Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CONSCIOUSNESS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed1999

A 15O-H2O PET study of meditation and the resting state of normal consciousness.

The aim of the present study was to examine whether the neural structures subserving meditation can be reproducibly measured, and, if so, whether they are different from those supporting the resting state of normal consciousness. Cerebral blood flow distribution was investigated with the 15O-H20 PET technique in nine young adults, who were highly experienced yoga teachers, during the relaxation meditation (Yoga Nidra), and during the resting state of normal consciousness. In addition, global CBF was measured in two of the subjects. Spectral EEG analysis was performed throughout the investigations. In meditation, differential activity was seen, with the noticeable exception of V1, in the posterior sensory and associative cortices known to participate in imagery tasks. In the resting state of normal consciousness (compared with meditation as a baseline), differential activity was found in dorso-lateral and orbital frontal cortex, anterior cingulate gyri, left temporal gyri, left inferior parietal lobule, striatal and thalamic regions, pons and cerebellar vermis and hemispheres, structures thought to support an executive attentional network. The mean global flow remained unchanged for both subjects throughout the investigation (39+/-5 and 38+/-4 ml/100 g/min, uncorrected for partial volume effects). It is concluded that the (H2)15O PET method may measure CBF distribution in the meditative state as well as during the resting state of normal consciousness, and that characteristic patterns of neural activity support each state. These findings enhance our understanding of the neural basis of different aspects of consciousness.

Adult↗
PubMed2004

Comparison of consciousness level assessment in the poisoned patient using the alert/verbal/painful/unresponsive scale and the Glasgow Coma Scale.

STUDY OBJECTIVE: We determine how the alert/verbal/painful/unresponsive (AVPU) responsiveness scale (alert, responsive to verbal stimulation, responsive to painful stimulation, and unresponsive) corresponds to the Glasgow Coma Scale (GCS) when assessing consciousness level in the poisoned patient. METHODS: Consciousness level was assessed using the AVPU responsiveness scale and the GCS in all patients admitted to the hospital during a 6-month period with deliberate or accidental poisoning. An AVPU responsiveness scale algorithm and details of the individual components of the GCS were provided. Data were recorded prospectively on admission to the toxicology ward by nursing staff in the majority of cases and from case records for the small number of patients admitted directly to the ICU. Nursing staff also recorded any difficulty assessing consciousness level using either scoring system. RESULTS: Of the 1,384 patients studied, 1,138 patients were alert, 114 patients responded to a verbal stimulus, 87 patients responded to a painful stimulus, and 15 patients were unresponsive. The median GCS scores with interquartile ranges (IQR) for each AVPU responsiveness category were 15 (IQR 15), 13 (IQR 12 to 14), 8 (IQR 7 to 9), and 3 (IQR 3), respectively. There was a degree of overlap between the range of GCS scores for each category. Nursing staff recorded more difficulty using the GCS than the AVPU responsiveness scale. Alcohol-intoxicated patients proved to be the most difficult to assess. All patients who were unresponsive required intubation. No patient with a GCS score greater than 6 was intubated. CONCLUSION: Each AVPU category can be shown to correspond to a range of GCS scores. The AVPU responsiveness scale appears to provide a rapid simple method of assessing consciousness level in most poisoned patients, but difficulty was still observed in assessing alcohol-intoxicated patients.

Cohort Studies↗
PubMed2004

Mania as a dysfunction of reentry: application of Edelman's and Tononi's hypothesis for consciousness in relation to a psychiatric disorder.

The concept of reentry as the most important element in a hypothesis for consciousness proposed by Edelman and Tononi is reviewed. Reentry, is a process of ongoing parallel and recursive signalling between separate neuronal groups along parallel reciprocally fibers that link these groups anatomically. Reentry alters the activity of the target areas it interconnects until a synchronous activity across these areas is created, this may be the direct biological mechanism of consciousness. The repetitive process of reentry may explain how the millisecond time scale of neural signalling is turned into the time scale of seconds characterizing our impression of the duration of a given content of consciousness. It is suggested that reentry may be faster in mania, and specifically that the repetitive recursive signalling is faster in mania, hereby allowing reentry to produce a conscious state, faster than usual. Faster reentry may on a molecular level be caused by faster propagation of nerve impulses, which may be in accordance with a number of hypotheses where mania is seen as a disorder of ionic conductance, nerve cell excitability, action potential firing, membrane abnormalities, and cortical instability. Also the antiepileptic drugs used to treat mania may point to reentry as a factor in this disorder. On a more integrated level faster reentry processes may explain several of the core symptoms of the manic state. Also the drug induced switch from depression to mania in bipolar patients may be explained by the concept of reentry.

