Biology subjects

Rohaut, B.

Publications and source records attributed to Rohaut, B..

7 recordsLinked to original sources

bioRxiv2026

Spontaneous slow waves index multiple dimensions of recovery in Disorders of Consciousness

Whether and how residual awareness is expressed in patients with Disorders of Consciousness (DoC) depends on the severity of brain damage and the transient functional state of the cortex at assessment. Classically, DoC are associated with electroencephalographic (EEG) slowing, marked by high-amplitude slow waves, even during the day. Yet, slow waves are also a hallmark of healthy sleep, where they are thought to serve restorative functions and to help maintain network homeostasis. Here, we asked whether slow waves in DoC can provide insights into the severity of cortical dysfunction or, conversely, into the preservation of residual awareness and recovery potential, by characterizing their spatial, temporal and morphological properties. We analyzed 256-channel EEG recorded during the Local-Global auditory paradigm in 236 DoC patients, including 123 in Unresponsive Wakefulness Syndrome (UWS), 62 in a Minimally Conscious State minus (MCS-) and 29 in MCS plus (MCS+). High-amplitude slow waves were detected as local events, and their density, amplitude and slopes were quantified scalp-wide and channel-wise, by mean level and temporal variability across the recording. Slow-wave features were related to concurrent (Coma Recovery Scale-Revised - CRS-R, Local-Global paradigm) and follow-up (one-year Glasgow Outcome Scale-Extended - GOS-E) assessments of consciousness and functional recovery. Associations with MRI-derived measures of cortical integrity and structural connectivity, and differences between anoxic and traumatic etiologies, were also examined. Slow waves were more frequent in less severe DoC patients (i.e., MCS) compared to UWS. Slow-wave slopes were also steeper frontally and increased at a faster rate in patients exhibiting higher levels of consciousness and/or markers of conscious access during the Local-Global paradigm. More frequent and steeper slow waves at baseline further predicted recovery of consciousness and of functional independence at one year. At the individual level, slow-wave features classified states of consciousness above chance (AUC = 0.62 and 0.71 for MCS- and MCS+ versus UWS), whereas outcome prediction remained modest (0.56-0.58). These clinical associations had a structural basis: slow-wave occurrence was greater after traumatic than anoxic injury and scaled with the integrity of subcortico-cortical projection fibers and consciousness-related cortical networks. Contrary to the classical view of delta activity as a non-specific marker of impaired consciousness, prominent spontaneous slow waves indexed behavioral and neurophysiological signs of awareness and better recovery. Beyond reflecting a propensity for pathological bistability, they may also signal the integrity of the networks required to generate them, together with their residual capacity for dynamic regulation.

neuroscience↗

bioRxiv2025

Individualised electrophysiological neural field models for the assessment of thalamocortical function in disorders of consciousness: a multicentre study

Understanding the neural mechanisms underlying disorders of consciousness (DoC) remains a major challenge, particularly in distinguishing limited awareness in minimally conscious state (MCS) and complete unawareness in unresponsive wakefulness syndrome, also coined vegetative state (UWS/VS). In this multicentre study, we fitted a biophysically informed corticothalamic neural field model to high-density EEG data from two large independent datasets, comprising 203 UWS patients, 270 MCS patients and 74 healthy controls. We then used the fitted parameters to simulate EEG time series on a per-subject basis and compared empirical and simulated complexity metrics. The model reliably captured the spectral features across different states of consciousness and revealed reduced corticothalamic integrity in DoC patients that was more pronounced in UWS than in MCS, supporting the mesocircuit hypothesis. Furthermore, the simulated EEG reproduced the complexity patterns of the empirical recordings, with permutation entropy emerging as a sensitive marker capable of distinguishing between MCS and UWS for both real and simulated time series.

neuroscience↗

bioRxiv2024

Dynamics of EEG Microstates Change Across the Spectrum of Disorders of Consciousness

