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PubMed1998

Brain electric microstates and momentary conscious mind states as building blocks of spontaneous thinking: I. Visual imagery and abstract thoughts.

Prompted reports of recall of spontaneous, conscious experiences were collected in a no-input, no-task, no-response paradigm (30 random prompts to each of 13 healthy volunteers). The mentation reports were classified into visual imagery and abstract thought. Spontaneous 19-channel brain electric activity (EEG) was continuously recorded, viewed as series of momentary spatial distributions (maps) of the brain electric field and segmented into microstates, i.e. into time segments characterized by quasi-stable landscapes of potential distribution maps which showed varying durations in the sub-second range. Microstate segmentation used a data-driven strategy. Different microstates, i.e. different brain electric landscapes must have been generated by activity of different neural assemblies and therefore are hypothesized to constitute different functions. The two types of reported experiences were associated with significantly different microstates (mean duration 121 ms) immediately preceding the prompts; these microstates showed, across subjects, for abstract thought (compared to visual imagery) a shift of the electric gravity center to the left and a clockwise rotation of the field axis. Contrariwise, the microstates 2 s before the prompt did not differ between the two types of experiences. The results support the hypothesis that different microstates of the brain as recognized in its electric field implement different conscious, reportable mind states, i.e. different classes (types) of thoughts (mentations); thus, the microstates might be candidates for the 'atoms of thought'.

Adult↗
PubMed2003

[Indications, efficacy and tolerance of drug therapy in view of improving recovery of consciousness following a traumatic brain injury].

OBJECTIVE: To review the literature about the indications, efficacy, limits and tolerance problems of drugs used with the aim of improving recovery of consciousness after a traumatic coma. METHODS: Query using Medline, Embase, Neurosciences and Pascal databases. Thirty-two references were selected, including:articles proposing a synthesis of recent knowledge concerning neurotransmitters involved in vigilance, the pathophysiological mechanisms of impairment and the related pharmacology;clinical studies examining the efficacy of large categories of pharmacological agents (dopaminergic drugs, psychostimulants, tricyclic antidepressants and others) on vigilance and on alteration of consciousness following brain lesions. RESULTS: The synthesis provides evidence about the theoretical actions and efficacy of the available pharmacological agents. The clinical studies are less convincing: indications and therapeutic choices are empirical. Studies report often single cases. Randomised studies are rare, often heterogeneous concerning the aetiology of the brain lesions. The evaluation scales are varied and too wide. In this context, amantadin, amphetamine, methylphenidate and bromocryptin showed some positive effects. Despite a pessimist general feeling, some cases of unexpected recovery as well as relapses during breaks in treatment were arguments in favour of the drug that was administered. DISCUSSION/CONCLUSION: This review suggests that drug treatments for awakening might become a useful and perhaps even indispensable, complement in case management. It is therefore urgent to design multicentre studies in order to set rational indications and to develop realistic therapeutic protocols.

Amphetamine↗
PubMed2002

Near death experiences in cardiac arrest: visions of a dying brain or visions of a new science of consciousness.

Very little is known about the dying process and in particular the state of the human mind at the end of life. Cardiac arrest is the final step in the dying process irrespective of cause, and is also the closest physiological model of the dying process. Recent studies in cardiac arrest survivors have indicated that although the majority of cardiac arrest survivors have no memory recall from the event, nevertheless approximately 10% develop memories that are consistent with typical near death experiences. These include an ability to 'see' and recall specific detailed descriptions of the resuscitation, as verified by resuscitation staff. Many studies in humans and animals have indicated that brain function ceases during cardiac arrest, thus raising the question of how such lucid, well-structured thought processes with reasoning and memory formation can occur at such a time. This has led to much interest as regards the potential implications for the study of consciousness and its relationship with the brain, which still remains an enigma. In this article, we will review published research examining brain physiology and function during cardiac arrest as well as its potential relationship with near death experiences during this time. Finally, we will explore the contribution that near death experiences during cardiac arrest may make to the wider understanding of human consciousness.

Attitude to Death↗
PubMed2000

Reduced metabolic rate accompanies the hemorrhage-induced hypothermia in conscious rats.

