Publications of Olivia Gosseries
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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 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

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See detailBrain Metabolism but Not Gray Matter Volume Underlies the Presence of Language Function in the Minimally Conscious State (MCS): MCS+ Versus MCS− Neuroimaging Differences
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, respectively, of high-level behavioral responses such as command-following ... [more ▼]

Background. The minimally conscious state (MCS) is subcategorized into MCS− and MCS+, depending on the absence or presence, respectively, 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 gray 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 with 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 with the MCS− group. The left angular gyrus was also functionally disconnected from the left prefrontal cortex in MCS− compared with MCS+ group. No significant differences were found in gray matter volume between patient groups. Conclusions. The clinical subcategorization of MCS is supported by differences in brain metabolism but not in gray 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. © The Author(s) 2020. [less ▲]

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See detailEuropean Academy of Neurology guideline on the diagnosis of coma and other disorders of consciousness
Kondziella, Daniel; Bender, Andreas; Diserens, Karin et al

in European Journal of Neurology (2020), 27(5), 741-756

Background and purpose: Patients with acquired brain injury and acute or prolonged disorders of consciousness (DoC) are challenging. Evidence to support diagnostic decisions on coma and other DoC is ... [more ▼]

Background and purpose: Patients with acquired brain injury and acute or prolonged disorders of consciousness (DoC) are challenging. Evidence to support diagnostic decisions on coma and other DoC is limited but accumulating. This guideline provides the state-of-the-art evidence regarding the diagnosis of DoC, summarizing data from bedside examination techniques, functional neuroimaging and electroencephalography (EEG). Methods: Sixteen members of the European Academy of Neurology (EAN) Scientific Panel on Coma and Chronic Disorders of Consciousness, representing 10 European countries, reviewed the scientific evidence for the evaluation of coma and other DoC using standard bibliographic measures. Recommendations followed the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. The guideline was endorsed by the EAN. Results: Besides a comprehensive neurological examination, the following suggestions are made: probe for voluntary eye movements using a mirror; repeat clinical assessments in the subacute and chronic setting, using the Coma Recovery Scale – Revised; use the Full Outline of Unresponsiveness score instead of the Glasgow Coma Scale in the acute setting; obtain clinical standard EEG; search for sleep patterns on EEG, particularly rapid eye movement sleep and slow-wave sleep; and, whenever feasible, consider positron emission tomography, resting state functional magnetic resonance imaging (fMRI), active fMRI or EEG paradigms and quantitative analysis of high-density EEG to complement behavioral assessment in patients without command following at the bedside. Conclusions: Standardized clinical evaluation, EEG-based techniques and functional neuroimaging should be integrated for multimodal evaluation of patients with DoC. The state of consciousness should be classified according to the highest level revealed by any of these three approaches. © 2020 European Academy of Neurology [less ▲]

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See detailPhenomenology and brain measures during cognitive trance: a case study.
Gosseries, Olivia ULiege; Sombrun, Corine; Thibaut, Aurore ULiege et al

Poster (2019, November 15)

Cognitive trance is a volitional and self-induced modified state of consciousness inherited from shamanic traditional practices that can be practiced by any individual. Little is known about its ... [more ▼]

Cognitive trance is a volitional and self-induced modified state of consciousness inherited from shamanic traditional practices that can be practiced by any individual. Little is known about its phenomenology and neural correlates. We here describe the case of an expert who underwent resting-state EEG, TMS-EEG and FDG-PET during normal wakefulness and cognitive trance. Phenomenological questionnaires were filled after each session. EEG analyses included spectral power and complexity measures. For TMS-evoked potential, diversity index and global mean field power were computed. For PET, global brain metabolism difference between rest and trance was measured. During trance, the participant felt more joy, visual imagery, body image, and an altered experience. She reported higher absorption and dissociation, with five-fold time-scale distortion. Trance was associated with increased spectral power in all frequency bands. Entropy also showed an increase, especially in posterior regions. TMS-EEG showed modifications in cortical reactivity, while PET revealed no significant difference in brain metabolism. Cognitive trance induced a modified state of consciousness characterized by changes in behavior and neurophysiological processes. [less ▲]

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See detailNeurophenomenology of near-death experience memory in hypnotic recall: a within-subject EEG study
Martial, Charlotte ULiege; Mensen, Armand ULiege; CHARLAND-VERVILLE, Vanessa ULiege et al

in Scientific Reports (2019)

The neurobiological basis of near-death experiences (NDEs) is unknown, but a few studies attempted to investigate it by reproducing in laboratory settings phenomenological experiences that seem to closely ... [more ▼]

