601
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Delle Fave A, Soosai-Nathan L. Meaning as inter-connectedness: theoretical perspectives and empirical evidence. JOURNAL OF PSYCHOLOGY IN AFRICA 2014. [DOI: 10.1080/14330237.2014.904090] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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602
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Paller KA, Suzuki S. The source of consciousness. Trends Cogn Sci 2014; 18:387-9. [PMID: 25023451 DOI: 10.1016/j.tics.2014.05.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 05/14/2014] [Accepted: 05/27/2014] [Indexed: 11/17/2022]
Abstract
Why does a relentless stream of experiences normally fill your mind? No answer is entirely satisfactory. We are not sure how the normal operation of the human brain might exude subjective experiences. Consciousness can thus seem miraculous, and research on consciousness a waste of time and money, ultimately doomed to fail. Yet, there are good reasons for optimism that should be shared with the public to justify research in this area.
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Affiliation(s)
- Ken A Paller
- Department of Psychology and Interdepartmental Neuroscience Program, Northwestern University, Evanston, IL 60208-2710, USA.
| | - Satoru Suzuki
- Department of Psychology and Interdepartmental Neuroscience Program, Northwestern University, Evanston, IL 60208-2710, USA.
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603
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Les mécanismes de la conscience. MEDECINE INTENSIVE REANIMATION 2014. [DOI: 10.1007/s13546-014-0898-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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604
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Automation of anaesthesia: a review on multivariable control. J Clin Monit Comput 2014; 29:231-9. [DOI: 10.1007/s10877-014-9590-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2013] [Accepted: 06/03/2014] [Indexed: 12/19/2022]
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605
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Abstract
Significant advances have been made in the behavioral assessment and clinical management of disorders of consciousness (DOC). In addition, functional neuroimaging paradigms are now available to help assess consciousness levels in this challenging patient population. The success of these neuroimaging approaches as diagnostic markers is, however, intrinsically linked to understanding the relationships between consciousness and the brain. In this context, a combined theoretical approach to neuroimaging studies is needed. The promise of such theoretically based markers is illustrated by recent findings that used a perturbational approach to assess the levels of consciousness. Further research on the contents of consciousness in DOC is also needed.
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Affiliation(s)
- Olivia Gosseries
- Coma Science Group, Cyclotron Research Center and Neurology Department, University of Liege, and University Hospital of Liege, 4000 Liege, Belgium; , , ,
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606
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Mashour GA. Top-down mechanisms of anesthetic-induced unconsciousness. Front Syst Neurosci 2014; 8:115. [PMID: 25002838 PMCID: PMC4066704 DOI: 10.3389/fnsys.2014.00115] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 05/27/2014] [Indexed: 11/18/2022] Open
Abstract
The question of how structurally and pharmacologically diverse general anesthetics disrupt consciousness has persisted since the nineteenth century. There has traditionally been a significant focus on “bottom-up” mechanisms of anesthetic action, in terms of sensory processing, arousal systems, and structural scales. However, recent evidence suggests that the neural mechanisms of anesthetic-induced unconsciousness may involve a “top-down” process, which parallels current perspectives on the neurobiology of conscious experience itself. This article considers various arguments for top-down mechanisms of anesthetic-induced unconsciousness, with a focus on sensory processing and sleep-wake networks. Furthermore, recent theoretical work is discussed to highlight the possibility that top-down explanations may be causally sufficient, even assuming critical bottom-up events.
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Affiliation(s)
- George A Mashour
- Neuroscience Graduate Program, Department of Anesthesiology, Center for Consciousness Science, University of Michigan Medical School Ann Arbor, MI, USA
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607
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Sitt JD, King JR, El Karoui I, Rohaut B, Faugeras F, Gramfort A, Cohen L, Sigman M, Dehaene S, Naccache L. Large scale screening of neural signatures of consciousness in patients in a vegetative or minimally conscious state. ACTA ACUST UNITED AC 2014; 137:2258-70. [PMID: 24919971 DOI: 10.1093/brain/awu141] [Citation(s) in RCA: 317] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In recent years, numerous electrophysiological signatures of consciousness have been proposed. Here, we perform a systematic analysis of these electroencephalography markers by quantifying their efficiency in differentiating patients in a vegetative state from those in a minimally conscious or conscious state. Capitalizing on a review of previous experiments and current theories, we identify a series of measures that can be organized into four dimensions: (i) event-related potentials versus ongoing electroencephalography activity; (ii) local dynamics versus inter-electrode information exchange; (iii) spectral patterns versus information complexity; and (iv) average versus fluctuations over the recording session. We analysed a large set of 181 high-density electroencephalography recordings acquired in a 30 minutes protocol. We show that low-frequency power, electroencephalography complexity, and information exchange constitute the most reliable signatures of the conscious state. When combined, these measures synergize to allow an automatic classification of patients' state of consciousness.
