References of "Laureys, Steven"
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See detailHow Does Your Formulation of Lesion-Induced States of Diminished Consciousness Fit with AIM? Do You Suppose That Brain Stem Damage Affects Activation (A) and Modulation (M)?
Charland-Verville, Vanessa ULg; Laureys, Steven ULg

in J. Allan Hobson, Nicholas Tranquillo (Ed.) Dream Consciousness: A New Approach to the Brain and Its Mind (2014)

Allan Hobson’s AIM model (Hobson, 1998) is build according to three main dimensions. The first component, Activation, describes brain’s activation processes and is closely linked to the level of ... [more ▼]

Allan Hobson’s AIM model (Hobson, 1998) is build according to three main dimensions. The first component, Activation, describes brain’s activation processes and is closely linked to the level of consciousness. According to the model, the brain is highly active in wakefulness and REM sleep but will show much less activity during NREM sleep. The second component, Input/output gateway, controls the inhibition of external stimuli. When slowly falling asleep, the gateway shuts down and inhibits the external stimuli; the brain is no longer involved in processing external perceptions. Then the brain starts its oniric phase and the focus switches to internal inputs. Finally, the third dimension, Modulation, refers to the different ways of cognitive processing (executive functions), judgment, volition and memory. According to the model, those cognitive processes are lacking in REM sleep (i.e., the brain cannot keep a record of its conscious experience during dreaming as opposed to waking state) because of the changes between the aminergic system (norepinephrine and serotonin; dominant in waking but ineffective in REM sleep) and the cholinergic system (acetylcholine; unfettered in REM sleep). These three dimensions maintain a dynamic and reciprocal interaction over the sleep-wake cycle’s variations (wakefulness, NREM and REM sleep) and each of them can be expressed with lower or higher intensities depending on the level of consciousness. [less ▲]

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See detailThe vegetative state/unresponsive wakefulness syndrome: a systematic review of prevalence studies
Van Erp, WS; Lavrijsen, JC; Van De Laar, FA et al

in European Journal of Neurology (2014)

One of the worst outcomes of acquired brain injury is the vegetative state, recently renamed ‘unresponsive wakefulness syndrome’ (VS/UWS). A patient in VS/UWS shows reflexive behaviour such as spontaneous ... [more ▼]

One of the worst outcomes of acquired brain injury is the vegetative state, recently renamed ‘unresponsive wakefulness syndrome’ (VS/UWS). A patient in VS/UWS shows reflexive behaviour such as spontaneous eye opening and breathing, but no signs of awareness of the self or the environment. We performed a systematic review of VS/UWS prevalence studies and assessed their reliability. Medline, Embase, the Cochrane Library, CINAHL and PsycINFO were searched in April 2013 for cross-sectional point or period prevalence studies explicitly stating the prevalence of VS/UWS due to acute causes within the general population. We additionally checked bibliographies and consulted experts in the field to obtain ‘grey data’ like government reports. Relevant publications underwent quality assessment and data-extraction. We retrieved 1032 papers out of which 14 met the inclusion criteria. Prevalence figures varied from 0.2 to 6.1 VS/UWS patients per 100 000 members of the population. However, the publications’ methodological quality differed substantially, in particular with regards to inclusion criteria and diagnosis verification. The reliability of VS/UWS prevalence figures is poor. Methodological flaws in available prevalence studies, the fact that 5/14 of the studies predate the identification of the minimally conscious state (MCS) as a distinct entity in 2002, and insufficient verification of included cases may lead to both overestimation and underestimation of the actual number of patients in VS/UWS. [less ▲]

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See detailPosterior Cingulate Cortex-Related Co-Activation Patterns: A Resting State fMRI Study in Propofol-Induced Loss of Consciousness
Amico, Enrico ULg; Gomez, Francisco; Di Perri, Carol et al

in PLoS ONE (2014), 9

Background: Recent studies have been shown that functional connectivity of cerebral areas is not a static phenomenon, but exhibits spontaneous fluctuations over time. There is evidence that fluctuating ... [more ▼]

