Contexte théorique : L’encéphalopathie hypoxique ischémique (EHI) est une condition du nouveau-né dans laquelle les mécanismes des variables métaboliques ne sont pas totalement compris. Cette population est particulièrement à risque d’hypo- ou d’hyperglycémie néonatales (HHN). Devant le manque de données sur le fonctionnement métabolique à la suite d’une EHI, cette étude vise à déterminer l’association entre une HHN et l’activité cérébrale mesurée par électroencéphalographie (EEG). Méthodologie : 49 participants avec EHI ont été recrutés au CHU Sainte-Justine peu après leur naissance. Ils ont été monitorés en continu à l’aide de l’EEG et des segments d’intérêt se retrouvant dans les 48 premières heures de vie ont été analysés. L’anormalité de l’activité cérébrale est déterminée selon une analyse quantitative du niveau de discontinuité caractérisée par une proportion de faibles amplitudes (seuils de 25, 15, 12,5, 10 et 7,5 uV) dans le tracé EEG. Les données de glycémie ont été recueillies de façon intermittente par le biais de prises de sang et de glucomètres de chevet. Les participants ont été répartis en 4 groupes : normoglycémie, hyperglycémie, hypoglycémie et glycémie variable (hypo- et hyper-). Résultats : L’analyse de covariation non -paramétrique a relevé une différence significative entre les ratios de discontinuité pour le seuil de 15 uV (F = 3,070 p = 0,037). Les analyses de comparaisons appariées ont montré une différence positive entre le groupe VARIABLE et le groupe contrôle (NORMO-) pour tous les seuils ainsi qu’une différence positive entre le groupe HYPER- et le groupe contrôle pour 4 des 5 seuils (25, 15, 12,5 et 7,5 uV). Aucune différence n’a été relevé entre le groupe HYPO- et le groupe contrôle pour tous les seuils. Conclusions : La variabilité glycémique et l’hyperglycémie seule ont été montrées comme étant associées à une activité cérébrale altérée caractérisée par un tracé de plus faible amplitude mesurée avec l’EEG. / Background: Hypoxic ischemic encephalopathy (HIE) is a newborn condition in which the underlying mechanisms still require further understanding. This clinical population is particularly prone to neonatal hypo- and hyperglycemia (NHH). Given the need to improve our understanding of metabolic functioning following HIE, this study aims to determine the association of NHH on the brain’s background electrophysiological activity measured by electroencephalography (EEG). Methodology: Forty-nine newborns with HIE were recruited at Sainte-Justine University Hospital Center. Continuous EEG monitoring was started as soon as possible and segments of interest in the first 48h of life were analyzed. Brain activity was quantitatively assessed according to an index of discontinuity characterized by the proportion of low EEG amplitudes per segment (< 25, 15, 12.5, 10 and 7.5 uV cutoffs). Glucose measurements were intermittently collected using blood samples and bedside glucometers and were retrospectively retrieved from medical charts. Participants were separated in 4 groups : normoglycemia, hyperglycemia, hypoglycemia and both (hyper- and hypo-). Results: The non-parametric covariance analyses revealed a significant difference between the discontinuity index for the 15 uV threshold (F = 3.070 p = 0.037). The pairwise comparisons showed a positive difference between the group BOTH and the control group (NORMO-) for every thresholds, the labile glucose group having a higher discontinuity index. A similar difference was found between the HYPERGLYCEMIA group and the control group for 4 out 5 thresholds (25, 15, 12.5 and 7.5 uV). No difference was found between the HYPOGLYCEMIA group and the control group. Conclusion: An abnormal glycemic profile, particularly glucose lability and hyperglycemia alone, were shown to be associated with abnormal brain activity characterized by a higher discontinuity index on the EEG.

