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PubMed2002

Using illusory line motion to differentiate misrepresentation (Stalinesque) and misremembering (Orwellian) accounts of consciousness.

It has been suggested that the difference between misremembering (Orwellian) and misrepresentation (Stalinesque) models of consciousness cannot be differentiated (Dennett, 1991). According to an Orwellian account a briefly presented stimulus is seen and then forgotten, whereas by a Stalinesque account it is never seen. At the same time, Dennett suggested a method for assessing whether an individual is conscious of something. An experiment was conducted which used the suggested method for assessing consciousness to look at Stalinesque and Orwellian distinctions. A visual illusion, illusory line motion, was presented and participants were requested to make judgments that reflected what they were aware of. The participants were able to make responses indicating that they were aware of the actual stimulus in some conditions, but only of the illusion in others. This finding supports a claim that the difference between the Orwellian and Stalinesque accounts may be empirically observable and that both types of events may occur depending on task and stimulus parameters.

Consciousness↗
PubMed2002

A neural correlate of consciousness related to repression.

In previous research Libet (1966) discovered that a critical time period for neural activation is necessary in order for a stimulus to become conscious. This necessary time period varies from subject to subject. In this current study, six subjects for whom the time for neural activation of consciousness had been previously determined were administered a battery of psychological tests on the basis of which ratings were made of degree of repressiveness. As hypothesized, repressive subjects had a longer critical time period for neural activation of consciousness, suggesting the possibility that this neurophysiological time factor is a necessary condition for the development of repression.

Brain↗
PubMed2002

Libet's research on the timing of conscious intention to act: a commentary.

S. Pockett (Consciousness and Cognition, this issue) and G. Gomes (Consciousness and Cognition, this issue) discuss a possible bias in the method by which Libet's subjects estimated the time at which they became aware of their intent to move their hands. The bias, caused by sensory delay processing the clock information, would be sufficient to alter Trevena and Miller's (Consciousness and Cognition, this issue) conclusions regarding the timing of the lateralized readiness potential. I show that the flash-lag effect would compensate for that bias. In the last part of my commentary I note that the other target articles do not examine the most interesting aspect of Libet's unfashionable views on free will. I point out that Libet's views are less strange than they at first appear to be.

Consciousness↗
PubMed1994

Will neuroscience explain consciousness?

This paper is a defence of a pragmatic version of mind-brain reductionism from a neuroscientist's point of view. It is claimed that there are good reasons to believe that future neuroscience will be able to explain (in a weak and pragmatic sense) the puzzling aspects of mind and consciousness. Opposition to reductionism comes from both philosophical and empirical quarters. It is argued here that philosophical arguments, such as semantic problems with the concept of identity, are unconvincing and should be regarded with the greatest suspicion. The most influential empirical result that has been claimed to constitute a problem for reductionism is the temporal delay and mental antedating of consciousness found by Benjamin Libet. It is argued that these results, far from being a problem for reductionism, constitute evidence for a particular view of the physiological origins of consciousness. Finally, it is argued that many subjective aspects of experience can already be given satisfactory scientific explanations and that scientific progress is likely to rob the mind and subjective experience of their mystery.

Brain↗
PubMed2002

Conscious and subconscious sensorimotor synchronization--prefrontal cortex and the influence of awareness.

One of the most compelling challenges for modern neuroscience is the influence of awareness on behavior. We studied prefrontal correlates of conscious and subconscious motor adjustments to changing auditory rhythms using regional cerebral blood flow measurements. At a subconscious level, movement adjustments were performed employing bilateral ventral mediofrontal cortex. Awareness of change without explicit knowledge of the nature of change led to additional ventral prefrontal and premotor but not dorsolateral prefrontal activations. Only fully conscious motor adaptations to a changing rhythmic pattern showed prominent involvement of anterior cingulate and dorsolateral prefrontal cortex. These results demonstrate that while ventral prefrontal areas may be engaged in motor adaptations performed subconsciously, only fully conscious motor control which includes motor planning will involve dorsolateral prefrontal cortex.

