1
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He Q, He J, Yang Y, Zhao J. Brain-Computer Interfaces in Disorders of Consciousness. Neurosci Bull 2023; 39:348-352. [PMID: 35941403 PMCID: PMC9905465 DOI: 10.1007/s12264-022-00920-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 06/03/2022] [Indexed: 11/25/2022] Open
Affiliation(s)
- Qiheng He
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, 100070, China
- China National Clinical Research Center for Neurological Diseases, Beijing, 100070, China
| | - Jianghong He
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, 100070, China.
| | - Yi Yang
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, 100070, China.
- Chinese Institute for Brain Research, Beijing, 100010, China.
- Beijing Institute of Brain Disorders, Beijing, 100069, China.
- China National Clinical Research Center for Neurological Diseases, Beijing, 100070, China.
| | - Jizong Zhao
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, 100070, China
- China National Clinical Research Center for Neurological Diseases, Beijing, 100070, China
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2
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Naci L, Owen AM. Uncovering consciousness and revealing the preservation of mental life in unresponsive brain-injured patients. Semin Neurol 2022; 42:299-308. [PMID: 35790202 DOI: 10.1055/a-1892-1715] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- Lorina Naci
- Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
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3
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Aubinet C, Schnakers C, Majerus S. Language Assessment in Patients with Disorders of Consciousness. Semin Neurol 2022; 42:273-282. [PMID: 36100226 DOI: 10.1055/s-0042-1755561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
The assessment of residual language abilities in patients with disorders of consciousness (DoC) after severe brain injury is particularly challenging due to their limited behavioral repertoire. Moreover, associated language impairment such as receptive aphasia may lead to an underestimation of actual consciousness levels. In this review, we examine past research on the assessment of residual language processing in DoC patients, and we discuss currently available tools for identifying language-specific abilities and their prognostic value. We first highlight the need for validated and sensitive bedside behavioral assessment tools for residual language abilities in DoC patients. As regards neuroimaging and electrophysiological methods, the tasks involving higher level linguistic commands appear to be the most informative about level of consciousness and have the best prognostic value. Neuroimaging methods should be combined with the most appropriate behavioral tools in multimodal assessment protocols to assess receptive language abilities in DoC patients in the most complete and sensitive manner.
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Affiliation(s)
- Charlène Aubinet
- Coma Science Group, GIGA Consciousness, University of Liège, Liège, Belgium.,Centre du Cerveau, University Hospital of Liège, Liège, Belgium.,Psychology and Neuroscience of Cognition Research Unit, University of Liège, Liège, Belgium
| | - Caroline Schnakers
- Research Institute, Casa Colina Hospital and Centers for Healthcare, Pomona, California
| | - Steve Majerus
- Psychology and Neuroscience of Cognition Research Unit, University of Liège, Liège, Belgium
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4
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Aubinet C, Chatelle C, Gosseries O, Carrière M, Laureys S, Majerus S. Residual implicit and explicit language abilities in patients with disorders of consciousness: A systematic review. Neurosci Biobehav Rev 2021; 132:391-409. [PMID: 34864003 DOI: 10.1016/j.neubiorev.2021.12.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 11/13/2021] [Accepted: 12/01/2021] [Indexed: 01/14/2023]
Abstract
Language assessment in post-comatose patients is difficult due to their limited behavioral repertoire; yet associated language deficits might lead to an underestimation of consciousness levels in unresponsive wakefulness syndrome (UWS) or minimally conscious state (MCS; -/+) diagnoses. We present a systematic review of studies from 2002 assessing residual language abilities with neuroimaging, electrophysiological or behavioral measures in patients with severe brain injury. Eighty-five articles including a total of 2278 patients were assessed for quality. The median percentages of patients showing residual implicit language abilities (i.e., cortical responses to specific words/sentences) were 33 % for UWS, 50 % for MCS- and 78 % for MCS + patients, whereas explicit language abilities (i.e., command-following using brain-computer interfaces) were reported in 20 % of UWS, 33 % of MCS- and 50 % of MCS + patients. Cortical responses to verbal stimuli increased along with consciousness levels and the progressive recovery of consciousness after a coma was paralleled by the reappearance of both implicit and explicit language processing. This review highlights the importance of language assessment in patients with disorders of consciousness.
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Affiliation(s)
- Charlène Aubinet
- Coma Science Group, GIGA Consciousness, University of Liège, Belgium; Centre du Cerveau, University Hospital of Liège, Belgium.
| | - Camille Chatelle
- Coma Science Group, GIGA Consciousness, University of Liège, Belgium; Centre du Cerveau, University Hospital of Liège, Belgium
| | - Olivia Gosseries
- Coma Science Group, GIGA Consciousness, University of Liège, Belgium; Centre du Cerveau, University Hospital of Liège, Belgium; Fund for Scientific Research, FNRS, Belgium
| | - Manon Carrière
- Coma Science Group, GIGA Consciousness, University of Liège, Belgium; Centre du Cerveau, University Hospital of Liège, Belgium
| | - Steven Laureys
- Coma Science Group, GIGA Consciousness, University of Liège, Belgium; Centre du Cerveau, University Hospital of Liège, Belgium; Fund for Scientific Research, FNRS, Belgium
| | - Steve Majerus
- Fund for Scientific Research, FNRS, Belgium; Psychology and Neuroscience of Cognition Research Unit, University of Liège, Belgium.
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5
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Picozzi M, Panzeri L, Torri D, Sattin D. Analyzing the paradigmatic cases of two persons with a disorder of consciousness: reflections on the legal and ethical perspectives. BMC Med Ethics 2021; 22:88. [PMID: 34238274 PMCID: PMC8268180 DOI: 10.1186/s12910-021-00656-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 06/30/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Media have increasingly reported on the difficulties associated with end-of-life decision-making in patients with Disorders of Consciousness (DOC), contextualizing such dilemma in detailed accounts of the patient's life. Two of the first stories debated in the scientific community were those related to the cases of two women, one American, the other Italian, who captured attention of millions of people in the first years of this third millennium. METHODS Much has been written about the challenges of surrogate decision-making for patients in DOC, but less has been written comparing these challenges across legal systems and cultures. In our paper, we propose a systematic analysis of the final legal documents written by the American and Italian Courts in relation to the two cases, developing our discussion around three areas: the level of certainty/reliability of diagnosis and prognosis, the reconstruction of self-expression, time of illness and time of care. They are examples of the typical issues discussed by legal authors and allow us to understand the link and the difference between the legal and ethical perspectives. RESULTS The legal approach to the two cases has some common elements: the need to be certain about the diagnosis and prognosis and the fact that the clinical criteria are necessary in determining the most appropriate treatments, although these criteria are not sufficient unless they are supplemented by the patient's will. The issue of relations takes on importance both from a legal and an ethical point of view, but from two different perspectives. While ethics safeguards relationships by guaranteeing their differences and makes them reconcilable, law safeguards relationships by guaranteeing the cold forms of respect, equality, impartiality, symmetry, reciprocity, and irreversibility. In this perspective, the link between the time of care and the decision of the family members assumes importance. CONCLUSIONS The most interesting point that emerges from our analysis is the issue of relationships and how they affect decisions, both from a legal and ethical point of view. For this reason, during the patients' hospitalization, it is necessary to identify ways in which they might give their opinion about the moral issues underlying their choices.
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Affiliation(s)
- Mario Picozzi
- Center for Clinical Ethics, Biotechnology and Life Sciences Department, University of Insubria, Varese, Italy.
- Clinical and Experimental Medicine and Medical Humanities-PhD Program, Via Ottorino Rossi 9, 21100, Varese, Italy.
| | - Lino Panzeri
- Department of Law, Economics and Cultures, University of Insubria, Via Sant'Abbondio 12, 22100, Como, Italy
| | - Davide Torri
- ASST Dei Sette Laghi - S.C. Medicina Legale, Viale Borri, 57, 21100, Varese, Italy
| | - Davide Sattin
- Clinical and Experimental Medicine and Medical Humanities-PhD Program, Via Ottorino Rossi 9, 21100, Varese, Italy
- Neurology Public Health and Disability Unit, Fondazione IRCCS Istituto Neurologico C. Besta, Via Celoria 11, 20133, Milan, Italy
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6
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Salvato G, Berlingeri M, De Maio G, Curto F, Chieregato A, Magnani FG, Sberna M, Rosanova M, Paulesu E, Bottini G. Autonomic responses to emotional linguistic stimuli and amplitude of low-frequency fluctuations predict outcome after severe brain injury. NEUROIMAGE-CLINICAL 2020; 28:102356. [PMID: 32750635 PMCID: PMC7397392 DOI: 10.1016/j.nicl.2020.102356] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 06/26/2020] [Accepted: 07/18/2020] [Indexed: 01/22/2023]
Abstract
Acute DOC patients with favourable outcome show preserved event-related electrodermal response. Acute DOC patients showed reduced fALFF in the posterior cingulate cortex. Event-related electrodermal activity correlated with the fALFFs in the PCC in the acute phase.
