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At least 1,531 records · Page 85Linked to original sources
PubMed2006

Hemispheric asymmetries for the conscious and unconscious perception of emotional words.

The current research examines the interactions between hemispheric asymmetries for visual perception and emotion. In a series of four experiments, participants completed tasks measuring both conscious and unconscious perception of linguistic stimuli. In these studies, stimulus-presentation parameters (brief exposure duration vs masking) and the emotional valence of the test stimuli (negative vs positive) were manipulated in order to create studies in which the visual and emotional asymmetries were congruent (favoured the same hemispheres) or were incongruent (favoured opposing hemispheres). The results demonstrated that negative emotional stimuli led to a right-hemisphere advantage for conscious perception only when stimuli were shown for brief exposures (17 ms). Positive emotional words did not elicit hemispheric asymmetries. The results are discussed in terms of their relevance for theories of emotional lateralisation.

Affect↗
PubMed2002

Star fruit (Averrhoa carambola) intoxication: an important cause of consciousness disturbance in patients with renal failure.

Star fruit intoxication is a rare cause of consciousness disturbance in patients with renal failure. Most cases in the literature are uremic patients on maintenance dialysis. We present a patient with chronic renal failure, who was not on dialysis program yet, suffered from star fruit intoxication with presentation of consciousness disturbance and successfully managed by a session of hemodialysis.

Consciousness Disorders↗
PubMed1988

Cardiovascular effects of central calcitonin gene-related peptide in conscious rats.

Calcitonin gene-related peptide (CGRP) is a potent peripheral vasodilator. In the present study, the cardiovascular effects of centrally administered CGRP were examined in conscious, normotensive rats. The rats were chronically instrumented with miniaturized pulsed Doppler flow probes to allow measurement of regional blood flow in the conscious animals. Injection of increasing doses of CGRP (0.3 to 3.0 micrograms/kg) in the lateral cerebroventricles transiently increased arterial pressure (maximal change = 13 +/- 3 mm Hg) and markedly increased heart rate (maximal increase = 88 +/- 10 b/min). The heart rate response was sustained over a period of 20 to 30 minutes. Central CGRP decreased hindquarter vascular resistance but had no effect on renal or mesenteric vascular resistances. In contrast, intravenous injections of CGRP reduced arterial pressure and renal, mesenteric, and hindquarter vascular resistances. The tachycardia response to central CGRP was attenuated by pretreatment with propranolol or hexamethonium, indicating that the heart rate response was mediated, in part, through increases in cardiac sympathetic tone. These data indicate that central CGRP may alter cardiovascular function through alterations in sympathetic outflow.

Animals↗
PubMed1988

The effect of area postrema lesions on hemodynamic responses to systemic methionine-enkephalin in conscious dogs.

In the intact conscious dog, intravenous methionine-enkephalin (ME) increases heart rate and mean arterial blood pressure (MAP). These hemodynamic responses are produced at lower dosages when ME is injected into the vertebral artery, but not the carotid artery, suggesting that ME receptors are localized in the vertebrobasilar artery circulation. The area postrema (AP), a circumventricular organ devoid of a functional blood-brain barrier, represents a likely site for these receptors. We have tested the effects of chronic AP ablation upon hemodynamic responses to ME in conscious dogs. In three dogs with subtotal AP destruction, ME responses were preserved. However, in another dog with complete ablation of both the AP and the area subpostrema, ME responses were eliminated. These results indicate that total destruction of the AP, and perhaps of deeper structures as well, is necessary to abolish hemodynamic responses to ME.

Animals↗
PubMed1990

Potency of propofol for loss of consciousness after a single dose.

A dose-response curve for loss of consciousness after administration of propofol was obtained using 56 unselected, premedicated patients presenting for surgery. Propofol was given in doses according to the calculated lean tissue mass (LTM) of the patient. The end-point for loss of consciousness was loss of ability to grasp a light object. Using probit analysis, the ED50 for propofol was found to be 1.34 mg/kg of LTM and the ED95 was found to be 2.56 mg/kg of LTM. Comparison with previously published data for thiopentone showed propofol to be approximately twice as potent as thiopentone at ED50 and the slope of its dose-response curve to be shallower than that of thiopentone.