Background: Recent studies have been shown that functional connectivity of cerebral areas is not a static phenomenon, but exhibits spontaneous fluctuations over time. There is evidence that fluctuating connectivity is an intrinsic phenomenon of brain dynamics that persists during anesthesia. Lately, point process analysis applied on functional data has revealed that much of the information regarding brain connectivity is contained in a fraction of critical time points of a resting state dataset. In the present study we want to extend this methodology for the investigation of resting state fMRI spatial pattern changes during propofol-induced modulation of consciousness, with the aim of extracting new insights on brain networks consciousness-dependent fluctuations. Methods: Resting-state fMRI volumes on 18 healthy subjects were acquired in four clinical states during propofol injection: wakefulness, sedation, unconsciousness, and recovery. The dataset was reduced to a spatio-temporal point process by selecting time points in the Posterior Cingulate Cortex (PCC) at which the signal is higher than a given threshold (i.e., BOLD intensity above 1 standard deviation). Spatial clustering on the PCC time frames extracted was then performed (number of clusters = 8), to obtain 8 different PCC co-activation patterns (CAPs) for each level of consciousness. Results: The current analysis shows that the core of the PCC-CAPs throughout consciousness modulation seems to be preserved. Nonetheless, this methodology enables to differentiate region-specific propofol-induced reductions in PCC-CAPs, some of them already present in the functional connectivity literature (e.g., disconnections of the prefrontal cortex, thalamus, auditory cortex), some others new (e.g., reduced co-activation in motor cortex and visual area). Conclusion: In conclusion, our results indicate that the employed methodology can help in improving and refining the characterization of local functional changes in the brain associated to propofol-induced modulation of consciousness. [less ▲]

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See detailVolitional electromyographic responses in disorders of consciousness
Habbal, Dina; Gosseries, Olivia ULg; Noirhomme, Quentin ULg et al

in Brain Injury (2014)

The aim of the study was to validate the use of electromyography (EMG) for detecting responses to command in patients in vegetative state/unresponsive wakefulness syndrome (VS/UWS) or in minimally ... [more ▼]

The aim of the study was to validate the use of electromyography (EMG) for detecting responses to command in patients in vegetative state/unresponsive wakefulness syndrome (VS/UWS) or in minimally conscious state (MCS). Methods: Thirty-eight patients were included in the study (23 traumatic, 25 patients >1 year post-onset), 10 diagnosed as being in VS/UWS, eight in MCS- (no response to command) and 20 in MCS+ (response to command). Eighteen age-matched controls participated in the experiment. The paradigm consisted of three commands (i.e. 'Move your hands', 'Move your legs' and 'Clench your teeth') and one control sentence (i.e. 'It is a sunny day') presented in random order. Each auditory stimulus was repeated 4-times within one block with a stimulus-onset asynchrony of 30 seconds. Results: Post-hoc analyses with Bonferroni correction revealed that EMG activity was higher solely for the target command in one patient in permanent VS/UWS and in three patients in MCS+. Conclusion: The use of EMG could help clinicians to detect conscious patients who do not show any volitional response during standard behavioural assessments. However, further investigations should determine the sensitivity of EMG as compared to neuroimaging and electrophysiological assessments. [less ▲]

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See detailNear-death experiences in non-life-threatening events and coma of different etiologies.
Charland-Verville, Vanessa ULg; Jourdan, Jean-Pierre; Thonnard, Marie ULg et al

in Frontiers in human neuroscience (2014), 8(203),

BACKGROUND: Near death experiences (NDEs) are increasingly being reported as a clearly identifiable physiological and psychological reality of clinical significance. However, the definition and causes of ... [more ▼]