An accurate prognosis on the outcome of brain-injured patients with disorders of consciousness (DOC) remains a significant challenge, especially in the acute stage. In this study, we applied a multiple-technique approach to provide accurate predictions on functional outcome after 6 months in 15 acute DOC patients. Electrophysiological correlates of implicit cognitive processing of verbal stimuli and data-driven voxel-wise resting-state fMRI signals, such as the fractional amplitude of low-frequency fluctuations (fALFF), were employed. Event-related electrodermal activity, an index of autonomic activation, was recorded in response to emotional words and pseudo-words at baseline (T0). On the same day, patients also underwent a resting-state fMRI scan. Six months later (T1), patients were classified as outcome-negative and outcome-positive using a standard functional outcome scale. We then revisited the baseline measures to test their predictive power for the functional outcome measured at T1. We found that only outcome-positive patients had an earlier, higher autonomic response for words compared to pseudo-words, a pattern similar to that of healthy awake controls. Furthermore, DOC patients showed reduced fALFF in the posterior cingulate cortex (PCC), a brain region that contributes to autonomic regulation and awareness. The event-related electrodermal marker of residual cognitive functioning was found to have a significant correlation with residual local neuronal activity in the PCC. We propose that a residual autonomic response to cognitively salient stimuli, together with a preserved resting-state activity in the PCC, can provide a useful prognostic index in acute DOC.
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Affiliation(s)
- Gerardo Salvato
- Cognitive Neuropsychology Centre, ASST "Grande Ospedale Metropolitano" Niguarda, Milano, Italy; Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy; NeuroMi, Milan Center for Neuroscience, Milano, Italy.
| | - Manuela Berlingeri
- NeuroMi, Milan Center for Neuroscience, Milano, Italy; Department of Humanistic Studies, University of Urbino Carlo Bo, Urbino, Italy; Center of Developmental Neuropsychology, Area Vasta 1, ASUR Marche, Pesaro, Italy.
| | - Gabriele De Maio
- Cognitive Neuropsychology Centre, ASST "Grande Ospedale Metropolitano" Niguarda, Milano, Italy
| | - Francesco Curto
- Department of Neuroresuscitation and Intensive Care, ASST "Grande Ospedale Metropolitano" Niguarda, Milano, Italy
| | - Arturo Chieregato
- Department of Neuroresuscitation and Intensive Care, ASST "Grande Ospedale Metropolitano" Niguarda, Milano, Italy
| | - Francesca Giulia Magnani
- Cognitive Neuropsychology Centre, ASST "Grande Ospedale Metropolitano" Niguarda, Milano, Italy; Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy; NeuroMi, Milan Center for Neuroscience, Milano, Italy
| | - Maurizio Sberna
- Department of Neuroradiology, ASST "Grande Ospedale Metropolitano" Niguarda, Milano, Italy
| | - Mario Rosanova
- Department of Biomedical and Clinical Sciences "Luigi Sacco", University of Milano, Italy; Fondazione Europea di Ricerca Biomedica, FERB Onlus, Milano, Italy
| | - Eraldo Paulesu
- Psychology Department and NeuroMI-Milan Center for Neuroscience, University of Milano-Bicocca, Milan, Italy; fMRI Unit, I.R.C.C.S. Galeazzi, Milano, Italy
| | - Gabriella Bottini
- Cognitive Neuropsychology Centre, ASST "Grande Ospedale Metropolitano" Niguarda, Milano, Italy; Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy; NeuroMi, Milan Center for Neuroscience, Milano, Italy
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7
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Petit S, Badcock NA, Woolgar A. Finding hidden treasures: A child-friendly neural test of task-following in individuals using functional Transcranial Doppler ultrasound. Neuropsychologia 2020; 146:107515. [PMID: 32504634 DOI: 10.1016/j.neuropsychologia.2020.107515] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 05/28/2020] [Accepted: 05/30/2020] [Indexed: 12/25/2022]
Abstract
Despite growing interest in the mental life of individuals who cannot communicate verbally, objective and non-invasive tests of covert cognition are still sparse. In this study, we assessed the ability of neurotypical children to understand and follow task instructions by measuring neural responses through functional transcranial Doppler ultrasound (fTCD). We recorded blood flow velocity for the two brain hemispheres of twenty children (aged 9 to 12) while they performed either a language task or a visuospatial memory task, on identical visual stimuli. We extracted measures of neural lateralisation for the two tasks separately to investigate lateralisation, and we compared the left-minus-right pattern of activation across tasks to assess task-following. At the group level, we found that neural responses were left-lateralised when children performed the language task, and not when they performed the visuospatial task. However, with statistically robust analyses and controlled paradigms, significant lateralisation in individual children was less frequent than expected from the literature. Nonetheless, the pattern of hemispheric activation for the two tasks allowed us to confirm task-following in the group of participants, as well as in over half of the individuals. This provides a promising avenue for a covert and inexpensive test of children's ability to follow task instructions and perform different mental tasks on identical stimuli.
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Affiliation(s)
- Selene Petit
- Perception in Action Research Centre, Macquarie University, Australia; Department of Cognitive Science, Macquarie University, Australia; ARC Centre of Excellence in Cognition and its Disorders (CCD), Australia.
| | - Nicholas A Badcock
- Perception in Action Research Centre, Macquarie University, Australia; Department of Cognitive Science, Macquarie University, Australia; ARC Centre of Excellence in Cognition and its Disorders (CCD), Australia; School of Psychological Science, University of Western Australia, Crawley, Australia
| | - Alexandra Woolgar
- Perception in Action Research Centre, Macquarie University, Australia; Department of Cognitive Science, Macquarie University, Australia; ARC Centre of Excellence in Cognition and its Disorders (CCD), Australia; Medical Research Council (UK), Cognition and Brain Sciences Unit, University of Cambridge, Cambridge, UK
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8
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Pennartz CMA, Farisco M, Evers K. Indicators and Criteria of Consciousness in Animals and Intelligent Machines: An Inside-Out Approach. Front Syst Neurosci 2019; 13:25. [PMID: 31379521 PMCID: PMC6660257 DOI: 10.3389/fnsys.2019.00025] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 06/24/2019] [Indexed: 01/02/2023] Open
Abstract
In today's society, it becomes increasingly important to assess which non-human and non-verbal beings possess consciousness. This review article aims to delineate criteria for consciousness especially in animals, while also taking into account intelligent artifacts. First, we circumscribe what we mean with "consciousness" and describe key features of subjective experience: qualitative richness, situatedness, intentionality and interpretation, integration and the combination of dynamic and stabilizing properties. We argue that consciousness has a biological function, which is to present the subject with a multimodal, situational survey of the surrounding world and body, subserving complex decision-making and goal-directed behavior. This survey reflects the brain's capacity for internal modeling of external events underlying changes in sensory state. Next, we follow an inside-out approach: how can the features of conscious experience, correlating to mechanisms inside the brain, be logically coupled to externally observable ("outside") properties? Instead of proposing criteria that would each define a "hard" threshold for consciousness, we outline six indicators: (i) goal-directed behavior and model-based learning; (ii) anatomic and physiological substrates for generating integrative multimodal representations; (iii) psychometrics and meta-cognition; (iv) episodic memory; (v) susceptibility to illusions and multistable perception; and (vi) specific visuospatial behaviors. Rather than emphasizing a particular indicator as being decisive, we propose that the consistency amongst these indicators can serve to assess consciousness in particular species. The integration of scores on the various indicators yields an overall, graded criterion for consciousness, somewhat comparable to the Glasgow Coma Scale for unresponsive patients. When considering theoretically derived measures of consciousness, it is argued that their validity should not be assessed on the basis of a single quantifiable measure, but requires cross-examination across multiple pieces of evidence, including the indicators proposed here. Current intelligent machines, including deep learning neural networks (DLNNs) and agile robots, are not indicated to be conscious yet. Instead of assessing machine consciousness by a brief Turing-type of test, evidence for it may gradually accumulate when we study machines ethologically and across time, considering multiple behaviors that require flexibility, improvisation, spontaneous problem-solving and the situational conspectus typically associated with conscious experience.
