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Hermann B, Sangaré A, Munoz-Musat E, Salah AB, Perez P, Valente M, Faugeras F, Axelrod V, Demeret S, Marois C, Pyatigorskaya N, Habert MO, Kas A, Sitt JD, Rohaut B, Naccache L. Importance, limits and caveats of the use of “disorders of consciousness” to theorize consciousness. Neurosci Conscious 2022; 2021:niab048. [PMID: 35369675 PMCID: PMC8966966 DOI: 10.1093/nc/niab048] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 12/21/2021] [Accepted: 01/27/2022] [Indexed: 11/13/2022] Open
Abstract
The clinical and fundamental exploration of patients suffering from disorders of consciousness (DoC) is commonly used by researchers both to test some of their key theoretical predictions and to serve as a unique source of empirical knowledge about possible dissociations between consciousness and cognitive and/or neural processes. For instance, the existence of states of vigilance free of any self-reportable subjective experience [e.g. “vegetative state (VS)” and “complex partial epileptic seizure”] originated from DoC and acted as a cornerstone for all theories by dissociating two concepts that were commonly equated and confused: vigilance and conscious state. In the present article, we first expose briefly the major achievements in the exploration and understanding of DoC. We then propose a synthetic taxonomy of DoC, and we finally highlight some current limits, caveats and questions that have to be addressed when using DoC to theorize consciousness. In particular, we show (i) that a purely behavioral approach of DoC is insufficient to characterize the conscious state of patients; (ii) that the comparison between patients in a minimally conscious state (MCS) and patients in a VS [also coined as unresponsive wakefulness syndrome (UWS)] does not correspond to a pure and minimal contrast between unconscious and conscious states and (iii) we emphasize, in the light of original resting-state positron emission tomography data, that behavioral MCS captures an important but misnamed clinical condition that rather corresponds to a cortically mediated state and that MCS does not necessarily imply the preservation of a conscious state.
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Affiliation(s)
| | - Aude Sangaré
- Brain institute-ICM, Inserm U1127, CNRS UMR 7225, Sorbonne Université, Paris 75013, France
- Department of Neurophysiology, AP-HP, Hôpital Pitié-Salpêtrière, Sorbonne Université, Paris 75006, France
| | - Esteban Munoz-Musat
- Brain institute-ICM, Inserm U1127, CNRS UMR 7225, Sorbonne Université, Paris 75013, France
| | - Amina Ben Salah
- Brain institute-ICM, Inserm U1127, CNRS UMR 7225, Sorbonne Université, Paris 75013, France
| | - Pauline Perez
- Brain institute-ICM, Inserm U1127, CNRS UMR 7225, Sorbonne Université, Paris 75013, France
| | - Mélanie Valente
- Brain institute-ICM, Inserm U1127, CNRS UMR 7225, Sorbonne Université, Paris 75013, France
- Department of Neurophysiology, AP-HP, Hôpital Pitié-Salpêtrière, Sorbonne Université, Paris 75006, France
| | - Frédéric Faugeras
- Department of Neurology, AP-HP, Hôpital Henri-Mondor-Albert Chenevier, Université Paris Est Creteil, Créteil 94 000, France
- Département d’Etudes Cognitives, École normale supérieure, PSL University, Paris 75005, France
- Inserm U955, Institut Mondor de Recherche Biomédicale, Equipe E01 NeuroPsychologie Interventionnelle, Créteil 94000, France
| | - Vadim Axelrod
- Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Sophie Demeret
- Department of Neurology, Neuro-ICU, AP-HP, Hôpital Pitié-Salpêtrière, Sorbonne Université, Paris 75006, France
| | - Clémence Marois
- Department of Neurology, Neuro-ICU, AP-HP, Hôpital Pitié-Salpêtrière, Sorbonne Université, Paris 75006, France
| | - Nadya Pyatigorskaya
- Brain institute-ICM, Inserm U1127, CNRS UMR 7225, Sorbonne Université, Paris 75013, France
- Department of Neuroradiology, AP-HP, Hôpital Pitié-Salpêtrière, Sorbonne Université, Paris 75006, France
| | - Marie-Odile Habert
- Department of Nuclear Medicine, AP-HP, Pitié-Salpêtrière Hospital, Paris, France
- Laboratoire d’Imagerie Biomédicale, LIB, INSERM, CNRS, Sorbonne Université, Paris, France
| | - Aurélie Kas
- Department of Nuclear Medicine, AP-HP, Pitié-Salpêtrière Hospital, Paris, France
- Laboratoire d’Imagerie Biomédicale, LIB, INSERM, CNRS, Sorbonne Université, Paris, France
| | - Jacobo D Sitt
- Brain institute-ICM, Inserm U1127, CNRS UMR 7225, Sorbonne Université, Paris 75013, France
| | - Benjamin Rohaut
- Brain institute-ICM, Inserm U1127, CNRS UMR 7225, Sorbonne Université, Paris 75013, France
- Department of Neurology, Neuro-ICU, AP-HP, Hôpital Pitié-Salpêtrière, Sorbonne Université, Paris 75006, France
| | - Lionel Naccache
- Brain institute-ICM, Inserm U1127, CNRS UMR 7225, Sorbonne Université, Paris 75013, France
- Department of Neurophysiology, AP-HP, Hôpital Pitié-Salpêtrière, Sorbonne Université, Paris 75006, France
- Medical Intensive Care Unit, AP-HP, Hôpital Européen Georges Pompidou, Paris 75015, France
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Porcaro C, Nemirovsky IE, Riganello F, Mansour Z, Cerasa A, Tonin P, Stojanoski B, Soddu A. Diagnostic Developments in Differentiating Unresponsive Wakefulness Syndrome and the Minimally Conscious State. Front Neurol 2022; 12:778951. [PMID: 35095725 PMCID: PMC8793804 DOI: 10.3389/fneur.2021.778951] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 12/08/2021] [Indexed: 12/12/2022] Open
Abstract
When treating patients with a disorder of consciousness (DOC), it is essential to obtain an accurate diagnosis as soon as possible to generate individualized treatment programs. However, accurately diagnosing patients with DOCs is challenging and prone to errors when differentiating patients in a Vegetative State/Unresponsive Wakefulness Syndrome (VS/UWS) from those in a Minimally Conscious State (MCS). Upwards of ~40% of patients with a DOC can be misdiagnosed when specifically designed behavioral scales are not employed or improperly administered. To improve diagnostic accuracy for these patients, several important neuroimaging and electrophysiological technologies have been proposed. These include Positron Emission Tomography (PET), functional Magnetic Resonance Imaging (fMRI), Electroencephalography (EEG), and Transcranial Magnetic Stimulation (TMS). Here, we review the different ways in which these techniques can improve diagnostic differentiation between VS/UWS and MCS patients. We do so by referring to studies that were conducted within the last 10 years, which were extracted from the PubMed database. In total, 55 studies met our criteria (clinical diagnoses of VS/UWS from MCS as made by PET, fMRI, EEG and TMS- EEG tools) and were included in this review. By summarizing the promising results achieved in understanding and diagnosing these conditions, we aim to emphasize the need for more such tools to be incorporated in standard clinical practice, as well as the importance of data sharing to incentivize the community to meet these goals.