The neurobiological basis of near-death experiences (NDEs) is unknown, but a few studies attempted to investigate it by reproducing in laboratory settings phenomenological experiences that seem to closely resemble NDEs. So far, no study has induced NDE-like features via hypnotic modulation while simultaneously measuring changes in brain activity using high-density EEG. Five volunteers who previously had experienced a pleasant NDE were invited to re-experience the NDE memory and another pleasant autobiographical memory (dating to the same time period), in normal consciousness and with hypnosis. We compared the hypnosis-induced subjective experience with the one of the genuine experience memory. Continuous high-density EEG was recorded throughout. At a phenomenological level, we succeeded in recreating NDE-like features without any adverse effects. Absorption and dissociation levels were reported as higher during all hypnosis conditions as compared to normal consciousness conditions, suggesting that our hypnosis-based protocol increased the felt subjective experience in the recall of both memories. The recall of a NDE phenomenology was related to an increase of alpha activity in frontal and posterior regions. This study provides a proof-of-concept methodology for studying the phenomenon, enabling to prospectively explore the NDE-like features and associated EEG changes in controlled settings. [less ▲]

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See detailGeneral Anesthesia: A Probe to Explore Consciousness
BONHOMME, Vincent ULiege; STAQUET, Cécile ULiege; Montupil, Javier ULiege et al

in Frontiers in Systems Neuroscience (2019)

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See detailGreater preserved baseline functional MRI connectivity in zolpidem responders compared to non-responders in patients with disorders of consciousness.
Ippoliti, Camilla ULiege; Larroque, Stephen Karl ULiege; Sanz, Leandro ULiege et al

Conference (2019, June 30)

Introduction Zolpidem is commonly used as sleep inducer but is one of the few available pharmacological treatments for patients with disorders of consciousness (DOC). Some DOC patients have exhibited ... [more ▼]

Introduction Zolpidem is commonly used as sleep inducer but is one of the few available pharmacological treatments for patients with disorders of consciousness (DOC). Some DOC patients have exhibited paradoxical improvements with zolpidem treatment but the neurological profile of responders remains unclear. No fMRI study has ever been conducted in a group of DOC patients. We investigated the baseline functional brain connectivity in DOC patients responding to zolpidem compared to non-responding patients. Methods Eleven patients in minimally conscious state and 5 who emerged received a 10 mg single dose of zolpidem. Patients were considered responders if a new behaviour was observed using the Coma Recovery Scale-Revised after zolpidem administration. All patients underwent resting-state fMRI (without zolpidem). Hypothesis-free and seed-based region (thalamus) analyses were conducted with age and gender covariates regressed out, comparing patients with 36 healthy volunteers. Results Seven patients qualified as responders (5 sedated, 2 non-sedated) and 9 as non-responders (6 sedated, 3 non-sedated). Hypothesis-free analyses in the sedated group revealed significantly increased intrinsic connectivity among responders in the occipital, occipito-temporal and parieto-occipital areas compared to non-responders. Seed-based analyses showed significantly more preserved positive connectivity of the fronto-insular network in responders compared to non-responders. No significant differences were found between responders and non-responders in the non-sedated condition, possibly due to smaller sample size. Conclusion Our findings suggest a greater preservation of global and local connectivity in zolpidem responders at baseline. Targeting more accurately potential responders to zolpidem can improve the clinical management of DOC patients. [less ▲]

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See detailTherapeutic interventions in patients with prolonged disorders of consciousness.
Thibaut, Aurore ULiege; Schiff, Nicholas; Giacino, Joseph et al

in Lancet Neurology (2019), 18(6), 600-614

The management of patients with severe brain injuries and prolonged disorders of consciousness raises important issues particularly with respect to their therapeutic options. The scarcity of treatment ... [more ▼]

The management of patients with severe brain injuries and prolonged disorders of consciousness raises important issues particularly with respect to their therapeutic options. The scarcity of treatment options is challenged by new clinical and neuroimaging data indicating that some patients with prolonged disorders of consciousness might benefit from therapeutic interventions, even years after the injury. Most studies of interventions aimed at improving patients' level of consciousness and functional recovery were behavioural and brain imaging open-label trials and case reports, but several randomised controlled trials have been done, particularly focused on the effects of drugs or use of non-invasive brain stimulation. However, only two studies on amantadine and transcranial direct current stimulation provided class II evidence. Although new therapeutic approaches seem to be valuable for patients with prolonged disorders of consciousness, optimised stimulation parameters, alternative drugs, or rehabilitation strategies still need to be tested and validated to improve rehabilitation and the quality of life of these patients. [less ▲]