BACKGROUND: Near death experiences (NDEs) are increasingly being reported as a clearly identifiable physiological and psychological reality of clinical significance. However, the definition and causes of the phenomenon as well as the identification of NDE experiencers is still a matter of debate. To date, the most widely used standardized tool to identify and characterize NDEs in research is the Greyson NDE scale. Using this scale, retrospective and prospective studies have been trying to estimate their incidence in various populations but few studies have attempted to associate the experiences' intensity and content to etiology. METHODS: This retrospective investigation assessed the intensity and the most frequently recounted features of self-reported NDEs after a non-life-threatening event (i.e., "NDE-like" experience) or after a pathological coma (i.e., "real NDE") and according to the etiology of the acute brain insult. We also compared our retrospectively acquired data in anoxic coma with historical data from the published literature on prospective post-anoxic studies using the Greyson NDE scale. RESULTS: From our 190 reports who met the criteria for NDE (i.e., Greyson NDE scale total score >7/32), intensity (i.e., Greyson NDE scale total score) and content (i.e., Greyson NDE scale features) did not differ between "NDE-like" (n = 50) and "real NDE" (n = 140) groups, nor within the "real NDE" group depending on the cause of coma (anoxic/traumatic/other). The most frequently reported feature was peacefulness (89-93%). Only 2 patients (1%) recounted a negative experience. The overall NDE core features' frequencies were higher in our retrospective anoxic cohort when compared to historical published prospective data. CONCLUSIONS: It appears that "real NDEs" after coma of different etiologies are similar to "NDE-like" experiences occurring after non-life threatening events. Subjects reporting NDEs retrospectively tend to have experienced a different content compared to the prospective experiencers. [less ▲]

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See detailAn independent SSVEP-based brain-computer interface in locked-in-syndrome
Lesenfants, Damien ULg; Habbal, Dina; Lugo et al

in Journal of Neural Engineering (2014)

OBJECTIVE: Steady-state visually evoked potential (SSVEP)-based brain-computer interfaces (BCIs) allow healthy subjects to communicate. However, their dependence on gaze control prevents their use with ... [more ▼]

OBJECTIVE: Steady-state visually evoked potential (SSVEP)-based brain-computer interfaces (BCIs) allow healthy subjects to communicate. However, their dependence on gaze control prevents their use with severely disabled patients. Gaze-independent SSVEP-BCIs have been designed but have shown a drop in accuracy and have not been tested in brain-injured patients. In the present paper, we propose a novel independent SSVEP-BCI based on covert attention with an improved classification rate. We study the influence of feature extraction algorithms and the number of harmonics. Finally, we test online communication on healthy volunteers and patients with locked-in syndrome (LIS). APPROACH: Twenty-four healthy subjects and six LIS patients participated in this study. An independent covert two-class SSVEP paradigm was used with a newly developed portable light emitting diode-based 'interlaced squares' stimulation pattern. MAIN RESULTS: Mean offline and online accuracies on healthy subjects were respectively 85 ± 2% and 74 ± 13%, with eight out of twelve subjects succeeding to communicate efficiently with 80 ± 9% accuracy. Two out of six LIS patients reached an offline accuracy above the chance level, illustrating a response to a command. One out of four LIS patients could communicate online. SIGNIFICANCE: We have demonstrated the feasibility of online communication with a covert SSVEP paradigm that is truly independent of all neuromuscular functions. The potential clinical use of the presented BCI system as a diagnostic (i.e., detecting command-following) and communication tool for severely brain-injured patients will need to be further explored. [less ▲]

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See detailDiagnostic precision of PET imaging and functional MRI in disorders of consciousness: a clinical validation study
Stender, Johan; Gosseries, Olivia ULg; Bruno, Marie-Aurélie ULg et al

in Lancet Neurology (2014)

Background: Bedside clinical examinations can have high rates of misdiagnosis of unresponsive wakefulness syndrome (vegetative state) or minimally conscious state. The diagnostic and prognostic usefulness ... [more ▼]