The mechanism for the hemorrhage-induced drop in body temperature is unknown. This study determined the alterations in cutaneous heat exchange and metabolic heat production caused by a moderate hemorrhage in conscious rats. Chronically instrumented rats were subjected to a 16 ml/kg hemorrhage, followed by a 4-h recovery period, while monitoring body core temperature and cutaneous temperature. Cutaneous heat transfer was disrupted by housing the animals at an elevated (28 degrees C) ambient temperature. A separate group of experiments measured the change in oxygen consumption in the post-hemorrhage period. Moderate hemorrhage caused a drop in body core temperature which stabilized at 0.7+/-0.3 degrees C below control in the second hour following hemorrhage. Disruption of cutaneous heat exchange by reducing the thermal gradient did not diminish the hemorrhage-induced hypothermia. Hemorrhage caused a significant decline of oxygen consumption (-0. 21+/-0.05 ml O(2)/g per h). This 16% drop in resting oxygen consumption was prevented by immediately retransfusing the aspirated blood back into the rat. These data indicate that a decrease in metabolic heat production mediates the drop in body core temperature caused by moderate hemorrhage in conscious rats.

Animals↗
PubMed2001

N-methyl-D-aspartate channel and consciousness: from signal coincidence detection to quantum computing.

Research on Blindsight, Neglect/Extinction and Phantom limb syndromes, as well as electrical measurements of mammalian brain activity, have suggested the dependence of vivid perception on both incoming sensory information at primary sensory cortex and reentrant information from associative cortex. Coherence between incoming and reentrant signals seems to be a necessary condition for (conscious) perception. General reticular activating system and local electrical synchronization are some of the tools used by the brain to establish coarse coherence at the sensory cortex, upon which biochemical processes are coordinated. Besides electrical synchrony and chemical modulation at the synapse, a central mechanism supporting such a coherence is the N-methyl-D-aspartate channel, working as a 'coincidence detector' for an incoming signal causing the depolarization necessary to remove Mg(2+), and reentrant information releasing the glutamate that finally prompts Ca(2+) entry. We propose that a signal transduction pathway activated by Ca(2+) entry into cortical neurons is in charge of triggering a quantum computational process that accelerates inter-neuronal communication, thus solving systemic conflict and supporting the unity of consciousness.

Animals↗
PubMed2003

Quantum monadology: a consistent world model for consciousness and physics.

The NL world model presented in the previous paper is embodied by use of relativistic quantum mechanics, which reveals the significance of the reduction of quantum states and the relativity principle, and locates consciousness and the concept of flowing time consistently in physics. This model provides a consistent framework to solve apparent incompatibilities between consciousness (as our interior experience) and matter (as described by quantum mechanics and relativity theory). Does matter have an inside? What is the flowing time now? Does physics allow the indeterminism by volition? The problem of quantum measurement is also resolved in this model.

Consciousness↗
PubMed1998

Consciousness as a self-organizing process: an ecological perspective.

The evolution of consciousness is seen in the context of energy-driven evolution in general, where energy and information are understood as two sides of the same coin. From this perspective consciousness is viewed as an ecological system in which streams of cognitive, perceptual, and emotional information form a rich complex of interactions, analogous to the interactive metabolism of a living cell. The result is an organic, self-generating, or 'autopoietic', system, continuously in the act of creating itself. Evidence suggests that this process is chaotic, or at least chaotic-like, and capable of assuming a number of distinct states best understood as chaotic attractors.

Consciousness↗
PubMed2003

Effects of aniracetam on extracellular levels of transmitter amino acids in the hippocampus of the conscious gerbils: an intracranial microdialysis study.

The effects of aniracetam on extracellular amino acid levels in the hippocampus of conscious gerbils, with or without transient cerebral ischemia/reperfusion, were measured by microdialysis and reverse phase-high performance liquid chromatography. Increased extracellular levels of aspartate and glutamate that were observed in the hippocampus of conscious gerbils during transient global forebrain ischemia were reversed by aniracetam. In contrast, the level of extracellular gamma-aminobutyric acid was increased, while taurine was maintained at a higher level than other amino acids by administration of aniracetam (100 mg/kg, p.o.) 60 min before ischemia. Further, in contrast to ischemic animals, administration of aniracetam (100 mg/kg, p.o.) enhanced the release of glutamate and aspartate in the normal gerbil hippocampus. The results suggest that these effects might be due to a partial calcium agonist activity of aniracetam, and that the effects of aniracetam on amino acid levels might be a mechanism of protection against delayed neuronal death in the ischemic hippocampus, thereby improving memory dysfunction induced by ischemia/reperfusion.