As a response to the environment and internal signals, brain networks reorganize on a sub-second scale. To capture this reorganization in patients with disorders of consciousness and understand their residual brain activity, we investigated the dynamics of electroencephalography (EEG) microstates. We analyze EEG microstate markers to quantify the periods of semi-stable topographies and the large-scale cortical networks they may reflect. To achieve this, EEG samples are clustered into four groups and then fit back into each time sample. We then obtain a time series of maps with different frequencies of occurrence and duration. One such occurrence of a map with a given duration is called a microstate. The goal of this work is to study the dynamics of these topographical patterns across patients with disorders of consciousness. Using the microstate time series, we calculate static and dynamic markers. In contrast to the static, the dynamic metrics depend on the specific temporal sequences of the maps. The static measure Ratio of Total Time covered (RTT) shows differences between healthy controls and patients, however, no differences were observed between the groups of patients. In contrast, some dynamic markers capture inter-patient group differences. The dynamic markers we investigated are Mean Microstate Durations (MMD), Microstate Duration Variances (MDV), Microstate Transition Matrices (MTM), and Entropy Production (EP). The MMD and MDV decrease with the state of consciousness, whereas the MTM non-diagonal transitions and EP increase. In other words, DoC patients have slower and closer to equilibrium (time-reversible) brain dynamics. In conclusion, static and dynamic EEG microstate metrics differ across consciousness levels, with the latter capturing the subtitler differences between groups of patients with disorders of consciousness. Abbreviated summaryThis study investigates EEG microstate dynamics in patients with disorders of consciousness (DoC) to understand residual brain activity and network reorganization. Entropy production, in addition to static markers, differs between patients and healthy controls, whereas the rest of the dynamic markers show differences across patient groups.

neuroscience↗

bioRxiv2023

Whole-brain modelling supports the use of serotonergic psychedelics for the treatment of disorders of consciousness

Disorders of consciousness (DoC) are a challenging and complex group of neurological conditions characterised by absent or impaired awareness. The current range of therapeutic options for DoC patients is limited, offering few non-invasive pharmacological alternatives. This situation has sprung a growing interest in the development of novel treatments, such as the proposal to study the efficacy of 5HT2A receptor agonists (also known as psychedelics) to restore impaired consciousness. Given the ethical implications of exploring novel compounds in non-communicative individuals, we assessed in silico their effects in the whole-brain dynamics of DoC patients. We embedded the whole-brain activity of patients in a low-dimensional space, and then used this representation to visualise the effects of simulated neuromodulation across a range of receptors representing potential drug targets. Our findings show that activation of serotonergic and opioid receptors shifted brain dynamics of DoC patients towards patterns typically seen in conscious and awake individuals, and that this effect was mediated by the brain-wide density of activated receptors. These results showcase the role of whole-brain models in the discovery of novel pharmacological treatments for neuropsychiatric conditions, while also supporting the feasibility of accelerating the recovery of consciousness with serotonergic psychedelics.

neuroscience↗

bioRxiv2019

Combined behavioral and electrophysiological evidence for a direct cortical effect of prefrontal tDCS on disorders of consciousness

Severe brain injuries can lead to long-lasting disorders of consciousness (DoC) such as vegetative state/unresponsive wakefulness syndrome (VS/UWS) or minimally conscious state (MCS). While behavioral assessment remains the gold standard to determine conscious state, EEG has proven to be a promising complementary tool to monitor the effect of new therapeutics. Encouraging results have been obtained with invasive electrical stimulation of the brain, and recent studies identified transcranial direct current stimulation (tDCS) as an effective approach in randomized controlled trials. This non-invasive and inexpensive tool may turn out to be the preferred treatment option. However, its mechanisms of action and physiological effects on brain activity remain unclear and debated. Here, we stimulated 60 DoC patients with the anode placed over left-dorsolateral prefrontal cortex in a prospective open-label study. Clinical behavioral assessment improved in twelve patients (20%) and none deteriorated. This behavioral response after tDCS coincided with an enhancement of putative EEG markers of consciousness: in comparison with non-responders, responders showed increases of power and long-range cortico-cortical functional connectivity in the theta-alpha band, and a larger and more sustained P300 suggesting improved conscious access to auditory novelty. The EEG changes correlated with electric fields strengths in prefrontal cortices, and no correlation was found on the scalp. Taken together, this prospective intervention in a large cohort of DoC patients strengthens the validity of the proposed EEG signatures of consciousness, and is suggestive of a direct causal effect of tDCS on consciousness.

neuroscience↗

bioRxiv2018

Deep structural brain lesions associated with consciousness impairment early after haemorrhagic stroke