Der Transkriptionsfaktor hypoxia inducible factor-1 (HIF-1) trägt zur Expression von adaptiven Genen unter hypoxischen Bedingungen bei. Zusätzlich wurde vermutet, dass HIF-1 eine Rolle in der Regulation des späten neuronalen Zelltodes spielt. Suspensionszellen und adhärenten PC12-Zellen mit Nervenwachstumsfaktor (NGF) behandelt, wurden als ein experimentelles Modell für die Untersuchung der Beziehung zwischen Hypoxie induziertem Zelltod und Aktivität von HIF-1 herangezogen. Zelltod wurde durchflusszytometrisch mit einer Doppelfärbung (Annexin V und Propidium-Jodid) der Zellen und durch eine Analyse der allgemeinen Zelltodparameter wie LDH und die mitochondriale Dehydrogenase bestimmt. Parallel wurden Zellen mit einem Kontrollvektor und einem hypoxiesensitiven Vektor mit drei Hypoxie-bindenden-Elementen (HBE) transfiziert und die durch HIF-1 aktivierte Luciferase gemessen. Hypoxieexposition der NGF-behandelten PC12-Zellen resultierte in einer höheren Zelltodrate verglichen mit den unbehandelten Kontrollzellen. PC12 Zellen, zwei Tage mit NGF behandelt, zeigten eine bis zu 10-fach verminderte HIF-1-Aktivität. Diese Verminderung könnte zu dem erhöhten hypoxie-induzierten Zelltod durch verminderte Expression von HIF-1alpha-regulierten Genen, welche für die Anpassung an Hypoxie verantwortlich sind, beitragen. Die Verminderung der HIF-1 Aktivität und der Anstieg der Hypoxiesensitivität könnte darauf hinweisen, dass NGF als eine Art hierarchisch organisiertes Signalmolekül fungiert. / The transcription factor hypoxia-inducible factor-1 (HIF-1) strongly contributes to the expression of adaptive genes under hypoxic conditions. In addition, HIF-1 has been implicated in the regulation of delayed neuronal cell death. Suspension-grown and adherent PC12 cells treated with NGF were used as an experimental model for studying the relationship between hypoxia-induced cell death and activation of HIF-1. Cell damage was assessed by flow cytometry of double-stained (annexin V and propidiumiodide) cells, and by analysis of the overall death parameters LDH and mitochondrial dehydrogenase. In parallel, cells were transfected with a control and a three-hypoxia-responsive-elements (HRE)-containing vector and HIF-1-driven luciferase activity was determined. Exposure of NGF-treated PC12 cells to hypoxia resulted in a higher cell death rate when compared to untreated controls. PC12 cells exposed for 2 days to NGF exhibited a decrease of HIF-1 activity up to a factor of ten. This decrease may contribute to the enhanced hypoxia-induced cell death via reduced expression of HIF-1alpha-regulated genes resposible for adaptation to hypoxia, like those for glucose transport proteins and enzymes of the glycolytic chain. The decrease in HIF-1 activity and the increase in hypoxia sensitivity may suggest that NGF act as an hierachically organized signaling molecule.

Introdução: O aperfeiçoamento da assistência pré-natal e neonatal contribuiu para maior sobrevida dos recém-nascidos com riscos para alterações do desenvolvimento. A detecção precoce e eficaz destes riscos é fundamental para a intervenção oportuna e minimização dos danos funcionais. A avaliação com melhor valor preditivo para anormalidades é pelos General Movements (GMs), porém a mais utilizada no Brasil é a Escala Motora Infantil de Alberta (EMIA). Objetivo: Verificar a validade dos GMs e da EMIA com um e três meses de idade para predizer o desfecho do desenvolvimento motor pela EMIA aos seis e 12 meses. Método: Estudo observacional longitudinal com 45 recém-nascidos e lactentes do Hospital Universitário da Universidade de São Paulo, avaliados do nascimento até os cinco meses de idade (corrigida, se prematuros) pelos GMs, e de um a 12 meses pela EMIA. Foi realizada análise descritiva e testes de kappa e curva roc para a comparação entre as avaliações. Resultados: Os participantes (masculino = 51,1%) apresentaram idade gestacional média de 34 semanas; 57,7% apresentaram alteração em pelo menos uma avaliação pelos GMs, com predomínio do repertório pobre (RP) e fidgety movements (FM) ausentes, enquanto 46,6% apresentaram alguma alteração na EMIA. A maioria (85,7%) apresentou avaliações normais aos 12 meses de idade pela EMIA; e os com avaliações anormais também tiveram GMs alterados em toda sua trajetória. Houve pobre confiabilidade entre os GMs e a EMIA no primeiro (kappa: 0,165) e no terceiro mês, ligeira confiabilidade (kappa: 0,259). Comparando os writhing movements (WM) com a EMIA com um mês, para prever desfecho aos seis meses de idade, foi encontrado uma sensibilidade dos WM de 78,6% e uma especificidade de 100%. Valores melhores de sensibilidade e especificidade também foram encontrados nos WM para desfecho com 12 meses de idade (sensibilidade de 75% e especificidade em 100%). Os lactentes que apresentavam alguma alteração nas avaliações eram encaminhados para fisioterapia. Conclusão: Foi possível observar um grande número de participantes com GMs alterados, porém com diminuição/normalização nas avaliações pela EMIA, podendo ser devido a intervenção fisioterapêutica nos casos mais graves. A avaliação com melhores valores para predição do desenvolvimento são os GMs na fase dos WMs. Não existe correlação entre a avaliação dos GMs com 1 mês e EMIA 1 com mês, nem entre estes dois métodos aos 3 meses / Introduction: Improvement of prenatal and neonatal care has contributed to a greater survival of newborns with risks for developmental disorders. Early and effective detection of these risks is essential for timely intervention and minimization of functional impairment. The most predictive value for abnormalities is the General Movements (GMs), but the most used in Brazil is the Alberta Infant Motor Scale (AIMS). Objective: To verify the validity of GMs and EMIA at one and three months of age to predict the outcome of motor development by EMIA at six and 12 months. Method: A longitudinal observational study with 45 newborns and infants of the University Hospital of the University of São Paulo, evaluated from birth to five months of age (corrected, if premature) by GMs, and from one to 12 months by EMIA. Descriptive analysis and kappa and roc curve tests were performed to compare the evaluations. Results: Participants (male = 51.1%) had a mean gestational age of 34 weeks; 57.7% presented alterations in at least one evaluation by GMs, with a predominance of poor repertoire (RP) and fidgety movements (FM) absent, while 46.6% had some alteration in EMIA. The majority (85.7%) presented normal evaluations at 12 months of age by EMIA; And those with abnormal ratings also had altered GMs throughout their trajectory. There was poor reliability between GMs and EMIA in the first (kappa: 0.165) and in the third month, slight reliability (kappa: 0.259). Comparing writhing movements (WM) with EMIA at one month, to predict outcome at six months of age, a WM sensitivity of 78.6% and a specificity of 100% was found. Better sensitivity and specificity values were also found in WM for 12-month-old outcome (75% sensitivity and 100% specificity). Infants who presented some alterations in the assessments were referred to physical therapy. Conclusion: It was possible to observe a large number of participants with altered GMs, but with a decrease / normalization in the evaluations by EMIA, and may be due to physiotherapeutic intervention in the most severe cases. The best predictive values for development prediction are GMs in the WM phase. There is no correlation between the evaluation of GMs at 1 month and EMIA 1 with month, nor between these two methods at 3 months

