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PubMed1996

[Can permanent sinus arrhythmia in conscious dogs be suppressed with anesthesia?].

OBJECTIVE: Large prospective studies in dogs with healed myocardial infarction (MI) recently show a positive relation between heart rate variability (HRV) and sudden cardiac death. METHODS: We have done similar experiments in dogs and we studied HRV, ECG and body surface potential maps (BSPM) in 26 normal mongrel dogs (10-15 kg) and 12 dogs with an experimental MI (ligation of LAD). A two-channel 8 hours lasting ECG recording was performed in all conscious dogs. The 2nd recording was done in Penthobarbital anaesthesia (30 mg/kg). RESULTS: We have found sinus arrhythmia (SA) in all 26 conscious dogs. The anaesthesia suppressed the sinus arrhythmia and HRV via compensatory tachycardia and alterations in baroreflexes. The suppression of arrhythmia was also present in dogs with myocardial infarction. CONCLUSIONS: It is suggested, that HRV and SA in dogs depend on conscious state and anaesthesia. On the basis of our results we can anticipate that the most important for HRV is the present status of the sympathetic nerve. We suggest, that our results are an important finding for experimental arrhythmology. (Fig. 4, Ref. 24.)

Anesthesia↗
PubMed1997

Intravenous infusion of low dose propofol for conscious sedation in cesarean section before spinal anesthesia.

BACKGROUND: Conscious sedation, not affecting the safety of both mother and fetus, is especially favorable in anxious patients undergoing Cesarean delivery. However, when sedation is started before performing intrathecal anesthesia, the infusion time before delivery will be prolonged. In this study, the incidence of maternal and fetal complications under propofol infusion were evaluated as well as the blood concentrations of propofol during delivery at different time of sedation. METHODS: Maternal and fetal effects of pre-spinal sedation with low dose propofol infusion technique (3 mg/mg/h following 0.3 mg/kg bolus) in 37 Cesarean parturients were evaluated, compared with another 33 parturients under spinal anesthesia without any sedatives. RESULTS: The induction to delivery time was 32.6 +/- 7.7 min. Satisfactory, airway-maintaining conscious sedation was shown without increasing the incidence of post-spinal hypotension and hypoxemia compared with non-sedative group. The plasma propofol concentrations in the mean time of delivery in maternal vein and umbilical vein were 0.86 +/- 0.29 and 0.33 +/- 0.11 microgram/ml, respectively. Umbilical venous concentration neither correlated with infusion time nor exceeded the maternal venous concentration. The 1-min and 5-min Apgar scores as well as umbilical venous blood gas analyses did not differ significantly between two groups. CONCLUSIONS: Conscious sedation by low dose propofol infusion is safe for both mother and fetus in spite of longer infusion time.

Adult↗
PubMed1998

[Pain as a biological phenomenon of consciousness].

Pain has not to be considered a false step of nature. On the contrary, it is an extremely effective warning mechanism through which the individual becomes aware of a danger to its own physical integrity from inside the body or from the environment. Pain therefore belongs to the biological devices for evading bodily danger. The conscious experience of pain is the most sophisticated stage of evolution of warning systems, whose simplest form is represented by an unicellular organism which moves away if it anticipates danger from an environmental state. Similar to all qualia, conscious experience of pain cannot be fully explained in terms of neurophysiological events. Conscious pain is a complex perceptual and affective experience influenced not by the amount of the bodily lesion alone, but also by the whole personality of the sufferer. This often makes surgical, medical and psychological treatment of pain difficult and disappointing.

Animals↗
PubMed1998

[Physiopathology of non-traumatic subarachnoid hemorrhage: loss of consciousness].

