Expression de la connexine 36 dans la moelle épinière au cours du développement postnatal de l'opossum Monodelphis domestica

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Altered Relationship Between Heart Rate Variability and fMRI-Based Functional Connectivity in People With Epilepsy

Background: Disruptions in central autonomic processes in people with epilepsy have been studied through evaluation of heart rate variability (HRV). Decreased HRV appears in epilepsy compared to healthy controls, suggesting a shift in autonomic balance toward sympathetic dominance; recent studies have associated HRV changes with seizure severity and outcome of interventions. However, the processes underlying these autonomic changes remain unclear. We examined the nature of these changes by assessing alterations in whole-brain functional connectivity, and relating those alterations to HRV.Methods: We examined regional brain activity and functional organization in 28 drug-resistant epilepsy patients and 16 healthy controls using resting-state functional magnetic resonance imaging (fMRI). We employed an HRV state-dependent functional connectivity (FC) framework with low and high HRV states derived from the following four cardiac-related variables: 1. RR interval, 2. root mean square of successive differences (RMSSD), 4. low-frequency HRV (0.04–0.15 Hz; LF-HRV) and high-frequency HRV (0.15–0.40 Hz; HF-HRV). The effect of group (epilepsy vs. controls), HRV state (low vs. high) and the interactions of group and state were assessed using a mixed analysis of variance (ANOVA). We assessed FC within and between 7 large-scale functional networks consisting of cortical regions and 4 subcortical networks, the amygdala, hippocampus, basal ganglia and thalamus networks.Results: Consistent with previous studies, decreased RR interval (increased heart rate) and decreased HF-HRV appeared in people with epilepsy compared to healthy controls. For both groups, fluctuations in heart rate were positively correlated with BOLD activity in bilateral thalamus and regions of the cerebellum, and negatively correlated with BOLD activity in the insula, putamen, superior temporal gyrus and inferior frontal gyrus. Connectivity strength in patients between right thalamus and ventral attention network (mainly insula) increased in the high LF-HRV state compared to low LF-HRV; the opposite trend appeared in healthy controls. A similar pattern emerged for connectivity between the thalamus and basal ganglia.Conclusion: The findings suggest that resting connectivity patterns between the thalamus and other structures underlying HRV expression are modified in people with drug-resistant epilepsy compared to healthy controls

Des géographes à l'œuvre: 50 ans de géographie à l’Université du Québec à Chicoutimi 1969-2019 Recueil de textes

L’idée de souligner les 50 ans d’existence des programmes de géographie à l’Université du Québec à Chicoutimi (UQAC) a germé en 2017; dès qu’ont surgi les premières réflexions sur la manière de rappeler l’évènement au sein de l’Institution. Il nous semblait important, nous géographes, de faire une pause, de regarder en arrière (et aussi en avant). En fait, de faire plus qu’une revue et plus qu’un bilan; en passant non seulement par les différentes activités qui se sont déroulées au cours de la période, mais aussi de faire part de nos préoccupations actuelles. Somme toute, de là l’importance de poser une pierre, de laisser une marque, de franchir un jalon. Pourquoi ne pas montrer comment les professeurs et les diplômés-es de l’UQAC ont occupé une place, disons enviable, à différentes échelles (régionale, nationale et internationale) par leur enseignement, par leur recherche, par leur implication dans l’aménagement du territoire, en matière de développement régional et auprès de la population? La publication d’un recueil de textes semblait une façon parfaite de regrouper dans un même élan des textes relatant ce que les géographes ont réalisé et ce qui les fait encore vibrer. Nous nous sommes limités aux professeurs de géographie actuels et retraités de même qu’aux étudiants diplômés des différents baccalauréats en géographie et des certificats qui leur étaient associés. Évidemment, ce qui a été rassemblé ne peut être qu’un échantillon de ce qu’ont effectué les géographes qui sont passés par l’UQAC. En effet, l’invitation à participer à ce volume, même si nous avons fouillé largement notre mémoire et nos réseaux, n’a pu rejoindre que les personnes dont les coordonnées nous étaient connues soit par les cercles d’amis et les réseaux sociaux ainsi que ceux ayant leur dossier à jour au sein de l’Association des diplômés-es de l’UQAC

Lifestyle factors and multimorbidity: a cross sectional study

Background: Lifestyle factors have been associated mostly with individual chronic diseases. We investigated the relationship between lifestyle factors (individual and combined) and the co-occurrence of multiple chronic diseases. Methods: Cross-sectional analysis of results from the Program of Research on the Evolution of a Cohort Investigating Health System Effects (PRECISE) in Quebec, Canada. Subjects aged 45 years and older. A randomly-selected cohort in the general population recruited by telephone. Multimorbidity (3 or more chronic diseases) was measured by a simple count of self-reported chronic diseases from a list of 14. Five lifestyle factors (LFs) were evaluated: 1) smoking habit, 2) alcohol consumption, 3) fruit and vegetable consumption, 4) physical activity, and 5) body mass index (BMI). Each LF was given a score of 1 (unhealthy) if recommended behavioural targets were not achieved and 0 otherwise. The combined effect of unhealthy LFs (ULFs) was evaluated using the total sum of scores. Results: A total of 1,196 subjects were analyzed. Mean number of ULFs was 2.6 ± 1.1 SD. When ULFs were considered separately, there was an increased likelihood of multimorbidity with low or high BMI [Odd ratio (95% Confidence Interval): men, 1.96 (1.11-3.46); women, 2.57 (1.65-4.00)], and present or past smoker [men, 3.16 (1.74-5.73)]. When combined, in men, 4-5 ULFs increased the likelihood of multimorbidity [5.23 (1.70-16.1)]; in women, starting from a threshold of 2 ULFs [1.95 (1.05-3.62)], accumulating more ULFs progressively increased the likelihood of multimorbidity. Conclusions: The present study provides support to the association of lifestyle factors and multimorbidity