Extraction of physiological and clinical information hidden in biosignals, such as cardiac and neural signals, is an important and fascinating field of research. Noninvasive assessment of the physiological parameters of a patient enables to study the physiology and pathophysiology of the investigated system, with minimal interference and inconvenience. This approach may also help to assess noninvasively the clinical condition of the patient. The primary focus of this study is therefore to extend the arsenal of research tools for the noninvasive investigation of the neural and cardiac systems. The approaches developed in this work concern two major directions: The first direction relies on the analysis of cardiac and neural responses during hypoxia. Hypoxia-ischemia remains a great challenge to the researchers, since it triggers complex responses at different levels in the organism. The functional recovery depends on a number of factors among which the state of autonomic nervous system (ANS) regulation plays an important role. Two different applications were considered in this framework. The first application studied the effect of global ischemic preconditioning on the heart rate variability (HRV) response to the asphyxia insult. Using linear (time and frequency domain) and nonlinear (approximate entropy and parameters of Poincare plots) measures, we evaluated the dynamic time course of the HRV response to the asphyxia insult and the effect of preconditioning on the autonomic neurocardiac control. Our results show for the first time that global ischemic preconditioning influences the HRV response to the asphyxia injury. The neuroprotective effect of preconditioning translates into a faster recovery of the basal HRV and the autonomic modulation of the heart. For the preconditioned group, at about 90 min after the asphyxic insult, the autonomic neural balance (measured by LF/HF ratio) appears fully recovered. Another application addressed the problem of phase synchronization analysis of EEG signals during monitoring of recovery process following brain injury episode. The concept of phase synchronization offers a new perspective on the understanding and quantification of the dynamical interactions established among coupled systems. In this thesis, we present a new approach for the identification of the degree of interaction between two complex dynamical systems from experimental data analysis. We use the empirical-mode-decomposition (EMD) technique to decompose the output signals into a number of elementary orthogonal modes with well defined instantaneous attributes (IMFs). The second direction addressed the problem of correlations between anticipatory pursuit eye movements and the neural response in the Supplementary Eye Fields (SEF) of the Macaque monkey. Anticipatory pursuit is a smooth movement of the eye occurring before the appearance of an expected moving target. The expectation of the subject is based on a subjective estimation of the probability that the target will move in a given direction. Recently, it has been suggested that the SEF could play a role in using past experience to guide anticipatory pursuit. This hypothesis is currently being tested at the single neuron level. In the behaving monkey, it has been shown that electrical microstimulation in the SEF can facilitate smooth pursuit initiation towards a moving target, suggesting that activation of the SEF might change the internal gain of the smooth pursuit pathway. In this study, we favored anticipatory responses in monkeys by using a cognitive cue, which produces a different anticipatory pursuit response than the one observed in previous studies, based on repetition. / H εξαγωγή φυσιολογικών και κλινικών πληροφοριών οι οποίες είναι κρυμμένες σε βιοσήματα όπως τα καρδιακά και νευροφυσιολογικά σήματα είναι ένας σημαντικός και πολύ ενδιαφέρον τομέας έρευνας. Μη επεμβατική αξιολόγηση των φυσιολογικών παραμέτρων ενός ασθενή επιτρέπει την μελέτη της φυσιολογίας και παθολογίας του μελετούμενου