The mechanisms underlying the loss of consciousness following the SAH can be only hypothesized at present time. The more convincing hypothesis appears to be the role of a cerebral circulatory insufficiency. Such an hypothesis stems from the following chain of events: 1) immediate increase of the intracranial pressure; 2) simultaneous constriction of the arteries of the poligone of Willis (early vasospasm); 3) decrease of the cerebral perfusion pressure; 4) cerebral ischemia. Different cerebral regions can be affected by the ischemia according to the prevalent location of the SAH, as for instance brain stem or telencephalon; consequently, different pathophysiological modalities can be responsible for the consciousness impairment. The entity of the SAH and of the consequent events responsible for the cerebral ischemia, influence the severity and reversibility of the loss of consciousness.

Brain Ischemia↗
PubMedDate not supplied

[Consciousness, its criteria and the possible mechanisms].

Consciousness is characterized by the objective and subjective criteria. Accordingly, this is the ability to operation with knowledge, its transmission to other people in abstract form and the feeling of "ego" as a subject of these actions. Objective and subjective signs of the consciousness are provided with the mechanism based on the synthesis of information coming from organs of sensation extracted from memory and coming from the centers of emotions and motivations. As a result of this synthesis the sensation of "ego", appears, and information estranged from it and offered for others is determined. An important role in the informational synthesis is played by the dynamic cortical structures--foci of interaction. In the process of perception they are localized mostly in projective zones of analyzers, at thinking--in associative zones of the cortex. Realization is closely connected with communication and formation of foci of interaction in the verbal zones of the left hemisphere.

Brain Mapping↗
PubMed1986

Is it possible to define a general "conscious level"?

The difficulties in defining a general conscious level are discussed as exemplified by Glasgow Coma Scale and Reaction Level Scale, a new scale recommended by Swedish neurosurgeons. Precise definitions of stimuli and of responses are needed since several studies have shown ambiguity of assessment within the same patient. Some of the difficulties arising from summing up and grouping levels of the Glasgow Coma Scores are discussed and as a consequence a new level for defining coma with a better reliability is proposed. We also briefly discuss the difficulty when to stop assessing conscious level.

Coma↗
PubMed1975

Homovanillic acid and 5-hydroxyindoleacetic acid cerebrospinal fluid levels. A study with and without probenecid administration of their relationship to the state of consciousness after head injury.

Homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) concentrations were measured in the lumbar cerebrospinal fluid of 98 patients after closed head injury. The HVA levels decreased in patients, whether or not they were given the drug probenecid, which inhibits the active transport of these acids from the brain. The decline of HVA was more notable in patients with the longest duration of unconsciousness. The HVA levels showed no correlation with the state of consciousness at the moment of the lumbar puncture. The 5-HIAA levels were below normal in the conscious patients, but paradoxically, at about normal levels in unconscious patients. The overall results suggest a decreased cerebral dopamine and serotonin metabolism after head injury.

Blood-Brain Barrier↗
PubMed1976

Cerebral dominance for consciousness.

In a prospective study we evaluated the relationship of level of consciousness to hemispheric side of lesion following acute cerebrovascular injury. Fifty-seven percent of patients with left hemispheric lesions had initial impairment of consciousness, in contrast to 25% with right-sided damage.

Cerebrovascular Disorders↗
PubMed1999

Conscious sedation: a new approach for peritonsillar abscess drainage in the pediatric population.