Adolescent↗
PubMed1996

Use of near infrared spectroscopy to estimate cerebral blood flow in conscious and anaesthetized adult subjects.

Near infrared spectroscopy (NIRS) can be used to quantify cerebral haemodynamic states non-invasively and to estimate cerebral blood flow (CBF). In the first part of this study we have compared CBF measurements in conscious and anaesthetized subjects. In the second part we have compared paired measurements made during anaesthesia, first on the scalp and then the dura after craniotomy. Mean CBF was 17 (SD 7) ml 100 g-1 min-1 in the conscious subjects compared with 21 (8) ml 100 g-1 min-1 on the scalp during anaesthesia (P > 0.1). Mean CBF on the dura was 68 (21) ml 100 g-1 min-1 (P < 0.0001). Computer modelling suggests that the difference in magnitude between scalp and dura measurements of CBF is likely to be caused by the optical effect of extracerebral tissue which powerfully scatters light passing through it but does not contribute significantly to the measured CBF because it has only a small blood content itself. The results lend support to this method of estimating CBF although formal validation by comparison with an established technique is needed.

Adult↗
PubMed1996

Haemodynamic effects of moderate normovolaemic haemodilution in conscious and anaesthetized patients.

We have assessed the haemodynamic effects of moderate normovolaemic haemodilution in ASA I patients, either conscious or during enflurane-fentanyl anaesthesia (10 patients in each group). Cardiac index (CI), stroke index (SI) and ejection fraction (EF) were measured by transthoracic electrical bioimpedance and, in the anaesthesia group, arterial and central venous blood samples were obtained to assess oxygen delivery (DO2), oxygen consumption (VO2) and oxygen extraction ratio (O2ER). In conscious patients, heart rate (HR) remained unchanged as SI, EF and CI increased. When haemodilution was performed during anaesthesia, CI remained stable in spite of a slight increase in SI, as HR decreased. This produced a reduction in DO2 which was compensated for by an increase in O2ER, allowing maintenance of VO2 without alteration in blood lactate concentration.

Adolescent↗
PubMed2001

Effects of the auditory stimuli of an auditory evoked potential system on levels of consciousness, and on the bispectral index.

Investigators in the field of depth of anaesthesia monitoring sometimes measure the auditory evoked potential (AEP) and the Bispectral Index (BIS) concurrently. However, the auditory stimuli required to generate an AEP may increase the level of consciousness, and cause an increase in the BIS. They may also alter the BIS by producing phase-locked harmonics in the surface electroencephalogram. The aim of this study was to determine if AEP stimuli have clinically significant effects on levels of consciousness and BIS values during sedation and general anaesthesia. Ten healthy adult patients were studied by measuring and recording the BIS for 6 epochs of 5 min each. The first 3 epochs took place during steady-state sedation, during which time the Observer's Assessment of Awareness/Sedation (OAA/S) score was also measured. The second 3 epochs took place during steady-state anaesthesia. During alternate epochs, patients were subjected to the auditory stimuli generated by an AEP system. The auditory stimuli were not associated with a change in BIS values (during sedation and anaesthesia) or OAA/S scores (sedation).

Acoustic Stimulation↗
PubMed2006

Transient decreases in Bispectral Index without associated changes in the level of consciousness during photic stimulation in an epileptic patient.

This case report describes a patient with a history of epileptic seizures who showed unusual decreases in the Bispectral Index (BIS) attributable to the induction of abnormal slow electroencephalographic (EEG) waves by photic stimulation, without any associated decrease in his level of consciousness. After starting anticonvulsive therapy, photic stimulation no longer induced abnormal EEG activity nor decreased BIS values. These findings suggest that BIS values may not accurately reflect a patient's actual level of consciousness in the presence of epilepsy-related abnormal EEG activity and that the BIS monitor may be able to track such EEG changes.

Adult↗
PubMed1985

Angiotensin-induced hypertension in conscious dogs: biochemical parameters and baroreceptor reflex.

