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PubMed2000

The feeling of knowing: some metatheoretical implications for consciousness and control.

The study of the feeling of knowing may have implications for some of the metatheoretical issues concerning consciousness and control. Assuming a distinction between information-based and experience-based metacognitive judgments, it is argued that the sheer phenomenological experience of knowing ("noetic feeling") occupies a unique role in mediating between implicit-automatic processes, on the one hand, and explicit-controlled processes, on the other. Rather than reflecting direct access to memory traces, noetic feelings are based on inferential heuristics that operate implicitly and unintentionally. Once such heuristics give rise to a conscious feeling that feeling can then affect controlled action. Examination of the cues that affect noetic feelings suggest that not only do these feelings inform controlled action, but they are also informed by feedback from the outcome of that action.

Cognition↗
PubMed2001

Consciousness in schizophrenia: a metacognitive approach to semantic memory.

Recent studies have shown that schizophrenia may be a disease affecting the states of consciousness. The present study is aimed at investigating metamemory, i.e., the knowledge about one's own memory capabilities, in patients with schizophrenia. The accuracy of the Confidence level (CL) in the correctness of the answers provided during a recall phase, and the predictability of the Feeling of Knowing (FOK) when recall fails were measured using a task consisting of general information questions and assessing semantic memory. Nineteen outpatients were paired with 19 control subjects with respect to age, sex, and education. Results showed that patients with schizophrenia exhibited an impaired semantic memory. CL ratings as well as CL and FOK accuracy were not significantly different in the schizophrenic and the control groups. However, FOK ratings were significantly reduced for the patient group, and discordant FOK judgments were also observed more frequently. Such results suggest that FOK judgments are impaired in patients with schizophrenia, which confirms that schizophrenia is an illness characterized by an impaired conscious awareness of one's own knowledge.

Adult↗
PubMed2001

On the correlation between synchronized oscillatory activities and consciousness.

Recent experiments have shown that the amplitudes of cortical gamma band oscillatory activities that occur during anesthesia are often greater than amplitudes of similar activities that occur without anesthesia. This result is apparently at odds with the hypothesis that synchronized oscillatory activities constitute the neural correlate of consciousness. We argue that while synchronization and oscillatory patterning are necessary conditions for consciousness, they are not sufficient. Based on the results of a binocular rivalry study of Fries et al. (1997), we propose that the degrees of oscillatory strength and synchronization of neuronal activities determine the degree of awareness those activities produce. On the other hand, the overal firing rates of neurons in cortical sensory areas are not correlated with the degree of awareness the activities of those neurons produce. The results of the experiment of Fries et al. (1997) appear to conflict with the results of another binocular rivalry experiment, in which monkeys were trained to pull a lever in order to report which stimulus object was being perceived (Leopold & Logothetis, 1996). In the latter experiment, it was demonstrated that the firing rates of neurons in striate cortex did not change during perceptual alterations, while 90% of neurons in inferior and superior temporal cortices changed their firing rate when the perceived image changed. This result led to the conclusion that activities in temporal cortex are correlated with visual awareness, but those in striate cortex are not. We argue that activities in temporal cortex contribute little, if anything, to perceptual awareness, and that their primary function is computational. Thus the correlation between the firing rates of neurons in these areas and the responses of the monkeys is due to the recognition of a particular stimulus object, which in turn is due to the computations made there.

Awareness↗
PubMed2002

Consciousness and control in task switching.

Participants were required to switch among randomly ordered tasks, and instructional cues were used to indicate which task to execute. In Experiments 1 and 2, the participants indicated their readiness for the task switch before they received the target stimulus; thus, each trial was associated with two primary dependent measures: (1) readiness time and (2) target reaction time. Slow readiness responses and instructions emphasizing high readiness were paradoxically accompanied by slow target reaction time. Moreover, the effect of task switching on readiness time was an order of magnitude smaller then the (objectively estimated) duration required for task preparation (Experiment 3). The results strongly suggest that participants have little conscious awareness of their preparedness and challenge commonly accepted assumptions concerning the role of consciousness in cognitive control.