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See detailTreating disorders of consciousness with apomorphine: protocol for a double-blind randomized controlled trial using multimodal assessments
Sanz, Leandro ULiege; Lejeune, Nicolas ULiege; Blandiaux, Séverine ULiege et al

in Frontiers in Neurology (2019), 10(248),

Background: There are few available therapeutic options to promote recovery among patients with chronic disorders of consciousness (DOC). Among pharmacological treatments, apomorphine, a dopamine agonist ... [more ▼]

Background: There are few available therapeutic options to promote recovery among patients with chronic disorders of consciousness (DOC). Among pharmacological treatments, apomorphine, a dopamine agonist, has exhibited promising behavioral effects and safety of use in small-sample pilot studies. The true efficacy of the drug and its neural mechanism are still unclear. Apomorphine may act through a modulation of the anterior forebrain mesocircuit, but neuroimaging and neurophysiological investigations to test this hypothesis are scarce. This clinical trial aims to (1) assess the treatment effect of subcutaneous apomorphine infusions in patients with DOC, (2) better identify the phenotype of responders to treatment, (3) evaluate tolerance and side effects in this population, and (4) examine the neural networks underlying its modulating action on consciousness. Methods/Design: This study is a prospective double-blind randomized parallel placebo-controlled trial. Forty-eight patients diagnosed with DOC will be randomized to receive a 30-day regimen of either apomorphine hydrochloride or placebo subcutaneous infusions. Patients will be monitored at baseline 30 days before initiation of therapy, during treatment and for 30 days after treatment washout, using standardized behavioral scales (Coma Recovery Scale-Revised, Nociception Coma Scale-Revised), neurophysiological measures (electroencephalography, body temperature, actigraphy) and brain imaging (magnetic resonance imaging, positron emission tomography). Behavioral follow-up will be performed up to 2 years using structured phone interviews. Analyses will look for changes in behavioral status, circadian rhythmicity, brain metabolism, and functional connectivity at the individual level (comparing before and after treatment) and at the group level (comparing apomorphine and placebo arms, and comparing responder and non-responder groups). Discussion: This study investigates the use of apomorphine for the recovery of consciousness in the first randomized placebo-controlled double-blind trial using multimodal assessments. The results will contribute to define the role of dopamine agonists for the treatment of these challenging conditions and identify the neural correlates to their action. Results will bring objective evidence to further assess the modulation of the anterior forebrain mesocircuit by pharmacological agents, which may open new therapeutic perspectives. Clinical Trial Registration: EudraCT n°2018-003144-23; Clinicaltrials.gov n°NCT03623828 (https://clinicaltrials.gov/ct2/show/NCT03623828). [less ▲]

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See detailNeural correlates of modified subjective state of consciousness induced by hypnosis using EEG-connectivity approach
Panda, Rajanikant ULiege; Gosseries, Olivia ULiege; VANHAUDENHUYSE, Audrey ULiege et al

Poster (2019, January 17)

Introduction: Hypnotic state has been shown to be of clinical utility, however its neural mechanisms still remain unclear [1]. This study investigates the neural basis of hypnosis using resting state EEG ... [more ▼]

Introduction: Hypnotic state has been shown to be of clinical utility, however its neural mechanisms still remain unclear [1]. This study investigates the neural basis of hypnosis using resting state EEG connectivity measurements. Methods: Ten healthy subjects (7 females, mean age 24±3years) underwent high density EEG recordings in both eye close awake resting state and hypnosis state. The hypnotic state instruction involved a 3-min induction procedure with muscle relaxation and eye fixation. After preprocessing EEG data, both hypothesis and data driven analysis were conducted using connectivity approach. Classical power spectral analysis was performed for delta (1-4Hz), theta (4.1-8Hz), alpha (8.1-12Hz), beta1 (12.1-20Hz) and beta2 (20.1-30Hz) frequency bands. Connectivity between every pair of electrodes was assessed using weighted Phase Lag Index. Hypothesis-based connectivity was computed for frontal, parietal and midline regions [2]. Data-driven graph theory connectivity was carried out to measure brain connectivity network properties and altered hub regions [3]. Results and Discussion: During hypnosis, increased spectral power was observed in delta and decreases were noted in the alpha and beta bands. From hypothesis based connectivity analysis, we observed an increased frontal interhemispheric connectivity in delta and left frontal to right parietal in theta band. Decreased connectivity was found both for alpha and beta bands in midline (upper central with lower central), right frontal with ‘right parietal and upper central’. Graph theory measures showed differences between hypnotic state and resting state both at the global and local level. Through integrated nodal clustering coefficient, we found increased frontoparietal connectivity in delta and theta bands and decreased bilateral frontal and parietal connectivity in alpha and beta-2 frequency bands. During hypnosis, we found increased connectivity in the lower frequency range (i.e., delta) and decreases at higher frequencies (i.e., beta) when considering frontal and parietal regions. These oscillations seems to characterise modified subjective state of consciousness induced by hypnosis, possibly reflecting states of efficient cognitive-processing and positive-emotional experiences. [less ▲]