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Affiliation(s)
- Cyriel M. A. Pennartz
- Department of Cognitive and Systems Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, Netherlands
- Research Priority Area, Brain and Cognition, University of Amsterdam, Amsterdam, Netherlands
| | - Michele Farisco
- Centre for Research Ethics and Bioethics, Uppsala University, Uppsala, Sweden
- Biogem, Biology and Molecular Genetics Institute, Ariano Irpino, Italy
| | - Kathinka Evers
- Centre for Research Ethics and Bioethics, Uppsala University, Uppsala, Sweden
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9
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Tang Q, Zhang C, Wu X, Duan W, Weng W, Feng J, Mao Q, Chen S, Jiang J, Gao G. Comprehensive Proteomic Profiling of Patients' Tears Identifies Potential Biomarkers for the Traumatic Vegetative State. Neurosci Bull 2018; 34:626-638. [PMID: 30019218 DOI: 10.1007/s12264-018-0259-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 06/22/2018] [Indexed: 01/03/2023] Open
Abstract
The vegetative state is a complex condition with unclear mechanisms and limited diagnostic, prognostic, and therapeutic methods. In this study, we aimed to explore the proteomic profile of tears from patients in a traumatic vegetative state and identify potential diagnostic markers using tears-a body fluid that can be collected non-invasively. Using iTRAQ quantitative proteomic technology, in the discovery phase, tear samples collected from 16 patients in a traumatic vegetative state and 16 normal individuals were analyzed. Among 1080 identified tear proteins, 57 were upregulated and 15 were downregulated in the patients compared to the controls. Bioinformatics analysis revealed that the differentially-expressed proteins were mainly involved in the wound response and immune response signaling pathways. Furthermore, we verified the levels of 7 differentially-expressed proteins in tears from 50 traumatic vegetative state patients and 50 normal controls (including the samples used in the discovery phase) using ELISA. The results showed that this 7-protein panel had a high discrimination ability for traumatic vegetative state (area under the curve = 0.999). In summary, the altered tear proteomic profile identified in this study provides a basis for potential tear protein markers for diagnosis and prognosis of the traumatic vegetative state and also provides novel insights into the mechanisms of traumatic vegetative state.
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Affiliation(s)
- Qilin Tang
- Department of Neurosurgery, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, China
- Shanghai Head Trauma Institute, Shanghai, 200127, China
| | - Chao Zhang
- Department of Neurosurgery, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, China
- Shanghai Head Trauma Institute, Shanghai, 200127, China
| | - Xiang Wu
- Department of Neurosurgery, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, China
- Shanghai Head Trauma Institute, Shanghai, 200127, China
| | - Wenbin Duan
- Department of Neurosurgery, Baoshan People's Hospital, Baoshan, 678000, China
| | - Weiji Weng
- Department of Neurosurgery, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, China
- Shanghai Head Trauma Institute, Shanghai, 200127, China
| | - Junfeng Feng
- Department of Neurosurgery, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, China
- Shanghai Head Trauma Institute, Shanghai, 200127, China
| | - Qing Mao
- Department of Neurosurgery, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, China
- Shanghai Head Trauma Institute, Shanghai, 200127, China
| | - Shubin Chen
- Department of Neurology, Anda Hospital, Shanghai, 201204, China
| | - Jiyao Jiang
- Department of Neurosurgery, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, China
- Shanghai Head Trauma Institute, Shanghai, 200127, China
| | - Guoyi Gao
- Department of Neurosurgery, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, China.
- Shanghai Head Trauma Institute, Shanghai, 200127, China.
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10
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Haugg A, Cusack R, Gonzalez-Lara LE, Sorger B, Owen AM, Naci L. Do Patients Thought to Lack Consciousness Retain the Capacity for Internal as Well as External Awareness? Front Neurol 2018; 9:492. [PMID: 29997565 PMCID: PMC6030833 DOI: 10.3389/fneur.2018.00492] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 06/06/2018] [Indexed: 01/04/2023] Open
Abstract
It is well established that some patients, who are deemed to have disorders of consciousness, remain entirely behaviorally non-responsive and are diagnosed as being in a vegetative state, yet can nevertheless demonstrate covert awareness of their external environment by modulating their brain activity, a phenomenon known as cognitive-motor dissociation. However, the extent to which these patients retain internal awareness remains unknown. To investigate the potential for internal and external awareness in patients with chronic disorders of consciousness (DoC), we asked whether the pattern of juxtaposition between the functional time-courses of the default mode (DMN) and fronto-parietal networks, shown in healthy individuals to mediate the naturally occurring dominance switching between internal and external aspects of consciousness, was present in these patients. We used a highly engaging movie by Alfred Hitchcock to drive the recruitment of the fronto-parietal networks, including the dorsal attention (DAN) and executive control (ECN) networks, and their maximal juxtaposition to the DMN in response to the complex stimulus, relative to rest and a scrambled, meaningless movie baseline condition. We tested a control group of healthy participants (N = 13/12) and two groups of patients with disorders of consciousness, one comprised of patients who demonstrated independent, neuroimaging-based evidence of covert external awareness (N = 8), and the other of those who did not (N = 8). Similarly to the healthy controls, only the group of patients with overt and, critically, covert external awareness showed significantly heightened differentiation between the DMN and the DAN in response to movie viewing relative to their resting state time-courses, which was driven by the movie's narrative. This result suggested the presence of functional integrity in the DMN and fronto-parietal networks and their relationship to one another in patients with covert external awareness. Similar to the effect in healthy controls, these networks became more strongly juxtaposed to one another in response to movie viewing relative to the baseline conditions, suggesting the potential for internal and external awareness during complex stimulus processing. Furthermore, our results suggest that naturalistic paradigms can dissociate between groups of DoC patients with and without covert awareness based on the functional integrity of brain networks.
