Publications of Steven Laureys
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See detailSwallowing in individuals with disorders of consciousness: A cohort study
MELOTTE, Evelyne ULiege; MAUDOUX, Audrey ULiege; DELHALLE, Sabrina ULiege et al

in Annals of Physical and Rehabilitation Medicine (in press)

Background. After a period of coma, a proportion of individuals with severe brain injury remain in an altered state of consciousness before regaining partial or complete recovery. Individuals with ... [more ▼]

Background. After a period of coma, a proportion of individuals with severe brain injury remain in an altered state of consciousness before regaining partial or complete recovery. Individuals with disorders of consciousness (DOC) classically receive hydration and nutrition through an enteral feeding tube. However, the real impact of the level of consciousness on an individual’s swallowing ability remains poorly investigated. Objective. We aimed to document the incidence and characteristics of dysphagia in DOC individuals and to evaluate the link between different components of swallowing and the level of consciousness. Methods. We analyzed clinical data on the respiratory status, oral feeding and otolaryngologic examination of swallowing in DOC individuals. Univariate and multivariate logistic regression was used to analyse the association of components of swallowing and participant groups (i.e., unresponsive wakefulness syndrome [UWS] and minimally conscious state [MCS]). Results. We included 92 individuals with DOC (26 UWS and 66 MCS). Overall, 99% of the participants showed deficits in the oral and/or pharyngeal phase of swallowing. As compared with the MCS group, the UWS group more frequently had a tracheostomy (69% vs 24%), with diminished cough reflex (27% vs 54%) and no effective oral phase (0% vs 21%). Conclusion. Almost all DOC participants had severe dysphagia. Some components of swallowing (i.e., tracheostomy, cough reflex and efficacy of the oral phase of swallowing) were related to consciousness. In particular, no UWS participant had an efficient oral phase, which suggests that its presence may be a sign of consciousness. In addition, no UWS participant could be fed entirely orally, whereas no MCS participant orally received ordinary food. Our study also confirms that objective swallowing assessment can be successfully completed in DOC individuals and that specific care is needed to treat severe dysphagia in DOC. [less ▲]

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See detailSECONDs administration guidelines: A fast tool for assessing consciousness in brain-injured patients
Sanz, Leandro ULiege; Aubinet, Charlène ULiege; Cassol, Helena ULiege et al

in Journal of Visualized Experiments (2021)

Establishing an accurate diagnosis is crucial for patients with disorders of consciousness (DoC) following a severe brain injury. The Coma Recovery Scale-Revised (CRS-R) is the recommended behavioral ... [more ▼]

Establishing an accurate diagnosis is crucial for patients with disorders of consciousness (DoC) following a severe brain injury. The Coma Recovery Scale-Revised (CRS-R) is the recommended behavioral scale for assessing the level of consciousness among these patients, but its long administration duration is a major hurdle in clinical settings. The Simplified Evaluation of CONsciousness Disorders (SECONDs) is a shorter scale that was developed to tackle this issue. It consists of six mandatory items, observation, command-following, visual pursuit, visual fixation, oriented behaviors, and arousal, and two conditional items, communication and localization to pain. The score ranges between 0 and 8 and corresponds to a specific diagnosis (i.e., coma, unresponsive wakefulness syndrome, minimally conscious state minus/plus, or emergence from the minimally conscious state). A first validation study on patients with prolonged DoC showed high concurrent validity and intra- and inter-rater reliability. The SECONDs requires less training than the CRS-R and its administration lasts about 7 minutes (interquartile range: 5-9 minutes). An additional index score allows the more precise tracking of a patient’s behavioral fluctuation or evolution over time. The SECONDs is therefore a fast and valid tool for assessing the level of consciousness in patients with severe brain injury. It can easily be used by healthcare staff and implemented in time-constrained clinical settings, such as intensive care units, to help decrease misdiagnosis rates and to optimize treatment decisions. These administration guidelines provide detailed instructions for administering the SECONDs in a standardized and reproducible manner, which is an essential requirement for achieving a reliable diagnosis. [less ▲]

