Distinct and dissociable EEG networks are associated with recovery of cognitive function following anesthesia-induced unconsciousness

The temporal trajectories and neural mechanisms of recovery of cognitive function after a major perturbation of consciousness is of both clinical and neuroscientific interest. The purpose of the present study was to investigate network-level changes in functional brain connectivity associated with the recovery and return of six cognitive functions after general anesthesia. High-density electroencephalograms (EEG) were recorded from healthy volunteers undergoing a clinically relevant anesthesia protocol (propofol induction and isoflurane maintenance), and age-matched healthy controls. A battery of cognitive tests (motor praxis, visual object learning test, fractal-2-back, abstract matching, psychomotor vigilance test, digital symbol substitution test) was administered at baseline, upon recovery of consciousness (ROC), and at half-hour intervals up to 3 h following ROC. EEG networks were derived using the strength of functional connectivity measured through the weighted phase lag index (wPLI). A partial least squares (PLS) analysis was conducted to assess changes in these networks: (1) between anesthesia and control groups; (2) during the 3-h recovery from anesthesia; and (3) for each cognitive test during recovery from anesthesia. Networks were maximally perturbed upon ROC but returned to baseline 30-60 min following ROC, despite deficits in cognitive performance that persisted up to 3 h following ROC. Additionally, during recovery from anesthesia, cognitive tests conducted at the same time-point activated distinct and dissociable functional connectivity networks across all frequency bands. The results highlight that the return of cognitive function after anesthetic-induced unconsciousness is task-specific, with unique behavioral and brain network trajectories of recovery

Detecting and assessing consciousness in behaviourally unresponsive populations:combining event-related and continuous electroencephalography analysis techniques

Patients diagnosed with disorders of consciousness are difficult to assess as their behavioural responsiveness may be attenuated by a variety of factors and may not be reflective of their actual level of consciousness. This thesis focuses on electroencephalography (EEG) methods for detecting and assessing consciousness directly from an individual's brain activity in populations with uncertain levels of awareness. By addressing some of the current controversy in the field, investigating new approaches to consciousness assessment, and by combining both event-related and continuous EEG analyses, this thesis establishes and presents a more robust and holistic approach to assessing disorders of consciousness. Critical factors to consider when using event-related potential methods to assess level of consciousness in unresponsive populations are investigated and presented in Chapter 1. Chapter 2 combines EEG based measures of functional connectivity and multivariate partial least squares analyses to present a novel approach for isolating significant network-level changes across cognitive states. A bedside approach that combines event-related and continuous EEG analysis techniques for the assessment of an acute traumatic brain injury (TBI) patient is explored in Chapter 3. Finally, a within-subject anesthesia-based approach to consciousness detection is presented in Chapter 4 as a chronic TBI patient is evaluated using the protocol.Les patients chez qui un diagnostic de trouble de la conscience est posé sont difficiles à évaluer parce que leurs réactions comportementales peuvent être atténuées par divers facteurs et ne pas refléter leur réel niveau de conscience. La présente thèse porte sur les méthodes électro-encéphalographiques (EEG) de dépistage et d'évaluation de la conscience directement de l'activité cérébrale dans des populations dont le niveau de conscience est incertain. En abordant certaines des controverses actuelles dans le domaine, en étudiant de nouvelles approches d'évaluation de la conscience et en combinant à la fois l'analyse en continu et l'analyse des potentiels évoqués cérébraux, cette thèse établit et présente une approche plus holistique et robuste à l'évaluation des troubles de la conscience.  Le chapitre 1 étudie et présente les facteurs essentiels à prendre en compte lors du recours à des méthodes de potentiels évoqués cérébraux pour évaluer le niveau de conscience de sujets non réactifs. Le chapitre 2 associe une analyse des mesures de connectivité fonctionnelle par EEG et une analyse multivariée partielle des moindres carrés pour présenter une approche inédite qui permet d'isoler des changements significatifs du réseau selon les états cognitifs. Le chapitre 3 explore une approche au chevet du patient qui combine des techniques d'analyse en continu et d'analyse des potentiels évoqués cérébraux par EEG afin d'évaluer le patient atteint d'un traumatisme cérébral aigu. Le chapitre 4, enfin, présente une approche par anesthésie intrasujet au dépistage de la conscience à l'aide de ce protocole, dans le cadre de l'évaluation d'un patient atteint d'un traumatisme cérébral chronique

A neurophysiological basis for aperiodic EEG and the background spectral trend

Abstract Electroencephalograms (EEGs) display a mixture of rhythmic and broadband fluctuations, the latter manifesting as an apparent 1/f spectral trend. While network oscillations are known to generate rhythmic EEG, the neural basis of broadband EEG remains unexplained. Here, we use biophysical modelling to show that aperiodic neural activity can generate detectable scalp potentials and shape broadband EEG features, but that these aperiodic signals do not significantly perturb brain rhythm quantification. Further model analysis demonstrated that rhythmic EEG signals are profoundly corrupted by shifts in synapse properties. To examine this scenario, we recorded EEGs of human subjects being administered propofol, a general anesthetic and GABA receptor agonist. Drug administration caused broadband EEG changes that quantitatively matched propofol’s known effects on GABA receptors. We used our model to correct for these confounding broadband changes, which revealed that delta power, uniquely, increased within seconds of individuals losing consciousness. Altogether, this work details how EEG signals are shaped by neurophysiological factors other than brain rhythms and elucidates how these signals can undermine traditional EEG interpretation

ESC Guidelines for the management of acute myocardial infarction in patients presenting with ST-segment elevation.

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2017 ESC Guidelines for the management of acute myocardial infarction in patients presenting with ST-segment elevation: The Task Force for the management of acute myocardial infarction in patients presenting with ST-segment elevation of the European Society of Cardiology (ESC).

The ESC Guidelines represent the views of the ESC and were produced after careful consideration of the scientific and medical knowledge and the evidence available at the time of their publication. The ESC is not responsible in the event of any contradiction, discrepancy and/or ambiguity between the ESC Guidelines and any other official recommendations or guidelines issued by the relevant public health authorities, in particular in relation to good use of healthcare or therapeutic strategies. Health professionals are encouraged to take the ESC Guidelines fully into account when exercising their clinical judgment, as well as in the determination and the implementation of preventive, diagnostic or therapeutic medical strategies; however, the ESC Guidelines do not override, in any way whatsoever, the individual responsibility of health professionals to make appropriate and accurate decisions in consideration of each patient's health condition and in consultation with that patient and, where appropriate and/or necessary, the patient's caregiver. Nor do the ESC Guidelines exempt health professionals from taking into full and careful consideration the relevant official updated recommendations or guidelines issued by the competent public health authorities, in order to manage each patient's case in light of the scientifically accepted data pursuant to their respective ethical and professional obligations. It is also the health professional's responsibility to verify the applicable rules and regulations relating to drugs and medical devices at the time of prescription