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Affiliation(s)
- Amelie Haugg
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland.,Neuroscience Center Zurich, Swiss Federal Institute of Technology, University of Zurich, Zurich, Switzerland
| | - Rhodri Cusack
- School of Psychology, Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
| | | | - Bettina Sorger
- Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, Netherlands
| | - Adrian M Owen
- The Brain and Mind Institute, University of Western Ontario, London, ON, Canada
| | - Lorina Naci
- School of Psychology, Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
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11
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Crone JS, Bio BJ, Vespa PM, Lutkenhoff ES, Monti MM. Restoration of thalamo-cortical connectivity after brain injury: recovery of consciousness, complex behavior, or passage of time? J Neurosci Res 2017; 96:671-687. [DOI: 10.1002/jnr.24115] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/12/2017] [Accepted: 06/19/2017] [Indexed: 01/13/2023]
Affiliation(s)
- Julia S. Crone
- Department of Psychology; University of California Los Angeles; Los Angeles CA 90095 USA
| | - Branden J. Bio
- Department of Psychology; University of California Los Angeles; Los Angeles CA 90095 USA
- Department of Psychology; Princeton University; Princeton NJ 08540 USA
| | - Paul M. Vespa
- Brain Injury Research Center (BIRC); Department of Neurosurgery, Geffen School of Medicine at UCLA; Los Angeles CA 90095 USA
- Department of Neurology; Geffen School of Medicine at UCLA; Los Angeles CA 90095 USA
| | - Evan S. Lutkenhoff
- Department of Psychology; University of California Los Angeles; Los Angeles CA 90095 USA
| | - Martin M. Monti
- Department of Psychology; University of California Los Angeles; Los Angeles CA 90095 USA
- Brain Injury Research Center (BIRC); Department of Neurosurgery, Geffen School of Medicine at UCLA; Los Angeles CA 90095 USA
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12
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Morlet D, Ruby P, André-Obadia N, Fischer C. The auditory oddball paradigm revised to improve bedside detection of consciousness in behaviorally unresponsive patients. Psychophysiology 2017; 54:1644-1662. [DOI: 10.1111/psyp.12954] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 06/09/2017] [Accepted: 06/12/2017] [Indexed: 11/30/2022]
Affiliation(s)
- Dominique Morlet
- Lyon Neuroscience Research Center (CRNL), Brain Dynamics and Cognition Team, INSERM U 1028, CNRS UMR 5292, University Lyon 1; Lyon France
| | - Perrine Ruby
- Lyon Neuroscience Research Center (CRNL), Brain Dynamics and Cognition Team, INSERM U 1028, CNRS UMR 5292, University Lyon 1; Lyon France
| | - Nathalie André-Obadia
- Functional Neurology and Epileptology Department; Neurological Hospital, Hospices Civils de Lyon; Lyon France
- Lyon Neuroscience Research Center (CRNL), Neuropain Team, INSERM U 1028, CNRS UMR 5292, University Lyon 1; Lyon France
| | - Catherine Fischer
- Lyon Neuroscience Research Center (CRNL), Brain Dynamics and Cognition Team, INSERM U 1028, CNRS UMR 5292, University Lyon 1; Lyon France
- Functional Neurology and Epileptology Department; Neurological Hospital, Hospices Civils de Lyon; Lyon France
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13
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Marino S, Bonanno L, Ciurleo R, Baglieri A, Morabito R, Guerrera S, Rifici C, Giorgio A, Bramanti P, De Stefano N. Functional Evaluation of Awareness in Vegetative and Minimally Conscious State. Open Neuroimag J 2017; 11:17-25. [PMID: 28553427 PMCID: PMC5427708 DOI: 10.2174/1874440001711010017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 01/31/2017] [Accepted: 03/21/2017] [Indexed: 11/30/2022] Open
Abstract
Objective: The aim of this study was to assess differences in brain activation in a large sample of Vegetative State (VS) and Minimally Conscious State (MCS) patients, using functional magnetic resonance imaging (fMRI). Methods: We studied 50 patients four to seven months after brain injury. By using international clinical criteria and validated behavioural scales such as the Glasgow Coma Scale and the Clinical Unawareness Assessment Scale, the patients were grouped into VS (n=23) and MCS (n=27). All patients underwent to fMRI examination. After 6 months, the patients were reassessed using Glasgow Outcome Scale and Revised Coma Recovery Scale. Results: fMRI showed significant (p<0.01, cluster-corrected) brain activation in the primary auditory cortex bilaterally during the acoustic stimuli in patients with both VS and MCS. However, ten patients clinically classified as VS, showed a pattern of brain activation very similar to that of MCS patients. Six months later, these ten VS patients had significant clinical improvement, evolving into MCS, whereas the other VS patients and patients with MCS remained clinically stable. Conclusion: Brain activity could help in discerning whether the status of wakefulness in VS is also accompanied by partial awareness, as occurs in MCS. This may have very important prognostic implications.
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Affiliation(s)
- Silvia Marino
- IRCCS Centro Neurolesi "Bonino Pulejo", Messina, Italy.,Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Italy
| | - Lilla Bonanno
- IRCCS Centro Neurolesi "Bonino Pulejo", Messina, Italy
| | | | | | - Rosa Morabito
- IRCCS Centro Neurolesi "Bonino Pulejo", Messina, Italy
| | | | | | - Antonio Giorgio
- UOSA Experimental Neurology, Dept. of Medicine, Surgery & Neuroscience, University of Siena, Italy
| | | | - Nicola De Stefano
- UOSA Experimental Neurology, Dept. of Medicine, Surgery & Neuroscience, University of Siena, Italy
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Canadian perspectives on the clinical actionability of neuroimaging in disorders of consciousness. Can J Neurol Sci 2016; 42:96-105. [PMID: 25804248 DOI: 10.1017/cjn.2015.8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND Acquired brain injury is a critical public health and socioeconomic problem in Canada, leaving many patients in vegetative, minimally conscious, or locked-in states, unresponsive and unable to communicate. Recent advances in neuroimaging research have demonstrated residual consciousness in a few exemplary patients with acquired brain injury, suggesting potential misdiagnosis and changes in prognosis. Such progress, in parallel with research using multimodal brain imaging technologies in recent years, has promising implications for clinical translation, notwithstanding the many challenges that impact health care and policy development. This study explored the perspectives of Canadian professionals with expertise either in neuroimaging research, disorders of consciousness, or both, on the potential clinical applications and implications of imaging technology. METHODS Twenty-two professionals from designated communities of neuroimaging researchers, ethicists, lawyers, and practitioners participated in semistructured interviews. Data were analyzed for emergent themes. RESULTS The five most dominant themes were: (1) validation and calibration of the methods; (2) informed consent; (3) burdens on the health care system; (4) implications for the Canadian health care system; and (5) possibilities for improved prognosis. CONCLUSIONS Movement of neuroimaging from research into clinical care for acquired brain injury will require careful consideration of legal and ethical issues alongside research reliability, responsible distribution of health care resources, and the interaction of technological capabilities with patient outcome.
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Lechinger J, Wielek T, Blume C, Pichler G, Michitsch G, Donis J, Gruber W, Schabus M. Event-related EEG power modulations and phase connectivity indicate the focus of attention in an auditory own name paradigm. J Neurol 2016; 263:1530-43. [PMID: 27216625 PMCID: PMC4971049 DOI: 10.1007/s00415-016-8150-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2015] [Revised: 04/26/2016] [Accepted: 04/27/2016] [Indexed: 11/28/2022]
Abstract
Estimating cognitive abilities in patients suffering from Disorders of Consciousness remains challenging. One cognitive task to address this issue is the so-called own name paradigm, in which subjects are presented with first names including the own name. In the active condition, a specific target name has to be silently counted. We recorded EEG during this task in 24 healthy controls, 8 patients suffering from Unresponsive Wakefulness Syndrome (UWS) and 7 minimally conscious (MCS) patients. EEG was analysed with respect to amplitude as well as phase modulations and connectivity. Results showed that general reactivity in the delta, theta and alpha frequency (event-related de-synchronisation, ERS/ERD, and phase locking between trials and electrodes) toward auditory stimulation was higher in controls than in patients. In controls, delta ERS and lower alpha ERD indexed the focus of attention in both conditions, late theta ERS only in the active condition. Additionally, phase locking between trials and delta phase connectivity was highest for own names in the passive and targets in the active condition. In patients, clear stimulus-specific differences could not be detected. However, MCS patients could reliably be differentiated from UWS patients based on their general event-related delta and theta increase independent of the type of stimulus. In conclusion, the EEG signature of the active own name paradigm revealed instruction-following in healthy participants. On the other hand, DOC patients did not show clear stimulus-specific processing. General reactivity toward any auditory input, however, allowed for a reliable differentiation between MCS and UWS patients.
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Affiliation(s)
- Julia Lechinger
- Laboratory for Sleep and Consciousness Research, Department of Psychology, University of Salzburg, Hellbrunnerstraße 34, 5020, Salzburg, Austria.
