psychoanalyst, proposes that this monitoring or oversight function of consciousness can be used to understand how conscious awareness facilitates change in the psychotherapeutic treatment of patients who repeat maladaptive patterns of behavior.

Adaptation, Psychological↗
PubMed1986

Concentrations of glycine and serine in cerebrospinal fluid during disturbed consciousness; a study of the therapeutic effect of thyrotropin-releasing hormone on the consciousness level.

The concentrations of aliphatic amino acids (glycine, serine, valine, threonine, alanine, leucine, isoleucine) in lumbar cerebrospinal fluid from patients with consciousness disturbances and normal controls were measured. Thyrotropin-releasing hormone (TRH) was administered to patients and the changes of levels of consciousness and amino acid concentrations were followed before and after TRH administration. The concentrations of glycine and serine from patients were significantly higher than those from controls; they returned to the control values with improvement of consciousness disturbances. The influence of TRH upon these amino acid concentrations was not observed. These results suggest that within the central nervous system, an alteration of the level of consciousness is associated with a distortion of glycine and serine metabolism and that TRH itself has no influence upon these amino acid concentrations.

Adolescent↗
PubMed1993

Demonstration of free radical generation in the "stunned" myocardium in the conscious dog and identification of major differences between conscious and open-chest dogs.

Conscious dogs undergoing a 15-min coronary occlusion were given alpha-phenyl N-tert-butyl nitrone (PBN) and the local coronary venous plasma was analyzed by electron paramagnetic resonance spectroscopy. A prolonged myocardial release of PBN radical adducts was observed, which exhibited a burst in the initial minutes of reflow (peaking at 3 min) and then abated but continued for 1-3 h after reperfusion. Computer simulation revealed the presence of at least two PBN adducts (aN = 15.2 G and a beta H = 6.0 G; aN = 14.6 G and a beta H = 3.0 G), both consistent with the trapping of secondary carbon-centered radicals. No appreciable PBN adduct production was observed when collateral flow exceeded 30-40% of nonischemic flow, indicating that a flow reduction of at least 60% is necessary to trigger free radical reactions. There was a direct relationship between the magnitude of PBN adduct production and the severity of contractile dysfunction (r = 0.77), suggesting that the radicals generated upon reperfusion play a causal role in the subsequent stunning. The total release of PBN adducts after 3 h of reperfusion following a 15-min coronary occlusion was found to be approximately five times greater in open-chest compared with conscious dogs; at the same time, the recovery of wall thickening was markedly less in open-chest dogs. This study represents the first application of spin trapping to a conscious animal model of myocardial ischemia. The results demonstrate (a) that free radicals are generated in the stunned myocardium in the absence of the artificial or abnormal conditions associated with previously used models (isolated hearts, open-chest preparations), and (b) that both the severity of postischemic dysfunction and the magnitude of the attendant free radical production are greatly exaggerated in the open-chest dog, implying that previous conclusions derived from this model may not be applicable to conscious animals or to humans. This investigation also provides a method to measure free radicals in awake animals.

Anesthesia, General↗
PubMed2004

Conscious sedation of children with propofol is anything but conscious.

OBJECTIVE: To determine the depth of sedation required for bone marrow aspiration and intrathecal injection of chemotherapeutic agents in children using a bispectral (BIS) index monitor and clinical assessment by an independent observer. METHODS: Sixteen children who were undergoing 19 intrathecal chemotherapy and bone marrow aspirations were enrolled in the study. Their ages ranged from 23 months to 190 months with a mean of 79 months. The BIS index was recorded every 5 minutes by an independent observer. The patients received only intravenous propofol for sedation. There were no complications during the procedures. RESULTS: The mean BIS score was 62.8+/- 9.6. The mean low BIS score was 29.7 +/- 13.7, indicating a level of deep sedation and/or general anesthesia was necessary to induce the desired stated of consciousness that would permit the practitioner to perform the procedure. The average dose of propofol was 166 +/- 47 microg/kg/min. Mean Aldrete score for level of consciousness was 0.9 +/- 0.4, indicating a depressed level of consciousness. The mean activity level was 1.0+/- 0.4, indicating impaired movement. CONCLUSIONS: Children who undergo conscious sedation with propofol for intrathecal chemotherapy and bone marrow aspiration demonstrate BIS values and clinical assessments consistent with deep sedation. Because of an increased risk of adverse events when children undergo deep sedation, appropriate parental informed consent, age-appropriate resuscitative equipment, and skilled anesthesia personnel should be present for rescue in the event of cardiovascular and respiratory complications from deep sedation.