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See detailHow hot is the hot zone? Computational modelling clarifies the role of parietal and frontoparietal connectivity during anaesthetic-induced loss of consciousness: Computational modelling of anaesthetic-induced LOC.
Ihalainen, Riku; Gosseries, Olivia ULiege; de Steen, Frederik Van et al

in NeuroImage (2021)

In recent years, specific cortical networks have been proposed to be crucial for sustaining consciousness, including the posterior hot zone and frontoparietal resting state networks (RSN). Here, we ... [more ▼]

In recent years, specific cortical networks have been proposed to be crucial for sustaining consciousness, including the posterior hot zone and frontoparietal resting state networks (RSN). Here, we computationally evaluate the relative contributions of three RSNs - the default mode network (DMN), the salience network (SAL), and the central executive network (CEN) - to consciousness and its loss during propofol anaesthesia. Specifically, we use dynamic causal modelling (DCM) of 10 minutes of high-density EEG recordings (N = 10, 4 males) obtained during behavioural responsiveness, unconsciousness and post-anaesthetic recovery to characterise differences in effective connectivity within frontal areas, the posterior 'hot zone', frontoparietal connections, and between-RSN connections. We estimate - for the first time - a large DCM model (LAR) of resting EEG, combining the three RSNs into a rich club of interconnectivity. Consistent with the hot zone theory, our findings demonstrate reductions in inter-RSN connectivity in the parietal cortex. Within the DMN itself, the strongest reductions are in feed-forward frontoparietal and parietal connections at the precuneus node. Within the SAL and CEN, loss of consciousness generates small increases in bidirectional connectivity. Using novel DCM leave-one-out cross-validation, we show that the most consistent out-of-sample predictions of the state of consciousness come from a key set of frontoparietal connections. This finding also generalises to unseen data collected during post-anaesthetic recovery. Our findings provide new, computational evidence for the importance of the posterior hot zone in explaining the loss of consciousness, highlighting also the distinct role of frontoparietal connectivity in underpinning conscious responsiveness, and consequently, suggest a dissociation between the mechanisms most prominently associated with explaining the contrast between conscious awareness and unconsciousness, and those maintaining consciousness. [less ▲]

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See detailThe Near-Death Experience Content (NDE-C) scale: Development and psychometric validation
Martial, Charlotte ULiege; Simon, Jessica ULiege; Puttaert, Ninon ULiege et al

in Consciousness and Cognition (2020)

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See detailSimplified Evaluation of CONsciousness Disorders (SECONDs) in individuals with severe brain injury: A validation study
Aubinet, Charlène ULiege; Cassol, Helena ULiege; BODART, Olivier ULiege et al

in Annals of Physical and Rehabilitation Medicine (2020)

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See detailDecreased evoked slow-activity after tDCS in disorders of consciousness
Mensen, Armand; BODART, Olivier ULiege; Thibaut, Aurore ULiege et al

in Frontiers in Systems Neuroscience (2020), 14(62),

Due to life-saving medical advances, the diagnosis and treatment of disorders of consciousness (DOC) has become a more commonly occurring clinical issue. One recently developed intervention option has ... [more ▼]

Due to life-saving medical advances, the diagnosis and treatment of disorders of consciousness (DOC) has become a more commonly occurring clinical issue. One recently developed intervention option has been non-invasive transcranial direct current stimulation. This dichotomy of patient responders may be better understood by investigating the mechanism behind the transcranial direct current stimulation (tDCS) intervention. The combination of transcranial magnetic stimulation and electroencephalography (TMS-EEG) has been an important diagnostic tool in DOC patients. We therefore examined the neural response using TMS-EEG both before and after tDCS in seven DOC patients (four diagnosed as in a minimally conscious state and three with unresponsive wakefulness syndrome). tDCS was applied over the dorsolateral prefrontal cortex, while TMS pulses were applied to the premotor cortex. None of the seven patients showed relevant behavioral change after tDCS. We did, however, find that the overall evoked slow activity was reduced following tDCS intervention. We also found a positive correlation between the strength of the slow activity and the amount of high-frequency suppression. However, there was no significant pre-post tDCS difference in high frequencies. In the resting-state EEG, we observed that both the incidence of slow waves and the positive slope of the wave were affected by tDCS. Taken together, these results suggest that the tDCS intervention can reduce the slow-wave activity component of bistability, but this may not directly affect high-frequency activity. We hypothesize that while reduced slow activity may be necessary for the recovery of neural function, especially consciousness, this alone is insufficient. [less ▲]