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Affiliation(s)
- Jacobo Diego Sitt
- 1 Cognitive Neuroimaging Unit, Institut National de la Santé et de la Recherche Médicale, U992, F-91191 Gif/Yvette, France2 NeuroSpin Centre, Institute of BioImaging Commissariat à l'Energie Atomique, F-91191 Gif/Yvette, France3 Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France
| | - Jean-Remi King
- 1 Cognitive Neuroimaging Unit, Institut National de la Santé et de la Recherche Médicale, U992, F-91191 Gif/Yvette, France2 NeuroSpin Centre, Institute of BioImaging Commissariat à l'Energie Atomique, F-91191 Gif/Yvette, France3 Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France
| | - Imen El Karoui
- 3 Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France
| | - Benjamin Rohaut
- 3 Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France4 AP-HP, Groupe hospitalier Pitié-Salpêtrière, Department of Neurology, Intensive Care Unit, Paris, France
| | - Frederic Faugeras
- 3 Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France5 AP-HP, Groupe hospitalier Pitié-Salpêtrière, Department of Neurophysiology, Paris, France
| | - Alexandre Gramfort
- 2 NeuroSpin Centre, Institute of BioImaging Commissariat à l'Energie Atomique, F-91191 Gif/Yvette, France6 Institut Mines-Télécom, Télécom ParisTech, CNRS LTCI, France
| | - Laurent Cohen
- 3 Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France4 AP-HP, Groupe hospitalier Pitié-Salpêtrière, Department of Neurology, Intensive Care Unit, Paris, France
| | - Mariano Sigman
- 7 Integrative Neuroscience Laboratory, Physics Department, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina8 Universidad Torcuato Di Tella, Almirante Juan Saenz Valiente 1010, C1428BIJ Buenos Aires, Argentina
| | - Stanislas Dehaene
- 1 Cognitive Neuroimaging Unit, Institut National de la Santé et de la Recherche Médicale, U992, F-91191 Gif/Yvette, France2 NeuroSpin Centre, Institute of BioImaging Commissariat à l'Energie Atomique, F-91191 Gif/Yvette, France9 Université Paris 11, Orsay, France10 Collège de France, F-75005 Paris, France
| | - Lionel Naccache
- 3 Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France5 AP-HP, Groupe hospitalier Pitié-Salpêtrière, Department of Neurophysiology, Paris, France
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608
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Hudetz AG, Liu X, Pillay S. Dynamic repertoire of intrinsic brain states is reduced in propofol-induced unconsciousness. Brain Connect 2014; 5:10-22. [PMID: 24702200 DOI: 10.1089/brain.2014.0230] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The richness of conscious experience is thought to scale with the size of the repertoire of causal brain states, and it may be diminished in anesthesia. We estimated the state repertoire from dynamic analysis of intrinsic functional brain networks in conscious sedated and unconscious anesthetized rats. Functional resonance images were obtained from 30-min whole-brain resting-state blood oxygen level-dependent (BOLD) signals at propofol infusion rates of 20 and 40 mg/kg/h, intravenously. Dynamic brain networks were defined at the voxel level by sliding window analysis of regional homogeneity (ReHo) or coincident threshold crossings (CTC) of the BOLD signal acquired in nine sagittal slices. The state repertoire was characterized by the temporal variance of the number of voxels with significant ReHo or positive CTC. From low to high propofol dose, the temporal variances of ReHo and CTC were reduced by 78% ± 20% and 76%± 20%, respectively. Both baseline and propofol-induced reduction of CTC temporal variance increased from lateral to medial position. Group analysis showed a 20% reduction in the number of unique states at the higher propofol dose. Analysis of temporal variance in 12 anatomically defined regions of interest predicted that the largest changes occurred in visual cortex, parietal cortex, and caudate-putamen. The results suggest that the repertoire of large-scale brain states derived from the spatiotemporal dynamics of intrinsic networks is substantially reduced at an anesthetic dose associated with loss of consciousness.