Acoustic Stimulation↗
PubMed2004

Disorders of consciousness: anatomical and physiological mechanisms.

The anatomical and physiological mechanisms of consciousness are reviewed, focussing on the wakefulness mechanisms, which are one aspect, albeit an indispensable one, of consciousness. In trying to understand disorders of consciousness, it must be remembered that wake physiology is linked to sleep physiology and a brief summary of the phenomenology and regulation of the wake sleep cycle is therefore presented. Wakefulness is produced and maintained by a complex neural network composed of at least ten groups of neurones, which spread out from the medulla oblongata to the telencephalic structures. Some of these elements (reticular formation and diffuse thalamic nuclei) contribute to the arousal and general activation of the brain, while others (aminergic and peptidergic neurones) contribute to the quality of wakefulness, as well as to general activation. Disorders of wakefulness may be due to dysfunction of one or several elements of the wake network or sleep disorders, as well as to sleep deprivation.

Animals↗
PubMed1996

Breakthrough to awareness: a preliminary neural network model of conscious and unconscious perception in word processing.

A neural network model is constructed to mimic the processing involved in semantic and working memory when subliminal effects are involved. These effects involve modifications of reaction time to later inputs, according to whether or not there has been conscious or unconscious processing of the earlier input. The model is constructed of two separate modules: one (a semantic memory module) allowing for processing at a semantic, but unconscious, level, and the other (a working memory module) for conscious experience. The latter module, although a replica of the earlier one, has different lateral connectivity and output function from the former. The model is shown to give a good fit to Marcel's data on the processing of polysemous words. Further tests are suggested for the model, and a possible cortical implementation suggested. The relevance of the model to recent approaches to consciousness is also explored.

Consciousness↗
PubMed1988

Assessing the conscious level in infants and young children: a paediatric version of the Glasgow Coma Scale.

The Glasgow Coma Scale is widely accepted as a measure of impaired consciousness both in clinical practice and in research. In its standard form, the scale is inapplicable to infants and children below the age of 5 years. We have devised a paediatric coma scale, which recognises that the expected normal verbal and motor responses must be related to the patient's age. This scale has been routinely used in a paediatric teaching hospital over a 10-year period and has appeared to be satisfactory, although it is less sensitive to changes in the conscious level than the adult scale. We have assessed the consistency of observer evaluation, using video tapes of infants and children exhibiting varying levels of consciousness: when conducted after formal instruction, assessments were reasonably consistent.

Child, Preschool↗
PubMed1994

Systemic phencyclidine administration is associated with increased dopamine, GABA, and 5-HIAA levels in the dorsolateral striatum of conscious rats: an in vivo microdialysis study.

In vivo microdialysis was used to study the effects of systemically administered phencyclidine (PCP, 10 mg/kg) on the extracellular levels of dopamine, dihydroxyphenylacetate (DOPAC), homovanillate (HVA), 5-hydroxy-indolacetate (5-HIAA), gamma-aminobutyrate (GABA), glutamate, and aspartate in the rat dorsolateral striatum. In order to demarcate the effects of anesthesia, tissue trauma and gliosis, the effect of PCP was studied in both anesthetized rats with long and short probe implantation periods and in conscious rats with a long probe implantation period. PCP significantly increased the extracellular levels of dopamine in all experimental groups, though the post-implantation interval and anesthesia modulated the degree of increase. PCP increased 5-HIAA levels in both conscious and anesthetized rats after a long post-implantation period and HVA only in anesthetized rats after a long post-implantation period. Glutamate, aspartate, and DOPAC were not affected by PCP challenge but our study indicated for the first time that systemic PCP elevates extracellular GABA in conscious rats.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1986

Effects of chronic renal denervation in conscious restrained rats.