Analysis of Variance↗
PubMed2002

In support of Pockett's critique of Libet's studies of the time course of consciousness.

Susan Pockett presents sound arguments supporting her reinterpretations of data that Libet and co-workers used to support a number of intriguing and influential conclusions regarding the microgenesis and timing of (a) conscious sensory experience and (b) volitionally controlled motor responses. The following analysis, extending and elaborating some of her main arguments, proposes that Libet's experimental methodologies and rationales, and thus also his interpretation of data, are flawed and that neglect or ignorance of methodological and empirical constraints well known to sensory psychologists risks drawing premature or faulty conclusions about the timing of conscious experience.

Chronobiology Phenomena↗
PubMed1994

A possible neural mechanism underlying consciousness based on the pattern processing capabilities of pyramidal neurons in the cerebral cortex.

This paper examines a possible neural mechanism underlying the phenomenon of consciousness by exploring the ability of cortical pyramidal cells to process patterns of information. A numerical model of a section of a neuron is described that enables the transient membrane potential distribution to be predicted following inputs to the cell. The neuron model incorporates learning by modelling the ability of dendritic spine receptors to undergo changes in their sensitivity if they receive inputs when their local membrane is depolarized. Simulations show the cell to be capable of recognizing patterns amongst its inputs, and to be able to extend its repertoire of learnt patterns by associating one pattern of inputs with another. These pattern processing capabilities can take place within the apical dendritic tree, whilst the soma sees a much attenuated and slower response that reflects the general level of pattern recognition taking place in the dendrites. It is argued here that the distribution of patterns stored in the apical dendrites of all the pyramidal cells represents the cortical knowledge base. Incoming patterns of information are compared with those stored in the cortical knowledge base to pick out components that have been experienced before. The resulting distribution of soma responses represents the way the incoming patterns of information are perceived. Most of the patterns learnt arise from other pyramidals and represent information about cortical behaviour itself. The distribution of soma responses therefore represents a perception of the self as well as a perception of the environment. It is argued here that this intimate perception of the self could underlie the phenomenon of consciousness.

Cerebral Cortex↗
PubMed1987

The origin of the human mind. A speculation on the emergence of language and human consciousness.

The study of human evolution has attracted scientists of various disciplines, judging by the attendance of the conferences devoted to it, and by the publications concerned. In the course of years I became amazed about the seeming absence of a synthesis of the available information. This article presents an attempt to combine some results of the various publications. The study of human evolution has become particularly focussed on the emergence of language and human consciousness with respect to the social behaviour and mental capacities of our closest relatives: the apes. Social relations imply communication, and mentation underlies the ability to communicate. The more it becomes apparent that the social behaviour of the apes resembles that of man in many respects, the greater the danger that typically, and perhaps even uniquely, human traits are ascribed to anthropoids. Anthropomorphic descriptions of animal behaviour tend to prevent a clear view on animal mentality. It will be argued that there is no direct evolutionary link between the apes' communication systems and language. Neither the language experiments, nor the speculations on the evolution of social behaviour have, so far, presented a basis for the explantation of the corresponding evolution of the neurological substrate of mentality, i.e. the central nervous system. It will be argued, instead, that language and human consciousness are rooted in a socially nonfunctional preadaptation that gave rise to their essentially independent evolution.

Animal Communication↗
PubMed1983

Effects of short-lasting and long-lasting blood pressure changes on the release of endogenous catecholamines in the hypothalamus of the conscious, freely moving rabbit.

In anaesthetized rabbits guide cannulae were stereotaxically inserted into the anterior hypothalamic area and into the posterior hypothalamic nucleus. Additionally, catheters were inserted into the carotid artery and the jugular vein. Some days after the operation push-pull cannulae were inserted through the guide cannulae into the hypothalamic regions of the conscious, freely moving animal. The areas were superfused with artificial CSF and the release of the endogenous catecholamines dopamine, noradrenaline and adrenaline was determined in the superfusates. In the two hypothalamic regions the resting release of the catecholamines rhythmically varied with time at approximately 70 min cycles. A rise in blood pressure induced by the intravenous injection of noradrenaline or tramazoline enhanced the rates of release of the catecholamines in the anterior hypothalamic area. A fall of blood pressure elicited by the intravenous injection of nitroprusside or chlorisondamine decreased the release of the catecholamines in this hypothalamic area. The changes in blood pressure coincided with the changes in the rates of release of the catecholamines in the anterior hypothalamic area. These and previous results concerning changes in the release of endogenous catecholamines in the posterior hypothalamic nucleus also indicate that in the conscious, freely moving rabbit changes in blood pressure lead to counteracting alterations in the release of catecholamines in the two hypothalamic regions.