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Affiliation(s)
- Anthony G Hudetz
- Department of Anesthesiology, Medical College of Wisconsin , Milwaukee, Wisconsin
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609
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Oizumi M, Albantakis L, Tononi G. From the phenomenology to the mechanisms of consciousness: Integrated Information Theory 3.0. PLoS Comput Biol 2014; 10:e1003588. [PMID: 24811198 PMCID: PMC4014402 DOI: 10.1371/journal.pcbi.1003588] [Citation(s) in RCA: 409] [Impact Index Per Article: 40.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Accepted: 03/11/2014] [Indexed: 12/27/2022] Open
Abstract
This paper presents Integrated Information Theory (IIT) of consciousness 3.0, which incorporates several advances over previous formulations. IIT starts from phenomenological axioms: information says that each experience is specific--it is what it is by how it differs from alternative experiences; integration says that it is unified--irreducible to non-interdependent components; exclusion says that it has unique borders and a particular spatio-temporal grain. These axioms are formalized into postulates that prescribe how physical mechanisms, such as neurons or logic gates, must be configured to generate experience (phenomenology). The postulates are used to define intrinsic information as "differences that make a difference" within a system, and integrated information as information specified by a whole that cannot be reduced to that specified by its parts. By applying the postulates both at the level of individual mechanisms and at the level of systems of mechanisms, IIT arrives at an identity: an experience is a maximally irreducible conceptual structure (MICS, a constellation of concepts in qualia space), and the set of elements that generates it constitutes a complex. According to IIT, a MICS specifies the quality of an experience and integrated information ΦMax its quantity. From the theory follow several results, including: a system of mechanisms may condense into a major complex and non-overlapping minor complexes; the concepts that specify the quality of an experience are always about the complex itself and relate only indirectly to the external environment; anatomical connectivity influences complexes and associated MICS; a complex can generate a MICS even if its elements are inactive; simple systems can be minimally conscious; complicated systems can be unconscious; there can be true "zombies"--unconscious feed-forward systems that are functionally equivalent to conscious complexes.
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Affiliation(s)
- Masafumi Oizumi
- Department of Psychiatry, University of Wisconsin, Madison, Wisconsin, United States of America
- RIKEN Brain Science Institute, Wako-shi, Saitama, Japan
| | - Larissa Albantakis
- Department of Psychiatry, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Giulio Tononi
- Department of Psychiatry, University of Wisconsin, Madison, Wisconsin, United States of America
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610
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Peng Z, Genewein T, Braun DA. Assessing randomness and complexity in human motion trajectories through analysis of symbolic sequences. Front Hum Neurosci 2014; 8:168. [PMID: 24744716 PMCID: PMC3978291 DOI: 10.3389/fnhum.2014.00168] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 03/07/2014] [Indexed: 11/23/2022] Open
Abstract
Complexity is a hallmark of intelligent behavior consisting both of regular patterns and random variation. To quantitatively assess the complexity and randomness of human motion, we designed a motor task in which we translated subjects' motion trajectories into strings of symbol sequences. In the first part of the experiment participants were asked to perform self-paced movements to create repetitive patterns, copy pre-specified letter sequences, and generate random movements. To investigate whether the degree of randomness can be manipulated, in the second part of the experiment participants were asked to perform unpredictable movements in the context of a pursuit game, where they received feedback from an online Bayesian predictor guessing their next move. We analyzed symbol sequences representing subjects' motion trajectories with five common complexity measures: predictability, compressibility, approximate entropy, Lempel-Ziv complexity, as well as effective measure complexity. We found that subjects' self-created patterns were the most complex, followed by drawing movements of letters and self-paced random motion. We also found that participants could change the randomness of their behavior depending on context and feedback. Our results suggest that humans can adjust both complexity and regularity in different movement types and contexts and that this can be assessed with information-theoretic measures of the symbolic sequences generated from movement trajectories.
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Affiliation(s)
- Zhen Peng
- Max Planck Institute for Biological Cybernetics Tübingen, Germany ; Max Planck Institute for Intelligent Systems Tübingen, Germany ; Graduate Training Centre of Neuroscience Tübingen, Germany
| | - Tim Genewein
- Max Planck Institute for Biological Cybernetics Tübingen, Germany ; Max Planck Institute for Intelligent Systems Tübingen, Germany ; Graduate Training Centre of Neuroscience Tübingen, Germany
| | - Daniel A Braun
- Max Planck Institute for Biological Cybernetics Tübingen, Germany ; Max Planck Institute for Intelligent Systems Tübingen, Germany
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611
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Affiliation(s)
- Nicholas D Schiff
- Feil Family Brain Mind Institute, Weill Cornell Medical College, New York, NY 10065, USA.