Bipolar Disorder↗
PubMed2006

A review of the literature on orientation as an indicator of level of consciousness.

PURPOSE: To review and compare the concepts of orientation and level of consciousness. METHODS: Literature review, including studies of orientation as an indicator of level of consciousness, in the domains of nursing, medicine, and neuropsychology. FINDINGS: Orientation to time, place, and person as a measure of level of consciousness is poorly understood. The nursing practice of assessing orientation is common in many practice settings, yet little research has been done to validate whether it is meaningful. CONCLUSIONS: This review lays important groundwork for future evidence-based research into the use of orientation as an indicator of level of consciousness.

Consciousness↗
PubMedDate not supplied

[Altered states of consciousness].

The review of modern ideas concerning the altered states of consciousness is presented in this article. Various methods of entry into the altered states of consciousness are looked over. It is shown that the altered states of consciousness are insufficiently known, but important aspects of human being existence. The role of investigation of the altered states of consciousness for the creation of integrative scientific conception base is discussed.

Autogenic Training↗
PubMedDate not supplied

[The asymmetrical brain--asymmetrical consciousness].

To substantiate a term "asymmetry of consciousness", to throw light on it are compared disturbances of consciousness in dextral and sinistral persons with selective lesions in the right or left brain hemispheres. Is supposed a fundamental role of the spatial-temporal factors. By them are mediated relations "brain-consciousness", asymmetry of consciousness. The latter is expressed in dextral persons by an opposite spatial-temporal organization of psycho-sensory (which are realized in individual present and past) and psychomotor (which are displayed in external present and future) processes. This contrast is not observed in sinistrals or only in some of them. Is assumed a probability of evolution of space and time with appearance of their forms having been absent before the human level. They are presumably described by the authors as individual space and time, on the one hand being determined by the functioning brain of each dextral and sinistral person, on the other hand defining the limits and limitations of the mental abilities of each person. Individual space and time may be other in a sinistral person than in a dextral one.

Consciousness↗
PubMed1977

[Development of the comprehension of localization in deranged consciousness].

The controversy between narrow localisationism and equipotentialism which exists even nowadays shows that these two trends are not in a position to solve the localisation problem. The attempts to localize consciousness either in the cortex or in the subcortex and the area of the third ventricle should be considered groundless, as well as the assumption that the cortex only gives the contents of consciousness while the source of consciousness is found in the area of the third ventricle. Consciousness represents the synthesis of the psychical activity. The basic weak points of both trends arise from the very formulation of the question discussed, from the striving to find the solution of the localisation problem without bearing in mind the physiological processes which lie in the basis of the higher psychical functions, i.e. behind the processes of the higher nervous activity, as well as from the incorrect understanding of the conceptions of "function" and "centre". Thanks to the school of I. P Pavlov and his followers the prerequistions have been created of a new trend in the field of the localisation problem--the teaching of the dynamic localisation of the cerebral function.

Action Potentials↗
PubMed2004

Auditory processing in severely brain injured patients: differences between the minimally conscious state and the persistent vegetative state.

BACKGROUND: The minimally conscious state (MCS) is a recently defined clinical condition; it differs from the persistent vegetative state (PVS) by the presence of inconsistent, but clearly discernible, behavioral evidence of consciousness. OBJECTIVE: To study auditory processing among patients who are in an MCS, patients who are in a PVS, and healthy control subjects. METHODS: By means of (15)O-radiolabeled water-positron emission tomography, we measured changes in regional cerebral blood flow induced by auditory click stimuli in 5 patients in an MCS, 15 patients in a PVS, and 18 healthy controls. RESULTS: In both patients in an MCS and the healthy controls, auditory stimulation activated bilateral superior temporal gyri (Brodmann areas 41, 42, and 22). In patients in a PVS, the activation was restricted to Brodmann areas 41 and 42 bilaterally. We also showed that, compared with patients in a PVS, patients in an MCS demonstrated a stronger functional connectivity between the secondary auditory cortex and temporal and prefrontal association cortices. CONCLUSIONS: Although assumptions about the level of consciousness in severely brain injured patients are difficult to make, our findings suggest that the cerebral activity observed in patients in an MCS is more likely to lead to higher-order integrative processes, thought to be necessary for the gain of conscious auditory perception.