Adolescent↗
PubMed1994

[Neurology of consciousness and of consciousness disorders].

The two physiologic components of conscious behaviour, namely arousal (vigilance) and content of consciousness (presence of mind), may be affected differently, depending on the type and distribution of the underlying brain disease. Disturbance of arousal primarily affects wakefulness and awareness and leads to obtundation, stupor and coma. States of reduced arousal are caused by bilateral lesions of the so-called ascending reticular activating system (ARAS), which is situated in the upper brainstem and the paramedian diencephalon. If, on the other hand, cognitive and mnemic function are degraded, the contents of consciousness are disordered; depending on the extent of the disturbance, confusion, lethargy and, finally, a vegetative state ensues. The chronic vegetative state (coma vigil) describes a condition of total mental loss with preserved vegetative functions and arousal. Degraded cognitive and mnenic functions results from either toxic-metabolic or extensive structural disorders of the cerebral cortex, where the limbic and mesial frontal areas play a dominant role for conscious behaviour. If the function of extensive areas of both hemispheres is suddenly depressed, temporarily reduced arousal also results. In order to differentiate between toxic-metabolic and structural brain diseases, the motor reactions, the ocular and the pupillary reflexes must be examined apart from responsiveness.

Arousal↗
PubMed1989

[Clinical study of bruxism. Comparison of muscle activity during sleep between patients conscious of bruxism and those not conscious of the condition].

Bruxism has been considered to be one of the most important factors in accelerating the progression of established periodontal lesions. However the objective diagnostic method has not yet been established. At present, diagnosing bruxism might mainly be dependent on interview. The purpose of this study was to compare and analyze the differences in frequency and duration of bruxism between a group of patients conscious of the problem and a group not conscious of bruxism. After interviewing, the subjects were divided into two groups; 1) group A consisted of 8 subjects who were conscious of bruxism and 2) group B of 8 subjects who were not conscious of bruxism. The frequencies and durations of muscle activity during sleep at night were compared between groups A and B using EMG with a telemetric method. In the one-night observation, muscle activity supposed to be bruxism was observed in both groups. Significant differences in frequencies of muscle activity were not found between the two groups. A similar result was obtained in the durations of muscle activity. In a seven-day observation, muscle activity was seen in all three volunteers, although marked differences were not found among them. A long duration of muscle activity was found under conditions of physical or mental stress. The results of this study showed the difficulty of diagnosing bruxism by interview and the necessity of an objective method.

Bruxism↗
PubMed1997

Conscious sedation clinical guideline. Conscious Sedation Working Group, Medical Association of South Africa.

OBJECTIVE: The objective of this guideline is to promote safe conscious sedation technique. OUTCOME: (I) The use of safe conscious sedation techniques with endpoints of patient comfort and anxiolysis without loss of protective reflexes; (II) the use of drugs with a wide margin of safety that will protect against unintended oversedation. EVIDENCE: Based on existing consensus statements and some research reports. VALIDATION: Relevant organisations involved in conscious sedation were asked to select a representative to participate in the MASA Conscious Sedation Working Group. All participants represented organisations. The working group met in January 1996 to consider a draft guideline. The document was amended and circulated to working group members, representative organisations and 35 interested persons for endorsement and comment using a modified Delphi technique. All respondents endorsed the guideline (with or without minor corrections.) The national organisations endorsing the guidelines are listed. RECOMMENDATIONS: The use of drugs, equipment and personnel as directed in such a way that enhances the safety of the patient. Pre-sedation screening for at-risk patients. Intra-sedation monitoring, especially the use of a pulse oximeter. Post-sedation care and discharge instructions for the patient.

