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Investigations into the effects of neuromodulations on the BOLD-fMRI signalMaczka, Melissa May January 2013 (has links)
The blood oxygen level dependent functional MRI (BOLD-fMRI) signal is an indirect measure of the neuronal activity that most BOLD studies are interested in. This thesis uses generative embedding algorithms to investigate some of the challenges and opportunities that this presents for BOLD imaging. It is standard practice to analyse BOLD signals using general linear models (GLMs) that assume fixed neurovascular coupling. However, this assumption may cause false positive or negative neural activations to be detected if the biological manifestations of brain diseases, disorders and pharmaceutical drugs (termed "neuromodulations") alter this coupling. Generative embedding can help overcome this problem by identifying when a neuromodulation confounds the standard GLM. When applied to anaesthetic neuromodulations found in preclinical imaging data, Fentanyl has the smallest confounding effect and Pentobarbital has the largest, causing extremely significant neural activations to go undetected. Half of the anaesthetics tested caused overestimation of the neuronal activity but the other half caused underestimation. The variability in biological action between anaesthetic modulations in identical brain regions of genetically similar animals highlights the complexity required to comprehensively account for factors confounding neurovascular coupling in GLMs generally. Generative embedding has the potential to augment established algorithms used to compensate for these variations in GLMs without complicating the standard (ANOVA) way of reporting BOLD results. Neuromodulation of neurovascular coupling can also present opportunities, such as improved diagnosis, monitoring and understanding of brain diseases accompanied by neurovascular uncoupling. Information theory is used to show that the discriminabilities of neurodegenerative-diseased and healthy generative posterior parameter spaces make generative embedding a viable tool for these commercial applications, boasting sensitivity to neurovascular coupling nonlinearities and biological interpretability. The value of hybrid neuroimaging systems over separate neuroimaging technologies is found to be greatest for early-stage neurodegenerative disease.
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Les différences sexuelles dans l’activation cérébrale durant l’accomplissement de la tâche de rotation mentale chez les patients atteints de schizophrénieJimenez, Jose A. 08 1900 (has links)
Dans la population générale plusieurs études ont démontré que les hommes ont, par comparaison aux femmes, de meilleures performances dans les tâches de rotation mentale à trois dimensions. A l’aide de l’imagerie par résonnance magnétique fonctionnelle, on a pu observer que l’exécution de cette tâche de rotation mentale s’accompagnait d’une activation du cortex pariétal chez l’homme mais du cortex prefrontal chez la femme. Ces différences entre les deux sexes suggèrent un fonctionnement neuronal différent dans l’appréhension des habiletés cognitives et comportementales. De fait, de nombreuses études ont signalé des différences notables entre les deux sexes quant à leur fonctionnement cérébral tant sur le plan émotionnel que de leurs habiletés visuo spatiales.
La schizophrénie est un trouble grave et persistant de la santé mentale dont l’origine est certes multifactorielle et dont les facteurs de protection sont partiellement biologiques, psychologiques et sociales. Cette maladie requiert une approche thérapeutique à la fois clinique médicamenteuse, psychologique et sociale visant à une réintégration des malades dans leur communauté. Le pronostic de cette maladie varie en fonction du sexe ainsi que les atteintes neurologiques, neuropsychologiques et socioculturelles. Il est donc surprenant que l’exploration des mécanismes neuronaux sous-tendant les anomalies fonctionnelles cognitivo-comportementales n’ait point, en schizophrénie, adressé à date la fonctionnalité différente de l’homme et de la femme.
Une étude pilote, réalisée dans mon laboratoire d’accueil, ayant suggéré chez le schizophrène, lors du traitement cognitif de stimuli émotionnels, une altération du dimorphisme sexuel observé dans la population normale, il devenait impératif de confirmer ces observations.
Ce mémoire vise à vérifier par résonnance magnétique fonctionnelle l’activité neuronale cérébrale témoignant de la performance neuropsychologique de schizophrènes des deux sexes et de la comparer à celle de sujets témoins sains appareillés pour l’âge, la dominance hémisphérique et le statut familial socio-économique. A cette fin, nous avons enregistré, lors d’une tâche de rotation mentale à trois dimensions, les variables neurocognitives traduisant la validité des réponses ainsi que leur rapidité d’exécution. Simultanément, nous avons enregistré, par résonnance magnétique fonctionnelle, les sites d’activation cérébrale ainsi que leur degré d’activation corticale. Les données expérimentales, neurocognitives et cérébro-fonctionnelles, furent analysées en comparant les deux sexes d’une part et les deux états de santé d’autre part. Les résultats de ce mémoire ont fait l’objet de deux articles qui sont inclus.