Sodium (Na), calcium (Ca), inorganic phosphate (Pi) and water excretion were measured in nondiuretic (ND) and extracellular fluid (ECF) volume expanded (VE) conscious restrained rats four weeks after denervation or sham-denervation of the left kidney. On the day of the study the animals were lightly anaesthetized with ether and the femoral vessels on one side were catheterized. Urine was collected from both kidneys. The animals were allowed to recover for 3 hours and studied in a restraining chamber. In ND animals isotonic saline containing inulin and para-amino-hippuric acid (PAH) were given at a rate of 0.067 +/- 0.002 (SE) ml/min/kg body weight (BW). In VE animals the infusion rate was 0.24 +/- 0.04 ml/min/kg BW. Kidney catecholamine content was measured after the experiments. Clearances of PAH and of inulin (GFR) were the same in both kidneys. Urine volume (V), sodium excretion (UNa V/GFR), inorganic phosphate excretion (UPi V/GFR) and calcium excretion (UCa V/GFR) were significantly higher in the denervated kidneys. Values in sham denervated kidneys were not greater than those of the right kidney. Denervation was proven by demonstrating absent or very low catecholamine content in the kidneys. The results demonstrate that: chronic renal denervation in rats leads to diuresis and natriuresis even in the conscious state, thus confirming previous results from our laboratory; such changes occur independently of the state of the ECF volume and of renal haemodynamic changes; the increased excretion of Ca++ and Pi after denervation demonstrates that renal nerves affect the reabsorption of these ions either independently or by way of their effect on sodium reabsorption. These data allow us to suggest that a renal tubular dysfunction, which was proved in anaesthetized denervated animals, can also be observed in the conscious state.

Animals↗
PubMed1989

Caerulein stimulates pancreatic secretory response in conscious newborn rats.

UNLABELLED: The aim of our study was to measure age-dependent, caerulein-stimulated pancreatic enzyme secretion of conscious CFY suckling rats without pancreatic duct cannulation. Pancreatic secretory response was expressed as the decrease in specific enzyme (trypsin, amylase) activity compared to saline-injected control. The study was performed in three phases. In 10-d-old conscious newborn rats, single 1 and 3 micrograms/kg sc doses of caerulein induced significant decreases in specific trypsin (42 and 47%) and amylase (34 and 33%) activity 15 min after the caerulein injection; the same doses injected at 0 and 30 min evoked a similar decrease 90 min after the first injection. The 0.5 microgram/kg dose was ineffective. In 10-d-old anesthetized rats, the 90-min-decrease in total pancreatic trypsin activity, induced by graded doses (1,3,10, and 30 micrograms/kg) of caerulein, was compared to the 90-min output of trypsin in their bile-pancreatic juice. Each of the applied doses induced significant change in the total trypsin activity both in the pancreas (-33-57%) and juice (+21 +/- 49%) and its decrease in the gland corresponded quantitatively well (r = 0.52; p less than 0.01) to the increase in the simultaneous 90-min trypsin output. The age- and dose-dependent pancreatic response of 3-, 5-, 10-, and 20-d-old conscious rats was investigated under the effect of 1,3,10, and 30 micrograms/kg sc doses of caerulein injected at 0 and 30 min. In 3-d-old rats, the 10 and 30 micrograms/kg and in 20-d-old rats, the 1 and 3 micrograms/kg doses were effective, whereas in 5- and 10-d-old rats each caerulein dose applied evoked a significant decrease in pancreatic-specific trypsin activity. CONCLUSION: The pancreas of newborn rats is in vivo less sensitive to caerulein between postnatal d 3 and 10 than in already weaned rats.

Aging↗
PubMed1980

Near-drowning: correlation of level of consciousness and survival.

This paper reports a retrospective review of 121 cases of near-drowning treated at university hospitals in Miami and Gainesville. The series included 57 adults and 64 children who were classified into three categories, Category A (Awake), Category B (Blunted) and Category C (Comatose), based on their level of consciousness on arrival at the primary hospital. Results based on the total 121 patients showed 87 per cent survived with apparently normal brain function, two per cent survived with impaired brain function and 11 per cent died. The survival rate of all patients who were awake when they entered the hospital was significantly greater than that of both those who were admitted and blunted consciousness (p = 0.05) and those who were comatose when admitted (p less then 0.0001). Further, the group whose members had blunted consciousness had a significantly greater number of normal survivors than the group whose members were comatose on admission (p less than 0.002). All treated adults survived without permanent neurological damage and only three surviving children in the series suffered residual brain damage. Whether the course of the seven patients, three adults and four children, who died without return of brain function, would have been altered by deliberate attempts to preserve the brain is a matter of speculation.