Animals↗
PubMed1998

Serotonin stimulates corticotropin-releasing factor gene expression in the hypothalamic paraventricular nucleus of conscious rats.

To examine the direct effects of serotonin (5-HT) on the release and synthesis of corticotropin-releasing factor (CRF) in the hypothalamic paraventricular nucleus (PVN), 5-HT was microinjected just onto the bilateral PVN of conscious rats. Plasma adrenocorticotropic hormone (ACTH) levels peaked at 30 min and returned to the basal levels in 90 min. Northern blot analysis revealed that the CRF messenger RNA (mRNA) level in the PVN as well as the proopiomelanocortin mRNA level in the anterior pituitary significantly increased 120 min after the 5-HT injections (50-250 nmol/side). Pretreatment with intracerebroventricular (i.c.v.) injection of pindobind 5-HT1A (5 nmol) or LY-278584 (500 nmol) completely abolished the 5-HT-induced ACTH response, whereas LY-53857 (100 nmol) was without effect. These results suggest that 5-HT stimulates CRF release, which has interactions with 5-HT1A and 5-HT3 receptors on CRF neurons in the PVN, and activates CRF synthesis in conscious rats.

Adrenocorticotropic Hormone↗
PubMed2003

More than synchrony: EEG chaoticity may be necessary for conscious brain functioning.

Transient phase synchronization of EEG oscillations was reported to be essential for conscious brain activity. However, it has been argued that EEG synchrony is not the only necessary factor, but at least must be accompanied by a sufficient complexity of brain dynamics. Here, we propose that, besides complexity, EEG chaoticity may be another necessary condition for conscious brain functioning.

Brain↗
PubMed2004

Daytime parahypnagogia: a state of consciousness that occurs when we almost fall asleep.

Based on a series of self-reports of a previously undescribed and undocumented experiential event, we are postulating the existence of a newly identified state of consciousness, daytime parahypnagogia (DPH). DPH is more likely to occur when one is tired, bored, suffering from attention fatigue, and/or engaged in a passive activity. Individuals describe DPH as a transient and fleeting episode that is dissociative, trance-like, dreamlike, uncanny, and often pleasurable; but, unlike a daydream, it is not self-directed. A DPH episode is spontaneous and may consist of a flash image, thought, and/or creative insight that is quickly forgotten. However, the individual remains aware of having had a DPH experience. This paper details the experiential characteristics associated with DPH. Through a brief review of the literature, the authors differentiate DPH from related phenomena and establish DPH as a unique and distinct altered state of consciousness.

Circadian Rhythm↗
PubMed2000

Coronary vascular responses to short-term cocaine administration in conscious baboons compared with dogs.

OBJECTIVES: Cardiovascular complications of cocaine use represent an important clinical problem, yet the mechanisms by which cocaine predisposes to myocardial ischemia are poorly understood. BACKGROUND: The effects of cocaine on the coronary circulation have been studied extensively in experimental animal models, but have failed to recapitulate the clinical findings reported in humans who use cocaine. METHODS: We studied 12 conscious, chronically instrumented dogs and 5 conscious, chronically instrumented baboons to determine whether there were important species differences in the response to cocaine. RESULTS: Comparable doses of intravenous cocaine caused similar increases in left ventricular systolic, diastolic and mean arterial pressure in the two species. However, the peak coronary blood flow response in baboons (+8 +/- 3 from 47 +/- 6 ml/min) was less compared with dogs (+15 +/- 4 from 41 +/- 4 ml/min), while the coronary vascular resistance response was greater in baboons (+0.60 +/- 0.09 from 1.94 +/- 0.09 mm Hg/ml/mm) compared with dogs (+0.35 +/- 0.09 from 2.24 +/- 0.10 mm Hg/ml/min). Although myocardial oxygen consumption responses were similar between species, there was a significant difference (p < 0.05) in oxygen delivery between baboons (+164 +/- 47 from 705 +/- 59 ml of oxygen per minute) and dogs (+397 +/-51 from 656 +/- 33 ml of oxygen per minute) that was attributable to a significant (p < 0.05) increase in hemoglobin concentration in dogs (+2.1 +/- 0.5 g/dl) that was not observed in baboons. Consequently, cocaine caused a significant increase in myocardial oxygen extraction and decreased coronary sinus pH in baboons, but not dogs. CONCLUSIONS: Cocaine caused greater coronary vasoconstriction and greater requirements for oxygen extraction in baboons compared with dogs.