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612
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Very early processing of emotional words revealed in temporoparietal junctions of both hemispheres by EEG and TMS. Exp Brain Res 2014; 232:1267-81. [PMID: 24496490 DOI: 10.1007/s00221-014-3843-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Accepted: 01/10/2014] [Indexed: 10/25/2022]
Abstract
We investigate the contribution of both hemispheres in a lateralised lexical decision paradigm with emotional and neutral words in healthy volunteers. In a first experiment, high-density EEG analysis using source imaging methods revealed early specific participation of the temporoparietal junctions (TPJ) in both hemispheres for the detection of words. Then, in an event-related transcranial magnetic stimulation experiment with the same task, the disruption of left or right TPJ compared with a control stimulation over the vertex showed a slowing that is more pronounced when words are emotional and presented in the left visual field (LVF). This indicates that interference with both left and right TPJ results in impaired processing of words that were presented to the LVF. In addition, these results point to a specific cooperative contribution of the right hemisphere in the processing of words with emotional content compared with neutral words at very early stages. Results from the two experiments can be integrated in a brain-based spatiotemporal model of the early detection of written words.
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613
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Barrett AB. An integration of integrated information theory with fundamental physics. Front Psychol 2014; 5:63. [PMID: 24550877 PMCID: PMC3912322 DOI: 10.3389/fpsyg.2014.00063] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 01/16/2014] [Indexed: 11/13/2022] Open
Abstract
To truly eliminate Cartesian ghosts from the science of consciousness, we must describe consciousness as an aspect of the physical. Integrated Information Theory states that consciousness arises from intrinsic information generated by dynamical systems; however existing formulations of this theory are not applicable to standard models of fundamental physical entities. Modern physics has shown that fields are fundamental entities, and in particular that the electromagnetic field is fundamental. Here I hypothesize that consciousness arises from information intrinsic to fundamental fields. This hypothesis unites fundamental physics with what we know empirically about the neuroscience underlying consciousness, and it bypasses the need to consider quantum effects.
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Affiliation(s)
- Adam B Barrett
- Sackler Centre for Consciousness Science, Department of Informatics, University of Sussex Brighton, UK
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614
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Assessing consciousness in coma and related states using transcranial magnetic stimulation combined with electroencephalography. ACTA ACUST UNITED AC 2014; 33:65-71. [PMID: 24393302 DOI: 10.1016/j.annfar.2013.11.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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615
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Disorders of consciousness after acquired brain injury: the state of the science. Nat Rev Neurol 2014; 10:99-114. [PMID: 24468878 DOI: 10.1038/nrneurol.2013.279] [Citation(s) in RCA: 445] [Impact Index Per Article: 44.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The concept of consciousness continues to defy definition and elude the grasp of philosophical and scientific efforts to formulate a testable construct that maps to human experience. Severe acquired brain injury results in the dissolution of consciousness, providing a natural model from which key insights about consciousness may be drawn. In the clinical setting, neurologists and neurorehabilitation specialists are called on to discern the level of consciousness in patients who are unable to communicate through word or gesture, and to project outcomes and recommend approaches to treatment. Standards of care are not available to guide clinical decision-making for this population, often leading to inconsistent, inaccurate and inappropriate care. In this Review, we describe the state of the science with regard to clinical management of patients with prolonged disorders of consciousness. We review consciousness-altering pathophysiological mechanisms, specific clinical syndromes, and novel diagnostic and prognostic applications of advanced neuroimaging and electrophysiological procedures. We conclude with a provocative discussion of bioethical and medicolegal issues that are unique to this population and have a profound impact on care, as well as raising questions of broad societal interest.
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616
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van Swinderen B, Kottler B. Explaining general anesthesia: a two-step hypothesis linking sleep circuits and the synaptic release machinery. Bioessays 2014; 36:372-81. [PMID: 24449137 DOI: 10.1002/bies.201300154] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Several general anesthetics produce their sedative effect by activating endogenous sleep pathways. We propose that general anesthesia is a two-step process targeting sleep circuits at low doses, and synaptic release mechanisms across the entire brain at the higher doses required for surgery. Our hypothesis synthesizes data from a variety of model systems, some which require sleep (e.g. rodents and adult flies) and others that probably do not sleep (e.g. adult nematodes and cultured cell lines). Non-sleeping systems can be made insensitive (or hypersensitive) to some anesthetics by modifying a single pre-synaptic protein, syntaxin1A. This suggests that the synaptic release machinery, centered on the highly conserved SNARE complex, is an important target of general anesthetics in all animals. A careful consideration of SNARE architecture uncovers a potential mechanism for general anesthesia, which may be the primary target in animals that do not sleep, but a secondary target in animals that sleep.