συστήματος με τις λιγότερες παρεμβολές και ενόχληση. Η προσέγγιση αυτή μπορεί επίσης να βοηθήσει στην μη επεμβατική αξιολόγηση της κλινικής κατάστασης του ασθενή. Η πρώτη προσέγγιση της μελέτης αυτής είναι να επεκτείνει το οπλοστάσιο των ερευνητικών εργαλείων για την μη επεμβατική αναζήτηση του νευρικού και καρδιακού συστήματος. Οι προσεγγίσεις που αναπτύσσονται σε αυτή τη δουλειά αφορούν δύο κύριες κατευθύνσεις: Η πρώτη κατεύθυνση υπόκειται στην ανάλυση των καρδιακών και νευροφυσιολογικών αποκρίσεων κατά τη διάρκεια της υποξίας. Η ισχεμία – υποξία παραμένει μια μεγάλη πρόκληση στους ερευνητές εφόσον πυροδοτεί πολύπλοκες αποκρίσεις σε διαφορετικά επίπεδα στον οργανισμό. Η λειτουργική αποκατάσταση εξαρτάται από έναν αριθμό συντελεστών μεταξύ των οποίων ο έλεγχος της κατάστασης του αυτόνομου νευρικού συστήματος παίζει έναν πολύ σημαντικό ρόλο. Δύο διαφορετικές εφαρμογές ελήφθησαν υπόψη στο πλαίσιο αυτό. Η πρώτη εφαρμογή μελέτησε το φαινόμενο της ολικής ισχαιμικής προκατάστασης στην μεταβλητότητα του καρδιακού ρυθμού (heart rate variability - HRV) σε προσβολή από ασφυξία. Χρησιμοποιώντας γραμμικές (στον τομέα του χρόνου και των συχνοτήτων) και μη γραμμικές (υπολογισμός εντροπίας και παραμέτρων των γραφημάτων Poincare) τεχνικές υπολογίσαμε την δυναμική χρονική εξέλιξη της HRV απόκρισης στην προσβολή από ασφυξία και η επίπτωση της προ-κατάστασης στο αυτόνομο νευροκαρδιολογικό έλεγχο. Τα αποτελέσματά μας έδειξαν για πρώτη φορά ότι η ολική ισχαιμική προκατάσταση επηρεάζει την HRV απόκριση στον τραυματισμό από την ασφυξία. Η νευροπροστατευτική επίπτωση της προκατάστασης μεταφράζεται σε μία γρηγορότερη αποκατάσταση του βασικού HRV και μία αυτόνομη εναρμόνιση της καρδιάς. Για την ομάδα με την προκατάσταση σε περίπου 90 λεπτά μετά την προσβολή από ασφυξία, η αυτόνομη νευρολογική ισορροπία (μετρούμενη από τον λόγο χαμηλών προς υψηλών συχνοτήτων εμφανίζεται πλήρως αποκαταστημένη. Μία άλλη εφαρμογή απευθύνεται στο πρόβλημα της ανάλυσης του συγχρονισμού φάσεων των σημάτων Ηλεκτροεγκεφαλογραφήματος κατά τη διάρκεια παρακολούθησης της διαδικασίας αποκατάστασης μετά από επεισόδιο εγκεφαλικής βλάβης. Η ιδέα του συγχρονισμού φάσεων προσφέρει μία νέα προοπτική στην κατανόηση και ποσοτικοποίηση των δυναμικών αλληλεπιδράσεων μεταξύ συστημάτων συζευγμένων ταλαντωτών. Σε αυτή τη διδακτορική διατριβή παρουσιάζουμε μια νέα προσέγγιση για την ανίχνευση του βαθμού της αλληλεπίδρασης μεταξύ δύο πολύπλοκων δυναμικών συστημάτων από την ανάλυση πειραματικών δεδομένων. Χρησιμοποιούμε την τεχνική του εμπειρικού τρόπου αποδόμησης (empirical-mode-decomposition EMD) για να διασπάσουμε τα σήματα εξόδου σε έναν αριθμό βασικών ορθογώνιων μερών με πολύ καλά καθορισμένες στιγμιαίες ιδιότητες (instantaneous attributes IMFs). Η δεύτερη κατεύθυνση είναι το πρόβλημα των συσχετίσεων μεταξύ προνοητικών κινήσεων των ματιών και των νευροφυσιολογικών αποκρίσεων στα παιδία των ματιών (Supplementary Eye Fields SEF) πιθήκων Macaque. Οι προνοητικές κινήσεις είναι απαλές κινήσεις των ματιών που συμβαίνουν πριν την εμφάνιση ενός αναμενόμενου κινούμενου στόχου. Η αναμονή από το υποκείμενο βασίζεται σε έναν υποκειμενικό υπολογισμό της πιθανότητας ότι ο στόχος θα κινηθεί σε μια δεδομένη κατεύθυνση. Πρόσφατα, έχει υποτεθεί ότι τα SEF μπορούν να παίζουν ρόλο στην χρησιμοποίηση παλαιών εμπειριών στην καθοδήγηση αναμενόμενων κινήσεων. Αυτή η υπόθεση έχει ελεγχθεί στο επίπεδο ενός μόνο νευρώνα. Στον πίθηκο έχει βρεθεί ότι ο ηλεκτρικός μικροερεθισμός στο SEF μπορεί να διευκολύνει την ομαλή έναρξη της κίνησης προς έναν κινούμενο στόχο, συνιστώντας ότι η ενεργοποίηση του SEF μπορεί να αλλάξει την εσωτερική απόδοση του δικτύου της ομαλής κίνησης. Σε αυτή τη μελέτη, ενισχύσαμε την εκκίνηση των ομαλών κινήσεων των πιθήκων προς ένα κινούμενο στόχο η οποία παράγει μία διαφορετική προνοητική κίνηση αυτής που παρατηρείται σε προηγούμενες μελέτες η οποία βασίζεται σε επανάληψη.