The effects of a continuous iv infusion (osmotic minipumps) of angiotensin II (80 ng . kg-1 . min-1) and isoprenaline (10 ng . kg-1 . min-1) lasting 28 days were studied in six normotensive, conscious dogs. The parameters measured were systolic and diastolic blood pressure, heart rate, levels of angiotensin II, renin activity, aldosterone and antidiuretic hormone in plasma, baroreceptor reflex sensitivity and body weight. The treatment resulted in an approximately sevenfold increase in plasma angiotensin II level from 62.9 +/- 24.5 pg . ml-1 to 455.3 +/- 95.6 pg . ml-1. Systolic and diastolic blood pressure, measured for the first time 2 days after implanting the minipumps, were markedly increased throughout the infusion period (pretreatment value: 123.8 +/- 5.3/68.3 +/- 3.8 mmHg; after 2 days: 159.8 +/- 12.0/100.5 +/- 9.8 mmHg; after 28 days: 159.8 +/- 7.1/98.3 +/- 6.4 mmHg, whereas the heart rate remained unchanged due to the combined effects of angiotensin II and the concomitantly given isoprenaline. A high correlation was found between angiotensin II level in plasma and mean arterial blood pressure (r = 0.846; p less than 0.001). Furthermore, plasma renin activity was markedly suppressed by the treatment, and aldosterone levels rose. Plasma antidiuretic hormone levels were found to be unchanged at the chosen sampling time. A decrease in baroreceptor reflex sensitivity accompanied the development of the hypertensive state. There was also a loss of body weight during the infusion of angiotensin II and isoprenaline. The data provide evidence for the usefulness of the presented experimental protocol as an alternative model of arterial hypertension in chronically instrumented, conscious dogs.

Aldosterone↗
PubMed2005

Self-discipline and self-consciousness predict subjective memory in older adults.

Research has shown the personality variables of conscientiousness and neuroticism to be related to subjective memory in older adults. This study was designed to determine the specific facets of these traits involved in the relation between personality and memory complaints. Subjective memory evaluations were examined in 85 community-dwelling people aged 56 to 94 years. Regression analysis revealed that one facet of conscientiousness (self-discipline) and two facets of neuroticism (self-consciousness and anxiety) explained almost one third of the variance in subjective memory complaints. Anxiety acted as a suppressor variable to enhance the contribution of self-consciousness. Objective measures of episodic and prospective memory were not related to subjective memory. Effective treatments of memory complaints in healthy older adults may have to focus on enhancing self-discipline and self-concept.

Aged↗
PubMed1990

Cardiovascular effects of acute changes in extracellular ionized calcium concentration induced by citrate and CaCl2 infusions in chronically instrumented dogs, conscious and during enflurane, halothane, and isoflurane anesthesia.

To study the cardiovascular effects of low blood ionized calcium ion concentrations [Ca2+] induced by citrate infusion followed by high [Ca2+], induced by CaCl2 infusion awake and during enflurane (2.5% ET), halothane (1.2% ET), and isoflurane (1.6% ET) anesthesia, dogs were chronically instrumented to measure heart rate, aortic, left atrial, and left ventricular (LV) blood pressures, and cardiac output. In conscious dogs low [Ca2+] (decreased 0.35 mM); increased heart rate (HR) and mean aortic pressure (MAP) and decreased stroke volume (SV) and LV dP/dtmax. Low [Ca2+] increased HR during all three anesthetics and decreased LV dP/dtmax except during isoflurane anesthesia. Low [Ca2+] produced more hemodynamic depression during enflurane anesthesia than during anesthesia with halothane or isoflurane increasing left atrial pressure and decreasing MAP and SV. The differences seen were partially related to decreased systemic vascular resistance during halothane and isoflurane anesthesia. In conscious dogs following high [Ca2+] (increased 0.37 mM); only MAP and LV dP/dtmax increased. LVdP/dtmax was also increased by high [Ca2+] during all three anesthetics without a change in MAP. Cardiac output increased during halothane and isoflurane anesthesia but was unchanged during enflurane. It would appear that the hemodynamic sensitivity for the effects of changing [Ca2+] was enflurane greater than halothane greater than isoflurane greater than awake. The results suggest that the effects of changes in [Ca2+] induced by citrate and CaCl2 infusion are modified by the three volatile anesthetics.