Adult↗
PubMed2003

Survival and recovery of consciousness in anoxic-ischemic coma after cardiopulmonary resuscitation.

OBJECTIVE: In patients who remain unconscious after cardiopulmonary resuscitation (CPR) poor outcome may be predicted with several tests. To use these tests, knowledge of a priori chances of poor outcome after varying periods of unconsciousness is needed. This study is aimed at providing such data. DESIGN AND PATIENTS: Data regarding survival and recovery of consciousness were extracted from registry-based and prospective cohort studies of patients with anoxic-ischemic coma. A survival analysis was done using Kaplan-Meier estimates and 28-day outcomes were calculated for all patients unconscious after 24 h and 72 h, and 5 days, 7 days and 14 days after CPR. Patient characteristics and outcomes in our cohort were compared with those of published patient series. RESULTS: After 28 days, 27% of 172 patients from the two cohort studies were alive and conscious, 9% were still unconscious, and 64% had died. The proportion of patients who regained consciousness decreased from 34% of those unconscious within the first 6 h post-CPR to 13% of those still unconscious after 2 weeks. The proportion surviving in an unconscious state increased from 6% of patients who were unconscious initially to 33% of those still unconscious after 2 weeks. The chance of survival remained unchanged up to 7 days after CPR, irrespective of the duration of unconsciousness. Patient characteristics and outcomes in our cohort were comparable to data available from the literature. CONCLUSIONS: The a priori chances of (poor) outcome vary with the duration of unconsciousness after CPR. This study provides data for different time-intervals after CPR.

Adult↗
PubMed2004

Consciousness monitoring in ventilated patients: bispectral EEG monitors arousal not delirium.

OBJECTIVE: Bispectral index (BIS) is being evaluated as a monitor of consciousness, yet it is unclear what components of consciousness (i.e., arousal vs. content of consciousness) the BIS measures. This study compared BIS levels to well-validated clinical measures of arousal and the presence or absence of delirium. DESIGN: A prospective, blinded, observational cohort study. PATIENTS: 124 mechanically ventilated, adult, medical ICU patients. MEASUREMENTS AND RESULTS: Using BIS 3.4 and BIS-XP 4.0 algorithms, BIS values were calculated immediately prior to clinical assessments. The clinical assessments included the Richmond Agitation-Sedation Scale (RASS) and presence or absence of delirium using the Confusion Assessment Method for the ICU. A total of 484 assessments were collected among 124 patients. BIS-XP values demonstrated greater correlation with RASS than BIS 3.4 ( R(2)=0.36 vs. 0.20), although considerable overlap of BIS-XP scores remained across RASS levels. Median BIS-XP values for delirious and nondelirious observations were 74 and 96, respectively, while BIS 3.4 values were 91 and 96, respectively. However, neither BIS 3.4 nor BIS-XP were significantly associated with delirium after controlling for RASS value. CONCLUSIONS: In comparison with clinical measures of arousal in mechanically ventilated patients, BIS-XP algorithm demonstrated stronger correlation with RASS levels than did BIS 3.4, yet marked overlap across different levels of arousal persist using both algorithms. After controlling for level of arousal, neither BIS-XP nor BIS 3.4 algorithms distinguished between the presence and absence of delirium.

Algorithms↗
PubMed2005

The consciousness continuum: from "qualia" to "free will".

The consciousness continuum is seen as extending from simple sensory experiences to complex subjective constructions resulting in the apparent exercise of conscious will. The phenomena between these two extremes include spontaneously occurring mental contents, unintended perceptual experiences, memory retrievals, and problem solving including feedback of conscious contents. Two factors describe this continuum: The presence or absence of intention (psychologically defined) and the complexity of the cognitive construction involved. Among other benefits, such an analysis is intended to provide an alternative to metaphysical and vague concepts such as qualia, free will, and intentionality.