Introdução: O aperfeiçoamento da assistência pré-natal e neonatal contribuiu para maior sobrevida dos recém-nascidos com riscos para alterações do desenvolvimento. A detecção precoce e eficaz destes riscos é fundamental para a intervenção oportuna e minimização dos danos funcionais. A avaliação com melhor valor preditivo para anormalidades é pelos General Movements (GMs), porém a mais utilizada no Brasil é a Escala Motora Infantil de Alberta (EMIA). Objetivo: Verificar a validade dos GMs e da EMIA com um e três meses de idade para predizer o desfecho do desenvolvimento motor pela EMIA aos seis e 12 meses. Método: Estudo observacional longitudinal com 45 recém-nascidos e lactentes do Hospital Universitário da Universidade de São Paulo, avaliados do nascimento até os cinco meses de idade (corrigida, se prematuros) pelos GMs, e de um a 12 meses pela EMIA. Foi realizada análise descritiva e testes de kappa e curva roc para a comparação entre as avaliações. Resultados: Os participantes (masculino = 51,1%) apresentaram idade gestacional média de 34 semanas; 57,7% apresentaram alteração em pelo menos uma avaliação pelos GMs, com predomínio do repertório pobre (RP) e fidgety movements (FM) ausentes, enquanto 46,6% apresentaram alguma alteração na EMIA. A maioria (85,7%) apresentou avaliações normais aos 12 meses de idade pela EMIA; e os com avaliações anormais também tiveram GMs alterados em toda sua trajetória. Houve pobre confiabilidade entre os GMs e a EMIA no primeiro (kappa: 0,165) e no terceiro mês, ligeira confiabilidade (kappa: 0,259). Comparando os writhing movements (WM) com a EMIA com um mês, para prever desfecho aos seis meses de idade, foi encontrado uma sensibilidade dos WM de 78,6% e uma especificidade de 100%. Valores melhores de sensibilidade e especificidade também foram encontrados nos WM para desfecho com 12 meses de idade (sensibilidade de 75% e especificidade em 100%). Os lactentes que apresentavam alguma alteração nas avaliações eram encaminhados para fisioterapia. Conclusão: Foi possível observar um grande número de participantes com GMs alterados, porém com diminuição/normalização nas avaliações pela EMIA, podendo ser devido a intervenção fisioterapêutica nos casos mais graves. A avaliação com melhores valores para predição do desenvolvimento são os GMs na fase dos WMs. Não existe correlação entre a avaliação dos GMs com 1 mês e EMIA 1 com mês, nem entre estes dois métodos aos 3 meses / Introduction: Improvement of prenatal and neonatal care has contributed to a greater survival of newborns with risks for developmental disorders. Early and effective detection of these risks is essential for timely intervention and minimization of functional impairment. The most predictive value for abnormalities is the General Movements (GMs), but the most used in Brazil is the Alberta Infant Motor Scale (AIMS). Objective: To verify the validity of GMs and EMIA at one and three months of age to predict the outcome of motor development by EMIA at six and 12 months. Method: A longitudinal observational study with 45 newborns and infants of the University Hospital of the University of São Paulo, evaluated from birth to five months of age (corrected, if premature) by GMs, and from one to 12 months by EMIA. Descriptive analysis and kappa and roc curve tests were performed to compare the evaluations. Results: Participants (male = 51.1%) had a mean gestational age of 34 weeks; 57.7% presented alterations in at least one evaluation by GMs, with a predominance of poor repertoire (RP) and fidgety movements (FM) absent, while 46.6% had some alteration in EMIA. The majority (85.7%) presented normal evaluations at 12 months of age by EMIA; And those with abnormal ratings also had altered GMs throughout their trajectory. There was poor reliability between GMs and EMIA in the first (kappa: 0.165) and in the third month, slight reliability (kappa: 0.259). Comparing writhing movements (WM) with EMIA at one month, to predict outcome at six months of age, a WM sensitivity of 78.6% and a specificity of 100% was found. Better sensitivity and specificity values were also found in WM for 12-month-old outcome (75% sensitivity and 100% specificity). Infants who presented some alterations in the assessments were referred to physical therapy. Conclusion: It was possible to observe a large number of participants with altered GMs, but with a decrease / normalization in the evaluations by EMIA, and may be due to physiotherapeutic intervention in the most severe cases. The best predictive values for development prediction are GMs in the WM phase. There is no correlation between the evaluation of GMs at 1 month and EMIA 1 with month, nor between these two methods at 3 months

No description available.