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Affiliation(s)
- Camillo Porcaro
- Department of Neuroscience and Padova Neuroscience Center (PNC), University of Padova, Padova, Italy
- Institute of Cognitive Sciences and Technologies (ISTC)–National Research Council (CNR), Rome, Italy
- Department of Information Engineering, Università Politecnica delle Marche, Ancona, Italy
- Centre for Human Brain Health, School of Psychology, University of Birmingham, Birmingham, United Kingdom
- *Correspondence: Camillo Porcaro ; orcid.org/0000-0003-4847-163X
| | - Idan Efim Nemirovsky
- Department of Physics and Astronomy, Brain and Mind Institute, University of Western Ontario, London, ON, Canada
| | - Francesco Riganello
- Sant'Anna Institute and Research in Advanced Neurorehabilitation (RAN), Crotone, Italy
| | - Zahra Mansour
- Department of Information Engineering, Università Politecnica delle Marche, Ancona, Italy
| | - Antonio Cerasa
- Sant'Anna Institute and Research in Advanced Neurorehabilitation (RAN), Crotone, Italy
- Institute for Biomedical Research and Innovation (IRIB), National Research Council, Messina, Italy
- Pharmacotechnology Documentation and Transfer Unit, Preclinical and Translational Pharmacology, Department of Pharmacy, Health Science and Nutrition, University of Calabria, Rende, Italy
| | - Paolo Tonin
- Sant'Anna Institute and Research in Advanced Neurorehabilitation (RAN), Crotone, Italy
| | - Bobby Stojanoski
- Faculty of Social Science and Humanities, University of Ontario Institute of Technology, Oshawa, ON, Canada
- Department of Psychology, Brain and Mind Institute, University of Western Ontario, London, ON, Canada
| | - Andrea Soddu
- Department of Physics and Astronomy, Brain and Mind Institute, University of Western Ontario, London, ON, Canada
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3
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Tivadar RI, Knight RT, Tzovara A. Automatic Sensory Predictions: A Review of Predictive Mechanisms in the Brain and Their Link to Conscious Processing. Front Hum Neurosci 2021; 15:702520. [PMID: 34489663 PMCID: PMC8416526 DOI: 10.3389/fnhum.2021.702520] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 07/12/2021] [Indexed: 01/22/2023] Open
Abstract
The human brain has the astonishing capacity of integrating streams of sensory information from the environment and forming predictions about future events in an automatic way. Despite being initially developed for visual processing, the bulk of predictive coding research has subsequently focused on auditory processing, with the famous mismatch negativity signal as possibly the most studied signature of a surprise or prediction error (PE) signal. Auditory PEs are present during various consciousness states. Intriguingly, their presence and characteristics have been linked with residual levels of consciousness and return of awareness. In this review we first give an overview of the neural substrates of predictive processes in the auditory modality and their relation to consciousness. Then, we focus on different states of consciousness - wakefulness, sleep, anesthesia, coma, meditation, and hypnosis - and on what mysteries predictive processing has been able to disclose about brain functioning in such states. We review studies investigating how the neural signatures of auditory predictions are modulated by states of reduced or lacking consciousness. As a future outlook, we propose the combination of electrophysiological and computational techniques that will allow investigation of which facets of sensory predictive processes are maintained when consciousness fades away.
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Affiliation(s)
| | - Robert T. Knight
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States
- Department of Psychology, University of California, Berkeley, Berkeley, CA, United States
| | - Athina Tzovara
- Institute of Computer Science, University of Bern, Bern, Switzerland
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States
- Sleep-Wake Epilepsy Center | NeuroTec, Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Wutzl B, Golaszewski SM, Leibnitz K, Langthaler PB, Kunz AB, Leis S, Schwenker K, Thomschewski A, Bergmann J, Trinka E. Narrative Review: Quantitative EEG in Disorders of Consciousness. Brain Sci 2021; 11:brainsci11060697. [PMID: 34070647 PMCID: PMC8228474 DOI: 10.3390/brainsci11060697] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 05/17/2021] [Accepted: 05/21/2021] [Indexed: 02/06/2023] Open
Abstract
In this narrative review, we focus on the role of quantitative EEG technology in the diagnosis and prognosis of patients with unresponsive wakefulness syndrome and minimally conscious state. This paper is divided into two main parts, i.e., diagnosis and prognosis, each consisting of three subsections, namely, (i) resting-state EEG, including spectral power, functional connectivity, dynamic functional connectivity, graph theory, microstates and nonlinear measurements, (ii) sleep patterns, including rapid eye movement (REM) sleep, slow-wave sleep and sleep spindles and (iii) evoked potentials, including the P300, mismatch negativity, the N100, the N400 late positive component and others. Finally, we summarize our findings and conclude that QEEG is a useful tool when it comes to defining the diagnosis and prognosis of DOC patients.
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Affiliation(s)
- Betty Wutzl
- Graduate School of Information Science and Technology, Osaka University, Suita 565-0871, Japan; (B.W.); (K.L.)
- Symbiotic Intelligent Systems Research Center, Osaka University, Suita 565-0871, Japan
| | - Stefan M. Golaszewski
- Department of Neurology, Christian Doppler Medical Center, and Centre for Cognitive Neuroscience, Paracelsus Medical University, Affiliated Member of the European Reference Network EpiCARE, 5020 Salzburg, Austria; (S.M.G.); (P.B.L.); (A.B.K.); (S.L.); (K.S.); (A.T.); (J.B.)
- Karl Landsteiner Institute for Neurorehabilitation and Space Neurology, 5020 Salzburg, Austria
- Neuroscience Institute, Christian Doppler Medical Center, and Centre for Cognitive Neuroscience, Paracelsus Medical University, 5020 Salzburg, Austria
| | - Kenji Leibnitz
- Graduate School of Information Science and Technology, Osaka University, Suita 565-0871, Japan; (B.W.); (K.L.)