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See detailEditorial: Between Theory and Clinic: The Contribution of Neuroimaging in the Field of Consciousness Disorders.
Gosseries, Olivia ULiege; Schnakers, Caroline; Laureys, Steven ULiege

in Frontiers in neurology (2019), 10

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See detailA Graph Signal Processing Approach to Study High Density EEG Signals in Patients with Disorders of Consciousness
Mortaheb, Sepehr ULiege; Annen, Jitka ULiege; Chatelle, Camille ULiege et al

in Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society (2019)

Graph signal processing (GSP) is a novel approach to analyse multi-dimensional neuroimaging data, constraining functional measures by structural characteristics in a single framework (i.e. graph signals ... [more ▼]

Graph signal processing (GSP) is a novel approach to analyse multi-dimensional neuroimaging data, constraining functional measures by structural characteristics in a single framework (i.e. graph signals). In this approach, functional time series are assigned to the vertices of the underlying weighted graph and GSP analysis is performed in each time point of the signal. Here we used GSP to study local brain connectivity changes in patients with disorders of consciousness based on resting state high density electroencephalography (hdEEG) recordings. Total variation of the graph signals is a measure of signal smoothness over the underlying graph. In this study, we constructed the underlying graph based on the geometrical distances between each electrode pairs in such a way that local smoothness of the signal can be studied. Total variation analysis in α-band showed that in the pathological states of altered consciousness, local short range communication of brain regions in this frequency band is stronger than in healthy states which shows that information is segregated in local regions in patients with disorders of consciousness. © 2019 IEEE. [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 (2019)

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See detailCausal connectivity according to conscious experience in non-rapid eye movement sleep
Lee, Minji; Baird, Benjamin; Gosseries, Olivia ULiege et al

in Conference Proceedings - IEEE International Conference on Systems, Man and Cybernetics (2019), 2019-October

The understanding of human consciousness based on brain connectivity is considered important for brain-machine interfacing. In this study, we investigated changes in causal connectivity in ... [more ▼]

The understanding of human consciousness based on brain connectivity is considered important for brain-machine interfacing. In this study, we investigated changes in causal connectivity in electroencephalography data related to conscious and unconscious experiences during non-rapid eye movement sleep after parietal transcranial magnetic stimulation (TMS). A serial awakening paradigm was used to determine whether subjects had had a conscious experience or not. We calculated direct transfer function (DTF) as a measure of effective connectivity in five frequency bands focusing on frontal and parietal-occipital regions. The DTF showed significant differences in frontal-to-parietal flow between reported unconsciousness and consciousness. During the first 100 ms after TMS, the outward links of the parietal region at low frequencies were higher in no conscious experience than in conscious experience. During the next 100 ms, however, the outward links of the frontal region were higher in the conscious experience than the no conscious experience at low frequencies. Changes with causal connectivity over time after TMS indicate that the spatial roles in brain regions associated with consciousness are different. These findings may help clarify the cortical mechanisms related to conscious experience. © 2019 IEEE. [less ▲]

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See detailCortical reactivations during sleep spindles following declarative learning
Jegou, A.; Schabus, M.; Gosseries, Olivia ULiege et al

in NeuroImage (2019), 195

Increasing evidence suggests that sleep spindles are involved in memory consolidation, but few studies have investigated the effects of learning on brain responses associated with spindles in humans. Here ... [more ▼]