Les enfants qui ont subi une asphyxie périnatale modérée (MPA) risquent de développer des déficits cognitifs et comportementaux subtils et durables, notamment des troubles d'apprentissage et des problèmes émotionnels. Comprendre les mécanismes sous-jacents est une étape essentielle pour concevoir une thérapie ciblée. Déterminer comment le développement du cerveau est corrélé entre les humains et les rongeurs n'est pas simple, mais il existe également un alignement inter-espèces considérable en termes d'étapes clés du développement. Sur la base des changements biochimiques et neuroanatomiques au cours du développement précoce, le consensus général est qu'un cerveau de rongeur P8-10 correspond à peu près au cerveau d'un enfant à terme ; par conséquent, nous avons utilisé cette fenêtre temporelle comme référence pour développer un modèle préclinique de MPA chez la souris. Nous avons d'abord établi un protocole qui nous permet d'observer de manière fiable les crises induites par l'hypoxie chez les souris postnatales. Nous avons constaté que l'exposition de chiots P8-9 directement à 4 % d'O2 pendant 8 minutes induit de manière fiable des crises avec une latence d'environ 5 minutes chez 3 souches de souris (FVB, C57Bl/6, 129S6). Cet aspect est cliniquement pertinent car les convulsions sont la caractéristique néonatale la plus importante de l'encéphalopathie de stade 2 (modérée) telle que définie par l'échelle de Sarnat. Les souris MPA adultes présentent des séquelles à long terme sur des performances cognitives spécifiques, notamment des déficits de la mémoire de reconnaissance et de la flexibilité cognitive, mais aucune altération du comportement moteur et émotionnel. Le cortex préfrontal (PFC) régule la flexibilité cognitive et le comportement émotionnel. Les neurones qui libèrent la sérotonine (5-HT) projettent vers le PFC, et les composés modulant l'activité 5-HT influencent l'émotion et la cognition. On ne sait pas si les dérégulations de la 5-HT contribuent aux problèmes cognitifs induits par le MPA. Dans une première étude, nous avons trouvé que les niveaux d'expression de 5-HT, quantifiés par immunohistochimie, et de libération de 5-HT, quantifiés par microdialyse in vivo chez des souris éveillées, sont réduits dans le PFC de souris MPA adultes. Les souris MPA présentent également une régulation de la température corporelle altérée après l'injection de l'agoniste des récepteurs 5-HT1A, 8-OH-DPAT, suggérant la présence de déficits dans la fonction des auto-récepteurs 5-HT sur les neurones du raphé. Enfin, le traitement chronique de souris MPA adultes avec de la fluoxétine, un inhibiteur du transporteur de recapture de la 5-HT, ou l'agoniste des récepteurs 5-HT1A, la tandospirone, sauve la flexibilité cognitive et les troubles de la mémoire. Ensemble, ces données démontrent que le développement de la fonction du système 5-HT est vulnérable à une asphyxie périnatale modérée. L'hypofonctionnement de la 5-HT pourrait à son tour contribuer à une déficience cognitive à long terme à l'âge adulte, indiquant une cible potentielle pour les thérapies pharmacologiques. Les circuits GABAergiques comprennent une variété étonnante de différents types de cellules, qui sont probablement recrutées par différents événements comportementaux. Un sous-type important de cellules GABAergiques, les cellules positives à la parvalbumine (PV), génèrent des potentiels d'action à haute fréquence et synchronisent l'activité des neurones pyramidaux excitateurs. Les cellules PV sont particulièrement importantes pour la génération d'oscillations gamma, qui à leur tour régulent de nombreuses fonctions cognitives, notamment le traitement attentionnel axé sur les objectifs et la mémoire de travail. Des découvertes récentes indiquent que les cellules PV utilisent beaucoup plus d'énergie que les autres neurones corticaux, ce qui peut les rendre très vulnérables aux conditions de stress métabolique et oxydatif causées par le MPA. Nos données ont montré que l'expression de PV est altérée chez les souris MPA adultes. Nous avons en outre constaté que le niveau d'expression du récepteur de la neurotrophine p75NTR, qui limite la maturation des cellules PV au cours de la première semaine postnatale, est augmenté chez les souris MPA. La suppression génétique de p75NTR dans les neurones GABAergiques exprimant le facteur de transcription Nkx2.1, qui comprend les cellules PV, protège les souris de la perte de niveaux de PV et des effets cognitifs à long terme du MPA. Enfin, un traitement d'une semaine avec un inhibiteur de p75NTR commençant après le MPA sauve complètement les déficits d'activité cognitive et corticale chez les souris adultes. L'ensemble de ces données révèle une cible moléculaire potentielle pour le traitement des altérations cognitives causées par le MPA. / Children who experienced moderate perinatal asphyxia (MPA) are at risk of developing long lasting subtle cognitive and behavioral deficits, including learning disabilities and emotional problems. Understanding the underlying mechanisms is an essential step for designing targeted therapy. Determining how brain development correlates between humans and rodents is not straightforward, however there is also considerable cross-species alignment in terms of key developmental milestones. Based on biochemical and neuroanatomical changes during early