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See detailComplete hemispherotomy leads to lateralized functional organization and lower level of consciousness in the isolated hemisphere
Blauwblomme, Thomas; Demertzi, Athina ULiege; Tacchela, Jean‐Marc et al

in Epilepsia Open (2020)

Objective To quantify whole‐brain functional organization after complete hemispherotomy, characterizing unexplored plasticity pathways and the conscious level of the dissected hemispheres. Methods ... [more ▼]

Objective To quantify whole‐brain functional organization after complete hemispherotomy, characterizing unexplored plasticity pathways and the conscious level of the dissected hemispheres. Methods Evaluation with multimodal magnetic resonance imaging in two pediatric patients undergoing right hemispherotomy including complete callosotomy with a perithalamic section. Regional cerebral blood flow and fMRI network connectivity assessed the functional integrity of both hemispheres after surgery. The level of consciousness was tested by means of a support vector machine classifier which compared the intrinsic organization of the dissected hemispheres with those of patients suffering from disorders of consciousness. Results After hemispherotomy, both patients showed typical daily functionality. We found no interhemispheric transfer of functional connectivity in either patient as predicted by the operation. The healthy left hemispheres displayed focal blood hyperperfusion in motor and limbic areas, with preserved network‐level organization. Unexpectedly, the disconnected right hemispheres showed sustained network organization despite low regional cerebral blood flow. Subcortically, functional connectivity was increased in the left thalamo‐cortical loop and between the cerebelli. One patient further showed unusual ipsilateral right cerebello‐cortical connectivity, which was explained by the mediation of the vascular system. The healthy left hemisphere had higher probability to be classified as in a minimally conscious state compared to the isolated right hemisphere. Significance Complete hemispherotomy leads to a lateralized whole‐brain organization, with the remaining hemisphere claiming most of the brain's energetic reserves supported by subcortical structures. Our results further underline the contribution of nonneuronal vascular signals on contralateral connectivity, shedding light on the nature of network organization in the isolated tissue. The disconnected hemisphere is characterized by a level of consciousness which is necessary but insufficient for conscious processing, paving the way for more specific inquiries about its role in awareness in the absence of behavioral output. [less ▲]

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See detailDe NDE als opkomend wetenschappelijk onderzoeksgebied
Martial, Charlotte ULiege; Cassol, Helena ULiege; LAUREYS, Steven ULiege

in Pim van Lommel (Ed.) Het geheim van Elysion: 45 jaar studie naar nabij-de-dood-ervaringen over bewustzijn in liefde zonder waarheen (2020)

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See detailSwallowing in patient with disorders of consciousness: A behavioral study
MELOTTE, Evelyne ULiege; MAUDOUX, Audrey ULiege; KAUX, Jean-François ULiege et al

in Abstract book of 22nd European Congress of Physical and Rehabilitation Medicine (2020, September)

Introduction: After a period of coma, a proportion of patients with severe brain injury remain in an altered state of consciousness before regaining partial or complete recovery. Patients with disorders ... [more ▼]

Introduction: After a period of coma, a proportion of patients with severe brain injury remain in an altered state of consciousness before regaining partial or complete recovery. Patients with disorders of consciousness (DOC) classically receive hydration and nutrition through an enteral feeding tube. However, the real impact of the level of consciousness on a patient’s swallowing ability remains poorly investigated. Objective: The aims of this study were to document the incidence and characteristics of dysphagia in patients DOC and to evaluate the link between different components of swallowing and the level of consciousness. Method: We retrospectively analyzed clinical data on the respiratory status, oral feeding and otolaryngologic examination of swallowing of DOC patients admitted for a one-week multimodal assessment of consciousness. Results: A total of 92 DOC patients were included, 26 patients with unresponsive wakefulness syndrome (UWS) and 66 in minimally conscious state (MCS). Deficits in the oral and/or pharyngeal phase of swallowing were present in 99% of the patients. Compared to MCS patients, UWS patients were more frequently tracheotomized (69% UWS vs 24% MCS) with diminished cough reflex (27% UWS vs 54% MCS) and no effective oral phase (0% UWS vs 21% MCS). Conclusion: almost all patients with DOC presented at least one swallowing disorder, which represents the most important proportion of dysphagia in neurological population. Some components of swallowing (i.e., tracheostomy, cough reflex and efficacy of the oral phase of swallowing) correlate with the level of consciousness. In particular, the efficacy of the oral phase was not observed in any of the UWS patients, suggesting that its presence may be a sign of consciousness, and consequently, it should be taken into account in DOC diagnosis. Our study also confirms that objective swallowing assessment can be completed in DOC patients, and that specific care is needed to treat severe dysphagia in DOC patients. [less ▲]