- Centre for Cognitive Neuroscience (CCNS), University of Salzburg, Salzburg, Austria.
| | - Tomasz Wielek
- Laboratory for Sleep and Consciousness Research, Department of Psychology, University of Salzburg, Hellbrunnerstraße 34, 5020, Salzburg, Austria
| | - Christine Blume
- Laboratory for Sleep and Consciousness Research, Department of Psychology, University of Salzburg, Hellbrunnerstraße 34, 5020, Salzburg, Austria
- Centre for Cognitive Neuroscience (CCNS), University of Salzburg, Salzburg, Austria
| | - Gerald Pichler
- Apallic Care Unit, Neurological Division, Albert-Schweitzer-Klinik, Graz, Austria
| | - Gabriele Michitsch
- Apallic Care Unit, Neurological Division, Sozialmedizinisches Zentrum Ost-Donauspital, Vienna, Austria
| | - Johann Donis
- Apallic Care Unit, Neurological Division, Sozialmedizinisches Zentrum Ost-Donauspital, Vienna, Austria
| | - Walter Gruber
- Centre for Cognitive Neuroscience (CCNS), University of Salzburg, Salzburg, Austria
| | - Manuel Schabus
- Laboratory for Sleep and Consciousness Research, Department of Psychology, University of Salzburg, Hellbrunnerstraße 34, 5020, Salzburg, Austria
- Centre for Cognitive Neuroscience (CCNS), University of Salzburg, Salzburg, Austria
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Monti MM, Rosenberg M, Finoia P, Kamau E, Pickard JD, Owen AM. Thalamo-frontal connectivity mediates top-down cognitive functions in disorders of consciousness. Neurology 2015; 84:167-73. [PMID: 25480912 PMCID: PMC4336082 DOI: 10.1212/wnl.0000000000001123] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Accepted: 08/06/2014] [Indexed: 01/28/2023] Open
Abstract
OBJECTIVE We employed functional MRI (fMRI) to assess whether (1) patients with disorders of consciousness (DOC) retain the ability to willfully engage in top-down processing and (2) what neurophysiologic factors distinguish patients who can demonstrate this ability from patients who cannot. METHODS Sixteen volunteers, 8 patients in vegetative state (VS), 16 minimally conscious patients (MCS), and 4 exit from MCS (eMCS) patients were enrolled in a prospective cross-sectional fMRI study. Participants performed a target detection task in which they counted the number of times a (changing) target word was presented amidst a set of distractors. RESULTS Three of 8 patients diagnosed as being in a VS exhibited significant activations in response to the task, thereby demonstrating a state of consciousness. Differential activations across tasks were also observed in 6 MCS patients and 1 eMCS patient. A psycho-physiologic interaction analysis revealed that the main factor distinguishing patients who responded to the task from those who did not was a greater connectivity between the anterior section of thalamus and prefrontal cortex. CONCLUSIONS In our sample of patients, the dissociation between overt behavior observable in clinical assessments and residual cognitive faculties is prevalent among DOC patients (37%). A substantial number of patients, including some diagnosed with VS, can demonstrate willful engagement in top-down cognition. While neuroimaging data are not the same as observable behavior, this suggests that the mental status of some VS patients exceeds what can be appreciated clinically. Furthermore, thalamo-frontal circuits might be crucial to sustaining top-down functions.
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Affiliation(s)
- Martin M Monti
- From the Department of Psychology (M.M.M., M.R.), University of California Los Angeles; the Department of Neurosurgery (M.M.M.), Brain Injury Research Center (BIRC), Geffen School of Medicine at UCLA, Los Angeles; the Cognition and Brain Sciences Unit (P.F.), Medical Research Council, Cambridge; the Division of Neurosurgery (P.F., E.K., J.D.P.), University of Cambridge, Addenbrooke's Hospital, Cambridge, UK; and the Natural Science Building (A.M.O.), Brain & Mind Institute, The University of Western Ontario, London, Canada.
| | - Matthew Rosenberg
- From the Department of Psychology (M.M.M., M.R.), University of California Los Angeles; the Department of Neurosurgery (M.M.M.), Brain Injury Research Center (BIRC), Geffen School of Medicine at UCLA, Los Angeles; the Cognition and Brain Sciences Unit (P.F.), Medical Research Council, Cambridge; the Division of Neurosurgery (P.F., E.K., J.D.P.), University of Cambridge, Addenbrooke's Hospital, Cambridge, UK; and the Natural Science Building (A.M.O.), Brain & Mind Institute, The University of Western Ontario, London, Canada
| | - Paola Finoia
- From the Department of Psychology (M.M.M., M.R.), University of California Los Angeles; the Department of Neurosurgery (M.M.M.), Brain Injury Research Center (BIRC), Geffen School of Medicine at UCLA, Los Angeles; the Cognition and Brain Sciences Unit (P.F.), Medical Research Council, Cambridge; the Division of Neurosurgery (P.F., E.K., J.D.P.), University of Cambridge, Addenbrooke's Hospital, Cambridge, UK; and the Natural Science Building (A.M.O.), Brain & Mind Institute, The University of Western Ontario, London, Canada
| | - Evelyn Kamau
- From the Department of Psychology (M.M.M., M.R.), University of California Los Angeles; the Department of Neurosurgery (M.M.M.), Brain Injury Research Center (BIRC), Geffen School of Medicine at UCLA, Los Angeles; the Cognition and Brain Sciences Unit (P.F.), Medical Research Council, Cambridge; the Division of Neurosurgery (P.F., E.K., J.D.P.), University of Cambridge, Addenbrooke's Hospital, Cambridge, UK; and the Natural Science Building (A.M.O.), Brain & Mind Institute, The University of Western Ontario, London, Canada
| | - John D Pickard
- From the Department of Psychology (M.M.M., M.R.), University of California Los Angeles; the Department of Neurosurgery (M.M.M.), Brain Injury Research Center (BIRC), Geffen School of Medicine at UCLA, Los Angeles; the Cognition and Brain Sciences Unit (P.F.), Medical Research Council, Cambridge; the Division of Neurosurgery (P.F., E.K., J.D.P.), University of Cambridge, Addenbrooke's Hospital, Cambridge, UK; and the Natural Science Building (A.M.O.), Brain & Mind Institute, The University of Western Ontario, London, Canada
| | - Adrian M Owen
- From the Department of Psychology (M.M.M., M.R.), University of California Los Angeles; the Department of Neurosurgery (M.M.M.), Brain Injury Research Center (BIRC), Geffen School of Medicine at UCLA, Los Angeles; the Cognition and Brain Sciences Unit (P.F.), Medical Research Council, Cambridge; the Division of Neurosurgery (P.F., E.K., J.D.P.), University of Cambridge, Addenbrooke's Hospital, Cambridge, UK; and the Natural Science Building (A.M.O.), Brain & Mind Institute, The University of Western Ontario, London, Canada
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Rosenbaum AM, Giacino JT. Clinical management of the minimally conscious state. HANDBOOK OF CLINICAL NEUROLOGY 2015; 127:395-410. [PMID: 25702230 DOI: 10.1016/b978-0-444-52892-6.00025-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The minimally conscious state (MCS) was defined as a disorder of consciousness (DoC) distinct from the vegetative state more than a decade ago. While this condition has become widely recognized, there are still no guidelines to steer the approach to assessment and treatment. The development of evidence-based practice guidelines for MCS has been hampered by ambiguity around the concept of consciousness, the lack of accurate methods of assessment, and the dearth of well-designed clinical trials. This chapter provides a critical review of existing assessment procedures, critically reviews available treatment options and identifies knowledge gaps. We close with practice-based recommendations for a rational approach to clinical management of this challenging population.
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Affiliation(s)
| | - Joseph T Giacino
- Department of Physical Medicine and Rehabilitation, Harvard Medical School and Spaulding Rehabilitation Hospital, Boston, MA, USA.
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Lutkenhoff ES, Rosenberg M, Chiang J, Zhang K, Pickard JD, Owen AM, Monti MM. Optimized brain extraction for pathological brains (optiBET). PLoS One 2014; 9:e115551. [PMID: 25514672 PMCID: PMC4267825 DOI: 10.1371/journal.pone.0115551] [Citation(s) in RCA: 141] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 11/24/2014] [Indexed: 11/24/2022] Open
Abstract
The study of structural and functional magnetic resonance imaging data has greatly benefitted from the development of sophisticated and efficient algorithms aimed at automating and optimizing the analysis of brain data. We address, in the context of the segmentation of brain from non-brain tissue (i.e., brain extraction, also known as skull-stripping), the tension between the increased theoretical and clinical interest in patient data, and the difficulty of conventional algorithms to function optimally in the presence of gross brain pathology. Indeed, because of the reliance of many algorithms on priors derived from healthy volunteers, images with gross pathology can severely affect their ability to correctly trace the boundaries between brain and non-brain tissue, potentially biasing subsequent analysis. We describe and make available an optimized brain extraction script for the pathological brain (optiBET) robust to the presence of pathology. Rather than attempting to trace the boundary between tissues, optiBET performs brain extraction by (i) calculating an initial approximate brain extraction; (ii) employing linear and non-linear registration to project the approximate extraction into the MNI template space; (iii) back-projecting a standard brain-only mask from template space to the subject’s original space; and (iv) employing the back-projected brain-only mask to mask-out non-brain tissue. The script results in up to 94% improvement of the quality of extractions over those obtained with conventional software across a large set of severely pathological brains. Since optiBET makes use of freely available algorithms included in FSL, it should be readily employable by anyone having access to such tools.