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Affiliation(s)
- Bruno van Swinderen
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
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617
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Sarasso S, Rosanova M, Casali AG, Casarotto S, Fecchio M, Boly M, Gosseries O, Tononi G, Laureys S, Massimini M. Quantifying cortical EEG responses to TMS in (un)consciousness. Clin EEG Neurosci 2014; 45:40-9. [PMID: 24403317 DOI: 10.1177/1550059413513723] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We normally assess another individual's level of consciousness based on her or his ability to interact with the surrounding environment and communicate. Usually, if we observe purposeful behavior, appropriate responses to sensory inputs, and, above all, appropriate answers to questions, we can be reasonably sure that the person is conscious. However, we know that consciousness can be entirely within the brain, even in the absence of any interaction with the external world; this happens almost every night, while we dream. Yet, to this day, we lack an objective, dependable measure of the level of consciousness that is independent of processing sensory inputs and producing appropriate motor outputs. Theoretically, consciousness is thought to require the joint presence of functional integration and functional differentiation, otherwise defined as brain complexity. Here we review a series of recent studies in which Transcranial Magnetic Stimulation combined with electroencephalography (TMS/EEG) has been employed to quantify brain complexity in wakefulness and during physiological (sleep), pharmacological (anesthesia) and pathological (brain injury) loss of consciousness. These studies invariably show that the complexity of the cortical response to TMS collapses when consciousness is lost during deep sleep, anesthesia and vegetative state following severe brain injury, while it recovers when consciousness resurges in wakefulness, during dreaming, in the minimally conscious state or locked-in syndrome. The present paper will also focus on how this approach may contribute to unveiling the pathophysiology of disorders of consciousness affecting brain-injured patients. Finally, we will underline some crucial methodological aspects concerning TMS/EEG measurements of brain complexity.
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Affiliation(s)
- Simone Sarasso
- Department of Biomedical and Clinical Sciences "Luigi Sacco," University of Milan, Milan, Italy
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618
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Affiliation(s)
- Quentin Noirhomme
- Coma Science Group, Cyclotron Research Centre, University of Liège, Liège, Belgium
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619
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Marinazzo D, Gosseries O, Boly M, Ledoux D, Rosanova M, Massimini M, Noirhomme Q, Laureys S. Directed information transfer in scalp electroencephalographic recordings: insights on disorders of consciousness. Clin EEG Neurosci 2014; 45:33-9. [PMID: 24403318 DOI: 10.1177/1550059413510703] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The neural mechanisms underlying electrophysiological changes observed in patients with disorders of consciousness following a coma remain poorly understood. The aim of this study is to investigate the mechanisms underlying the differences in spontaneous electroencephalography (EEG) between patients in vegetative/unresponsive wakefulness syndrome, minimally conscious state, emergence of the minimally conscious state and age-matched healthy control subjects. Forty recordings of spontaneous scalp EEG were performed in 27 patients who were comatose on admission, and on healthy controls. Multivariate Granger causality and transfer entropy were applied to the data. Distinctive patterns of putative bottlenecks of information were associated with each conscious state. Healthy controls are characterized by a greater amount of synergetic contributions from duplets of variables. In conclusion a novel set of measures was tested to get a new insight on the pattern of information transfer in a network of scalp electrodes in patients with disorders of consciousness.
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Affiliation(s)
- Daniele Marinazzo
- Department of Data Analysis, Faculty of Psychology and Pedagogical Sciences, Ghent University, Ghent, Belgium
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620
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Bob P. Nonlinear measures and dynamics in psychophysiology of consciousness. Curr Top Behav Neurosci 2014; 21:331-43. [PMID: 24891146 DOI: 10.1007/7854_2014_321] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
According to recent findings nonlinear dynamic processes related to neural chaos and complexity likely play a crucial role in neural synchronization of distributed neural activities that enable information integration and conscious experience. Disturbances in these interactions produce patterns of temporal and spatial disorganization with decreased or increased functional connectivity and complexity that underlie specific changes of perceptual and cognitive states. These perceptual and cognitive changes may be characterized by neural chaos with significantly increased brain sensitivity that may underlie sensitization and kindling, and cognitive hypersensitivity in some mental disorders. Together these findings suggest that processes related to more irregular neural states with higher complexity that may lead to neural chaos, negatively affect information integration and processing in the brain, and may influence disintegrated conscious experience.
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Affiliation(s)
- Petr Bob
- 1st Faculty of Medicine, Department of Psychiatry and UHSL, Center for Neuropsychiatric Research of Traumatic Stress, Charles University, Prague, Ke Karlovu 11, 128 00, Prague, Czech Republic,
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621
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Farisco M, Laureys S, Evers K. Externalization of consciousness. Scientific possibilities and clinical implications. Curr Top Behav Neurosci 2014; 19:205-22. [PMID: 25146416 DOI: 10.1007/7854_2014_338] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The paper starts by analyzing recent advancements in neurotechnological assessment of residual consciousness in patients with disorders of consciousness and in neurotechnology-mediated communication with them. Ethical issues arising from these developments are described, with particular focus on informed consent. Against this background, we argue for the necessity of further scientific efforts and ethical reflection in neurotechnological assessment of consciousness and 'cerebral communication' with verbally non-communicative patients.