Animals↗
PubMed1987

Application of end-systolic pressure-volume and pressure-wall thickness relations in conscious dogs.

The usefulness of end-systolic measures of ventricular function was compared with that of standard contractility indexes in conscious dogs. End-systolic relations between left ventricular pressure and volume and between pressure and wall thickness were analyzed in dogs previously instrumented with ultrasonic crystals. Progressive angiotensin infusions were used to generate computer-averaged pressure-volume and pressure-wall thickness loops. Both relations were linear in every study and highly reproducible. With low and high dose dobutamine, the end-systolic pressure-volume relations were significantly displaced, with increased slope and inconsistent changes in intercept. This relation was more useful than the ejection fraction for detecting contractility increases at different afterloads, but it showed no advantage over maximal left ventricular dP/dt at all ranges of preload and afterload. The end-systolic pressure-volume relations were insensitive for detecting mild decreases in inotropic state produced by propranolol, and maximal dP/dt was superior for detecting such mild acutely reduced contractility. The end-systolic pressure-wall thickness relations showed displacement with dobutamine, although slope and intercept changes were not significant; these relations did not detect mild decreases in contractility produced by propranolol. It is concluded that the end-systolic pressure-volume relation and a simplified end-systolic measure using pressure and wall thickness provide sensitive, load-independent and reproducible approaches for defining acute increases in left ventricular contractility in conscious animals. Maximal dP/dt was equally effective for defining these increases in contractility and more sensitive for detecting slight acute decreases in contractility.

Angiotensin II↗
PubMed2003

Feelings of relation in the fringe of consciousness: implications for the subjective experience of addiction and the nurse-client relationship.

Individuals who compulsively abuse psychoactive drugs experience alterations in consciousness. Little is known about the value of these alterations in the spectrum of human experience. William James's concept of the fringe of consciousness describes a function of knowing that emphasizes direct sensory experience. This experience encompasses feelings of relation between an individual's sense of self and idea of self, between self and world, and between self and sense of future possibilities. These feelings can be shown in written narratives of some individuals addicted to psychoactive drugs. Access to the feeling of relation in the fringe suggests meaning for the individual and implications for the nurse-client relationship.

Consciousness Disorders↗
PubMed1998

A novel alpha 2-adrenoceptor antagonist attenuates the early, but preserves the late cardiovascular effects of intravenous dexmedetomidine in conscious dogs.