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See detailAn Echo of Consciousness: Brain Function During Preferred Music
Carrière, Manon ULiege; Larroque, Stephen Karl ULiege; Martial, Charlotte ULiege et al

in Brain Connectivity (2020)

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See detailNear-Death Experience Memories Include More Episodic Components Than Flashbulb Memories
Cassol, Helena ULiege; Bonin, Estelle ULiege; Bastin, Christine ULiege et al

in Frontiers in Psychology (2020), 11(888),

Memories of near-death experiences (NDEs) are recalled as “realer” than memories of other real or imagined events. Given their rich phenomenology, emotionality and consequentiality, it was hypothesized ... [more ▼]

Memories of near-death experiences (NDEs) are recalled as “realer” than memories of other real or imagined events. Given their rich phenomenology, emotionality and consequentiality, it was hypothesized that they could meet some aspects of the definition of flashbulb memories. We aimed to identify and compare the episodic and non-episodic information provided in verbal recollections of NDE, flashbulb, and control autobiographical memories. The phenomenological characteristics and centrality of the memories were also compared. Twenty-five participants who had lived a NDE in a life-threatening situation were interviewed and completed the Memory Characteristics Questionnaires as well as the Centrality of Event Scale for their NDE, a flashbulb and another autobiographical memory used as control. Overall, transcribed NDE verbal recollections included a higher overall amount of details and more internal/episodic information than control autobiographical and flashbulb memories. Moreover, flashbulb memories were associated to a lower intensity of feelings while remembering and a lower personal importance, and are less reactivated and less susceptible to be remembered from a first person perspective compared to NDE and control autobiographical memories. Finally, NDE memories are the most central memories to experiencers’ identity, followed by control autobiographical and then by flashbulb memories. These findings corroborate previous studies highlighting the impact and uniqueness of NDE memories. [less ▲]

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See detailNear-death experience as a probe to explore (disconnected) consciousness
Martial, Charlotte ULiege; Cassol, Helena ULiege; Laureys, Steven ULiege et al

in Trends in Cognitive Sciences (2020)

Forty-five years ago, the first evidence of near-death experience (NDE) during comatose state was provided, setting the stage for a new paradigm for studying the neural basis of consciousness in ... [more ▼]

Forty-five years ago, the first evidence of near-death experience (NDE) during comatose state was provided, setting the stage for a new paradigm for studying the neural basis of consciousness in unresponsive states. At present, the state of consciousness associated with NDEs remains an open question. In the common view, consciousness is said to disappear in a coma with the brain shutting down, but it is oversimplified. This article argues that the novel framework distinguishing awareness, wakefulness and connectedness is relevant to comprehend the phenomenon. Classical NDEs correspond to internal awareness experienced in unresponsive conditions, thereby corresponding to an episode of disconnected consciousness. Our proposal suggests new directions for NDE research, and more broadly, consciousness science. [less ▲]

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See detailBehavioural and brain responses in cognitive trance: A TMS-EEG case study.
Gosseries, Olivia ULiege; Fecchio, Matteo; Wolff, Audrey ULiege et al

in Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology (2020), 131(2), 586-588

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See detailCharacterization of near-death experiences using text mining analyses: a preliminary study
Charland-Verville, Vanessa ULiege; Ribeiro de Paula, Demetrius; Martial, Charlotte ULiege et al

in PLoS ONE (2020)