Animals↗
PubMed1983

Estimation of glomerular filtration rate in conscious dogs following a bolus of creatinine. Comparison with simultaneously determined inulin clearance.

The renal clearance of creatinine was measured following orogastric administration in conscious dogs. Values of creatinine clearance were compared with simultaneously determined values of inulin clearance, when urine volume, glomerular filtration rate and volume status were acutely altered by a variety of experimental manoeuvres. At urine volumes greater than 20 microliters X min-1 X kg-1, creatinine clearance was not significantly different from inulin clearance. At low urine volumes there was some evidence of creatinine reabsorption. It is concluded that the bolus creatinine technique provides reliable estimates of glomerular filtration rate and is particularly applicable to long-term studies in conscious dogs.

Animals↗
PubMed1989

Central angiotensin II stimulates arteriolar vasomotion in conscious hamsters.

The effects of intracerebroventricular (icv) injections of 10 ng angiotensin II (ANG II) on mean arteriolar diameter and spontaneous arteriolar vasomotion were studied in subcutaneous tissue of conscious, restrained hamsters, using the skin fold window chamber preparation. Angiotensin II caused a significant decrease in mean arteriolar diameter which was associated with a significant elevation in the amplitude of vasomotion. The frequency of vasomotion did not change significantly. The central ANG II-induced effects on arteriolar vasomotion were not significantly altered by continuous intravenous (iv) infusion of hexamethonium (1 mg.kg-1.min-1). In contrast, iv bolus injection of the vascular vasopressin receptor antagonist d(CH2)5Tyr(Me)AVP (10 micrograms.kg-1) 5 min prior to icv injection of ANG II significantly attenuated the effects of the neuropeptide on mean arteriolar diameter and the amplitude of vasomotion. These data indicate that central ANG II stimulation enhances arteriolar vasomotion in peripheral subcutaneous tissue of conscious hamsters and that this effect may be mediated by release of vasopressin.

Angiotensin II↗
PubMed1996

Hyponatremia with consciousness disturbance caused by omeprazole administration. A case report and literature review.

A 68-year-old man developed severe consciousness disturbance after daily administration of 20 mg omeprazole for four days for the treatment of bleeding gastric ulcer. Systemic investigation revealed severe hyponatremia (111 meq/liter). Consciousness did not become clear until his sodium intake was increased to 480 meq/day, and his serum sodium concentrations reached 130 meq/liter. After the discontinuation of omeprazole, his serum sodium levels returned to the normal range with only minimum supplementation of sodium in the form of dietary sodium chloride intake of 10 g/day. Although the mechanism of hyponatremia induced by omeprazole is not clear, an excessive loss of urinary sodium appears to be more likely than water retention with an increase in fluid intake. The literature was also reviewed.

Aged↗
PubMedDate not supplied

Problems of the analysis of altered states of consciousness.

It is assumed on the basis of data that have been obtained that altered states of consciousness (ASC) arise during the performance of operator activity under conditions of monotony, when modulating influences in the minute range of fluctuations are experienced in the process. This modulation promotes the attenuation or intensification of the degree of ASC; this is reflected in corresponding shifts in attention and in the quality of operator actions relating to recognition of visual images. These results point to the important role of the modulating system of the brain, and of its infraslow wave manifestations in the activity of consciousness whose content is determined by informational processes.

Adult↗
PubMed2001

Cocaine-induced brain activation determined by positron emission tomography neuroimaging in conscious rhesus monkeys.