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Affiliation(s)
- Michele Farisco
- Centre for Research Ethics and Bioethics, Uppsala University, Uppsala, Sweden,
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622
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Dehaene S, Charles L, King JR, Marti S. Toward a computational theory of conscious processing. Curr Opin Neurobiol 2013; 25:76-84. [PMID: 24709604 DOI: 10.1016/j.conb.2013.12.005] [Citation(s) in RCA: 224] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 11/01/2013] [Accepted: 12/05/2013] [Indexed: 11/30/2022]
Abstract
The study of the mechanisms of conscious processing has become a productive area of cognitive neuroscience. Here we review some of the recent behavioral and neuroscience data, with the specific goal of constraining present and future theories of the computations underlying conscious processing. Experimental findings imply that most of the brain's computations can be performed in a non-conscious mode, but that conscious perception is characterized by an amplification, global propagation and integration of brain signals. A comparison of these data with major theoretical proposals suggests that firstly, conscious access must be carefully distinguished from selective attention; secondly, conscious perception may be likened to a non-linear decision that 'ignites' a network of distributed areas; thirdly, information which is selected for conscious perception gains access to additional computations, including temporary maintenance, global sharing, and flexible routing; and finally, measures of the complexity, long-distance correlation and integration of brain signals provide reliable indices of conscious processing, clinically relevant to patients recovering from coma.
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Affiliation(s)
- Stanislas Dehaene
- Collège de France, F-75005 Paris, France; Cognitive Neuroimaging Unit, Institut National de la Santé et de la Recherche Médicale, U992, F-91191 Gif/Yvette, France; NeuroSpin Center, Institute of BioImaging Commissariat à l'Energie Atomique, F-91191 Gif/Yvette, France; Université Paris 11, Orsay, France.
| | - Lucie Charles
- Cognitive Neuroimaging Unit, Institut National de la Santé et de la Recherche Médicale, U992, F-91191 Gif/Yvette, France; NeuroSpin Center, Institute of BioImaging Commissariat à l'Energie Atomique, F-91191 Gif/Yvette, France; Université Paris 11, Orsay, France
| | - Jean-Rémi King
- Cognitive Neuroimaging Unit, Institut National de la Santé et de la Recherche Médicale, U992, F-91191 Gif/Yvette, France; NeuroSpin Center, Institute of BioImaging Commissariat à l'Energie Atomique, F-91191 Gif/Yvette, France; Université Paris 11, Orsay, France
| | - Sébastien Marti
- Cognitive Neuroimaging Unit, Institut National de la Santé et de la Recherche Médicale, U992, F-91191 Gif/Yvette, France; NeuroSpin Center, Institute of BioImaging Commissariat à l'Energie Atomique, F-91191 Gif/Yvette, France; Université Paris 11, Orsay, France
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623
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Abstract
How does general anesthesia (GA) work? Anesthetics are pharmacological agents that target specific central nervous system receptors. Once they bind to their brain receptors, anesthetics modulate remote brain areas and end up interfering with global neuronal networks, leading to a controlled and reversible loss of consciousness. This remarkable manipulation of consciousness allows millions of people every year to undergo surgery safely most of the time. However, despite all the progress that has been made, we still lack a clear and comprehensive insight into the specific neurophysiological mechanisms of GA, from the molecular level to the global brain propagation. During the last decade, the exponential progress in neuroscience and neuro-imaging led to a significant step in the understanding of the neural correlates of consciousness, with direct consequences for clinical anesthesia. Far from shutting down all brain activity, anesthetics lead to a shift in the brain state to a distinct, highly specific and complex state, which is being increasingly characterized by modern neuro-imaging techniques. There are several clinical consequences and challenges that are arising from the current efforts to dissect GA mechanisms: the improvement of anesthetic depth monitoring, the characterization and avoidance of intra-operative awareness and post-anesthesia cognitive disorders, and the development of future generations of anesthetics.