OBJECTIVE: To assess the safety and efficacy of conscious sedation (CS) in children undergoing emergency department incision and drainage (I&D) of peritonsillar abscesses (PTAs). DESIGN: A 33-month retrospective chart review of all children presenting to the emergency department with the diagnosis of a PTA or peritonsillar cellulitis. Children who underwent CS prior to I&D were compared with children without CS for complications and efficacy. SETTING: St Louis Children's Hospital, an academic tertiary care pediatric hospital. PATIENTS: Fifty-two children were enrolled; 30 PTAs were drained with CS in 27 children (3 underwent I&D twice), and 25 PTAs were drained in 25 children without CS. INTERVENTIONS: The CS team included an otolaryngologist, a pediatric emergency department physician, and a registered nurse. A standardized CS protocol assessing vital signs and level of consciousness was employed during each procedure. A combination of midazolam, ketamine hydrochloride, and glycopyrrolate was used in appropriately weighted calculated doses. Patients were assessed for major and minor airway complications. MAIN OUTCOME MEASURES: Airway complications related to CS were reviewed. Patients who underwent I&D with and without CS were compared with regard to purulent drainage. RESULTS: There were no major airway complications in patients undergoing I&D with CS. There was 1 minor complication in this group, oxygen desaturation to 88%, which resolved with stimulation. Of the 55 procedures, 45 (82%) yielded purulence: 29 (97%) of 30 in the CS group and 16 (64%) of 25 in the non-CS group (chi2 = 9.8; P = .002). Of those children undergoing CS, 3 (10%) of 30 were admitted to the hospital from the emergency department as compared with 6 (24%) of 25 without CS (chi2 = 1.95; P = .16). In the CS group, PTAs had a low recurrence rate of 1 (3.3%) of 30 compared with 2 (8%) of 25 in the non-CS group (chi2 = 0.57; P = .45). No one in the CS group required a secondary procedure under general anesthesia. CONCLUSIONS: This preliminary study demonstrates CS to be a potentially safe and efficacious approach to drainage of PTAs in children. Given its efficacy and its associated lower levels of anxiety and pain for the patient, CS seems to be a promising new approach to caring for children with PTAs.

Adolescent↗
PubMed2004

What happened in the origin of human consciousness?

At some point in its evolutionary history, our species Homo sapiens ceased to be a nonlinguistic, nonsymbolic organism, living in the world as presented to it by Nature, and instead began to exist in a world that it reconstructs in its own mind. Most scientists since Darwin have been content to explain this extraordinary transformation in human consciousness by the operation of natural selection. However, the human fossil and archaeological records indicate that modern human symbolic consciousness is not the culmination of the long trend that natural selection would predict. Instead, it shows that major change in the human past has been episodic and rare and that, as far as can be determined from the archaeological record, the passage from nonsymbolic to symbolic cognition is a recent event as well as an unprecedented one. So recent, indeed, that it significantly postdates the acquisition of modern human anatomy as expressed in skeletal structure. It, thus, appears most likely that the biological (neural) capacity underwriting the radically new behavioral mode arose as an incidental exaptation in the same process that produced the new skeletal structure of Homo sapiens, but that it lay unexpressed until it was "discovered" by means of a cultural innovation, plausibly the invention of language. As in the case of the modern anatomical structure, it appears that the new capacity was initially expressed in Africa and that its various behavioral potentials were sequentially discovered in a drawn-out process that is continuing today. An "accidental" origin of the human capacity helps understand why so many human behaviors have proven self-destructive and contradictory, a feature of our species that reductionist, selection-based scenarios are hard-put to explain.

Animals↗
PubMed2006

Cough-induced hemiplegic migraine with impaired consciousness in cystic fibrosis.

The coughing paroxysms of patients with cystic fibrosis may occasion neurological symptoms. Although cough syncope is well-known, and is associated with headache and paralysis, a migrainous mechanism has not been reported. We reviewed the medical records, autonomic testing results, and responses to treatment in two cystic fibrosis patients with similar presentations of cough-induced impairment of consciousness followed by headache and paralysis. A 24-year-old woman and an unrelated 38-year-old man, both with cystic fibrosis, developed post-tussive neurologic deficits. Both patients reported infrequent dramatic spells, always preceded by major hemoptysis, and associated with left-sided paralysis, transient blindness, nausea, and severe pulsating headaches. Autonomic testing demonstrated only postural tachycardia and a near-vasodepressor episode in the woman, and mild, generalized sympathetic dysfunction in the man. Treatment for presumptive migraine with aura with verapamil nearly eradicated symptoms in both patients. Discontinuation of verapamil in the woman was associated with symptom recurrence and a stroke, with significant persistent residual left hemiparesis. In conclusion, cough-induced neurologic deficits were previously reported with cystic fibrosis, without clear understanding of the mechanism of impairment of consciousness. Based on the hemiparesis, nausea, and throbbing headache, which repeatedly followed the events in both patients, and based on the response to verapamil, we hypothesize a migrainous mechanism in both of our patients. The pathophysiology that links the hemoptysis to the spells deserves further investigation.