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Affiliation(s)
- Evan S Lutkenhoff
- Department of Psychology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Matthew Rosenberg
- Department of Psychology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Jeffrey Chiang
- Department of Psychology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Kunyu Zhang
- Department of Psychology, University of California Los Angeles, Los Angeles, California, United States of America
| | - John D Pickard
- Division of Neurosurgery, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Adrian M Owen
- Brain & Mind Institute, Natural Science Building, The University of Western Ontario, London, Ontario, Canada
| | - Martin M Monti
- Department of Psychology, University of California Los Angeles, Los Angeles, California, United States of America; Brain Injury Research Center (BIRC), Department of Neurosurgery, Ronald Reagan Medical Center, University of California Los Angeles, Los Angeles, California, United States of America
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Di Perri C, Thibaut A, Heine L, Soddu A, Demertzi A, Laureys S. Measuring consciousness in coma and related states. World J Radiol 2014; 6:589-597. [PMID: 25170396 PMCID: PMC4147439 DOI: 10.4329/wjr.v6.i8.589] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 05/09/2014] [Accepted: 06/16/2014] [Indexed: 02/06/2023] Open
Abstract
Consciousness is a prismatic and ambiguous concept that still eludes any universal definition. Severe acquired brain injuries resulting in a disorder of consciousness (DOC) provide a model from which insights into consciousness can be drawn. A number of recent studies highlight the difficulty in making a diagnosis in patients with DOC based only on behavioral assessments. Here we aim to provide an overview of how neuroimaging techniques can help assess patients with DOC. Such techniques are expected to facilitate a more accurate understanding of brain function in states of unconsciousness and to improve the evaluation of the patient’s cognitive abilities by providing both diagnostic and prognostic indicators.
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20
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Connectivity biomarkers can differentiate patients with different levels of consciousness. Clin Neurophysiol 2014; 125:1545-55. [DOI: 10.1016/j.clinph.2013.12.095] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 12/08/2013] [Accepted: 12/11/2013] [Indexed: 11/22/2022]
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21
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Comparison of EEG-features and classification methods for motor imagery in patients with disorders of consciousness. PLoS One 2013; 8:e80479. [PMID: 24282545 PMCID: PMC3839976 DOI: 10.1371/journal.pone.0080479] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 10/03/2013] [Indexed: 12/01/2022] Open
Abstract
Current research aims at identifying voluntary brain activation in patients who are behaviorally diagnosed as being unconscious, but are able to perform commands by modulating their brain activity patterns. This involves machine learning techniques and feature extraction methods such as applied in brain computer interfaces. In this study, we try to answer the question if features/classification methods which show advantages in healthy participants are also accurate when applied to data of patients with disorders of consciousness. A sample of healthy participants (N = 22), patients in a minimally conscious state (MCS; N = 5), and with unresponsive wakefulness syndrome (UWS; N = 9) was examined with a motor imagery task which involved imagery of moving both hands and an instruction to hold both hands firm. We extracted a set of 20 features from the electroencephalogram and used linear discriminant analysis, k-nearest neighbor classification, and support vector machines (SVM) as classification methods. In healthy participants, the best classification accuracies were seen with coherences (mean = .79; range = .53−.94) and power spectra (mean = .69; range = .40−.85). The coherence patterns in healthy participants did not match the expectation of central modulated -rhythm. Instead, coherence involved mainly frontal regions. In healthy participants, the best classification tool was SVM. Five patients had at least one feature-classifier outcome with p0.05 (none of which were coherence or power spectra), though none remained significant after false-discovery rate correction for multiple comparisons. The present work suggests the use of coherences in patients with disorders of consciousness because they show high reliability among healthy subjects and patient groups. However, feature extraction and classification is a challenging task in unresponsive patients because there is no ground truth to validate the results.
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22
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Chennu S, Finoia P, Kamau E, Monti MM, Allanson J, Pickard JD, Owen AM, Bekinschtein TA. Dissociable endogenous and exogenous attention in disorders of consciousness. NEUROIMAGE-CLINICAL 2013; 3:450-61. [PMID: 24273727 PMCID: PMC3830059 DOI: 10.1016/j.nicl.2013.10.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 09/23/2013] [Accepted: 10/09/2013] [Indexed: 01/19/2023]
Abstract
Recent research suggests that despite the seeming inability of patients in vegetative and minimally conscious states to generate consistent behaviour, some might possess covert awareness detectable with functional neuroimaging. These findings motivate further research into the cognitive mechanisms that might support the existence of consciousness in these states of profound neurological dysfunction. One of the key questions in this regard relates to the nature and capabilities of attention in patients, known to be related to but distinct from consciousness. Previous assays of the electroencephalographic P300 marker of attention have demonstrated its presence and potential clinical value. Here we analysed data from 21 patients and 8 healthy volunteers collected during an experimental task designed to engender exogenous or endogenous attention, indexed by the P3a and P3b components, respectively, in response to a pair of word stimuli presented amongst distractors. Remarkably, we found that the early, bottom-up P3a and the late, top-down P3b could in fact be dissociated in a patient who fitted the behavioural criteria for the vegetative state. In juxtaposition with healthy volunteers, the patient's responses suggested the presence of a relatively high level of attentional abilities despite the absence of any behavioural indications thereof. Furthermore, we found independent evidence of covert command following in the patient, as measured by functional neuroimaging during tennis imagery. Three other minimally conscious patients evidenced non-discriminatory bottom-up orienting, but no top-down engagement of selective attentional control. Our findings present a persuasive case for dissociable attentional processing in behaviourally unresponsive patients, adding to our understanding of the possible levels and applications of consequent conscious awareness. We dissociated endogenous and exogenous attention in disorders of consciousness. 21 vegetative (VS) and minimally conscious (MCS) patients tested with EEG task Exogenous bottom-up P3a found in 3 minimally conscious and 1 vegetative patient Endogenous top-down P3b found in one VS patient who performed fMRI tennis imagery Discriminative attention can be preserved in disorders of consciousness.
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Affiliation(s)
- Srivas Chennu
- Division of Neurosurgery, University of Cambridge, Box 167, Level 4, A Block, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK ; Medical Research Council, Cognition and Brain Sciences Unit, 15 Chaucer Road, Cambridge CB2 7EF, UK
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Abstract
Recent developments in functional neuroimaging have provided a number of new tools for assessing patients who clinically appear to be in a vegetative state. These techniques have been able to reveal awareness and even allow rudimentary communication in some patients who remain entirely behaviourally non-responsive. The implications of these results extend well beyond the immediate clinical and scientific findings to influencing legal proceedings, raising new ethical questions about the withdrawal of nutrition and hydration and providing new options for patients and families in that decision-making process. The findings have also motivated significant public discourse about the role of neuroscience research in society.
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EEG-response consistency across subjects in an active oddball task. PLoS One 2013; 8:e74572. [PMID: 24073216 PMCID: PMC3779217 DOI: 10.1371/journal.pone.0074572] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Accepted: 08/05/2013] [Indexed: 11/19/2022] Open
Abstract
The active oddball paradigm is a candidate task for voluntary brain activation. Previous research has focused on group effects, and has largely overlooked the potential problem of interindividual differences. Interindividual variance causes problems with the interpretation of group-level results. In this study we want to demonstrate the degree of consistency in the active oddball task across subjects, in order to answer the question of whether this task is able to reliably detect conscious target processing in unresponsive patients. We asked 18 subjects to count rare targets and to ignore frequent standards and rare distractors in an auditory active oddball task. Event-related-potentials (ERPs) and time-frequency data were analyzed with permutation-t-tests on a single subject level. We plotted the group-average ERPs and time-frequency data, and evaluated the numbers of subjects showing significant differences between targets and distractors in certain time-ranges. The distinction between targets/distractors and standards was found to be significant in the time-range of the P300 in all participants. In contrast, significant differences between targets and distractors in the time-range of the P3a/b were found in 8 subjects, only. By including effects in the N1 and in a late negative component there remained 2 subjects who did not show a distinction between targets and distractors in the ERP. While time-frequency data showed prominent effects for target/distractor vs. standard, significant differences between targets and distractors were found in 2 subjects, only. The results suggest that time-frequency- and ERP-analysis of the active oddball task may not be sensitive enough to detect voluntary brain activation in unresponsive patients. In addition, we found that time-frequency analysis was even less informative than ERPs about the subject’s task performance. Despite suggesting the use of more sensitive paradigms and/or analysis techniques, the present results give further evidence that electroencephalographic research should rely more strongly on single-subject analysis because interpretations of group-effects may be misleading.