- Center for Information and Neural Networks, National Institute of Information and Communications Technology, Suita 565-0871, Japan
| | - Patrick B. Langthaler
- Department of Neurology, Christian Doppler Medical Center, and Centre for Cognitive Neuroscience, Paracelsus Medical University, Affiliated Member of the European Reference Network EpiCARE, 5020 Salzburg, Austria; (S.M.G.); (P.B.L.); (A.B.K.); (S.L.); (K.S.); (A.T.); (J.B.)
- Department of Mathematics, Paris Lodron University of Salzburg, 5020 Salzburg, Austria
- Team Biostatistics and Big Medical Data, IDA Lab Salzburg, Paracelsus Medical University, 5020 Salzburg, Austria
| | - Alexander B. Kunz
- Department of Neurology, Christian Doppler Medical Center, and Centre for Cognitive Neuroscience, Paracelsus Medical University, Affiliated Member of the European Reference Network EpiCARE, 5020 Salzburg, Austria; (S.M.G.); (P.B.L.); (A.B.K.); (S.L.); (K.S.); (A.T.); (J.B.)
- Karl Landsteiner Institute for Neurorehabilitation and Space Neurology, 5020 Salzburg, Austria
| | - Stefan Leis
- Department of Neurology, Christian Doppler Medical Center, and Centre for Cognitive Neuroscience, Paracelsus Medical University, Affiliated Member of the European Reference Network EpiCARE, 5020 Salzburg, Austria; (S.M.G.); (P.B.L.); (A.B.K.); (S.L.); (K.S.); (A.T.); (J.B.)
- Spinal Cord Injury and Tissue Regeneration Center Salzburg, Paracelsus Medical University, 5020 Salzburg, Austria
| | - Kerstin Schwenker
- Department of Neurology, Christian Doppler Medical Center, and Centre for Cognitive Neuroscience, Paracelsus Medical University, Affiliated Member of the European Reference Network EpiCARE, 5020 Salzburg, Austria; (S.M.G.); (P.B.L.); (A.B.K.); (S.L.); (K.S.); (A.T.); (J.B.)
- Karl Landsteiner Institute for Neurorehabilitation and Space Neurology, 5020 Salzburg, Austria
- Neuroscience Institute, Christian Doppler Medical Center, and Centre for Cognitive Neuroscience, Paracelsus Medical University, 5020 Salzburg, Austria
- Spinal Cord Injury and Tissue Regeneration Center Salzburg, Paracelsus Medical University, 5020 Salzburg, Austria
| | - Aljoscha Thomschewski
- Department of Neurology, Christian Doppler Medical Center, and Centre for Cognitive Neuroscience, Paracelsus Medical University, Affiliated Member of the European Reference Network EpiCARE, 5020 Salzburg, Austria; (S.M.G.); (P.B.L.); (A.B.K.); (S.L.); (K.S.); (A.T.); (J.B.)
- Neuroscience Institute, Christian Doppler Medical Center, and Centre for Cognitive Neuroscience, Paracelsus Medical University, 5020 Salzburg, Austria
- Spinal Cord Injury and Tissue Regeneration Center Salzburg, Paracelsus Medical University, 5020 Salzburg, Austria
| | - Jürgen Bergmann
- Department of Neurology, Christian Doppler Medical Center, and Centre for Cognitive Neuroscience, Paracelsus Medical University, Affiliated Member of the European Reference Network EpiCARE, 5020 Salzburg, Austria; (S.M.G.); (P.B.L.); (A.B.K.); (S.L.); (K.S.); (A.T.); (J.B.)
- Neuroscience Institute, Christian Doppler Medical Center, and Centre for Cognitive Neuroscience, Paracelsus Medical University, 5020 Salzburg, Austria
| | - Eugen Trinka
- Department of Neurology, Christian Doppler Medical Center, and Centre for Cognitive Neuroscience, Paracelsus Medical University, Affiliated Member of the European Reference Network EpiCARE, 5020 Salzburg, Austria; (S.M.G.); (P.B.L.); (A.B.K.); (S.L.); (K.S.); (A.T.); (J.B.)
- Karl Landsteiner Institute for Neurorehabilitation and Space Neurology, 5020 Salzburg, Austria
- Neuroscience Institute, Christian Doppler Medical Center, and Centre for Cognitive Neuroscience, Paracelsus Medical University, 5020 Salzburg, Austria
- Spinal Cord Injury and Tissue Regeneration Center Salzburg, Paracelsus Medical University, 5020 Salzburg, Austria
- Correspondence: ; Tel.: +43-5-7255-34600
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Devalle G, Castiglioni P, Arienti C, Abbate C, Mazzucchi A, Agnello L, Merati G. Cardio-respiratory autonomic responses to nociceptive stimuli in patients with disorders of consciousness. PLoS One 2018; 13:e0201921. [PMID: 30208114 PMCID: PMC6135369 DOI: 10.1371/journal.pone.0201921] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 07/24/2018] [Indexed: 12/26/2022] Open
Abstract
The autonomic response to pain might discriminate among consciousness disorders. Therefore, aim of this study was to describe differences between minimally conscious state (MCS) and unresponsive wakefulness syndrome (UWS) patients in their autonomic response to a nociceptive stimulus. ECG, respiration, finger blood pressure (BP) and total peripheral resistances (TPR) were continuously recorded before, during and after a standardized noxious stimulus in 20 adult brain-injured patients, 14 in UWS and 6 in MCS. Occurrence of fast autonomic responses synchronous with the stimulus was detected by visual inspection of the tracings; short-term (<20 s) and long-term (between 20s and 50 s from the stimulus) responses were evaluated by beat-by-beat quantitative analysis. The noxious stimulus elicited fast responses in both groups, but only MCS patients showed a significant short-term response in TPR and long-term response in HR. Thus, short- and long-term cardiovascular responses to pain might integrate neuro-behavioural assessments to discriminate between MCS and UWS.