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Affiliation(s)
- L Uhrig
- CEA, NeuroSpin center, 91191 Gif-sur-Yvette, France; Avenir-Bettencourt-Schueller, Inserm, 91191 Gif-sur-Yvette, France; Cognitive neuroimaging unit, Inserm, U992, 91191 Gif-sur-Yvette, France.
| | - S Dehaene
- CEA, NeuroSpin center, 91191 Gif-sur-Yvette, France; Cognitive neuroimaging unit, Inserm, U992, 91191 Gif-sur-Yvette, France; Collège de France, 75231 Paris, France; Université Paris-Sud, 91405 Orsay, France
| | - B Jarraya
- CEA, NeuroSpin center, 91191 Gif-sur-Yvette, France; Avenir-Bettencourt-Schueller, Inserm, 91191 Gif-sur-Yvette, France; Neuromodulation unit, department of neurosurgery, Foch Hospital, 92150 Suresnes, France; Université Versailles Saint-Quentin-en-Yvelines, 78000 Versailles, France
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624
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Schicktanz N, Schwegler K, Fastenrath M, Spalek K, Milnik A, Papassotiropoulos A, Nyffeler T, de Quervain DJF. Motor threshold predicts working memory performance in healthy humans. Ann Clin Transl Neurol 2013; 1:69-73. [PMID: 25356384 PMCID: PMC4207507 DOI: 10.1002/acn3.22] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 10/24/2013] [Accepted: 11/07/2013] [Indexed: 11/18/2022] Open
Abstract
Cognitive functions, such as working memory, depend on neuronal excitability in a distributed network of cortical regions. It is not known, however, if interindividual differences in cortical excitability are related to differences in working memory performance. In the present transcranial magnetic stimulation study, which included 188 healthy young subjects, we show that participants with lower resting motor threshold, which is related to higher corticospinal excitability, had increased 2-back working memory performance. The findings may help to better understand the link between cortical excitability and cognitive functions and may also have important clinical implications with regard to conditions of altered cortical excitability.
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Affiliation(s)
- Nathalie Schicktanz
- Division of Cognitive Neuroscience, Department of Psychology, University of Basel Basel, Switzerland ; Psychiatric University Clinics, University of Basel Basel, Switzerland
| | - Kyrill Schwegler
- Division of Cognitive Neuroscience, Department of Psychology, University of Basel Basel, Switzerland ; Psychiatric University Clinics, University of Basel Basel, Switzerland
| | - Matthias Fastenrath
- Division of Cognitive Neuroscience, Department of Psychology, University of Basel Basel, Switzerland
| | - Klara Spalek
- Division of Cognitive Neuroscience, Department of Psychology, University of Basel Basel, Switzerland
| | - Annette Milnik
- Division of Molecular Neuroscience, Department of Psychology, University of Basel Basel, Switzerland
| | - Andreas Papassotiropoulos
- Psychiatric University Clinics, University of Basel Basel, Switzerland ; Division of Molecular Neuroscience, Department of Psychology, University of Basel Basel, Switzerland ; Life Sciences Training Facility, Department Biozentrum, University of Basel Basel, Switzerland
| | - Thomas Nyffeler
- Departments of Neurology and Clinical Research, Perception and Eye Movement Laboratory Inselspital, Bern University Hospital, University of Bern Bern, Switzerland ; Center of Neurology and Neurorehabilitation, Luzerner Kantonsspital Luzern, Switzerland
| | - Dominique J-F de Quervain
- Division of Cognitive Neuroscience, Department of Psychology, University of Basel Basel, Switzerland ; Psychiatric University Clinics, University of Basel Basel, Switzerland
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625
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Lee GMH, Fattinger S, Mouthon AL, Noirhomme Q, Huber R. Electroencephalogram approximate entropy influenced by both age and sleep. Front Neuroinform 2013; 7:33. [PMID: 24367328 PMCID: PMC3852001 DOI: 10.3389/fninf.2013.00033] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Accepted: 11/19/2013] [Indexed: 12/03/2022] Open
Abstract
The use of information-based measures to assess changes in conscious state is an increasingly popular topic. Though recent results have seemed to justify the merits of such methods, little has been done to investigate the applicability of such measures to children. For our work, we used the approximate entropy (ApEn), a measure previously shown to correlate with changes in conscious state when applied to the electroencephalogram (EEG), and sought to confirm whether previously reported trends in adult ApEn values across wake and sleep were present in children. Besides validating the prior findings that ApEn decreases from wake to sleep (including wake, rapid eye movement (REM) sleep, and non-REM sleep) in adults, we found that previously reported ApEn decreases across vigilance states in adults were also present in children (ApEn trends for both age groups: wake > REM sleep > non-REM sleep). When comparing ApEn values between age groups, adults had significantly larger ApEn values than children during wakefulness. After the application of an 8 Hz high-pass filter to the EEG signal, ApEn values were recalculated. The number of electrodes with significant vigilance state effects dropped from all 109 electrodes with the original 1 Hz filter to 1 electrode with the 8 Hz filter. The number of electrodes with significant age effects dropped from 10 to 4. Our results support the notion that ApEn can reliably distinguish between vigilance states, with low-frequency sleep-related oscillations implicated as the driver of changes between vigilance states. We suggest that the observed differences between adult and child ApEn values during wake may reflect differences in connectivity between age groups, a factor which may be important in the use of EEG to measure consciousness.