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Harrison AH, Connolly JF. Finding a way in: A review and practical evaluation of fMRI and EEG for detection and assessment in disorders of consciousness. Neurosci Biobehav Rev 2013; 37:1403-19. [PMID: 23680699 DOI: 10.1016/j.neubiorev.2013.05.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 04/26/2013] [Accepted: 05/06/2013] [Indexed: 01/28/2023]
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Affiliation(s)
- Adrian M. Owen
- The Brain and Mind Institute, Department of Psychology, The University of Western Ontario, London, Ontario N6A 5B7, Canada;
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Höller Y, Bergmann J, Kronbichler M, Crone JS, Schmid EV, Thomschewski A, Butz K, Schütze V, Höller P, Trinka E. Real movement vs. motor imagery in healthy subjects. Int J Psychophysiol 2012; 87:35-41. [PMID: 23123181 DOI: 10.1016/j.ijpsycho.2012.10.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Revised: 09/30/2012] [Accepted: 10/24/2012] [Indexed: 10/27/2022]
Abstract
Motor imagery tasks are well established procedures in brain computer interfaces, but are also used in the assessment of patients with disorders of consciousness. For testing awareness in unresponsive patients it is necessary to know the natural variance of brain responses to motor imagery in healthy subjects. We examined 22 healthy subjects using EEG in three conditions: movement of both hands, imagery of the same movement, and an instruction to hold both hands still. Single-subject non-parametric statistics were applied to the fast-Fourier transformed data. Most effects were found in the α- and β-frequency ranges over central electrodes, that is, in the μ-rhythm. We found significant power changes in 18 subjects during movement and in 11 subjects during motor imagery. In 8 subjects these changes were consistent over both conditions. The significant power changes during movement were a decrease of μ-rhythm. There were 2 subjects with an increase and 9 subjects with a decrease of μ-rhythm during imagery. α and β are the most responsive frequency ranges, but there is a minor number of subjects who show a synchronization instead of the more common desynchronization during motor imagery. A (de)synchronization of μ-rhythm can be considered to be a normal response.
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Affiliation(s)
- Yvonne Höller
- Department of Neurology, Christian-Doppler-Klinik, Paracelsus Medical University, Salzburg, Austria.
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Chatelle C, Chennu S, Noirhomme Q, Cruse D, Owen AM, Laureys S. Brain-computer interfacing in disorders of consciousness. Brain Inj 2012; 26:1510-22. [PMID: 22759199 DOI: 10.3109/02699052.2012.698362] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Recent neuroimaging research has strikingly demonstrated the existence of covert awareness in some patients with disorders of consciousness (DoC). These findings have highlighted the potential for the development of simple brain-computer interfaces (BCI) as a diagnosis in behaviourally unresponsive patients. OBJECTIVES This study here reviews current EEG-based BCIs that hold potential for assessing and eventually assisting patients with DoC. It highlights key areas for further development that might eventually make their application feasible in this challenging patient group. METHODS The major types of BCIs proposed in the literature are considered, namely those based on the P3 potential, sensorimotor rhythms, steady state oscillations and slow cortical potentials. In each case, a brief overview of the relevant literature is provided and then their relative merits for BCI applications in DoC are considered. RESULTS A range of BCI designs have been proposed and tested for enabling communication in fully conscious, paralysed patients. Although many of these have potential applicability for patients with DoC, they share some key challenges that need to be overcome, including limitations of stimulation modality, feedback, user training and consistency. CONCLUSION Future work will need to address the technical and practical challenges facing reliable implementation at the patient's bedside.
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Affiliation(s)
- Camille Chatelle
- Coma Science Group, Cyclotron Research Centre, University of Liège, Liège, Belgium.
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Wieser M, Buetler L, Vallery H, Schaller J, Mayr A, Kofler M, Saltuari L, Zutter D, Riener R. Quantification of clinical scores through physiological recordings in low-responsive patients: a feasibility study. J Neuroeng Rehabil 2012; 9:30. [PMID: 22647145 PMCID: PMC3443429 DOI: 10.1186/1743-0003-9-30] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 04/20/2012] [Indexed: 11/10/2022] Open
Abstract
Clinical scores represent the gold standard in characterizing the clinical condition of patients in vegetative or minimally conscious state. However, they suffer from problems of sensitivity, specificity, subjectivity and inter-rater reliability.In this feasibility study, objective measures including physiological and neurophysiological signals are used to quantify the clinical state of 13 low-responsive patients. A linear regression method was applied in nine patients to obtain fixed regression coefficients for the description of the clinical state. The statistical model was extended and evaluated with four patients of another hospital. A linear mixed models approach was introduced to handle the challenges of data sets obtained from different locations.Using linear backward regression 12 variables were sufficient to explain 74.4% of the variability in the change of the clinical scores. Variables based on event-related potentials and electrocardiogram account for most of the variability.These preliminary results are promising considering that this is the first attempt to describe the clinical state of low-responsive patients in such a global and quantitative way. This new model could complement the clinical scores based on objective measurements in order to increase diagnostic reliability. Nevertheless, more patients are necessary to prove the conclusions of a statistical model with 12 variables.
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Affiliation(s)
- Martin Wieser
- Sensory-Motor Systems Lab, Institute of Robotics and Intelligent Systems, Department of Health Science and Technologies, ETH Zurich, Tannenstrasse 1, Zurich, 8092, Switzerland
- Medical Faculty, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Lilith Buetler
- Sensory-Motor Systems Lab, Institute of Robotics and Intelligent Systems, Department of Health Science and Technologies, ETH Zurich, Tannenstrasse 1, Zurich, 8092, Switzerland
- HELIOS Clinic Zihlschlacht, Center for Neurological Rehabilitation, Zihlschlacht, Switzerland
| | - Heike Vallery
- Sensory-Motor Systems Lab, Institute of Robotics and Intelligent Systems, Department of Health Science and Technologies, ETH Zurich, Tannenstrasse 1, Zurich, 8092, Switzerland
- Medical Faculty, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Biomedical Engineering, Khalifa University, Abu Dhabi, UAE
| | | | - Andreas Mayr
- Department of Neurology, Hochzirl Hospital, Zirl, Austria
| | - Markus Kofler
- Department of Neurology, Hochzirl Hospital, Zirl, Austria
| | - Leopold Saltuari
- Department of Neurology, Hochzirl Hospital, Zirl, Austria
- Research Unit for Neurorehabilitation South Tyrol, Bolzano, Italy
| | - Daniel Zutter
- HELIOS Clinic Zihlschlacht, Center for Neurological Rehabilitation, Zihlschlacht, Switzerland
| | - Robert Riener
- Sensory-Motor Systems Lab, Institute of Robotics and Intelligent Systems, Department of Health Science and Technologies, ETH Zurich, Tannenstrasse 1, Zurich, 8092, Switzerland
- Medical Faculty, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
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Monti MM, Pickard JD, Owen AM. Visual cognition in disorders of consciousness: from V1 to top-down attention. Hum Brain Mapp 2012; 34:1245-53. [PMID: 22287214 DOI: 10.1002/hbm.21507] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 09/27/2011] [Accepted: 10/10/2011] [Indexed: 11/12/2022] Open
Abstract
What is it like to be at the lower boundaries of consciousness? Disorders of consciousness such as coma, the vegetative state, and the minimally conscious state are among the most mysterious and least understood conditions of the human brain. Particularly complicated is the assessment of residual cognitive functioning and awareness for diagnostic, rehabilitative, legal, and ethical purposes. In this article, we present a novel functional magnetic resonance imaging exploration of visual cognition in a patient with a severe disorder of consciousness. This battery of tests, first developed in healthy volunteers, assesses increasingly complex transformations of visual information along a known caudal to rostral gradient from occipital to temporal cortex. In the first five levels, the battery assesses (passive) processing of light, color, motion, coherent shapes, and object categories (i.e., faces, houses). At the final level, the battery assesses the ability to voluntarily deploy visual attention in order to focus on one of two competing stimuli. In the patient, this approach revealed appropriate brain activations, undistinguishable from those seen in healthy and aware volunteers. In addition, the ability of the patient to focus one of two competing stimuli, and switch between them on command, also suggests that he retained the ability to access, to some degree, his own visual representations.