Background: Bedside clinical examinations can have high rates of misdiagnosis of unresponsive wakefulness syndrome (vegetative state) or minimally conscious state. The diagnostic and prognostic usefulness of neuroimaging-based approaches has not been established in a clinical setting. We did a validation study of two neuroimaging-based diagnostic methods: PET imaging and functional MRI (fMRI). Methods: For this clinical validation study, we included patients referred to the University Hospital of Liège, Belgium, between January, 2008, and June, 2012, who were diagnosed by our unit with unresponsive wakefulness syndrome, locked-in syndrome, or minimally conscious state with traumatic or non-traumatic causes. We did repeated standardised clinical assessments with the Coma Recovery Scale—Revised (CRS—R), cerebral 18F-fluorodeoxyglucose (FDG) PET, and fMRI during mental activation tasks. We calculated the diagnostic accuracy of both imaging methods with CRS—R diagnosis as reference. We assessed outcome after 12 months with the Glasgow Outcome Scale—Extended. Findings: We included 41 patients with unresponsive wakefulness syndrome, four with locked-in syndrome, and 81 in a minimally conscious state (48=traumatic, 78=non-traumatic; 110=chronic, 16=subacute). 18F-FDG PET had high sensitivity for identification of patients in a minimally conscious state (93%, 95% CI 85—98) and high congruence (85%, 77—90) with behavioural CRS—R scores. The active fMRI method was less sensitive at diagnosis of a minimally conscious state (45%, 30—61) and had lower overall congruence with behavioural scores (63%, 51—73) than PET imaging. 18F-FDG PET correctly predicted outcome in 75 of 102 patients (74%, 64—81), and fMRI in 36 of 65 patients (56%, 43—67). 13 of 42 (32%) of the behaviourally unresponsive patients (ie, diagnosed as unresponsive with CRS—R) showed brain activity compatible with (minimal) consciousness (ie, activity associated with consciousness, but diminished compared with fully conscious individuals) on at least one neuroimaging test; 69% of these (9 of 13) patients subsequently recovered consciousness. Interpretation: Cerebral 18F-FDG PET could be used to complement bedside examinations and predict long-term recovery of patients with unresponsive wakefulness syndrome. Active fMRI might also be useful for differential diagnosis, but seems to be less accurate. Funding: The Belgian National Funds for Scientific Research (FNRS), Fonds Léon Fredericq, the European Commission, the James McDonnell Foundation, the Mind Science Foundation, the French Speaking Community Concerted Research Action, the University of Copenhagen, and the University of Liège. [less ▲]

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See detailBiased binomial assessment of cross-validated estimation of classification accuracies illustrated in diagnosis predictions
Noirhomme, Quentin ULg; Lesenfants, Damien ULg; Gomez, Francisco et al

in NeuroImage: Clinical (2014), 4

Multivariate classification is used in neuroimaging studies to infer brain activation or in medical applications to infer diagnosis. Their results are often assessed through either a binomial or a ... [more ▼]

Multivariate classification is used in neuroimaging studies to infer brain activation or in medical applications to infer diagnosis. Their results are often assessed through either a binomial or a permutation test. Here, we simulated classification results of generated random data to assess the influence of the cross-validation scheme on the significance of results. Distributions built from classification of random data with crossvalidation did not follow the binomial distribution. The binomial test is therefore not adapted. On the contrary, the permutation test was unaffected by the cross-validation scheme. The influence of the crossvalidation was further illustrated on real-data from a brain–computer interface experiment in patients with disorders of consciousness and from an fMRI study on patients with Parkinson disease. Three out of 16 patients with disorders of consciousness had significant accuracy on binomial testing, but only one showed significant accuracy using permutation testing. In the fMRI experiment, the mental imagery of gait could discriminate significantly between idiopathic Parkinson’s disease patients and healthy subjects according to the permutation test but not according to the binomial test. Hence, binomial testing could lead to biased estimation of significance and false positive or negative results. In our view, permutation testing is thus recommended for clinical application of classification with cross-validation. [less ▲]

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See detailRegional cerebral metabolic patterns demonstrate the role of anterior forebrain mesocircuit dysfunction in the severely injured brain
Fridman, Esteban A; Beattie, Bradley J; Broft, Allegra et al

in Proceedings of the National Academy of Sciences of the United States of America (2014)

Although disorders of consciousness (DOCs) demonstrate widely varying clinical presentations and patterns of structural injury, global down-regulation and bilateral reductions in metabolism of the ... [more ▼]

Although disorders of consciousness (DOCs) demonstrate widely varying clinical presentations and patterns of structural injury, global down-regulation and bilateral reductions in metabolism of the thalamus and frontoparietal network are consistent findings. We test the hypothesis that global reductions of background synaptic activity in DOCs will associate with changes in the pattern of metabolic activity in the central thalamus and globus pallidus. We compared 32 [18F]fluorodeoxyglucose PETs obtained from severely brain-injured patients (BIs) and 10 normal volunteers (NVs). We defined components of the anterior forebrain mesocircuit on high-resolution T1-MRI (ventral, associative, and sensorimotor striatum; globus pallidus; central thalamus and noncentral thalamus). Metabolic profiles for BI and NV demonstrated distinct changes in the pattern of uptake: ventral and association striatum (but not sensorimotor) were significantly reduced relative to global mean uptake after BI; a relative increase in globus pallidus metabolism was evident in BI subjects who also showed a relative reduction of metabolism in the central thalamus. The reversal of globus pallidus and central thalamus profiles across BIs and NVs supports the mesocircuit hypothesis that broad functional (or anatomic) deafferentation may combine to reduce central thalamus activity and release globus pallidus activity in DOCs. In addition, BI subjects showed broad frontoparietal metabolic down-regulation consistent with prior studies supporting the link between central thalamic/pallidal metabolism and down-regulation of the frontoparietal network. Recovery of left hemisphere frontoparietal metabolic activity was further associated with command following. [less ▲]