Procedural Sedation↗
PubMed1995

Tutorial commentary: surprisingly small subcortical structures are needed for the state of waking consciousness, while cortical projection areas seem to provide perceptual contents of consciousness.

The evidence can therefore be summarized as follows: (1) RF, nRt, and ILN activity seem to be necessary but not sufficient for conscious experience. (2) Stimulus representation in primary sensory projection areas also seems to be necessary but not sufficient for conscious perceptual experience (Weiskrantz, 1980). The simplest hypothesis is that both components are necessary and sufficient to support conscious perceptual experience.

Attention↗
PubMed2006

Human Development IX: a model of the wholeness of man, his consciousness, and collective consciousness.

In this paper we look at the rational and the emotional interpretation of reality in the human brain and being, and discuss the representation of the brain-mind (ego), the body-mind (Id), and the outer world in the human wholeness (the I or "soul"). Based on this we discuss a number of factors including the coherence between perception, attention and consciousness, and the relation between thought, fantasies, visions and dreams. We discuss and explain concepts as intent, will, morals and ethics. The Jungian concept of the human collective conscious and unconscious is also analyzed. We also hypothesis on the nature of intuition and consider the source of religious experience of man. These phenomena are explained based on the concept of deep quantum chemistry and infinite dancing fractal spirals making up the energetic backbone of the world. In this paper we consider man as a real wholeness and debate the concepts of subjectivity, consciousness and intent that can be deduced from such a perspective.

Consciousness↗
PubMed1998

Epilepsy and recursive consciousness with special attention to Jackson's theory of consciousness.

John Hughlings Jackson's theory of consciousness has been reconsidered. The author stressed that his uniqueness as a neuroscientist lay in his keen interest in the recursive nature of human consciousness. Two clinical symptoms of interest to Jackson were discussed: recurrent utterances and mental diplopia. Recurrent utterances were believed to represent an exceptional state, in which the unconscious process in speech production, otherwise destined to be swept away automatically, became manifest and observable. Jackson regarded mental diplopia as a revelation of otherwise inaccessible duality of all healthy mental actions. Therefore, he supposed that the essence of recursive consciousness resided in a transformation of multiple, multidirectional, unconscious processes into a linear, unidirectional process.

Cognition↗
PubMed1991

Postischemic myocardial "stunning". Identification of major differences between the open-chest and the conscious dog and evaluation of the oxygen radical hypothesis in the conscious dog.

Recent studies suggest that oxygen-derived free radicals contribute to the pathogenesis of postischemic myocardial dysfunction (myocardial "stunning"). This concept, however, is predicated exclusively on results obtained in open-chest preparations, which are subject to the confounding influence of many unphysiological conditions. The lack of supporting evidence in more physiological animal models represents a major persisting limitation of the oxy-radical hypothesis of myocardial stunning. The goal of this study was to address two fundamental (and related) questions: 1) Does the open-chest animal model alter the phenomenon of myocardial stunning? 2) If so, how valid are the concepts, derived from such a model, regarding the pathogenetic role of oxy-radicals? In part 1 of the study, myocardial stunning after a 15-minute coronary occlusion was compared in 30 pentobarbital-anesthetized open-chest dogs and in 19 conscious dogs. For any given level of collateral flow during occlusion, the recovery of systolic wall thickening after reperfusion was markedly less in open-chest animals. In an additional group of five open-chest dogs, a close inverse relation was noted between body temperature and postischemic wall thickening, indicating that the recovery of the stunned myocardium in acute experiments may vary markedly depending on how temperature is controlled. Because of these major differences between open-chest and conscious dogs, the oxy-radical hypothesis needs to be tested in the latter model. Thus, in part 2 of the study, conscious unsedated dogs undergoing a 15-minute coronary occlusion were randomized to an intravenous infusion of either saline (19 coronary occlusions) or superoxide dismutase (SOD) plus catalase (CAT) (21 coronary occlusions). Despite the fact that the plasma levels of SOD and CAT declined rapidly after reperfusion, postischemic wall thickening was significantly greater in treated compared with control dogs throughout the first 6 hours of reflow. Thus, a brief (60-minute) infusion of SOD and CAT produced a sustained improvement of recovery of contractility. The magnitude of this beneficial effect was a function of the severity of ischemia: the lower the collateral perfusion, the greater the improvement effected by the enzymes. The accelerated recovery produced by SOD and CAT was not followed by any deterioration of contractility, suggesting that postischemic dysfunction is not a teleologically "protective" phenomenon. In conclusion, the severity of myocardial stunning is greatly exaggerated by the unphysiological conditions present in the barbiturate-anesthetized open-chest dog.(ABSTRACT TRUNCATED AT 400 WORDS)