RATIONALE: Cerebral blood flow can provide a useful dependent measure to characterize cocaine-induced changes in brain function. The acute effects of cocaine administration on cerebral blood flow may have direct relevance to the etiology of cocaine addiction. OBJECTIVES: The present study used positron emission tomography (PET) neuroimaging techniques to characterize the acute effects of cocaine administration on cerebral blood flow in conscious rhesus monkeys. METHODS: Functional changes in cerebral blood flow were determined in four drug-naive subjects with the positron-emitting tracer 15O water following acute i.v. administration of cocaine (0.3 and 1.0 mg/kg). Specific attention was devoted to the development of an effective and comfortable head restraint device to use in the imaging of conscious monkeys. Experimental sessions comprised eight consecutive i.v. injections of 15O water at 10-min intervals. PET scans of 90 s duration occurred 10 s after each injection. RESULTS: Repeated baseline determinations of cerebral blood flow prior to drug administration were reliable. Cocaine had significant, dose-related effects on cerebral blood flow at 5 min postinjection that diminished relative to control (saline) conditions by 15 min postinjection. Brain activation maps normalized to global flow showed prominent cocaine-induced activation of prefrontal cortex localized primarily to dorsolateral regions. Importantly, cocaine-induced brain activation was blocked by pretreatment with the selective serotonin uptake inhibitor, alaproclate (3.0 and 10.0 mg/kg). The results document a distinct pattern of cocaine-induced brain activation that is sensitive to pharmacological manipulation. CONCLUSION: The pattern of brain activation induced by acute administration of cocaine may provide a useful means to evaluate medication effectiveness for treating cocaine addiction.

Animals↗
PubMed2006

Systemic and renal hemodynamic effects of the AT1 receptor antagonist, ZD 7155, and the AT2 receptor antagonist, PD 123319, in conscious lambs.

Experiments were carried out to investigate age- and dose-dependent effects of the selective AT(1) receptor antagonist, ZD 7155, and the selective AT(2) receptor antagonist, PD 123319, on systemic and renal hemodynamics in conscious, chronically instrumented lambs aged approximately 1 and approximately 6 weeks of postnatal life. Mean arterial pressure (MAP), mean venous pressure (MVP), and renal blood flow (RBF) were measured for 10 min before and for 120 min after ZD 7155, PD 123319, or vehicle. In both age groups, administration of ZD 7155 decreased renal vascular resistance (RVR) and increased RBF within 5 min. These responses lasted less than 90 min but were not dose-dependent. MAP decreased by 30 min after administration of ZD 7155 in both age groups at doses >/=400 microg kg(-1); the remaining decreased for up to 120 min, depending upon the dose. Pressor responses to angiotensin II (ANG II) were abolished within 5 min of administration of all doses of ZD 7155, at both 1- and 6 weeks. PD 123319 had no detectable effects on systemic or renal hemodynamics or on the pressor responses to ANG II. Therefore, under physiological conditions in conscious newborn animals, ANG II modulates both resting blood pressure and RVR through activation of AT(1) but not AT(2) receptors.

Angiotensin II↗
PubMed2005

Statistical approaches to language acquisition and the self-organizing consciousness: a reversal of perspective.

Recent years have seen the upsurge of a new approach to language that moves away from the rule-based conventional framework. In this approach, mostly supported by the success of connectionist models, children learn language by exploiting the distributional properties of the input. It is argued in this paper that, in the same way as conforming to rules does not imply the existence of mental rules, conforming to statistical regularities does not imply that statistical computations are performed mentally. Sensitivity to statistical regularities can alternatively be conceived of as a by-product of the recurrent interplay between the properties of the current conscious content and the properties of the linguistic and extralinguistic environment. The validity of including the content of conscious experiences in an otherwise standard dynamical approach rooted in the notion of self-organization is discussed.

Consciousness↗
PubMed2001

Effect of prepyloric gastric transection and anastomosis on sphincter of Oddi cyclic motility in conscious dogs.