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Affiliation(s)
- Martin M Monti
- Department of Psychology, University of California-Los Angeles, CA, USA.
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Abstract
Awake but not aware: This puzzling dissociation of the two central elements of consciousness defines the vegetative state. Traditionally, this condition has been believed to imply a brain with preserved hypothalamic and brainstem autonomic functions but with no capacity for cortical cognitive processes. As is discussed in this review, over a 20-year span neuroimaging techniques have clearly demonstrated that this characterization of patients in a vegetative state is incorrect. Contrary to the initial belief, the "vegetative" brain can retain several high-level aspects of cognitive functions, across sensory modalities, including language processing and learning dynamics. Nonetheless, the residual cognitive functions observed in vegetative patients might reflect intact but functionally disconnected cortical modules that do not give rise to the subjective feeling of phenomenological awareness.
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Affiliation(s)
- Martin M Monti
- Department of Psychology, University of California, Los Angeles, Los Angeles, California 90095, USA.
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Fellinger R, Klimesch W, Schnakers C, Perrin F, Freunberger R, Gruber W, Laureys S, Schabus M. Cognitive processes in disorders of consciousness as revealed by EEG time–frequency analyses. Clin Neurophysiol 2011; 122:2177-84. [PMID: 21511524 DOI: 10.1016/j.clinph.2011.03.004] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Revised: 02/04/2011] [Accepted: 03/06/2011] [Indexed: 11/19/2022]
Affiliation(s)
- R Fellinger
- Department of Psychology, Laboratory for Sleep and Consciousness Research and Division of Physiological Psychology, University of Salzburg, Hellbrunnerstraße 34, 5020 Salzburg, Austria
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Cruse D, Monti MM, Owen AM. Neuroimaging in disorders of consciousness: contributions to diagnosis and prognosis. FUTURE NEUROLOGY 2011. [DOI: 10.2217/fnl.10.87] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Conventional assessment of the level of awareness that is retained by a patient with a disorder of consciousness following a brain injury is made on the basis of exhibited behaviors. This is particularly challenging for clinicians who must decide whether a certain behavior, which might be inconsistent or incomplete, reflects a conscious or an unconscious process. These assessments are not only highly subjective, but also dependent upon the ability of the patient to produce an appropriate motor response. Recent developments in neuroimaging techniques can provide a measure of the levels of awareness that these patients may retain, and importantly, they overcome the necessity for these patients to produce detectable movements by instead relying on their adopting appropriate ‘mind-sets’ as instructed by the task. In this article, we review recent advances in this field and discuss how they may accompany behavioral assessments in future in order to provide diagnostic and prognostic information.
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Affiliation(s)
| | - Martin M Monti
- Medical Research Council, Cognition & Brain Sciences Unit, 15 Chaucer Road, Cambridge, CB2 7EF, UK
| | - Adrian M Owen
- Medical Research Council, Cognition & Brain Sciences Unit, 15 Chaucer Road, Cambridge, CB2 7EF, UK
- Centre for Brain & Mind, Natural Sciences Centre, Room 237, University of Western Ontario, London, ON N6A 5B7, Canada
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Consciousness revealed: new insights into the vegetative and minimally conscious states. Curr Opin Neurol 2010; 23:656-60. [DOI: 10.1097/wco.0b013e32833fd4e7] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Rodriguez Moreno D, Schiff ND, Giacino J, Kalmar K, Hirsch J. A network approach to assessing cognition in disorders of consciousness. Neurology 2010; 75:1871-8. [PMID: 20980667 DOI: 10.1212/wnl.0b013e3181feb259] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE Conventional assessments of consciousness rely on motor responses to indicate awareness. However, overt behaviors may be absent or ambiguous in patients with disorders of consciousness (DOC) resulting in underrating capacity for cognition. fMRI during a silent picture-naming task was evaluated as an indicator of command following when conventional methods are not sufficient. METHODS A total of 10 patients with and without conventional evidence of awareness, who met diagnostic criteria for the minimally conscious state (MCS) (n = 5), vegetative state (VS) (n = 3), emerged from MCS (EMCS) (n = 1), and locked-in syndrome (LIS) (n = 1), participated in this observational fMRI study. RESULTS The LIS and EMCS patients engaged a complete network of essential language-related regions during the object-naming task. The MCS and 2 of the VS patients demonstrated both complete and partial preservation of the object-naming system. Patients who engaged a complete network scored highest on the Coma Recovery Scale-Revised. CONCLUSIONS This study supports the view that fMRI during object naming can elicit brain activations in patients with DOC similar to those observed in healthy subjects during command following, and patients can be stratified by completeness of the engaged neural system. These results suggest that activity of the language network may serve as an indicator of high-level cognition and possibly volitional processes that cannot be discerned through conventional behavioral assessment alone.
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Affiliation(s)
- D Rodriguez Moreno
- Department of Radiology, Functional MRI Research Center, Neurological Institute B41, Box 108, 710 West 168th Street, New York, NY 10032, USA.
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Monti MM, Vanhaudenhuyse A, Coleman MR, Boly M, Pickard JD, Tshibanda L, Owen AM, Laureys S. Willful modulation of brain activity in disorders of consciousness. N Engl J Med 2010; 362:579-89. [PMID: 20130250 DOI: 10.1056/nejmoa0905370] [Citation(s) in RCA: 766] [Impact Index Per Article: 54.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND The differential diagnosis of disorders of consciousness is challenging. The rate of misdiagnosis is approximately 40%, and new methods are required to complement bedside testing, particularly if the patient's capacity to show behavioral signs of awareness is diminished. METHODS At two major referral centers in Cambridge, United Kingdom, and Liege, Belgium, we performed a study involving 54 patients with disorders of consciousness. We used functional magnetic resonance imaging (MRI) to assess each patient's ability to generate willful, neuroanatomically specific, blood-oxygenation-level-dependent responses during two established mental-imagery tasks. A technique was then developed to determine whether such tasks could be used to communicate yes-or-no answers to simple questions. RESULTS Of the 54 patients enrolled in the study, 5 were able to willfully modulate their brain activity. In three of these patients, additional bedside testing revealed some sign of awareness, but in the other two patients, no voluntary behavior could be detected by means of clinical assessment. One patient was able to use our technique to answer yes or no to questions during functional MRI; however, it remained impossible to establish any form of communication at the bedside. CONCLUSIONS These results show that a small proportion of patients in a vegetative or minimally conscious state have brain activation reflecting some awareness and cognition. Careful clinical examination will result in reclassification of the state of consciousness in some of these patients. This technique may be useful in establishing basic communication with patients who appear to be unresponsive.
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Affiliation(s)
- Martin M Monti
- Medical Research Council Cognition and Brain Sciences Unit, Cambridge, United Kingdom
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Abstract
Recent evidence has suggested that functional neuroimaging may play a crucial role in assessing residual cognition and awareness in brain injury survivors. In particular, brain insults that compromise the patient’s ability to produce motor output may render standard clinical testing ineffective. Indeed, if patients were aware but unable to signal so via motor behavior, they would be impossible to distinguish, at the bedside, from vegetative patients. Considering the alarming rate with which minimally conscious patients are misdiagnosed as vegetative, and the severe medical, legal, and ethical implications of such decisions, novel tools are urgently required to complement current clinical-assessment protocols. Functional neuroimaging may be particularly suited to this aim by providing a window on brain function without requiring patients to produce any motor output. Specifically, the possibility of detecting signs of willful behavior by directly observing brain activity (i.e., “brain behavior”), rather than motoric output, allows this approach to reach beyond what is observable at the bedside with standard clinical assessments. In addition, several neuroimaging studies have already highlighted neuroimaging protocols that can distinguish automatic brain responses from willful brain activity, making it possible to employ willful brain activations as an index of awareness. Certainly, neuroimaging in patient populations faces some theoretical and experimental difficulties, but willful, task-dependent, brain activation may be the only way to discriminate the conscious, but immobile, patient from the unconscious one.
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