Increasing evidence suggests that sleep spindles are involved in memory consolidation, but few studies have investigated the effects of learning on brain responses associated with spindles in humans. Here we used simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) during sleep to assess haemodynamic brain responses related to spindles after learning. Twenty young healthy participants were scanned with EEG/fMRI during (i) a declarative memory face sequence learning task, (ii) subsequent sleep, and (iii) recall after sleep (learning night). As a control condition an identical EEG/fMRI scanning protocol was performed after participants over-learned the face sequence task to complete mastery (control night). Results demonstrated increased responses in the fusiform gyrus both during encoding before sleep and during successful recall after sleep, in the learning night compared to the control night. During sleep, a larger response in the fusiform gyrus was observed in the presence of fast spindles during the learning as compared to the control night. Our findings support a cortical reactivation during fast spindles of brain regions previously involved in declarative learning and subsequently activated during memory recall, thereby promoting the cortical consolidation of memory traces. © 2019 Elsevier Inc. [less ▲]

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See detailConnectivity differences between consciousness and unconsciousness in non-rapid eye movement sleep: a TMS-EEG study.
Lee, Minji; Baird, Benjamin; Gosseries, Olivia ULiege et al

in Scientific Reports (2019), 9(1), 5175

The neuronal connectivity patterns that differentiate consciousness from unconsciousness remain unclear. Previous studies have demonstrated that effective connectivity, as assessed by transcranial ... [more ▼]

The neuronal connectivity patterns that differentiate consciousness from unconsciousness remain unclear. Previous studies have demonstrated that effective connectivity, as assessed by transcranial magnetic stimulation combined with electroencephalography (TMS-EEG), breaks down during the loss of consciousness. This study investigated changes in EEG connectivity associated with consciousness during non-rapid eye movement (NREM) sleep following parietal TMS. Compared with unconsciousness, conscious experiences during NREM sleep were associated with reduced phase-locking at low frequencies (<4 Hz). Transitivity and clustering coefficient in the delta and theta bands were also significantly lower during consciousness compared to unconsciousness, with differences in the clustering coefficient observed in scalp electrodes over parietal-occipital regions. There were no significant differences in Granger-causality patterns in frontal-to-parietal or parietal-to-frontal connectivity between reported unconsciousness and reported consciousness. Together these results suggest that alterations in spectral and spatial characteristics of network properties in posterior brain areas, in particular decreased local (segregated) connectivity at low frequencies, is a potential indicator of consciousness during sleep. [less ▲]

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See detailThe spectral exponent of the resting EEG indexes the presence of consciousness during unresponsiveness induced by propofol, xenon, and ketamine
Colombo, M. A.; Napolitani, Martino; Boly, Mélanie et al

in NeuroImage (2019), 189

Despite the absence of responsiveness during anesthesia, conscious experience may persist. However, reliable, easily acquirable and interpretable neurophysiological markers of the presence of ... [more ▼]

Despite the absence of responsiveness during anesthesia, conscious experience may persist. However, reliable, easily acquirable and interpretable neurophysiological markers of the presence of consciousness in unresponsive states are still missing. A promising marker is based on the decay-rate of the power spectral density (PSD) of the resting EEG. We acquired resting electroencephalogram (EEG) in three groups of healthy participants (n = 5 each), before and during anesthesia induced by either xenon, propofol or ketamine. Dosage of each anesthetic agent was tailored to yield unresponsiveness (Ramsay score = 6). Delayed subjective reports assessed whether conscious experience was present (‘Conscious report’) or absent/inaccessible to recall (‘No Report’). We estimated the decay of the PSD of the resting EEG—after removing oscillatory peaks—via the spectral exponent β, for a broad band (1–40 Hz) and narrower sub-bands (1–20 Hz, 20–40 Hz). Within-subject anesthetic changes in β were assessed. Furthermore, based on β, ‘Conscious report’ states were discriminated against ‘no report’ states. Finally, we evaluated the correlation of the resting spectral exponent with a recently proposed index of consciousness, the Perturbational Complexity Index (PCI), derived from a previous TMS-EEG study. The spectral exponent of the resting EEG discriminated states in which consciousness was present (wakefulness, ketamine) from states where consciousness was reduced or abolished (xenon, propofol). Loss of consciousness substantially decreased the (negative) broad-band spectral exponent in each subject undergoing xenon or propofol anesthesia—indexing an overall steeper PSD decay. Conversely, ketamine displayed an overall PSD decay similar to that of wakefulness—consistent with the preservation of consciousness—yet it showed a flattening of the decay in the high-frequencies (20–40 Hz)—consistent with its specific mechanism of action. The spectral exponent was highly correlated to PCI, corroborating its interpretation as a marker of the presence of consciousness. A steeper PSD of the resting EEG reliably indexed unconsciousness in anesthesia, beyond sheer unresponsiveness. © 2019 The Authors [less ▲]

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