Adult↗
PubMed2004

Evaluation of [18F]fluorinated sigma receptor ligands in the conscious monkey brain.

PET-imaging of the sigma receptors is very helpful to understand processes, e.g., several central nervous system (CNS)-diseases in which the sigma receptors are involved. The [(18)F]fluoroethylated analogs of SA4503 and SA5845 ([(18)F]FE-SA4503 and [(18)F]FE-SA5845) were evaluated in conscious monkeys to estimate its suitability for human application for PET. Conscious monkeys (Macaca Mulatta) were either scanned with [(18)F]FE-SA4503 or [(18)F]FE-SA5845 (n = 3 for both groups, 220-802 MBq). After a dynamic study of 120 min, radioactivity was displaced by intravenous (i.v.) injection of haloperidol (1 mg/kg). One month later the same set of three monkeys were scanned with [(18)F]FE-SA4503 for 120 min and "cold" SA4503 (1 mg/kg) was infused to displace the radioactivity, and the other three monkeys were pretreated with haloperidol (1 mg/kg) before the 120-min PET-scan with [(18)F]FE-SA5845. Cortical areas (cingulate, frontal, occipital, parietal, temporal), striatum, and thalamus showed high radioactivity uptake. Infusion of haloperidol displaced the radioactivity levels of the two radioligands. The same effect was found for [(18)F]FE-SA4503 after SA4503 displacement. Pretreatment with haloperidol blocked the [(18)F]FE-SA5845 binding to give PET-images with low and uniform uptake in the brain. The findings demonstrated the reversible binding of the two radioligands. Metabolite analysis showed that 14% and 23% parent compound of [(18)F]FE-SA5845 and [(18)F]FE-SA4503, respectively, at 120 min postinjection was present in plasma. Kinetic analysis showed that the binding potential of [(18)F]FE-SA5845 was higher in all brain regions than that of [(18)F]FE-SA4503 (4.75-8.79 vs. 1.65-4.04). The highest binding potential was found in the hippocampus, followed by the cortical regions, thalamus, cerebellar hemisphere, striatum and vermis. Both [(18)F]FE-SA compounds bound specifically to cerebral sigma receptors of the monkey and have potential for mapping sigma receptors in the human brain.

Animals↗
PubMed2004

Potential of [(18)F]beta-CFT-FE (2beta-carbomethoxy-3beta-(4-fluorophenyl)-8-(2-[(18)F]fluoroethyl)nortropane) as a dopamine transporter ligand: A PET study in the conscious monkey brain.

A dopamine transporter (DAT) ligand 2beta-carbomethoxy-3beta-(4-fluoro-phenyl)-8-(2-[(18)F]fluoroethyl)nortropane ([(18)F]beta-CFT-FE) was synthesized and evaluated in comparison with [(11)C]beta-CFT in monkey brain using animal positron emission tomography (PET). [(18)F]beta-CFT-FE and [(11)C]beta-CFT were injected intravenously to conscious monkeys for a 91-min PET scan with arterial blood sampling for metabolite analysis. In the conscious state, [(18)F]beta-CFT-FE provided a peak about 20 min after the injection and declined thereafter in the striatum of monkey brain, while [(11)C]beta-CFT continuously increased with time up to 91 min after injection. Metabolite analysis revealed that [(18)F]beta-CFT-FE was more rapidly metabolized in plasma than [(11)C]beta-CFT. The striatal binding of both ligands was dose-dependently displaced by preadministration of a specific DAT inhibitor, GBR12909, at doses of 0.5 and 5 mg/kg; however, the displacement degree of [(11)C]beta-CFT-FE was higher than that of [(18)F]beta-CFT. The effects of the anesthetics, ketamine and isoflurane, on binding were more prominent in [(11)C]beta-CFT than [(18)F]beta-CFT-FE. Specificity and affinity of beta-CFT-FE to DAT were evaluated in an in vitro assay using cloned human DAT, serotonin transporter, and norepinephrine transporter in comparison with other conventional DAT ligands, showing that beta-CFT-FE had lower affinity and higher specificity to DAT than beta-CFT and beta-CIT. These results suggested that [(18)F]beta-CFT-FE could be a potential imaging agent for DAT, providing excellent selectivity and tracer kinetics for quantitative PET imaging.