Anesthesia, Inhalation↗
PubMed1997

Dose comparison of remifentanil and alfentanil for loss of consciousness.

BACKGROUND: This study evaluated the efficacy and safety of remifentanil, a potent mu agonist opioid with a rapid onset and offset of effect, as a sole induction agent for loss of consciousness (LOC) and compared it with alfentanil. METHODS: Remifentanil and alfentanil were administered intravenously over 2 min in ascending doses (remifentanil 2, 3, 4, 5, 6, 8, 10, 15, 20 microg/kg; alfentanil 40, 60, 80, 100, 120, 160, 200 microg/kg) to unpremedicated healthy patients. Patients were observed for rigidity and LOC for 30 s after the end of infusion. If patients had not lost consciousness, 2 mg x kg(-1) x min(-1) thiopental was administered until LOC was achieved. Arterial blood samples, obtained at specified time intervals, were analyzed for remifentanil and alfentanil whole-blood concentration. Blood pressure and heart rate were also recorded at preset time intervals. RESULTS: Neither drug could reliably produce LOC. With both drugs, there was a dose-dependent decrease in thiopental requirements and a dose-dependent increase in the incidence and severity of rigidity (P < 0.05). The median effective dose (ED50) for LOC with remifentanil was 12 microg/kg, and for alfentanil it was 176 mcrog/kg. The median effective concentration (EC50; whole-blood concentration) of remifentanil was 53.8 ng/ml and for alfentanil it was 1,012 ng/ml. Minimal hemodynamic changes were observed after either drug was given. CONCLUSIONS: Remifentanil is 15 times more potent than alfentanil, based on the ED50 to achieve loss of response to a verbal command and 20 times more potent than alfentanil based on the EC50. Neither opioid is suitable as a sole induction agent.

Adult↗
PubMed2002

Effect of truncal vagotomy on sphincter of oddi cyclic motility in conscious dogs.

OBJECTIVE: To evaluate the effects of truncal vagotomy at the diaphragmatic level on the sphincter of Oddi (SO) motility. SUMMARY BACKGROUND DATA: Cholelithiasis is a well-known late complication after gastrectomy and/or vagotomy. The mechanism of gallstone formation is only partly understood, and few studies address the effects of vagotomy on SO cyclic motility in conscious subjects. METHODS: In conscious dogs, SO motility was recorded by retrograde infusion manometry through a duodenal cannula before and after bilateral truncal vagotomy at the diaphragmatic level. Effects of cholecystokinin-octapeptide and feeding were also evaluated before and after vagotomy. RESULTS: SO cyclic motility and the gastroduodenal migrating motor complex continued to occur during postvagotomy fasting. Intermittent inhibitions of the SO and duodenal contractions disappeared during phase 3 of the migrating motor complex. SO basal pressure significantly decreased, whereas the amplitude significantly increased. Cholecystokinin-octapeptide inhibited SO contractions before and after vagotomy. The amplitude of SO contractions increased and their frequency decreased after feeding; however, these effects disappeared after vagotomy. CONCLUSIONS: SO cyclic motility and the effects of feeding change after truncal vagotomy at the diaphragmatic level. These facts may at least partly explain gallstone formation after gastric surgery and/or vagotomy.

Animals↗
PubMed1998

Initial disturbances of consciousness and resultant impaired awareness in Spanish patients with traumatic brain injury.

The purpose of this prospective, between-subjects study was to look at impaired awareness cross-culturally in patients with traumatic brain injury (TBI) and to relate impaired awareness after injury to the initial estimates of disturbed consciousness at time of injury. The study was conducted in community and inpatient and outpatient rehabilitation centers in Barcelona and Madrid. Participants were 30 persons with primarily moderate to severe TBI who could complete a written questionnaire concerning their functioning and 28 age- and gender-matched controls. A Spanish translation of the Patient Competency Rating Scale (PCRS) was administered to each participant. Relatives or significant others also completed this scale on each participant using the relative's version (PCRS-R). Difference scores, obtained by subtracting PCRS-R from PCRS-P (PCRS-P minus PCRS-R), were used as a marker of impaired awareness. Individuals with TBI were rated (by self and significant others) as being less competent than controls. Forty percent of Spanish patients with TBI who suffered severe injuries tended to overestimate their behavioral competencies. The PCRS-P minus the PCRS-R difference scores tended to correlate with admitting Glasgow Coma Scale (GCS) scores and retrospective estimates of posttraumatic amnesia (PTA). Initial disturbances of consciousness, one measure of severity of brain injury, appeared to relate to later measures of impaired self-awareness in Spanish patients with TBI. Non-brain-injured controls did not tend to report levels of competency that differed from their relatives' reports.