Anesthesia, General↗
PubMed2000

Pure consciousness: distinct phenomenological and physiological correlates of "consciousness itself".

This paper explores subjective reports and physiological correlates of the experience of "consciousness itself"--self awareness isolated from the processes and objects of experience during Transcendental Meditation practice. Subjectively, this state is characterized by the absence of the very framework (time, space, and body sense) and content (qualities of inner and outer perception) that define waking experiences. Physiologically, this state is distinguished by the presence of apneustic breathing, autonomic orienting at the onset of breath changes, and increases in the frequency of peak EEG power. A model, called the junction point model, is presented that integrates pure consciousness with waking, dreaming, or sleeping. It could provide a structure to generate a coherent program of research to test the full range of consciousness and so enable us to understand what it means to be fully human.

Adult↗
PubMed1997

Learning, action and consciousness: a hybrid approach toward modelling consciousness.

This paper is an attempt at understanding the issue of consciousness through investigating its functional role, especially in learning, and through devising hybrid neural network models that (in a qualitative manner) approximate characteristics of human consciousness. In doing so, the paper examines explicit and implicit learning in a variety of psychological experiments and delineates the conscious/unconscious distinction in terms of the two types of learning and their respective products. The distinctions are captured in a two-level action-based model CLARION. Some fundamental theoretical issues are also clarified with the help of the model. Comparisons with existing models of consciousness are made to accentuate the present approach.

Journal Article↗
PubMed1983

Ventricular refractory periods in relation to rate and test-site VT intervals in anesthetized and conscious dogs: a canine model for conscious state measurements.

The functional relationship of ventricular effective refractory period (ERP) with basic cycle length (BCL) of stimulated ventricular depolarization and VT intervals of test-site unipolar ventricular electrograms were studied in five conscious and eight anesthetized (sodium pentobarbital, 30 mg/kg) open-chested dogs. The range of BCLs studied was 300 to 1000 ms, achieved through ventricular stimulation following chemically-induced complete AV block. In the conscious animal model developed for this study, two-to-four ventricular electrode leads were exteriorized and the ventricular rate was maintained by an implanted programmable VVI pacemaker. In all animals studied, the BCL-ERP relation was closely represented by the empirical equation ERP = A-B.Exp(-k.BCL), and the VT-ERP relation over the same range of BCLs was linear: ERP = C + D.VT. The correlation coefficients were in the range of 0.991 to 0.999. The mean values of the parameters in the above equations determined by the appropriate non-linear or linear regression analysis showed significant differences between the two groups of animals studied. In three conscious animals a strong linear correlation between the test-site VT intervals and simultaneously measured QT intervals measured from the lead II surface electrogram was demonstrated (r = 0.993 to 0.998). For a fixed site of stimulation, the morphology of ventricular depolarization complexes as well as the corresponding T-waves remained essentially unaltered with BCL for both myocardial and surface electrograms. The possible applications of developed canine model and the results of the present study include: (1) the study of the rate-dependent effects of cardioactive drugs on ventricular electrophysiology and, (2) the improved design of electronic refractory periods of rate programmable pacemakers.

Anesthetics↗
PubMed1999

Pure Consciousness: Distinct Phenomenological and Physiological Correlates of "Consciousness Itself"

This paper explores subjective reports and physiological correlates of the experience of "consciousness itself" - self awareness isolated from the processes and objects of experience during Transcendental Meditation practice. Subjectively, this state is characterized by the absence of the very framework (time, space, and body sense) and content (qualities of inner and outer perception) that define waking experiences. Physiologically, this state is distinguished by the presence of apneustic breathing, autonomic orienting at the onset of breath changes, and increases in the frequency of peak EEG power. A model, called the junction point model, is presented that integrates pure consciousness with waking, dreaming, or sleeping. It could provide a structure to generate a coherent program of research to test the full range of consciousness and so enable us to understand what it means to be fully human.