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Affiliation(s)
- Guya Devalle
- Vegetative State Unit, IRCCS Fondazione Don Carlo Gnocchi, Milan, Italy
| | | | - Chiara Arienti
- Vegetative State Unit, IRCCS Fondazione Don Carlo Gnocchi, Milan, Italy
| | - Carlo Abbate
- Geriatric Unit, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Anna Mazzucchi
- Rete Gravi Cerebrolesioni Acquisite, IRCCS Fondazione Don Carlo Gnocchi, Santa Maria dei Servi, Parma, Italy
| | - Luca Agnello
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
| | - Giampiero Merati
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
- Center of Sports Medicine, IRCCS Fondazione Don Carlo Gnocchi, Milan, Italy
- * E-mail:
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Naro A, Calabrò RS, Pollicino P, Lombardo C, Bramanti P. Unexpected recovery from a vegetative state or misdiagnosis? Lesson learned from a case report. NeuroRehabilitation 2018; 41:735-738. [PMID: 28946586 PMCID: PMC5734120 DOI: 10.3233/nre-172160] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND Growing research is focusing on the identification of markers predicting recovery and demonstrating covert awareness in patients with chronic disorders of consciousness (DOC). Herein, we describe the case of a woman who emerged from unresponsive wakefulness syndrome (UWS) after four years, in whom an experimental protocol assessing brain connectivity predicted her awareness recovery, indicating a functional locked-in syndrome (FLIS) diagnosis. CASE DESCRIPTION A 68-year-old woman was admitted to our institute in 2012 in a UWS secondary to a severe brain hemorrhage, with a Coma Recovery Scale-Revised score of five. Her clinical conditions were stable for about two years, despite the intensive neurorehabilitation treatment. During hospitalization, she underwent a neurophysiological protocol demonstrating an extensive nociceptive processing within the pain matrix. After 3 years, our subject emerged from UWS, and then from minimally conscious state, being able to communicate properly. DISCUSSION Approaches investigating brain connectivity may be useful in DOC diagnosis and prognosis, highlighting residual brain networks subtending covert awareness. Hence, our case supports the necessity of taking into account FLIS diagnosis in DOC differential diagnosis and implementing paraclinical follow-up to intercept cases of possible, late recovery of consciousness, thus optimizing the most appropriate management and rehabilitative setting.
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Affiliation(s)
- Antonino Naro
- IRCCS centro Neurolesi "Bonino-Pulejo", Messina, Italy
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Howard R, Eriksson S, Hirsch N, Kitchen N, Kullmann D, Taylor C, Walker M. Disorders of Consciousness, Intensive Care Neurology and Sleep. Neurology 2016. [DOI: 10.1002/9781118486160.ch20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Oizumi M, Amari SI, Yanagawa T, Fujii N, Tsuchiya N. Measuring Integrated Information from the Decoding Perspective. PLoS Comput Biol 2016; 12:e1004654. [PMID: 26796119 PMCID: PMC4721632 DOI: 10.1371/journal.pcbi.1004654] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Accepted: 11/13/2015] [Indexed: 11/19/2022] Open
Abstract
Accumulating evidence indicates that the capacity to integrate information in the brain is a prerequisite for consciousness. Integrated Information Theory (IIT) of consciousness provides a mathematical approach to quantifying the information integrated in a system, called integrated information, Φ. Integrated information is defined theoretically as the amount of information a system generates as a whole, above and beyond the amount of information its parts independently generate. IIT predicts that the amount of integrated information in the brain should reflect levels of consciousness. Empirical evaluation of this theory requires computing integrated information from neural data acquired from experiments, although difficulties with using the original measure Φ precludes such computations. Although some practical measures have been previously proposed, we found that these measures fail to satisfy the theoretical requirements as a measure of integrated information. Measures of integrated information should satisfy the lower and upper bounds as follows: The lower bound of integrated information should be 0 and is equal to 0 when the system does not generate information (no information) or when the system comprises independent parts (no integration). The upper bound of integrated information is the amount of information generated by the whole system. Here we derive the novel practical measure Φ* by introducing a concept of mismatched decoding developed from information theory. We show that Φ* is properly bounded from below and above, as required, as a measure of integrated information. We derive the analytical expression of Φ* under the Gaussian assumption, which makes it readily applicable to experimental data. Our novel measure Φ* can generally be used as a measure of integrated information in research on consciousness, and also as a tool for network analysis on diverse areas of biology.
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Affiliation(s)
- Masafumi Oizumi
- RIKEN Brain Science Institute, Wako, Saitama, Japan
- School of Psychological Sciences, Faculty of Biomedical and Psychological Sciences, Monash University, Clayton, Victoria, Australia
| | | | | | | | - Naotsugu Tsuchiya
- School of Psychological Sciences, Faculty of Biomedical and Psychological Sciences, Monash University, Clayton, Victoria, Australia
- Japan Science and Technology Agency, Kawaguchi, Saitama, Japan
- Monash Institute of Cognitive and Clinical Neurosciences, Monash University, Clayton, Victoria, Australia
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9
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The 9th International Symposium on Memory and Awareness in Anesthesia (MAA9). Br J Anaesth 2015. [DOI: 10.1093/bja/aev204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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10
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Gilutz Y, Lazary A, Karpin H, Vatine JJ, Misha T, Fortinsky H, Sharon H. Detailed behavioral assessment promotes accurate diagnosis in patients with disorders of consciousness. Front Hum Neurosci 2015; 9:87. [PMID: 25788882 PMCID: PMC4349183 DOI: 10.3389/fnhum.2015.00087] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 02/03/2015] [Indexed: 11/16/2022] Open
Abstract
Introduction: Assessing the awareness level in patients with disorders of consciousness (DOC) is made on the basis of exhibited behaviors. However, since motor signs of awareness (i.e., non-reflex motor responses) can be very subtle, differentiating the vegetative from minimally conscious states (which is in itself not clear-cut) is often challenging. Even the careful clinician relying on standardized scales may arrive at a wrong diagnosis. Aim: To report our experience in tackling this problem by using two in-house use assessment procedures developed at Reuth Rehabilitation Hospital, and demonstrate their clinical significance by reviewing two cases. Methods: (1) Reuth DOC Response Assessment (RDOC-RA) –administered in addition to the standardized tools, and emphasizes the importance of assessing a wide range of motor responses. In our experience, in some patients the only evidence for awareness may be a private specific movement that is not assessed by standard assessment tools. (2) Reuth DOC Periodic Intervention Model (RDOC-PIM) – current literature regarding assessment and diagnosis in DOC refers mostly to the acute phase of up to 1 year post injury. However, we have found major changes in responsiveness occurring 1 year or more post-injury in many patients. Therefore, we conduct periodic assessments at predetermined times points to ensure patients are not misdiagnosed or neurological changes overlooked. Results: In the first case the RDOC-RA promoted a more accurate diagnosis than that based on standardized scales alone. The second case shows how the RDOC-PIM allowed us to recognize late recovery and promoted reinstatement of treatment with good results. Conclusion: Adding a detailed periodic assessment of DOC patients to existing scales can yield critical information, promoting better diagnosis, treatment, and clinical outcomes. We discuss the implications of this observation for the future development and validation of assessment tools in DOC patients.