Les résultats obtenus confirment l’hypothèse d’un dimorphisme homme/femme dans la population générale ainsi que chez le schizophrène. Ces résultats appuient aussi l’hypothèse de l’altération, chez le schizophrène, du dimorphisme observé dans la population générale. / Sex differences in visuo-spatial abilities have been well documented in the general population, but there are only a few reports in schizophrenia. The purpose of the present study was to examine potential sex differences in performance and pattern of brain activations during mental rotation in schizophrenia patients relative to control participants.
First study: ¬Reports mainly the results of mental rotation behavioural data, collected from 17 men and 13 women with schizophrenia and the same number of healthy subjects matched for age and sex. The findings revealed the expected sex difference in the control participants (men faster and more accurate than women) and the unexpected reversal of normal sexual dimorphism in patients (women more accurate and faster than men).
Second Study: Reports mainly fMRI results investigating the neural correlates of mental rotation in men and women with schizophrenia relative to healthy controls. Thirty three schizophrenia patients (17 women and 16 men) were compared to thirty five healthy control participants (17 women and 18 men), while performing a classic mental rotation of 3-D figures. BOLD echo planar images were acquired on a 3Tesla Siemens TRIO system. Analyses were performed using SPM5 (UK Welcome Institute). Behavior data revealed a diagnosis-by-sex interaction with healthy men (HM) performing significantly better than schizophrenia men (SZ-M), and no significant difference between healthy women (HW) and schizophrenia women (SZ-W). fMRI results revealed that overall similar pattern of extensive cerebral activations (in the parietal and the prefrontal cortices) in HM and SZ-W, and deactivation during performance of the mental rotation task versus control task. In contrast, both HW and SZ-M showed much more restricted activations and deactivations in these regions.
The whole of these results suggests that sex differences in the cerebral activations during mental rotation in schizophrenia patients deviates from what we and others have observed in the general population and thus supports and extends existing evidence of a disturbed cerebral sexual dimorphism in schizophrenia. Moreover, the results emphasize the importance of including sex as a variable in neurocognitive and neuroimaging studies of schizophrenia.
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Vieillissement et réorganisation neurofonctionnelle pour le traitement du sens métaphorique des motsMejía-Constaín, Beatriz 03 1900 (has links)
Compte tenu de l ’importante augmentation de l ’espérance de vie de la population générale observée dans les dernières décennies, les études portant sur les modifications des fonctions cognitives lors du vieillissement normal et pathologique se révèlent d'un grand intérêt. Les résultats rapportés dans cette thèse contribuent à une meilleure compréhension de la nature des modifications avec l ’âge du traitement du sens métaphorique des mots et du phénomène de réorganisation fonctionnelle sous-tendant ces processus.
Après une revue de littérature (chapitre 1), un premier article définissant la problématique générale du traitement du langage lors du vieillissement normal inaugure la série de travaux présentés dans cette thèse. Cet article, présenté dans le chapitre 2, confirme l ’importance du développement d ’études spécifiques permettant de faire le lien entre les différentes hypothèses portant sur les changements cognitifs propres au vieillissement normal et celles portant sur les changements propres au substrat neurobiologique du langage.
Le chapitre 3 présente une étude comportementale ayant pour objectif d ’évaluer la disponibilité des ressources attentionnelles pour le traitement phonologique et sémantique des mots ainsi que son évolution possible avec l ’âge. Les conclusions tirées de cette étude vont dans le sens d ’une restriction des ressources attentionnelles particulièrement pour le traitement du sens métaphorique des mots lors du vieillissement normal.
Le chapitre 4 présente une étude en neuroimagerie fonctionnelle. Cette étude a été réalisée afin de comparer les profils d'activation cérébrale des participants jeunes et âgés lors du traitement du sens métaphorique des mots. Les résultats obtenus soulignent qu ’autant pour les participants jeunes que pour les participants âgés, le traitement du sens métaphorique des mots pourrait imposer au cerveau le partage des ressources attentionnelles. Néanmoins, ils montrent une réorganisation fonctionnelle chez les participants âgés.
L ’ensemble des travaux présentés appuie l ’hypothèse d ’une attribution différentielle des ressources attentionnelles ainsi que celle d ’une réorganisation fonctionnelle chez les participants âgés pour le traitement du sens métaphorique des mots. Les résultats viennent enrichir la compréhension des modèles neurocognitifs du vieillissement en ce qui concerne l ’évolution des bases neurobiologiques du langage. / Given the significant increase in life expectancy of the general population observed in recent decades, the study of alterations in cognitive functions during normal and pathological ageing is of great importance. The results reported in this thesis contribute to a better understanding of the nature of the age-related changes on processing metaphoric meaning of words and the phenomenon of functional reorganization underlying these processes.