Detection of human papillomavirus in laryngeal squamous cell carcinoma: systematic review and meta-analysis

Background: Recent studies have reported a human papillomavirus (HPV) prevalence of 20% to 30% in laryngeal squamous cell carcinoma (LSCC), although clinical data on HPV involvement remain largely inconsistent, ascribed by some to differences in HPV detection methods or in geographic origin of the studies. Objective To perform a systematic review and formal meta-analysis of the literature reporting on HPV detection in LSCC. Methods Literature was searched from January 1964 until March 2015. The effect size was calculated as event rates (95% confidence interval [CI]), with homogeneity testing using Cochran's Q and I2 statistics. Meta-regression was used to test the impact of study-level covariates (HPV detection method, geographic origin) on effect size. Potential publication bias was estimated using funnel plot symmetry. Results One hundred seventy nine studies were eligible, comprising a sample size of 7,347 LSCCs from different geographic regions. Altogether, 1,830 (25%) cases tested HPV-positive considering all methods, with effect size of 0.269 (95% CI: 0.242 to 0.297; random-effects model). In meta-analysis stratified by the 1) HPV detection technique and 2) geographic study origin, the between-study heterogeneity was significant only for geographic origin (P = .0001). In meta-regression, the HPV detection method (P = .876) or geographic origin (P = .234) were not significant study-level covariates. Some evidence for publication bias was found only for studies from North America and those using non–polymerase chain reaction methods, with a marginal effect on adjusted point estimates for both. Conclusions Variability in HPV detection rates in LSCC is explained by geographic origin of study but not by HPV detection method. However, they were not significant study-level covariates in formal meta-regression

Autonomous quantum error correction of Gottesman-Kitaev-Preskill states

The Gottesman-Kitaev-Preskill (GKP) code encodes a logical qubit into a bosonic system with resilience against single-photon loss, the predominant error in most bosonic systems. Here we present experimental results demonstrating quantum error correction of GKP states based on reservoir engineering of a superconducting device. Error correction is made autonomous through an unconditional reset of an auxiliary transmon qubit. The lifetime of the logical qubit is shown to be increased from quantum error correction, therefore reaching the point at which more errors are corrected than generated.Comment: 6 pages, 3 figures + 26 pages, 12 figure

Causal hierarchy within the thalamo-cortical network in spike and wave discharges

Background: Generalised spike wave (GSW) discharges are the electroencephalographic (EEG) hallmark of absence seizures, clinically characterised by a transitory interruption of ongoing activities and impaired consciousness, occurring during states of reduced awareness. Several theories have been proposed to explain the pathophysiology of GSW discharges and the role of thalamus and cortex as generators. In this work we extend the existing theories by hypothesizing a role for the precuneus, a brain region neglected in previous works on GSW generation but already known to be linked to consciousness and awareness. We analysed fMRI data using dynamic causal modelling (DCM) to investigate the effective connectivity between precuneus, thalamus and prefrontal cortex in patients with GSW discharges. Methodology and Principal Findings: We analysed fMRI data from seven patients affected by Idiopathic Generalized Epilepsy (IGE) with frequent GSW discharges and significant GSW-correlated haemodynamic signal changes in the thalamus, the prefrontal cortex and the precuneus. Using DCM we assessed their effective connectivity, i.e. which region drives another region. Three dynamic causal models were constructed: GSW was modelled as autonomous input to the thalamus (model A), ventromedial prefrontal cortex (model B), and precuneus (model C). Bayesian model comparison revealed Model C (GSW as autonomous input to precuneus), to be the best in 5 patients while model A prevailed in two cases. At the group level model C dominated and at the population-level the p value of model C was ∼1. Conclusion: Our results provide strong evidence that activity in the precuneus gates GSW discharges in the thalamo-(fronto) cortical network. This study is the first demonstration of a causal link between haemodynamic changes in the precuneus - an index of awareness - and the occurrence of pathological discharges in epilepsy. © 2009 Vaudano et al

Interictal Functional Connectivity of Human Epileptic Networks Assessed by Intracerebral EEG and BOLD Signal Fluctuations