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See detailWhite Matter Changes in Comatose Survivors of Anoxic Ischemic Encephalopathy and Traumatic Brain Injury: Comparative Diffusion-Tensor Imaging Study
Van Der Eerden, Anke; Khalilzadeh, Omid; Perlbarg, Vincent et al

in Radiology (2014), 270

Purpose:To analyze white matter pathologic abnormalities by using diffusion-tensor (DT) imaging in a multicenter prospective cohort of comatose patients following cardiac arrest or traumatic brain injury ... [more ▼]

Purpose:To analyze white matter pathologic abnormalities by using diffusion-tensor (DT) imaging in a multicenter prospective cohort of comatose patients following cardiac arrest or traumatic brain injury (TBI). Materials and Methods: Institutional review board approval and informed consent from proxies and control subjects were obtained. DT imaging was performed 5–57 days after insult in 49 cardiac arrest and 40 TBI patients. To control for DT imaging–processing variability, patients’ values were normalized to those of 111 control subjects. Automated segmentation software calculated normalized axial diffusivity (λ1) and radial diffusivity (λ) in 19 predefined white matter regions of interest (ROIs). DT imaging variables were compared by using general linear modeling, and side-to-side Pearson correlation coefficients were calculated. P values were corrected for multiple testing (Bonferroni). Results:In central white matter, λ1 differed from that in control subjects in six of seven TBI ROIs and five of seven cardiac arrest ROIs (all P < .01). The λ differed from that in control subjects in all ROIs in both patient groups (P < .01). In hemispheres, λ1 was decreased compared with that in control subjects in three of 12 TBI ROIs (P < .05) and nine of 12 cardiac arrest ROIs (P < .01). The λ was increased in all TBI ROIs (P < .01) and in seven of 12 cardiac arrest ROIs (P < .05). Cerebral hemisphere λ1 was lower in cardiac arrest than in TBI in six of 12 ROIs (P < .01), while λ was higher in TBI than in cardiac arrest in eight of 12 ROIs (P < .01). Diffusivity values were symmetrically distributed in cardiac arrest (P < .001 for side-to-side correlation) but not in TBI patients. Conclusion:DT imaging findings are consistent with the known predominance of cerebral hemisphere axonal injury in cardiac arrest and chiefly central myelin injury in TBI. This consistency supports the validity of DT imaging for differentiating axon and myelin damage in vivo in humans. [less ▲]

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See detailEffect of zolpidem in chronic disorders of consciousness: a prospective open-label study.
Thonnard, Marie ULg; Gosseries, Olivia ULg; Demertzi, Athina ULg et al

in Functional Neurology (2014)

Zolpidem has been reported as an "awakening drug" in some patients with disorders of consciousness (DOC). We here present the results of a prospective openlabel study in chronic DOC patients. Sixty ... [more ▼]

Zolpidem has been reported as an "awakening drug" in some patients with disorders of consciousness (DOC). We here present the results of a prospective openlabel study in chronic DOC patients. Sixty patients (35±15 years; 18 females; mean time since insult ± SD: 4±5.5 years; 31 with traumatic etiology) with a diagnosis of vegetative state/unresponsive wakefulness syndrome (n=28) or minimally conscious state (n=32) were behaviorally assessed using the Coma Recovery Scale-Revised (CRS-R) before and one hour after administration of 10 mg of zolpidem. At the group level, the diagnosis did not change after intake of zolpidem (p=0.10) and CRS-R total scores decreased (p=0.01). Twelve patients (20%) showed improved behaviors and/or CRS-R total scores after zolpidem administration but in only one patient was the diagnosis after zolpidem intake found to show a significant improvement (functional object use), which suggested a change of diagnosis. However, in this patient, a double-blind placebo-controlled trial was performed in order to better specify the effects of zolpidem, but the patient, on this trial, failed to show any clinical improvements. The present open-label study therefore failed to show any clinically significant improvement (i.e., change of Effect of zolpidem in chronic disorders of consciousness: a prospective open-label study diagnosis) in any of the 60 studied chronic DOC patients. [less ▲]