PURPOSE: We previously reported significant changes in sphincter of Oddi cyclic motility after proximal duodenal transection and anastomosis. However, the role of intrinsic myoneural continuity between the antrum and duodenum in this respect is not understood. The aim of this study was to elucidate the effects of prepyloric gastric transection on sphincter of Oddi motility in animals in the conscious state. METHODS: Pressures in the bile duct, duodenum, stomach, and sphincter of Oddi and their response to an injection of cholecystokinin-octapeptide were measured in four conscious dogs, with a duodenal cannula, before and after gastric transection and anastomosis 1.5 cm proximal to the pylorus. RESULTS: Gastric transection did not affect the initiation and propagation of the gastroduodenal migration motor complex. Biliary pressure (5.7 +/- 0.15 to 5.5 +/- 0.2 mmHg; P = 0.91), sphincter of Oddi basal pressure (10.6 +/- 0.3 to 10.7 +/- 0.2 mmHg; P = 0.97), and amplitude (26.0 +/- 1.2 to 32.9 +/- 1.7 mmHg; P = 0.304) did not change after gastric transection. Biliary pressure decreased from phase II to phase III of the duodenal migrating motor complex. Cholecystokinin-octapeptide inhibited sphincter of Oddi phasic waves before and after gastric transection. CONCLUSIONS: Intrinsic myoneural transection at the prepyloric region does not influence sphincter of Oddi cyclic motility. Preservation of pyloroduodenal myoneural continuity in pylorus-preserving gastrectomy would be beneficial to maintain normal sphincter of Oddi motility.

Anastomosis, Surgical↗
PubMed2001

Sleepiness, troika of consciousness cycle, and the Epworth sleepiness scale.

Excessive daytime sleepiness (EDS) is an important indicator when diagnosing sleep-disordered breathing and evaluating its treatment results. However, there appears to be some confusion as to what exactly is sleepiness; Dorland's Illustrated Medical Dictionary does not help. The medical literature was reviewed in order to assemble a schematic model that would suggest a definition of sleepiness and how it can be measured. The derived model is entitled the troika of consciousness cycle (TCC). It assumes that the presence of wakefulness, nonrapid eye movement sleep (NREMS), and rapid eye movement sleep (REMS) is determined by the interactions of four drives: two promoting wakefulness and one each for the two sleep states. The TCC illustrates that inadequate sleep results in sleep debt, but that sleepiness is determined solely by the nearness of the secondary wake drive line to the NREMS drive line. Contact of these lines indicates dozing, a change in consciousness state, an observable event. The probability of this event may be defined as objective sleepiness; this is what the Epworth sleepiness scale (ESS) attempts to measure. Studies indicate that the ESS can determine EDS with greater sensitivity and selectivity than either the multiple sleep latency test or the maintenance of wakefulness test.

Activity Cycles↗
PubMed2006

Mapping slow waves and spikes in chronically instrumented conscious dogs: implantation techniques and recordings.

Myoelectric recordings from the intestines in conscious animals have been limited to a few electrode sites with relatively large inter-electrode distances. The aim of this project was to increase the number of recording sites to allow high-resolution reconstruction of the propagation of myoelectrical signals. Sets of six unipolar electrodes, positioned in a 3x2 array, were constructed. A silver ring close to each set served as the reference electrodes. Inter-electrode distances varied from 4 to 8 mm. Electrode sets, to a maximum of 4, were implanted in various configurations allowing recording from 24 sites simultaneously. Four sets of 6 electrodes each were implanted successfully in 11 female Beagles. Implantation sites evaluated were the upper small intestine (n=10), the lower small intestine (n=4) and the stomach (n=3). The implants remained functional for 7.2 months (median; range 1.4-27.3 months). Recorded signals showed slow waves at regular intervals and spike potentials. In addition, when the sets were positioned close together, it was possible to re-construct the propagation of individual slow waves, to determine their direction of propagation and to calculate their propagation velocity. No signs or symptoms of interference with normal GI-function were observed in the tested animals. With this approach, it is possible to implant 24 extracellular electrodes on the serosal surface of the intestines without interfering with its normal physiology. This approach makes it possible to study the electrical activities of the GI system at high resolution in vivo in the conscious animal.

Action Potentials↗