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Affiliation(s)
- Yael Gilutz
- Department of Occupational Therapy, Reuth Rehabilitation Hospital Tel Aviv, Israel ; Brain Injury Division, Reuth Rehabilitation Hospital Tel Aviv, Israel
| | - Avraham Lazary
- Brain Injury Division, Reuth Rehabilitation Hospital Tel Aviv, Israel
| | - Hana Karpin
- Department of Occupational Therapy, Reuth Rehabilitation Hospital Tel Aviv, Israel
| | - Jean-Jacques Vatine
- Outpatient and Research Division, Reuth Rehabilitation Hospital Tel Aviv, Israel ; Sackler School of Medicine, Tel Aviv University Tel Aviv Israel
| | - Tamar Misha
- Department of Occupational Therapy, Reuth Rehabilitation Hospital Tel Aviv, Israel ; Brain Injury Division, Reuth Rehabilitation Hospital Tel Aviv, Israel
| | - Hadassah Fortinsky
- Department of Occupational Therapy, Reuth Rehabilitation Hospital Tel Aviv, Israel
| | - Haggai Sharon
- Sackler School of Medicine, Tel Aviv University Tel Aviv Israel ; Institute of Pain Medicine, Tel Aviv Sourasky Medical Center Tel Aviv, Israel ; Center for Brain Functions, Tel Aviv Sourasky Medical Center Tel Aviv, Israel
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Tagliazucchi E, Laufs H. Decoding wakefulness levels from typical fMRI resting-state data reveals reliable drifts between wakefulness and sleep. Neuron 2014; 82:695-708. [PMID: 24811386 DOI: 10.1016/j.neuron.2014.03.020] [Citation(s) in RCA: 441] [Impact Index Per Article: 44.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/13/2014] [Indexed: 01/18/2023]
Abstract
The mining of huge databases of resting-state brain activity recordings represents state of the art in the assessment of endogenous neuronal activity-and may be a promising tool in the search for functional biomarkers. However, the resting state is an uncontrolled condition and its heterogeneity is neither sufficiently understood nor accounted for. We test the hypothesis that subjects exhibit unstable wakefulness, i.e., drift into sleep during typical resting-state experiments. Analyzing 1,147 resting-state functional magnetic resonance data sets, we revealed a reliable loss of wakefulness in a third of subjects within 3 min and demonstrated the dynamic nature of the resting state, with fundamental changes in the associated functional neuroanatomy. Implications include the necessity of wakefulness monitoring and modeling, taking measures to maintain a state of wakefulness, acknowledging the possibility of sleep and exploring its consequences, and especially the critical assessment of possible false-positive or false-negative results.
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Affiliation(s)
- Enzo Tagliazucchi
- Department of Neurology and Brain Imaging Center, Goethe University Frankfurt am Main, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany
| | - Helmut Laufs
- Department of Neurology and Brain Imaging Center, Goethe University Frankfurt am Main, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; Department of Neurology, University Hospital Schleswig Holstein, Arnold-Heller-Straße 3, 24105 Kiel, Germany.
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Consciousness and responsiveness: lessons from anaesthesia and the vegetative state. Curr Opin Anaesthesiol 2014; 26:444-9. [PMID: 23743554 DOI: 10.1097/aco.0b013e3283628b5d] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PURPOSE OF REVIEW The aim of this article is to review recent behavioural and neuroimaging studies in anaesthesia and the vegetative state. RECENT FINDINGS These studies highlight possible dissociations between consciousness and responsiveness in both these states. SUMMARY We discuss future avenues of research in the field, in order to improve the detection of awareness during anaesthesia and the vegetative state using neuroimaging and neurophysiologic techniques.
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Spectral parameters modulation and source localization of blink-related alpha and low-beta oscillations differentiate minimally conscious state from vegetative state/unresponsive wakefulness syndrome. PLoS One 2014; 9:e93252. [PMID: 24676098 PMCID: PMC3970990 DOI: 10.1371/journal.pone.0093252] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 03/03/2014] [Indexed: 12/03/2022] Open
Abstract
Recently, the cortical source of blink-related delta oscillations (delta BROs) in resting healthy subjects has been localized in the posterior cingulate cortex/precuneus (PCC/PCu), one of the main core-hubs of the default-mode network. This has been interpreted as the electrophysiological signature of the automatic monitoring of the surrounding environment while subjects are immersed in self-reflecting mental activities. Although delta BROs were directly correlated to the degree of consciousness impairment in patients with disorders of consciousness, they failed to differentiate vegetative state/unresponsive wakefulness syndrome (VS/UWS) from minimally conscious state (MCS). In the present study, we have extended the analysis of BROs to frequency bands other than delta in the attempt to find a biological marker that could support the differential diagnosis between VS/UWS and MCS. Four patients with VS/UWS, 5 patients with MCS, and 12 healthy matched controls (CTRL) underwent standard 19-channels EEG recordings during resting conditions. Three-second-lasting EEG epochs centred on each blink instance were submitted to time-frequency analyses in order to extract the normalized Blink-Related Synchronization/Desynchronization (nBRS/BRD) of three bands of interest (low-alpha, high-alpha and low-beta) in the time-window of 50–550 ms after the blink-peak and to estimate the corresponding cortical sources of electrical activity. VS/UWS nBRS/BRD levels of all three bands were lower than those related to both CTRL and MCS, thus enabling the differential diagnosis between MCS and VS/UWS. Furthermore, MCS showed an intermediate signal intensity on PCC/PCu between CTRL and VS/UWS and a higher signal intensity on the left temporo-parieto-occipital junction and inferior occipito-temporal regions when compared to VS/UWS. This peculiar pattern of activation leads us to hypothesize that resting MCS patients have a bottom-up driven activation of the task positive network and thus are tendentially prone to respond to environmental stimuli, even though in an almost unintentional way.
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Lancioni GE, Bosco A, Olivetti Belardinelli M, Singh NN, O'Reilly MF, Sigafoos J, Buonocunto F, Navarro J, Lanzilotti C, D'Amico F, De Tommaso M. Assessing learning as a possible sign of consciousness in post-coma persons with minimal responsiveness. Front Hum Neurosci 2014; 8:25. [PMID: 24574989 PMCID: PMC3918875 DOI: 10.3389/fnhum.2014.00025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 01/11/2014] [Indexed: 11/13/2022] Open
Abstract
A learning test procedure based on operant principles may be useful in the diagnosis (and eventually rehabilitation) of post-coma persons with minimal responsiveness. This study was aimed at extending the evaluation of such a procedure with seven participants who presented with very limited behavior and apparently severe disorders of consciousness. The procedure was evaluated through an ABACB design, in which A represented baseline phases without stimulation, B intervention phases with brief stimulation periods contingent on specific responses of the participants, and C a control phase in which stimulation was available all the time. Increased responding during the B phases, as opposed to the A and C phases, was taken to indicate learning and possibly a non-reflective expression of phenomenal consciousness. All participants were also evaluated with the coma recovery scale-revised (CRS-R) prior to the start of the learning test procedure and at the end of it. The results of the learning test showed that all participants had significantly higher responding levels during the B phases. The CRS-R scores suggested minimally conscious state for four of them prior to the learning test and for five of them after the completion of the learning test. The implications of the findings are discussed in terms of potential and time cost of the learning test.