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Affiliation(s)
- Gerick M H Lee
- Institute of Neuroinformatics, University of Zurich and ETH Zurich Zurich, Switzerland ; Child Development Center, University Children's Hospital Zurich Zurich, Switzerland
| | - Sara Fattinger
- Child Development Center, University Children's Hospital Zurich Zurich, Switzerland
| | - Anne-Laure Mouthon
- Child Development Center, University Children's Hospital Zurich Zurich, Switzerland
| | - Quentin Noirhomme
- Coma Science Group, Neurology Department, Cyclotron Research Centre, University Hospital of Liège, University of Liège Liège, Belgium
| | - Reto Huber
- Child Development Center, University Children's Hospital Zurich Zurich, Switzerland
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626
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Large-scale brain dynamics in disorders of consciousness. Curr Opin Neurobiol 2013; 25:7-14. [PMID: 24709594 DOI: 10.1016/j.conb.2013.10.007] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 10/25/2013] [Accepted: 10/30/2013] [Indexed: 11/23/2022]
Abstract
Brain injury profoundly affects global brain dynamics, and these changes are manifest in the electroencephalogram (EEG). Despite the heterogeneity of injury mechanisms and the modularity of brain function, there is a commonality of dynamical features that characterize the EEG along the gamut from coma to recovery. After severest injury, EEG activity is concentrated below 1 Hz. In minimally conscious state during wakefulness, there is a peak of activity in the 3-7 Hz range, often coherent across the brain, and often also activity in the beta (15-30 Hz) range. These spectral changes likely result from varying degrees of functional deafferentation at thalamic and cortical levels. EEG-based indices of brain dynamics that go beyond these simple spectral measures may provide further diagnostic information and physiologic insights.
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627
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George MS, Massimini M. Using Brain Stimulation to Create Thoughts, Retrieve and Alter Memories, and Measure Consciousness – A Discussion of Recent Research. Brain Stimul 2013; 6:835-6. [DOI: 10.1016/j.brs.2013.09.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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628
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Sitt JD, King JR, Naccache L, Dehaene S. Ripples of consciousness. Trends Cogn Sci 2013; 17:552-4. [DOI: 10.1016/j.tics.2013.09.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Accepted: 09/15/2013] [Indexed: 11/29/2022]
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629
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Boly M, Seth AK, Wilke M, Ingmundson P, Baars B, Laureys S, Edelman DB, Tsuchiya N. Consciousness in humans and non-human animals: recent advances and future directions. Front Psychol 2013; 4:625. [PMID: 24198791 PMCID: PMC3814086 DOI: 10.3389/fpsyg.2013.00625] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 08/24/2013] [Indexed: 12/30/2022] Open
Abstract
This joint article reflects the authors' personal views regarding noteworthy advances in the neuroscience of consciousness in the last 10 years, and suggests what we feel may be promising future directions. It is based on a small conference at the Samoset Resort in Rockport, Maine, USA, in July of 2012, organized by the Mind Science Foundation of San Antonio, Texas. Here, we summarize recent advances in our understanding of subjectivity in humans and other animals, including empirical, applied, technical, and conceptual insights. These include the evidence for the importance of fronto-parietal connectivity and of “top-down” processes, both of which enable information to travel across distant cortical areas effectively, as well as numerous dissociations between consciousness and cognitive functions, such as attention, in humans. In addition, we describe the development of mental imagery paradigms, which made it possible to identify covert awareness in non-responsive subjects. Non-human animal consciousness research has also witnessed substantial advances on the specific role of cortical areas and higher order thalamus for consciousness, thanks to important technological enhancements. In addition, much progress has been made in the understanding of non-vertebrate cognition relevant to possible conscious states. Finally, major advances have been made in theories of consciousness, and also in their comparison with the available evidence. Along with reviewing these findings, each author suggests future avenues for research in their field of investigation.
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Affiliation(s)
- Melanie Boly
- Department of Neurology, University of Wisconsin Madison, WI, USA ; Department of Psychiatry, Center for Sleep and Consciousness, University of Wisconsin Madison, WI, USA ; Coma Science Group, Cyclotron Research Centre and Neurology Department, University of Liege and CHU Sart Tilman Hospital Liege, Belgium
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630
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New index for objective determination of consciousness. Nat Rev Neurol 2013. [DOI: 10.1038/nrneurol.2013.185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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631
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Shen H. Metric for consciousness tracks waking states. Nature 2013. [DOI: 10.1038/nature.2013.13556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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