Adult↗
PubMedDate not supplied

Multimodal neuroimaging approaches to disorders of consciousness.

Advances in neuroimaging techniques hold significant promise for improving understanding of disorders of consciousness arising from severe brain injuries. We review neuroimaging studies of the vegetative state (VS) and minimally conscious state (MCS), and findings in an unusual case of late emergence from MCS. Multimodal neuroimaging studies using positron emission tomography techniques, functional magnetic resonance imaging, and quantitative electroencephalography and magnetoencephalography quantify variations of residual cerebral activity across these patient populations. The results suggest models to distinguish the pathophysiologic basis of VS and MCS. Less clear are potential brain mechanisms underlying late recovery of communication in rare MCS patients. Diffusion tensor magnetic resonance imaging studies and recent experimental findings suggest that structural remodeling of the brain following severe injury may play a role in late functional recoveries. More generally, relatively long time courses of recovery following severe brain injury emphasize the need to develop markers for identifying patients who may harbor potential for further meaningful recovery. Introduction of neuroimaging into the clinical evaluation process will require developing frameworks for longitudinal assessments of cerebral function. Although limited in number, available studies already provide important insights into underlying brain mechanisms that may help guide development of such assessment strategies.

Arousal↗
PubMed2003

Are neural correlates of visual consciousness retinotopic?

Some visual neurons code what we see, their defining characteristic being a response profile which mirrors conscious percepts rather than veridical sensory attributes. One issue yet to be resolved is whether, within a given cortical area, conscious visual perception relates to diffuse activity across the entire population of such cells or focal activity within the sub-population mapping the location of the perceived stimulus. Here we investigate the issue in the human brain with fMRI, using a threshold stimulation technique to dissociate perceptual from non-perceptual activity. Our results point to a retinotopic organisation of perceptual activity in early visual areas, with independent perceptual activations for different regions of visual space.

Brain Mapping↗
PubMed1991

Different effects of low and high doses of endothelin on haemodynamics and hormones in the normotensive conscious dog.

The effects of low-dose endothelin on systemic haemodynamics and vasoactive hormones were examined in conscious dogs. In addition, we examined the effects of endothelin on pressor responses to noradrenaline and angiotensin II and the baroreflex regulation of heart rate in conscious dogs. Continuous infusion of 40 fmol/kg per min endothelin for 40 min induced a mild but significant reduction in mean arterial pressure from 89.1 +/- 1.7 to 82.7 +/- 2.0 mmHg (P less than 0.05), associated with decreases in total peripheral resistance 20 min later. A 400 fmol/kg per min dose of endothelin, on the other hand, induced a gradual elevation of mean arterial pressure from 89.2 +/- 2.3 to 96.8 +/- 2.0 mmHg (P less than 0.05), associated with increases in total peripheral resistance over 30 min. The 40 fmol/kg per min dose of endothelin infusion induced a significant reduction in plasma arginine vasopressin (AVP; P less than 0.05) and elevations of plasma atrial natriuretic peptide (ANP; P less than 0.05), plasma prostaglandin E2 (PGE2; P less than 0.05) and plasma 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha; P less than 0.05). The 400 fmol/kg per min dose produced elevations of AVP, ANP, PGE2 and 6-keto-PGF1 alpha (P less than 0.05). Pressor responses to noradrenaline and angiotensin II were significantly attenuated during continuous infusion of 40 fmol/kg per min endothelin, whereas 400 fmol/kg per min endothelin did not induce any significant changes compared with the control. Furthermore, baroreflex sensitivity was attenuated with 40 fmol/kg per min endothelin but did not show any significant changes at 400 fmol/kg per min.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