Acoustic Stimulation↗
PubMed1993

Consciousness, schizophrenia and scientific theory.

The positive symptoms of acute schizophrenia are, of their very nature, aberrations of conscious experience. A recent theory of the mechanisms underlying their occurrence spans four levels: neuroanatomical, neurochemical, cognitive and the symptoms themselves. The theory is capable of being tested in animals and human subjects, and it has passed a number of experimental tests at both levels with success. Implications of the theory for the scientific treatment of consciousness are considered. Although the theory permits useful questions relating to consciousness to be put and even to some extent to be answered, it leaves the most basic issue--the theoretical link between the occurrence of conscious experience and the neural substrate of the brain--unresolved, as do all similar theories so far.

Animals↗
PubMed1993

The neural time factor in conscious and unconscious events.

Our earlier evidence had indicated that a substantial duration of appropriate cerebral activity (up to about 0.5 s) is required for the production of a conscious sensory experience; this means the sensory world is experienced delayed with respect to real time. Subjective timing of the experience can be retroactively referred to the time of the earliest signal arriving at the cortex. Our 'time-on' theory states that the transition from an unconscious to a conscious mental function is determined, at least in part, by an increase in the duration of appropriate neural activities. Our experimental finding that conscious intention to act appears only after a delay of about 350 ms from the onset of specific cerebral activity that precedes a voluntary act provided indirect evidence for the theory. In a direct experimental test a signal (stimulus to somatosensory thalamus) was correctly detected in a forced-choice test even when the stimulus duration was too short to produce any awareness of the signal; to go from correct detection with no awareness to detection with awareness required an additional 400 ms of the repetitive identical neural volleys ascending to sensory cortex. 'Time-on' theory has important implications for a variety of unconscious-conscious interactions.

Brain↗
PubMed1977

A divided mind: observations on the conscious properties of the separated hemispheres.

Each cerebral hemisphere in Patient O.S., a callosum-sectioned patient, appears to possess mental properties deserving of conscious status. The observations seem to answer many questions concerning the issue of whether the mechanisms of consciousness can be split and doubled by split-brain surgery. As P.S. is the first split-brain patient clearly to possess double conscious processes as well as the first with extensive bilateral linguistic skills, the observations suggest that the special nature of human conscious experience is closely tied to linguistic processes.

Child↗
PubMed1999

Conscious and unconscious processes: the effects of motivation.

The process-dissociation procedure has been used in a variety of experimental contexts to assess the contributions of conscious and unconscious processes to task performance. To evaluate whether motivation affects estimates of conscious and unconscious processes, participants were given incentives to follow inclusion and exclusion instructions in a perception task and a memory task. Relative to a control condition in which no performance incentives were given, the results for the perception task indicated that incentives increased the participants' ability to exclude previously presented information, which in turn both increased the estimate of conscious processes and decreased the estimate of unconscious processes. However, the results also indicated that incentives did not influence estimates of conscious or unconscious processes in the memory task. The findings suggest that the process-dissociation procedure is relatively immune to influences of motivation when used with a memory task, but that caution should be exercised when the process-dissociation is used with a perception task.

Analysis of Variance↗
PubMed1999

A software agent model of consciousness.

Baars (1988, 1997) has proposed a psychological theory of consciousness, called global workspace theory. The present study describes a software agent implementation of that theory, called "Conscious" Mattie (CMattie). CMattie operates in a clerical domain from within a UNIX operating system, sending messages and interpreting messages in natural language that organize seminars at a university. CMattie fleshes out global workspace theory with a detailed computational model that integrates contemporary architectures in cognitive science and artificial intelligence. Baars (1997) lists the psychological "facts that any complete theory of consciousness must explain" in his appendix to In the Theater of Consciousness; global workspace theory was designed to explain these "facts." The present article discusses how the design of CMattie accounts for these facts and thereby the extent to which it implements global workspace theory.