OBJECTIVES: To test the hypothesis that L-659,066, a peripherally acting alpha 2-adrenoceptor agonist, will abolish the early pressor response but preserve the late depressor action of intravenous dexmedetomidine in conscious, unsedated dogs. DESIGN: A prospective investigation. SETTING: A laboratory research. PARTICIPANTS: Nine chronically instrumented dogs. INTERVENTIONS: Dogs received dexmedetomidine, 5 micrograms/kg intravenously, in the presence or absence of L-659,066, 0.1, 0.2, or 0.4 mg/kg intravenously, pretreatment in a random fashion determined with a Latin square design on different experimental days. MEASUREMENTS AND MAIN RESULTS: Systemic and coronary hemodynamics were assessed under control conditions, 30 minutes after administration of L-659,066 and 5 and 60 minutes after intravenous administration of dexmedetomidine. Dexmedetomidine alone acutely increased mean arterial pressure (106 +/- 3 to 175 +/- 4 mmHg; p < 0.05), left ventricular (LV) systolic and end-diastolic pressures, systemic vascular resistance (3,400 +/- 350 to 13,360 +/- 2,290 dyne.s.cm-5; p < 0.05), and coronary vascular resistance (2.69 +/- 0.19 to 4.18 +/- 0.43 mmHg.Hz-1.10(-2); p < 0.05) and decreased LV +dP/dtmax and cardiac output (2.6 +/- 0.3 to 1.3 +/- 0.2 L/min; p < 0.05). Dexmedetomidine alone decreased heart rate, mean arterial pressure, and LV systolic pressure and caused sustained reductions in +dP/dtmax and cardiac output up to 60 minutes after administration. L-659,066 alone increased heart rate, +dP/dtmax, cardiac output, and coronary blood flow velocity and decreased systemic vascular resistance. Mean arterial and LV pressures and coronary vascular resistance were unchanged. Pretreatment with L-659,066 abolished the acute dexmedetomidine-induced increases in mean arterial pressure, LV pressures, systemic and coronary vascular resistance and decreases in +dP/dtmax and cardiac output. In contrast, reductions in mean arterial pressure and LV systolic pressure observed 60 minutes after administration of dexmedetomidine were preserved in dogs receiving L-659,066. Cardiac performance, systemic vascular resistance, and coronary hemodynamics were also maintained to a greater degree 60 minutes after dexmedetomidine administration in the presence of L-659,066. CONCLUSION: L-659,066 prevents the immediate pressor effects of 5 micrograms/kg of intravenous dexmedetomidine but preserves the majority of the late beneficial cardiovascular effects of this selective alpha 2-adrenoceptor agonist in conscious dogs.

Adrenergic alpha-Agonists↗
PubMed2002

A comparison of conscious and automatic memory processes for picture and word stimuli: a process dissociation analysis.

Four experiments were conducted to evaluate explanations of picture superiority effects previously found for several tasks. In a process dissociation procedure (Jacoby, 1991) with word stem completion, picture fragment completion, and category production tasks, conscious and automatic memory processes were compared for studied pictures and words with an independent retrieval model and a generate-source model. The predictions of a transfer appropriate processing account of picture superiority were tested and validated in "process pure" latent measures of conscious and unconscious, or automatic and source, memory processes. Results from both model fits verified that pictures had a conceptual (conscious/source) processing advantage over words for all tasks. The effects of perceptual (automatic/word generation) compatibility depended on task type, with pictorial tasks favoring pictures and linguistic tasks favoring words. Results show support for an explanation of the picture superiority effect that involves an interaction of encoding and retrieval processes.

Adult↗
PubMed2002

Integrating experiential-phenomenological methods and neuroscience to study neural mechanisms of pain and consciousness.

Understanding the nature of pain at least partly depends on recognizing its inherent first person epistemology and on using a first person experiential and third person experimental approach to study it. This approach may help to understand some of the neural mechanisms of pain and consciousness by integrating experiential-phenomenological methods with those of neuroscience. Examples that approximate this strategy include studies of second pain summation and its relationship to neural activities and brain imaging-psychophysical studies wherein sensory and affective qualities of pain are correlated with cerebral cortical activity. The experiential paradigm of offers the possibility of improved designs and methods for investigating neural mechanisms underlying pain and consciousness.

Brain↗
PubMed2003

Impaired strategic regulation of contents of conscious awareness in schizophrenia.

Conscious awareness comprises two distinct states, autonoetic and noetic awareness. Schizophrenia impairs autonoetic, but not noetic, awareness. We investigated the strategic regulation of relevant and irrelevant contents of conscious awareness in schizophrenia using a directed forgetting paradigm. Twenty-one patients with schizophrenia and 21 normal controls were presented with words and told to learn some of them and forget others. In a subsequent test, they were asked to recognize all the words they had seen previously and give remember, know or guess responses according to whether they recognized words on the basis of autonoetic awareness, noetic awareness, or guessing. Overall, patients showed the same degree of a directed forgetting effect as normal subjects. However, whereas the effect was observed both for remember and know responses in normal subjects, it was observed for know, but not for remember, responses in patients. These results indicate that patients with schizophrenia exhibit an impaired strategic regulation of contents of autonetic awareness for relevant and irrelevant information.

Adult↗