Anesthetics↗
PubMed1995

Memory and consciousness: an appreciation of Claparède and recognition et moiïtè.

Claparède's report of a case of amnesic syndrome is an early example of the cognitive neuropsychology paradigm, by which studies of brain-damaged patients are used to shed light on the nature of normal mental processes. The case illustrates the selective impairment of episodic memory, with procedural and semantic memory remaining intact. Moreover, the several demonstrations of preserved learning during amnesia comprise an early illustration of the dissociation between explicit and implicit memory. However, its greatest contemporary relevance is for theories of conscious recollection. Claparède underscored the role of the self, viewed as a knowledge structure, in conscious mental life, and he drew attention to three different modes of recognition: remembering, inferring, and knowing.

Cognition↗
PubMed1999

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.

Brain Mapping↗
PubMed1999

Consciousness: some basic issues--A neurophilosophical perspective.

This paper concentrates on the basic properties of "consciousness" that temporal coding is postulated to relate to. A description of phenomenal consciousness based on what introspection tells us about its contents is offered. This includes a consideration of the effect of various brain lesions that result in cortical blindness, apperceptive and associative agnosia, and blindsight, together with an account of the manner in which sight is regained after cortical injuries. I then discuss two therories of perception-Direct Realism and the Representative Theory. This includes a discussion of the concept of the body-image, phantom limbs, the alleged projection of sensations, the ontological status of phenomenal space, the homunculus argument, the validity of topographic coding, the difference between the stimulus field and the visual field, and two theories of brain-mind relationship-the Identity Theory and the Bohr-Heisenberg theory of brain-mind complementarity. Finally I suggest that the binocular rivalry obtained in the case of the stroboscopic patterns that result from intermittent photic stimulation of one eye, when used in animal expeiments with unit recording, offers a good experimental method of investigating the binding problem.

Consciousness↗
PubMed1999

Temporal binding, binocular rivalry, and consciousness.

Cognitive functions like perception, memory, language, or consciousness are based on highly parallel and distributed information processing by the brain. One of the major unresolved questions is how information can be integrated and how coherent representational states can be established in the distributed neuronal systems subserving these functions. It has been suggested that this so-called "binding problem" may be solved in the temporal domain. The hypothesis is that synchronization of neuronal discharges can serve for the integration of distributed neurons into cell assemblies and that this process may underlie the selection of perceptually and behaviorally relevant information. As we intend to show here, this temporal binding hypothesis has implications for the search of the neural correlate of consciousness. We review experimental results, mainly obtained in the visual system, which support the notion of temporal binding. In particular, we discuss recent experiments on the neural mechanisms of binocular rivalry which suggest that appropriate synchronization among cortical neurons may be one of the necessary conditions for the buildup of perceptual states and awareness of sensory stimuli.

Arousal↗
PubMed2000

I like it, but I'm not sure why: can evaluative conditioning occur without conscious awareness?

There is good evidence that, in general, autonomic conditioning in humans occurs only when subjects can verbalize the contingencies of conditioning. However, one form of conditioning, evaluative conditioning (EC), seems exceptional in that a growing body of evidence suggests that it can occur without conscious contingency awareness. As such, EC offers a unique insight into what role contingency awareness might play in associative learning. Despite this evidence, there are reasons to doubt that evaluative conditioning can occur without conscious awareness. This paper aims to critically review the EC literature and to draw some parallels to what is known about autonomic conditioning. In doing so, some important general issues about measuring contingency awareness are raised. These issues are illustrated with a brief report of an experiment in which a sensitive measure of contingency awareness is compared against a commonly used measure.

Autonomic Nervous System↗