Cognition↗
PubMed2000

Vector subtraction implemented neurally: a neurocomputational model of some sequential cognitive and conscious processes.

Although great progress in neuroanatomy and physiology has occurred lately, we still cannot go directly to those levels to discover the neural mechanisms of higher cognition and consciousness. But we can use neurocomputational methods based on these details to push this project forward. Here we describe vector subtraction as an operation that computes sequential paths through high-dimensional vector spaces. Vector-space interpretations of network activity patterns are a fruitful resource in recent computational neuroscience. Vector subtraction also appears to be implemented neurally in primate frontal eye field activity, which computes dimensions of saccadic eye movements. We use this apparent neural implementation as a model and construct from it a general neurocomputational account of an important type of sequential cognitive and conscious process. We defend the biological plausibility of all components of the general model and show that it yields testable anatomical and physiological predictions. We close by suggesting some interesting consequences for consciousness if our model characterizes correctly the neural mechanisms producing a common type of episode in our conscious streams.

Cognition↗
PubMed2001

The central role of the parietal lobes in consciousness.

There are now various approaches to understand where and how in the brain consciousness arises from neural activity, none of which is universally accepted. Difficulties among these approaches are reviewed, and a missing ingredient is proposed here to help adjudicate between them, that of "perspectivalness." In addition to a suitable temporal duration and information content of the relevant bound brain activity, this extra component is posited as being a further important ingredient for the creation of consciousness from neural activity. It guides the development of what is termed the "Central Representation," which is supposed to be present in all mammals and extended in humans to support self-consciousness as well as phenomenal consciousness. Experimental evidence and a theoretical framework for the existence of the central representation are presented, which relates the extra component to specific buffer working memory sites in the inferior parietal lobes, acting as attentional coordinators on the spatial maps making up the central representation. The article closes with a discussion of various open questions.

Attention↗
PubMed2002

The time of consciousness and vice versa.

The temporal granularity of consciousness may be far less fine than the real-time information processing mechanisms that underlie our sensitivity to small temporal differences. It is suggested that conscious time perception, like space perception, is subject to errors that belie a unitary underlying representation. E. R. Clay's (The Alternative: A Study in Psychology, 1882) concept of the "specious present," an extended moment represented in consciousness, is suggested as an alternative to the more common notion of instantaneous experience that underlies much reasoning based on the "time of arrival" in consciousness.

Chronobiology Phenomena↗
PubMed1997

On the coevolution of cognition and consciousness.

In this article it is argued that an evolutionary perspective leads to the view that adaptation and learning is a widespread and old property of living organisms, even as old as life itself. Cognition, defined as knowledge processing mediated by a centralised nervous system, is suggested mainly to be based on the same principles as non-neural adaptive processes. The emergence of conscious cognition, however, is seen as a major transition in the evolution of life, although it appears in different degrees and at various stages in evolution. Both cognition and consciousness depend on the organisation and complexity of the organism, primarily with regard to the nervous system. Computational and neurophysiological approaches are discussed, in particular some experimental attempts to determine anatomical, physiological and physical correlates to consciousness. It is argued that an evolutionary perspective suggests an interactionistic solution to the mind-brain problem, i.e. the question of subjective experience. In an interactionistic perspective consciousness can be understandable as a biological phenomenon. It can be regarded as a driving force in evolution, amplifying and improving the adaptive and cognitive processes of an organism.

Biological Evolution↗
PubMed1997

Consciousness and biological evolution.

It has been suggested that if the preservation and development of consciousness in the biological evolution is a result of natural selection, it is plausible that consciousness not only has been influenced by neural processes, but has had a survival value itself; and it could only have had this, if it had also been efficacious. This argument for mind-brain interaction is examined, both as the argument has been developed by William James and Karl Popper and as it has been discussed by C.D. Broad. The problem of identifying mental phenomena with certain neural phenomena is also addressed. The main conclusion of the analysis is that an explanation of the evolution of consciousness in Darwinian terms of natural selection does not rule out that consciousness may have evolved as a mere causally inert effect of the evolution of the nervous system, or that mental phenomena are identical with certain neural phenomena. However, the interactionistic theory still seems, more plausible and more fruitful for other reasons brought up in the discussion.

Biological Evolution↗