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Affiliation(s)
- Giulio E Lancioni
- Department of Neuroscience and Sense Organs, University of Bari Bari, Italy
| | - Andrea Bosco
- Department of Educational Science, Psychology, Communication, University of Bari Bari, Italy
| | | | - Nirbhay N Singh
- Medical College of Georgia, Georgia Regents University Augusta, GA, USA
| | | | - Jeff Sigafoos
- Victoria University of Wellington Wellington, New Zealand
| | | | - Jorge Navarro
- S. Raffaele Rehabilitation and Care Centers Ceglie and Alberobello, Italy
| | | | - Fiora D'Amico
- S. Raffaele Rehabilitation and Care Centers Ceglie and Alberobello, Italy
| | - Marina De Tommaso
- Department of Neuroscience and Sense Organs, University of Bari Bari, Italy
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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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Sharon H, Pasternak Y, Ben Simon E, Gruberger M, Giladi N, Krimchanski BZ, Hassin D, Hendler T. Emotional processing of personally familiar faces in the vegetative state. PLoS One 2013; 8:e74711. [PMID: 24086365 PMCID: PMC3783455 DOI: 10.1371/journal.pone.0074711] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 08/04/2013] [Indexed: 01/04/2023] Open
Abstract
Background The Vegetative State (VS) is a severe disorder of consciousness in which patients are awake but display no signs of awareness. Yet, recent functional magnetic resonance imaging (fMRI) studies have demonstrated evidence for covert awareness in VS patients by recording specific brain activations during a cognitive task. However, the possible existence of incommunicable subjective emotional experiences in VS patients remains largely unexplored. This study aimed to probe the question of whether VS patients retain a brain ability to selectively process external stimuli according to their emotional value and look for evidence of covert emotional awareness in patients. Methods and Findings In order to explore these questions we employed the emotive impact of observing personally familiar faces, known to provoke specific perceptual as well as emotional brain activations. Four VS patients and thirteen healthy controls first underwent an fMRI scan while viewing pictures of non-familiar faces, personally familiar faces and pictures of themselves. In a subsequent imagery task participants were asked to actively imagine one of their parent's faces. Analyses focused on face and familiarity selective regional brain activations and inter-regional functional connectivity. Similar to controls, all patients displayed face selective brain responses with further limbic and cortical activations elicited by familiar faces. In patients as well as controls, Connectivity was observed between emotional, visual and face specific areas, suggesting aware emotional perception. This connectivity was strongest in the two patients who later recovered. Notably, these two patients also displayed selective amygdala activation during familiar face imagery, with one further exhibiting face selective activations, indistinguishable from healthy controls. Conclusions Taken together, these results show that selective emotional processing can be elicited in VS patients both by external emotionally salient stimuli and by internal cognitive processes, suggesting the ability for covert emotional awareness of self and the environment in VS patients.
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Affiliation(s)
- Haggai Sharon
- Functional Brain Center, Wohl Institute for Advanced Imaging, Sourasky Medical Center, Tel Aviv, Israel
- Department of Internal Medicine, Sourasky Medical Center, Tel Aviv, Israel
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
- * E-mail:
| | - Yotam Pasternak
- Functional Brain Center, Wohl Institute for Advanced Imaging, Sourasky Medical Center, Tel Aviv, Israel
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Eti Ben Simon
- Functional Brain Center, Wohl Institute for Advanced Imaging, Sourasky Medical Center, Tel Aviv, Israel
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Michal Gruberger
- Functional Brain Center, Wohl Institute for Advanced Imaging, Sourasky Medical Center, Tel Aviv, Israel
- School of Psychological Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Nir Giladi
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
- Department of Neurology, Sourasky Medical Center, Tel Aviv, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Ben Zion Krimchanski
- Rehabilitation Intensive Care Unit, Loewenstein Rehabilitation Hospital, Raanana, Israel
| | - David Hassin
- Department of Internal Medicine, Sourasky Medical Center, Tel Aviv, Israel
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Talma Hendler
- Functional Brain Center, Wohl Institute for Advanced Imaging, Sourasky Medical Center, Tel Aviv, Israel
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
- School of Psychological Sciences, Tel Aviv University, Tel Aviv, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
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Casali AG, Gosseries O, Rosanova M, Boly M, Sarasso S, Casali KR, Casarotto S, Bruno MA, Laureys S, Tononi G, Massimini M. A Theoretically Based Index of Consciousness Independent of Sensory Processing and Behavior. Sci Transl Med 2013; 5:198ra105. [DOI: 10.1126/scitranslmed.3006294] [Citation(s) in RCA: 645] [Impact Index Per Article: 58.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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18
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Varotto G, Fazio P, Rossi Sebastiano D, Duran D, D'Incerti L, Parati E, Sattin D, Leonardi M, Franceschetti S, Panzica F. Altered resting state effective connectivity in long-standing vegetative state patients: an EEG study. Clin Neurophysiol 2013; 125:63-8. [PMID: 23927942 DOI: 10.1016/j.clinph.2013.06.016] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Revised: 05/21/2013] [Accepted: 06/11/2013] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Recent evidence mainly based on hemodynamic measures suggests that the impairment of functional connections between different brain areas may help to clarify the neuronal dysfunction occurring in patients with disorders of consciousness (DOC). The aim of this study was to evaluate effective EEG connectivity in a cohort of 18 patients in a chronic vegetative state (VS) observed years after the occurrence of hypoxic (eight) and traumatic or hemorrhagic brain insult. METHODS we analysed the EEG signals recorded under resting conditions using a frequency domain linear index of connectivity (partial directed coherence: PDC) estimated from a multivariate autoregressive model. The results were compared with those obtained in ten healthy controls. RESULTS Our findings indicated significant connectivity changes in EEG activities in delta and alpha bands. The VS patients showed a significant and widespread decrease in delta band connectivity, whereas the alpha activity was hyper-connected in the central and posterior cortical regions. CONCLUSION These changes suggest the occurrence of severe circuitry derangements probably due to the loose control of the subcortical connections. The alpha hyper-synchronisation may be due to simplified networks mainly involving the short-range connections between intrinsically oscillatory cortical neurons that generate aberrant EEG alpha sources. This increased connectivity may be interpreted as a reduction in information capacity, implying an increasing prevalence of stereotypic activity patterns. SIGNIFICANCE Our observations suggest a remarkable rearrangement of connectivity in patients with long-standing VS. We hypothesize that in persistent VS, after a first period characterized by a breakdown of cortical connectivity, neurodegenerative processes, largely independent from the type of initial insult, lead to cortex de-afferentation and to a severe reduction of possible cortical activity patterns and states.