In this study, we aimed to demonstrate whether spontaneous fluctuations in the blood oxygen level dependent (BOLD) signal derived from resting state functional magnetic resonance imaging (fMRI) reflect spontaneous neuronal activity in pathological brain regions as well as in regions spared by epileptiform discharges. This is a crucial issue as coherent fluctuations of fMRI signals between remote brain areas are now widely used to define functional connectivity in physiology and in pathophysiology. We quantified functional connectivity using non-linear measures of cross-correlation between signals obtained from intracerebral EEG (iEEG) and resting-state functional MRI (fMRI) in 5 patients suffering from intractable temporal lobe epilepsy (TLE). Functional connectivity was quantified with both modalities in areas exhibiting different electrophysiological states (epileptic and non affected regions) during the interictal period. Functional connectivity as measured from the iEEG signal was higher in regions affected by electrical epileptiform abnormalities relative to non-affected areas, whereas an opposite pattern was found for functional connectivity measured from the BOLD signal. Significant negative correlations were found between the functional connectivities of iEEG and BOLD signal when considering all pairs of signals (theta, alpha, beta and broadband) and when considering pairs of signals in regions spared by epileptiform discharges (in broadband signal). This suggests differential effects of epileptic phenomena on electrophysiological and hemodynamic signals and/or an alteration of the neurovascular coupling secondary to pathological plasticity in TLE even in regions spared by epileptiform discharges. In addition, indices of directionality calculated from both modalities were consistent showing that the epileptogenic regions exert a significant influence onto the non epileptic areas during the interictal period. This study shows that functional connectivity measured by iEEG and BOLD signals give complementary but sometimes inconsistent information in TLE

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

The slow oscillation as an intrinsic and emergent property of the neocortex

Le sommeil est présent chez pratiquement tous les animaux mais a atteint le plus haut niveau d’organisation chez les mammifères et les oiseaux avec le sommeil à ondes lentes et le sommeil paradoxal. De nombreuses études ont suggéré que le sommeil est généré par le cerveau pour ses propres besoins. L’oscillation lente est une caractéristique électroencéphalographique du sommeil à ondes lentes se traduisant par une alternance entre des états actif et silencieux du réseau thalamocortical. Elle a attiré le focus de plusieurs études étant donné son implication dans la plasticité synaptique et la consolidation de la mémoire. Plusieurs questions restent néanmoins en suspens. Quel est le rôle du thalamus dans l’oscillation lente? Quelles conditions mènent à l’état silencieux? Y a-t-il une variabilité entre espèces dans la synchronisation des ondes lentes? Dans la première étude de cette thèse, nous montrons que le thalamus est crucial à la genèse et à la propagation de l’oscillation lente alors que le cortex a la propriété intrinsèque de la restaurer en absence d’afférence fonctionnelle. Dans la seconde étude, nous nous intéressons aux conditions qui mènent à l’initiation des états silencieux dans le néocortex. Nous avons trouvé que l’inhibition dépendante du chlore est impliquée dans la terminaison des états actifs et que les afférences thalamocorticales jouent un rôle dans la synchronisation des états silencieux. Dans la troisième étude, nous comparons le niveau de synchronisation de l’oscillation lente dans les régions somatosensorielle et associative du néocortex chez le chat et le lapin. Nous rapportons que la synchronisation de l’oscillation lente corrèle avec le niveau de gyrification du cortex cérébral et le niveau hiérarchique dans le traitement de l’information d’une région néocorticale. Nous concluons que l’oscillation lente est une propriété intrinsèque du néocortex qui émerge du dialogue entre le néocortex et le thalamus, de la balance entre l’inhibition et l’excitation dans le réseau néocortical et dont la synchronisation a évolué avec le développement du cortex cérébral.Sleep is a defining feature of animals that achieved the highest degree of organization in mammals with two distinct types of sleep: the slow wave sleep (SWS) and the rapid eye movements sleep. A large body of evidences suggests that the sleep is generated by the brain to fulfill its own need. Among the electroencephalographic signatures of SWS and anesthesia, the slow oscillation (< 1 Hz), a rhythmic alternation of active and silent states of the thalamocortical network, has attracted a lot of attention owing to its implication in synaptic plasticity and memory consolidation. Several questions remain unanswered on the mechanisms underlying the slow oscillation. For instance, what is the role of the thalamus in the slow oscillation? Which conditions lead to the onset of the silent state? Is there inter-species variability in the synchronization? In the first study of this thesis, we have investigated the respective contribution of the neocortex and the thalamus in the generation of the slow oscillation. We report that the thalamus is crucial to the generation and propagation of the active states of the slow oscillation while the neocortex has the intrinsic ability to recover the slow oscillation in absence of afferents. In the second study, we address the question regarding the conditions that lead to the onset of the silent state in the neocortex. We have found that chloride-mediated inhibition and functional thalamocortical afferents are involved in terminating the active states. In the third study, we compare the synchronization of the slow oscillation in the somatosensory and associative cortices of cats and rabbits. We have found that the synchronization of the slow waves correlates with the level of gyrification of the cerebral cortex and the hierarchical level of information processing of a neocortical region. We conclude that the slow oscillation is an intrinsic property of the neocortex that emerges from the dialogue between the neocortex and thalamus, the balance of inhibition and excitation in the neocortical network and that the synchronization of the slow oscillation evolved with the development of the cerebral cortex