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See detailBrain metabolism but not grey matter volume underlies the presence of language function in the minimally conscious state
Aubinet, Charlène ULiege; Cassol, Helena ULiege; Gosseries, Olivia ULiege et al

in Neurorehabilitation and Neural Repair (2020), 34(2), 172-184

Background. The minimally conscious state (MCS) is subcategorized into MCS- and MCS+, depending on the absence or presence of high-level behavioral responses such as command following. Objective. We aim ... [more ▼]

Background. The minimally conscious state (MCS) is subcategorized into MCS- and MCS+, depending on the absence or presence of high-level behavioral responses such as command following. Objective. We aim to investigate the functional and structural neuroanatomy underlying the presence of these responses in MCS- and MCS+ patients. Methods. In this cross-sectional retrospective study, chronic MCS patients were diagnosed using repeated Coma Recovery Scale-Revised assessments. Fluorodeoxyglucose-positron emission tomography data were acquired on 57 patients (16 MCS-; 41 MCS+) and magnetic resonance imaging with voxel-based morphometry analysis was performed on 66 patients (17 MCS-; 49 MCS+). Brain glucose metabolism and grey matter integrity were compared between patient groups and control groups. A metabolic functional connectivity analysis testing the hypothesis of preserved language network in MCS+ compared to MCS- was also done. Results. Patients in MCS+ presented higher metabolism mainly in the left middle temporal cortex, known to be important for semantic processing, compared to the MCS- group. The left angular gyrus was also functionally disconnected from the left prefrontal cortex in MCS- compared to MCS+. No significant differences were found in grey matter volume between patient groups. Conclusions. The clinical sub-categorization of MCS is supported by differences in brain metabolism but not in grey matter structure, suggesting that brain function in the language network is the main support for recovery of command-following, intelligible verbalization and/or intentional communication in the MCS. Better characterizing the neural correlates of residual cognitive abilities of MCS patients contributes to reduce their misdiagnosis and to adapt therapeutic approaches. [less ▲]

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See detailIslands of Awareness or Cortical Complexity?
Cecconi, Benedetta ULiege; LAUREYS, Steven ULiege; Annen, Jitka ULiege

in Trends in Neurosciences (2020)

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See detailTranscutaneous Auricular Vagal Nerve Stimulation and Disorders of Consciousness: A Hypothesis for Mechanisms of Action
Briand, Marie-Michèle ULiege; Gosseries, Olivia ULiege; Staumont, Bernard ULiege et al

in Frontiers in Neurology (2020), 11

Disorders of consciousness (DoC) are the hallmark of severe acquired brain injuries characterized by abnormal activity in important brain areas and disruption within and between brain networks. As DoC's ... [more ▼]

Disorders of consciousness (DoC) are the hallmark of severe acquired brain injuries characterized by abnormal activity in important brain areas and disruption within and between brain networks. As DoC's therapeutic arsenal is limited, new potential therapies such as transcutaneous auricular vagal nerve stimulation (taVNS) have recently been explored. The potential of taVNS in the process of consciousness recovery has been highlighted in recent studies with DoC patients. However, it is not clear how taVNS plays a role in the recovery of consciousness. In this article, we first describe the neural correlates of consciousness, the vagus nerve anatomy and functions, along with the results of functional magnetic resonance imaging studies using taVNS. Based on consciousness recovery and taVNS mechanisms, we propose the Vagal Cortical Pathways model. This model highlights four consecutive pathways (A. Lower brainstem activation, B. Upper brainstem activation, C. Norepinephrine pathway, and D. Serotonin pathway) likely to have an impact on patients with a brain injury and DoC. Additionally, we suggest six different mechanisms of action: (1) Activation of the ascending reticular activating system; (2) Activation of the thalamus; (3) Re-establishment of the cortico-striatal-thalamic-cortical loop; (4) Promotion of negative connectivity between external and default mode networks by the activation of the salience network; (5) Increase in activity and connectivity within the external network through the norepinephrine pathway; and (6) Increase in activity within the default mode network through the serotonin pathway. This model aims to explain the potential therapeutic effects that taVNS has on brain activity in the process of consciousness recovery. © Copyright © 2020 Briand, Gosseries, Staumont, Laureys and Thibaut. [less ▲]

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