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See detailAssessing consciousness in coma and related states using transcranial magnetic stimulation combined with electroencephalography.
Gosseries, Olivia ULg; Thibaut, Aurore ULg; Boly, Mélanie ULg et al

in Annales Françaises d'Anesthésie et de Réanimation (2014)

Thanks to advances in medical care, an increased number of patients recover from coma. However, some remain in vegetative/unresponsive wakefulness syndrome or in a minimally conscious state. Detection of ... [more ▼]

Thanks to advances in medical care, an increased number of patients recover from coma. However, some remain in vegetative/unresponsive wakefulness syndrome or in a minimally conscious state. Detection of awareness in severely brain-injured patients is challenging because it relies on behavioral assessments, which can be affected by motor, sensory and cognitive impairments of the patients. Other means of evaluation are needed to improve the accuracy of the diagnosis in this challenging population. We will here review the different altered states of consciousness occurring after severe brain damage, and explain the difficulties associated with behavioral assessment of consciousness. We will then describe a non-invasive technique, transcranial magnetic stimulation combined with high-density electroencephalography (TMS-EEG), which has allowed us to detect the presence or absence of consciousness in different physiological, pathological and pharmacological states. Some potential underlying mechanisms of the loss of consciousness will then be discussed. In conclusion, TMS-EEG is highly promising in identifying markers of consciousness at the individual level and might be of great value for clinicians in the assessment of consciousness. [less ▲]

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See detailQuantifying cortical EEG responses to TMS in (un)consciousness
Sarasso, S; Rosanova, M; Casali, A.G et al

in Clinical EEG and Neuroscience : Official Journal of the EEG and Clinical Neuroscience Society (ENCS) (2014)

We normally assess another individual's level of consciousness based on her or his ability to interact with the surrounding environment and communicate. Usually, if we observe purposeful behavior ... [more ▼]

We normally assess another individual's level of consciousness based on her or his ability to interact with the surrounding environment and communicate. Usually, if we observe purposeful behavior, appropriate responses to sensory inputs, and, above all, appropriate answers to questions, we can be reasonably sure that the person is conscious. However, we know that consciousness can be entirely within the brain, even in the absence of any interaction with the external world; this happens almost every night, while we dream. Yet, to this day, we lack an objective, dependable measure of the level of consciousness that is independent of processing sensory inputs and producing appropriate motor outputs. Theoretically, consciousness is thought to require the joint presence of functional integration and functional differentiation, otherwise defined as brain complexity. Here we review a series of recent studies in which Transcranial Magnetic Stimulation combined with electroencephalography (TMS/EEG) has been employed to quantify brain complexity in wakefulness and during physiological (sleep), pharmacological (anesthesia) and pathological (brain injury) loss of consciousness. These studies invariably show that the complexity of the cortical response to TMS collapses when consciousness is lost during deep sleep, anesthesia and vegetative state following severe brain injury, while it recovers when consciousness resurges in wakefulness, during dreaming, in the minimally conscious state or locked-in syndrome. The present paper will also focus on how this approach may contribute to unveiling the pathophysiology of disorders of consciousness affecting brain-injured patients. Finally, we will underline some crucial methodological aspects concerning TMS/EEG measurements of brain complexity. [less ▲]

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See detailConsciousness and Unconsciousness: An EEG Perspective
Noirhomme, Quentin ULg; Laureys, Steven ULg

in Clinical EEG and Neuroscience (2014), 45

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See detailDIRECTED INFORMATION TRANSFER IN SCALP ELECTROENCEPHALOGRAPHIC RECORDINGS: INSIGHTS ON DISORDERS OF CONSCIOUSNESS
Marinazzo, Daniele; Gosseries, Olivia ULg; Boly, Mélanie ULg et al

in Clinical EEG and Neuroscience : Official Journal of the EEG and Clinical Neuroscience Society (ENCS) (2014)