Journal Article↗
PubMed2005

Information processing in severe disorders of consciousness: vegetative state and minimally conscious state.

OBJECTIVE: To study the presence of electrophysiological indicators of remaining cortical functions in patients with persistent vegetative state (PVS) and minimally conscious state (MCS). Previous electrophysiological and PET data indicated that some PVS patients have partially intact cortical processing functions. However, it remains unclear whether the reported patients were representative for PVS population or just some exceptional cases. METHODS: Event-related brain responses to stimuli of different complexity levels, recorded in 98 patients with extremely severe diffuse brain injuries, 50 of which in PVS. Four main indicators of cortical functions were: (i) N1-P2 complex as an index of simple, undifferentiated cortical processing; (ii) mismatch negativity as an index of pre-attentive, probably unconscious, cortical orientation; (iii) P3 wave as an index of deep cortical analysis of physical stimuli, and (iv) brain responses to semantic stimuli. RESULTS: Cortical responses were found in all PVS patients with a background EEG activity > 4 Hz. All responses investigated, including those to semantic stimuli that indicated comprehension of meaning, occurred significantly above chance, though less frequently than in patients with severe brain injuries who were conscious. CONCLUSIONS: Cortical responses were lacking in most patients with severe EEG slowing (< 4 Hz). Follow-up data revealed that the presence of a mismatch negativity, a short disease duration, and the traumatic etiology were related to a better outcome. SIGNIFICANCE: The data show that in a subpopulation of PVS patients with preserved thalamocortical feedback connections, remaining cortical information processing is a consistent finding and may even involve semantic levels of processing.

Auditory Cortex↗
PubMed1997

Safety and efficacy of flumazenil in reversing conscious sedation in the emergency department. Emergency Medicine Conscious Sedation Study Group.

OBJECTIVES: To evaluate the safety and efficacy of flumazenil vs placebo in reversing fentanyl and midazolam-induced conscious sedation in ED patients undergoing a short, painful procedure. METHODS: This was a multicenter, randomized, parallel, double-blind, placebo-controlled study conducted at 9 university-affiliated teaching hospitals. Patients > 18 years of age requiring conscious sedation for a painful procedure expected to last < 20 minutes were eligible for inclusion in the study. Patients received 2 micrograms/kg of fentanyl, followed by midazolam titrated to the desired level of sedation. Patients were then randomized to receive either flumazenil or placebo in a 3:1 ratio (flumazenil:placebo). Vital signs, O2 saturation, and alertness were recorded at regular intervals. Prior to ED release, patients were asked to rate the amount of discomfort they experienced and the level of relaxation achieved on a 10-cm visual analog scale (VAS). They also were questioned about their recall for the procedure and satisfaction with the drug regimen. Physicians also rated their satisfaction with the drug regimen on a 10-cm VAS. RESULTS: Overall, 133 patients received flumazenil and 46 patients received placebo. Patients in the 2 groups received similar doses of midazolam. The patients who received flumazenil returned to baseline alertness earlier (11.1 min vs 24.8 min, p < 0.001) and at a faster rate than did the patients given placebo. Actual intervals from procedure completion until release from the ED did not differ between the 2 groups (98.2 +/- 3.6 min flumazenil vs 96.9 +/- 5.8 min placebo; p = 0.89). The amounts of discomfort experienced, levels of relaxation achieved, recalls for the procedure, and both patient and physician satisfactions were also similar for the 2 groups. There were no serious adverse effects related to the study drug, and minor adverse effects were similar for the 2 groups. CONCLUSION: Flumazenil is safe and efficacious in reversing midazolam-induced sedation in ED patients given a combination of fentanyl and midazolam to facilitate the performance of a short, painful procedure. The patients given flumazenil returned to baseline alertness earlier and at a faster rate than did the patients given placebo. However, flumazenil did not alter the actual interval from procedure completion until ED release.

Adolescent↗