Consciousness↗
PubMed2006

Artificial consciousness, artificial emotions, and autonomous robots.

Nowadays for robots, the notion of behavior is reduced to a simple factual concept at the level of the movements. On another hand, consciousness is a very cultural concept, founding the main property of human beings, according to themselves. We propose to develop a computable transposition of the consciousness concepts into artificial brains, able to express emotions and consciousness facts. The production of such artificial brains allows the intentional and really adaptive behavior for the autonomous robots. Such a system managing the robot's behavior will be made of two parts: the first one computes and generates, in a constructivist manner, a representation for the robot moving in its environment, and using symbols and concepts. The other part achieves the representation of the previous one using morphologies in a dynamic geometrical way. The robot's body will be seen for itself as the morphologic apprehension of its material substrata. The model goes strictly by the notion of massive multi-agent's organizations with a morphologic control.

Adaptation, Psychological↗
PubMed2006

Role of the cyclooxygenase pathway in the protection against postischemic stunning in conscious sheep.

OBJECTIVE: There are controversial reports in conscious animals regarding the role of cyclooxygenase-2 in late preconditioning (LP). This study analyzed the effect of COX-2 involvement in non-preconditioned hearts (NP) and in mediation of LP protection against stunning in conscious sheep submitted to a prolonged reversible ischemia. METHODS: Six groups were considered: NP: 12 min ischemia and 120 min reperfusion; LP consisting of six periods of 5 min-ischemia-5 min reperfusion 24 h before the 12 min ischemia; NP and LP with either the non-selective COX-1 and COX-2 inhibitor, aspirin (20 mg/kg), or the specific COX-2 inhibitor, celecoxib (3 mg/kg) before the 12 min ischemic period. RESULTS: Mean postischemic wall thickening fraction (as % of preischemic values) improved from 49.6 +/- 4.0% in NP to 72.5 +/- 3.5% in LP (p < 0.01) and a similar protection was obtained with aspirin and celecoxib in NP hearts (p < 0.01). Neither aspirin nor celecoxib administration prior to the prolonged ischemia on day 2 abrogated LP improvement of postischemic dysfunction. Moreover, LP with aspirin improved the protective response (80.7 +/- 2.6%) over that obtained with aspirin in NP hearts (66.6 +/- 4.7%, p < 0.05). This effect was not obtained with celecoxib. CONCLUSIONS: Aspirin and celecoxib showed that COX-2 has a detrimental effect on mechanical cardioprotection in NP hearts of conscious sheep submitted to a prolonged reversible ischemia, and does not seem to participate as mediator of LP. Aspirin revealed a similar COX-1 deleterious action, since only when both COX-1 and COX-2 were inhibited, LP was put in evidence adding functional improvement over that obtained in NP hearts treated with aspirin.

Animals↗
PubMed2006

The physiological changes of cumulative hemorrhagic shock in conscious rats.

Hemorrhagic shock is a common cause of death in emergency rooms. Current animal models of hemorrhage encounter a major problem that the volume and the rate of blood loss cannot be controlled. In addition, the use of anesthesia obscures physiological responses. Our experiments were designed to establish an animal model based on the clinical situation for studying hemorrhagic shock. Hemorrhagic shock was induced by withdrawing blood from a femoral arterial catheter. The blood volume withdrawn was 40% of the total blood volume for group 1 and 30% for group 2 and 3. Group 3 was anesthetized with sodium pentobarbital (25 mg/kg, i.v.) at the beginning of blood withdrawal. Our data showed that the survival rate was 87.5% at 48 h in the conscious group and 0% at 9 h in anesthetic group after hemorrhage. The levels of mean arterial pressure, heart rate, white blood count, TNF-alpha, IL1-beta, CPK, and LDH after blood withdrawal in the anesthetic group were generally lower than those in conscious groups. These results indicated that anesthetics significantly affected the physiology of experimental animals. The conscious, unrestrained and cumulative volume-controlled hemorrhagic shock model was a good experimental model to investigate the physical phenomenon without anesthetic interfernce.

Anesthesia↗