Introduction: The neural mechanisms underlying electrophysiological changes observed in patients with disorders of consciousness following a coma remain poorly understood. The aim of this article is to ... [more ▼]

Introduction: The neural mechanisms underlying electrophysiological changes observed in patients with disorders of consciousness following a coma remain poorly understood. The aim of this article is to investigate the mechanisms underlying the differences in spontaneous electroencephalography between patients in vegetative/unresponsive wakefulness syndrome, minimally conscious state, emergence of the minimally conscious state and age-matched healthy control subjects. <br />Methods: Forty recording of spontaneous scalp electroencephalography were performed in 27 patients who were comatose on admission, and on healthy controls. Multivariate Granger Causality and Transfer Entropy were applied on the data. <br />Results: Distinctive patterns of putative bottlenecks of information were associated to each conscious state. Healthy controls are characterized by a greater amount of synergetic contributions from duplets of variables. <br />Conclusion: A novel set of measures was tested to get a novel insight on the pattern of information transfer in a network of scalp electrodes in patients with disorders of consciousness. [less ▲]

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See detailAutomated analysis of background EEG and reactivity during therapeutic hypothermia in comatose patients after cardiac arrest
Noirhomme, Quentin ULg; Lehembre, Rémy; Lugo, Zulay et al

in Clinical EEG and Neuroscience : Official Journal of the EEG and Clinical Neuroscience Society (ENCS) (2014)

Visual analysis of electroencephalography (EEG) background and reactivity during therapeutic hypothermia provides important outcome information, but is time-consuming and not always consistent between ... [more ▼]

Visual analysis of electroencephalography (EEG) background and reactivity during therapeutic hypothermia provides important outcome information, but is time-consuming and not always consistent between reviewers. Automated EEG analysis may help quantify the brain damage. Forty-six comatose patients in therapeutic hypothermia, after cardiac arrest, were included in the study. EEG background was quantified with burst-suppression ratio (BSR) and approximate entropy, both used to monitor anesthesia. Reactivity was detected through change in the power spectrum of signal before and after stimulation. Automatic results obtained almost perfect agreement (discontinuity) to substantial agreement (background reactivity) with a visual score from EEG-certified neurologists. Burst-suppression ratio was more suited to distinguish continuous EEG background from burst-suppression than approximate entropy in this specific population. Automatic EEG background and reactivity measures were significantly related to good and poor outcome. We conclude that quantitative EEG measurements can provide promising information regarding current state of the patient and clinical outcome, but further work is needed before routine application in a clinical setting. [less ▲]

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See detailA vibrotactile P300-based BCI for consciousness detection and communication
Lugo, Zulay; Rodriguez, Javi; Lechner, Alexander et al

in Clinical EEG and Neuroscience : Official Journal of the EEG and Clinical Neuroscience Society (ENCS) (2014)

Brain–computer interface (BCI) has been used for many years for communication in severely disabled patients. BCI based on electrophysiological signals has enabled communication, using auditory or visual ... [more ▼]

Brain–computer interface (BCI) has been used for many years for communication in severely disabled patients. BCI based on electrophysiological signals has enabled communication, using auditory or visual stimuli to elicit event-related potentials (ERPs). The aim of this study was to determine whether patients with locked-in syndrome (LIS) could elicit a P300 wave, using a vibrotactile oddball paradigm for establishing somatosensory BCI-based communication. Six chronic LIS patients performed 2electroencephalography (EEG)-based vibrotactile P300 oddball tasks. After a simple mental counting task of the target stimuli, participants were instructed to answer 5 questions by counting the vibration on either the right wrist for “yes” or the left wrist for “no.” All participants were able to elicit a P300 wave using the vibrotactile oddball paradigm BCI task. In the counting task, 4 patients got accuracies of 100% (average above chance). In the communication task, one patient achieved 100% accuracy (average above chance). We have shown the feasibility of eliciting a P300 response using vibrotactile stimulation in patients with LIS. The present study provides evidence that this approach can be used for EEG-based BCI communications in this patient group. This is the first study to prove the feasibility of a BCI based on somatosensory (vibratory) stimulation in a group of braininjured patients. Furthermore, this approach could be used for the detection of consciousness in non-communicating patients due to severe brain injuries. [less ▲]

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