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Affiliation(s)
- Giulia Varotto
- Dept. of Neurophysiology and Diagnostic Epileptology, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy
| | - Patrik Fazio
- Dept. of Neurophysiology and Diagnostic Epileptology, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy; Dept. of Medical and Surgical Sciences of Communication and Behaviour, Neurology Section, University of Ferrara, Italy
| | - Davide Rossi Sebastiano
- Dept. of Neurophysiology and Diagnostic Epileptology, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy
| | - Dunja Duran
- Dept. of Neurophysiology and Diagnostic Epileptology, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy
| | - Ludovico D'Incerti
- Dept. of Neuroradiology, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy
| | - Eugenio Parati
- Dept. of Cerebrovascular Diseases, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy
| | - Davide Sattin
- Unit of Neurology, Public Health, Disability Unit, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy; Coma Research Centre, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy
| | - Matilde Leonardi
- Unit of Neurology, Public Health, Disability Unit, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy; Coma Research Centre, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy
| | - Silvana Franceschetti
- Dept. of Neurophysiology and Diagnostic Epileptology, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy
| | - Ferruccio Panzica
- Dept. of Neurophysiology and Diagnostic Epileptology, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy.
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Liu X, Pillay S, Li R, Vizuete JA, Pechman KR, Schmainda KM, Hudetz AG. Multiphasic modification of intrinsic functional connectivity of the rat brain during increasing levels of propofol. Neuroimage 2013; 83:581-92. [PMID: 23851326 DOI: 10.1016/j.neuroimage.2013.07.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 06/28/2013] [Accepted: 07/01/2013] [Indexed: 01/13/2023] Open
Abstract
The dose-dependent effects of anesthetics on brain functional connectivity are incompletely understood. Resting-state functional magnetic resonance imaging (rsfMRI) is widely used to assess the functional connectivity in humans and animals. Propofol is an anesthetic agent with desirable characteristics for functional neuroimaging in animals but its dose-dependent effects on rsfMRI functional connectivity have not been determined. Here we tested the hypothesis that brain functional connectivity undergoes specific changes in distinct neural networks at anesthetic depths associated with loss of consciousness. We acquired spontaneous blood oxygen level-dependent (BOLD) signals simultaneously with electroencephalographic (EEG) signals from rats under steady-state, intravenously administered propofol at increasing doses from light sedation to deep anesthesia (20, 40, 60, 80, and 100 mg/kg/h IV). Power spectra and burst suppression ratio were calculated from the EEG to verify anesthetic depth. Functional connectivity was determined from the whole brain correlation of BOLD data in regions of interest followed by a segmentation of the correlation maps into anatomically defined regional connectivity. We found that propofol produced multiphasic, dose dependent changes in functional connectivity of various cortical and subcortical networks. Cluster analysis predicted segregation of connectivity into two cortical and two subcortical clusters. In one cortical cluster (somatosensory and parietal), the early reduction in connectivity was followed by transient reversal; in the other cluster (sensory, motor and cingulate/retrosplenial), this rebound was absent. The connectivity of the subcortical cluster (brainstem, hippocampal and caudate) was strongly reduced, whereas that of another (hypothalamus, medial thalamus and n. basalis) did not. Subcortical connectivity increased again in deep anesthesia associated with EEG burst suppression. Regional correlation analysis confirmed the breakdown of connectivity within and between specific cortical and subcortical networks with deepening propofol anesthesia. Cortical connectivity was suppressed before subcortical connectivity at a critical propofol dose associated with loss of consciousness.
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Affiliation(s)
- Xiping Liu
- Department of Anesthesiology, Medical College of Wisconsin, USA
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20
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CRS-R score in disorders of consciousness is strongly related to spectral EEG at rest. J Neurol 2013; 260:2348-56. [PMID: 23765089 DOI: 10.1007/s00415-013-6982-3] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 05/23/2013] [Accepted: 05/25/2013] [Indexed: 10/26/2022]
Abstract
Patients suffering from disorders of consciousness still present a diagnostic challenge due to the fact that their assessment is mainly based on behavioral scales with their motor responses often being strongly impaired. We therefore focused on resting electroencephalography (EEG) in order to reveal potential alternative measures of the patient's current state independent of rather complex abilities (e.g., language comprehension). Resting EEG was recorded in nine minimally conscious state (MCS) and eight vegetative state/unresponsive wakefulness syndrome (VS/UWS) patients. Behavioral assessments were conducted using the Coma-Recovery Scale-Revised (CRS-R). The signal was analyzed in the frequency domain and association between resting EEG and CRS-R score as well as clinical diagnosis were calculated using Pearson correlation and repeated-measures ANOVAs. The analyses revealed robust positive correlations between CRS-R score and ratios between frequencies above 8 Hz and frequencies below 8 Hz. Furthermore, the frequency of the spectral peak was also highly indicative of the patient's CRS-R score. Concerning differences between clinical diagnosis and healthy controls, it could be revealed that while VS/UWS patients showed higher delta and theta activity than controls, MCS did not differ from controls in this frequency range. Alpha activity, on the other hand, was strongly decreased in both patient groups as compared to controls. The strong relationship between various resting EEG parameters and CRS-R score provides significant clinical relevance. Not only is resting activity easily acquired at bedside, but furthermore, it does not depend on explicit cooperation of the patient. Especially in cases where behavioral assessment is difficult or ambiguous, spectral analysis of resting EEG can therefore complement clinical diagnosis.