BackgroundThe significance of deep structural lesions on level of consciousness early after intracerebral haemorrhage (ICH) is largely unknown.\n\nMethodsWe studied a consecutive series of patients with spontaneous ICH that underwent MRI within 7 days of the bleed. We assessed consciousness by testing for command following from time of MRI to hospital discharge, and determined 3-months functional outcomes using the Glasgow Outcome Scale-Extended (GOS-E). ICH and oedema volumes, intraventricular haemorrhage (IVH), and midline shift (MLS) were quantified. Presence of blood and oedema in deep brain regions previously implicated in consciousness were assessed. A machine learning approach using logistic regression with elastic net regularization was applied to identify parameters that best predicted consciousness at discharge controlling for confounders.\n\nResultsFrom 158 ICH patients that underwent MRI, 66% (N=105) were conscious and 34% (N=53) unconscious at the time of MRI. Almost half of unconscious patients (49%, N= 26) recovered consciousness by ICU discharge. Focal lesions within subcortical structures predicted persistent impairment of consciousness at discharge together with MLS, IVH, and ICH and oedema volumes (AUC 0.74; 95%-CI 0.73-0.75). Caudate nucleus, midbrain peduncle, and pontine tegmentum were implicated as critical structures. Unconscious patients predicted to recover consciousness had better 3-month functional outcomes than those predicted to remain unconscious (35% vs 0% GOS-E [≥]4; p-value=0.02).\n\nConclusionMRI lesions within key subcortical structures together with measures reflecting the mass effect of the haemorrhage (lesion volumes, IVH, MLS) obtained within one week of ICH can help predict early recovery of consciousness and 3-month functional outcome.

neuroscience↗

bioRxiv2018

\"DoC-feeling\": a new behavioural tool to help diagnose the Minimally Conscious State.

ObjectivesThe clinical distinction between vegetative state/unresponsive wakefulness syndrome (UWS) and minimally conscious state (MCS) is a key step to elaborate a prognosis and formulate an appropriate medical plan for any patient suffering from disorders of consciousness (DoC). However, this assessment is often challenging and may require specialized expertise. In this study, we hypothesized that pooling subjective reports of the level of consciousness of a given patient across several nursing staff members can be used to clinically detect MCS.\n\nSetting and ParticipantsPatients referred for consciousness assessment were prospectively screened. MCS (target condition) was defined according to the best Coma Recovery Scale-Revised score (CRS-R) obtained from expert physicians (reference standard). \"DoC-feeling\" score consisted in the median value of multiple ratings of patients behavior observation pooled from multiple staff members during a week of hospitalisation (index test). Individual ratings were collected at the end of each shift using a 100mm visual analog scale, blinded from the reference standard. Diagnostic accuracy was evaluated using area under the receiver operating characteristic curve (AUC), sensitivity and specificity metrics.\n\nResults692 ratings performed by 83 nursing staff members were collected from 47 patients. Twenty patients were in a UWS and 27 in a MCS. DoC-feeling scores obtained by pooling all individual ratings obtained for a given patient were significantly greater in MCS than in UWS patients (59.2 mm [IQR: 27.3-77.3] vs. 7.2 mm [IQR: 2.4-11.4]; p<0.001) yielding an AUC of 0.92 (95%CI: 0.84-0.99).\n\nConclusionsDoC-feeling capitalizes on the expertise of nursing staff to evaluate patients consciousness. Together with the CRS-R as well as with brain imaging, DoC-feeling might improve diagnostic and prognostic accuracy of DoC patients.\n\nStrengths and limitations of this studyO_LIWe designed a new behavioural tool called \"DoC-feeling\" to help face the clinical challenge of the detection of Minimally Conscious State in patients suffering from disorders of consciousness (DoC)\nC_LIO_LI\"DoC-feeling score\" quantifies nursing staffs subjective perception of patients consciousness by pooling multiple assessments obtained from multiple caregivers (\"wisdom of the crowds\")\nC_LIO_LIThis score which requires no particular training showed a very good accuracy when compared to the gold standard (repeated expert clinical assessment using the Coma Recovery Scale - Revised (CRS-R))\nC_LIO_LIA validation in a separate cohort would help to determine its place in consciousness assessment\nC_LIO_LIThis score should be tested not only against the CRS-R but also against brain-imaging techniques to test for its capacity to detect covert signs of consciousness\nC_LI

neuroscience↗