development, the general consensus is that a P8-10 rodent brain corresponds roughly to the brain of a term infant; therefore, we used this time window as reference to develop a preclinical model of MPA in mouse. We first established a protocol that allows us to reliably observe hypoxia-induced seizures in postnatal mice. We found that exposing P8-9 pups directly to 4% O2 for 8 minutes reliably induces seizures with a latency of about 5’ in 3 mouse strains (FVB, C57Bl/6, 129S6). This aspect is clinically relevant as seizures are the most prominent neonatal hallmark of Stage 2 (Moderate) encephalopathy as defined by the Sarnat Scale. Adult MPA mice show long-term sequelae on specific cognitive performance, including deficits in recognition memory and cognitive flexibility, but no impairment in motor and emotional behavior. The prefrontal cortex (PFC) regulates cognitive flexibility and emotional behavior. Neurons that release serotonin (5-HT) project to the PFC, and compounds modulating 5-HT activity influence emotion and cognition. Whether 5-HT dysregulations contribute to MPA-induced cognitive problems is unknown. In a first study, we found that 5-HT expression levels, quantified by immunohistochemistry, and 5-HT release, quantified by in vivo microdialysis in awake mice, are reduced in PFC of adult MPA mice. MPA mice also show impaired body temperature regulation following injection of the 5-HT1A receptor agonist 8-OH-DPAT, suggesting the presence of deficits in 5-HT auto-receptor function on raphe neurons. Finally, chronic treatment of adult MPA mice with fluoxetine, an inhibitor of 5-HT reuptake transporter, or the 5-HT1A receptor agonist tandospirone rescues cognitive flexibility and memory impairments. All together, these data demonstrate that the development of 5-HT system function is vulnerable to moderate perinatal asphyxia. 5-HT hypofunction might in turn contribute to long-term cognitive impairment in adulthood, indicating a potential target for pharmacological therapies. GABAergic circuits comprise an astonishing variety of different cell types, which are likely recruited by different behavioral events. An important subtype of GABAergic cells, the fast-spiking, parvalbumin-positive (PV) cells, generate action potentials at high frequency and synchronize the activity of excitatory pyramidal neurons. PV cells are particularly important for the generation of gamma oscillations, which in turn regulate many cognitive functions including goal-directed attentional processing and working memory. Recent findings indicate that PV cells utilize much more energy than other cortical neurons, which may render them highly vulnerable to conditions of metabolic and oxidative stress caused by MPA. Our data showed that PV expression is impaired in adult MPA mice. We further found that the expression level of the neurotrophin receptor p75NTR, which limits PV cell maturation during the first postnatal week, is increased in MPA mice. Genetic deletion of p75NTR in GABAergic neurons expressing the transcription factor Nkx2.1, which include PV cells, protects mice from PV levels loss and the long-term cognitive effects of MPA. Finally, one week treatment with a p75NTR inhibitor starting after MPA completely rescues the cognitive and cortical activity deficits in adult mice. All together this data reveals a potential molecular target for the treatment of the cognitive alterations caused by MPA.

Infants with hypoxic-ischaemic encephalopathy (birth asphyxia) have a high risk of death or disability. Those with poor prognosis are sometimes allowed to die after withdrawal of intensive care. In recent years, doctors have used new types of brain scan, magnetic resonance imaging (MRI), to predict the type and severity of impairment if the infant survives and to help with such decisions. In this thesis, I analyse the issues arising from the use of MRI for prognostication and decision-making in newborn infants. I argue that previous prognostic research has been hampered by a failure to identify and focus on the most important practical question and that this contributes to uncertainty in practice. I outline recommendations for improving research. I then look at existing guidelines about withdrawal of life-sustaining treatment. I identify several problems with these guidelines; they are vague and fail to provide practical guidance, they provide little or no genuine scope for parental involvement in decisions, and they give no weight to the interests of others. I argue that parental interests should be given some weight in decisions for newborn infants. I develop a new model of decision-making that, using the concept of a Restricted Life, attempts to set out clearly the boundaries of parental discretion in decision-making. I argue that where infants are predicted to have severe cognitive or very severe physical impairment parents should be permitted to request either withdrawal or continuation of treatment. I justify this model on the basis of overlapping interests, (prognostic, experiential and moral) uncertainty, asymmetrical harms, and the burden of care. In the conclusion, I set out a guideline for the use of MRI in newborn infants with hypoxic-ischaemic encephalopathy. I suggest that this guideline would provide a more robust, coherent and practical basis for decision-making in newborn intensive care.