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21
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Eeles E, Pandy S, Ray J. Delirium: A disorder of consciousness? Med Hypotheses 2013; 80:399-404. [DOI: 10.1016/j.mehy.2012.12.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Revised: 12/21/2012] [Accepted: 12/29/2012] [Indexed: 10/27/2022]
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Shi C, Flanagan SR, Samadani U. Vagus nerve stimulation to augment recovery from severe traumatic brain injury impeding consciousness: a prospective pilot clinical trial. Neurol Res 2013; 35:263-76. [PMID: 23485054 PMCID: PMC4568744 DOI: 10.1179/1743132813y.0000000167] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
OBJECTIVES Traumatic brain injury (TBI) has high morbidity and mortality in both civilian and military populations. Blast and other mechanisms of TBI damage the brain by causing neurons to disconnect and atrophy. Such traumatic axonal injury can lead to persistent vegetative and minimally conscious states (VS and MCS), for which limited treatment options exist, including physical, occupational, speech, and cognitive therapies. More than 60 000 patients have received vagus nerve stimulation (VNS) for epilepsy and depression. In addition to decreased seizure frequency and severity, patients report enhanced mood, reduced daytime sleepiness independent of seizure control, increased slow wave sleep, and improved cognition, memory, and quality of life. Early stimulation of the vagus nerve accelerates the rate and extent of behavioral and cognitive recovery after fluid percussion brain injury in rats. METHODS We recently obtained Food and Drug Administration (FDA) approval for a pilot prospective randomized crossover trial to demonstrate objective improvement in clinical outcome by placement of a vagus nerve stimulator in patients who are recovering from severe TBI. Our hypothesis is that stimulation of the vagus nerve results in increased cerebral blood flow and metabolism in the forebrain, thalamus, and reticular formation, which promotes arousal and improved consciousness, thereby improving outcome after TBI resulting in MCS or VS. DISCUSSION If this study demonstrates that VNS can safely and positively impact outcome, then a larger randomized prospective crossover trial will be proposed.
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Affiliation(s)
- Chen Shi
- Department of Neurosurgery, New York University School of Medicine and NYU Langone Medical Center, 550 First Ave. New York, NY 10016
| | - Steven R. Flanagan
- Department of Rehabilitation Medicine, New York University School of Medicine and NYU Langone Medical Center, 240 E. 38 St. New York, NY 10016
| | - Uzma Samadani
- Department of Neurosurgery, New York University School of Medicine and NYU Langone Medical Center, 550 First Ave. New York, NY 10016
- Division of Neurosurgery, New York Harbor Healthcare System Manhattan Veterans Hospital, 423 E. 23 St. New York, NY 10010
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Naci L, Monti MM, Cruse D, Kübler A, Sorger B, Goebel R, Kotchoubey B, Owen AM. Brain-computer interfaces for communication with nonresponsive patients. Ann Neurol 2012; 72:312-23. [DOI: 10.1002/ana.23656] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
One of the greatest challenges of modern neuroscience is to discover the neural mechanisms of consciousness and to explain how they produce the conscious state. We sought the underlying neural substrate of human consciousness by manipulating the level of consciousness in volunteers with anesthetic agents and visualizing the resultant changes in brain activity using regional cerebral blood flow imaging with positron emission tomography. Study design and methodology were chosen to dissociate the state-related changes in consciousness from the effects of the anesthetic drugs. We found the emergence of consciousness, as assessed with a motor response to a spoken command, to be associated with the activation of a core network involving subcortical and limbic regions that become functionally coupled with parts of frontal and inferior parietal cortices upon awakening from unconsciousness. The neural core of consciousness thus involves forebrain arousal acting to link motor intentions originating in posterior sensory integration regions with motor action control arising in more anterior brain regions. These findings reveal the clearest picture yet of the minimal neural correlates required for a conscious state to emerge.
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Boly M, Massimini M, Garrido MI, Gosseries O, Noirhomme Q, Laureys S, Soddu A. Brain connectivity in disorders of consciousness. Brain Connect 2012; 2:1-10. [PMID: 22512333 DOI: 10.1089/brain.2011.0049] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The last 10 years witnessed a considerable increase in our knowledge of brain function in survivors to severe brain injuries with disorders of consciousness (DOC). At the same time, a growing interest developed for the use of functional neuroimaging as a new diagnostic tool in these patients. In this context, particular attention has been devoted to connectivity studies-as these, more than measures of brain metabolism, may be more appropriate to capture the dynamics of large populations of neurons. Here, we will review the pros and cons of various connectivity methods as potential diagnostic tools in brain-damaged patients with DOC. We will also discuss the relevance of the study of the level versus the contents of consciousness in this context.
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Affiliation(s)
- Mélanie Boly
- Coma Science Group, Cyclotron Research Centre and Neurology Department, University of Liège and CHU Sart Tilman Hospital, Liège, Belgium.
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26
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Lancioni G, Singh N, O'Reilly M, Olivetti M, de Tommaso M, Navarro J, Colonna F, Lanzilotti C, Buonocunto F, Sacco V. A learning assessment procedure as a test supplement for monitoring progress with two post-coma persons with a diagnosis of vegetative state. Dev Neurorehabil 2012; 14:358-65. [PMID: 21950340 DOI: 10.3109/17518423.2011.605076] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Evaluating a learning assessment procedure for monitoring progress with two post-coma adults with a diagnosis of vegetative state. METHOD ABABCBCB and ABABCB designs were used for the two participants, with A representing baseline, B intervention and C control conditions. Participants' activation of an optic microswitch by eyelid closure produced stimulation during B phases. RESULTS One participant increased responding during B phases and decreased it during the C condition, suggesting a non-reflective minimal level of consciousness. She showed P300 and mismatch negativity responses and scored at the vegetative level on the Coma Recovery Scale-Revised (CRS-R). The other participant increased responding during the initial B phases without decline during the first (viable) part of the C condition, suggesting a pre-conscious level. He showed indistinct P300 and mismatch negativity responses and vegetative-level scores on the CRS-R. CONCLUSION Learning data seemed reconcilable with neurophysiological measures and more positive than CRS-R scores.
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Hierarchical clustering of brain activity during human nonrapid eye movement sleep. Proc Natl Acad Sci U S A 2012; 109:5856-61. [PMID: 22451917 DOI: 10.1073/pnas.1111133109] [Citation(s) in RCA: 149] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Consciousness is reduced during nonrapid eye movement (NREM) sleep due to changes in brain function that are still poorly understood. Here, we tested the hypothesis that impaired consciousness during NREM sleep is associated with an increased modularity of brain activity. Cerebral connectivity was quantified in resting-state functional magnetic resonance imaging times series acquired in 13 healthy volunteers during wakefulness and NREM sleep. The analysis revealed a modification of the hierarchical organization of large-scale networks into smaller independent modules during NREM sleep, independently from EEG markers of the slow oscillation. Such modifications in brain connectivity, possibly driven by sleep ultraslow oscillations, could hinder the brain's ability to integrate information and account for decreased consciousness during NREM sleep.
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