After a brief literature review (chapter 1), a first article offering a general view of the problem of language processing in normal aging introduces the series of studies presented in this thesis. This article, presented in Chapter 2, points out the importance of developing specific protocols aiming to establish a link between the different hypotheses concerning cognitive changes during normal aging and those related to changes in neurobiological substrate of language.
Chapter 3 presents a behavioural study aiming to assess the availability of attentional resources for the phonological and semantic processing of words and its possible evolution with age. The findings of this study are consistent with the idea of an age- related restriction of available attentional resources for the processing of metaphorical meaning of words.
Chapter 4 presents a neuroimaging study. This study was conducted to compare patterns of brain activation of young and older participants during the processing of metaphoric meaning of words. The results emphasize that both, younger and older participants, require the sharing of attentional resources during processing metaphorical meaning of words, but show a functional reorganization in the older group.
Taken together, the studies presented here support the hypothesis of an age-related restriction of available attentional resources and of an age-related functional reorganization for the processing of metaphorical meaning of words. The results enrich our understanding of neurocognitive aging models regarding the evolution of neurobiological bases of language.
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Impact des polymorphismes 5-HTTLPR et rs4675690 sur les corrélats neuronaux de la tristesse chez les enfantsFortier, Emilie 05 1900 (has links)
Les avancées technologiques rendent maintenant possible d’étudier l’impact de gènes spécifiques sur les corrélats cérébraux des psychopathologies. En rapport avec ce nouveau champ de recherche, la présente thèse décrit l’impact du 5-HTTLPR et du rs4675690 – deux polymorphismes semblant jouer un rôle dans le trouble dépressif majeur - sur les corrélats neuronaux de l’expérience subjective de la tristesse chez les enfants.
Après une mise en contexte (Chapitre 1), les deux études incluses dans cette thèse seront décrites (Chapitre 2 et 3). Ces études d’imagerie par résonance magnétique fonctionnelle visaient à comparer les patrons d’activation – durant un état temporaire de tristesse - chez des enfants de 8 ans porteurs d’allèles différents. La tristesse était induite grâce au visionnement passif d’extraits d’un film triste. Les résultats suggèrent que les deux polymorphismes ont un impact sur les activations cérébrales associées à la tristesse. Spécifiquement, les enfants porteurs des allèles associés à un plus grand risque de développer un trouble dépressif majeur, soit les porteurs de l’allèle court du 5-HTTLPR et les individus homozygotes pour l’allèle T du rs4675690, ont présenté des activations cérébrales altérées dans des régions qui sont impliquées dans la tristesse normale et pathologique. Le Chapitre 4 présente la mise en perspective des résultats dans le cadre de la littérature actuelle. / Recent technological advances allow us to study the impact of genes on the specific cerebral correlates of psychopathologies. In accordance with this new specific area of research, the present thesis describes the impact of the 5-HTTLPR and the rs4675690 - two polymorphisms who seem to play a role in major depressive disorder - on the neural correlates of the subjective experience of sadness in children.
Following a review of the literature (Chapter 1), the two studies included in this thesis will be described (Chapter 2 and 3). These functional magnetic resonance imaging studies aimed to compare the activation pattern – during a transient state of sadness - in children of 8 years old carriers of different alleles. Sadness was induced by the passive viewing of sad film extracts. The results suggest that both polymorphisms have an impact on the cerebral activation associated with sadness. Specifically, children who were carriers of the allele associated with greater risk to develop major depressive disorder - carriers of the short allele of the 5-HTTLPR and homozygote for the T allele of the rs4675690) - showed altered cerebral activations in regions known to be implicated in normal and pathological sadness. Chapter 4 present an integration of the result to the current literature.
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Contribution des régions fronto-striatales dans les fonctions exécutivesProvost, Jean-Sébastien 08 1900 (has links)
Des études récentes ont montré que le noyau caudé interagissait avec le cortex
préfrontal et qu’il pourrait être impliqué dans les fonctions exécutives. Le but
de cette thèse était d’étudier la contribution du noyau caudé dans les fonctions
exécutives, plus précisément dans des tâches de monitoring et de changement
de règle, et d’observer comment ces régions fronto-striatales interagissent avec
le réseau par défaut (RPD).
Dans un premier temps, nous avons étudié le rôle du noyau caudé dans les deux
types de monitoring : le monitoring d’origine interne, consistant à effectuer un
suivi sur l’état de l’information en mémoire de travail afin de pouvoir faire un
choix subséquent, et dans le monitoring d’origine externe où le suivi sur l’état
des items est effectué par l’individu, mais la sélection est exécutée par une
source externe. Il a été montré que le cortex préfrontal dorsolatéral (CPFDL)
est impliqué dans les deux types de monitoring. À l’aide de l’imagerie par
résonance magnétique fonctionnelle (IRMf), nos résultats ont montré une
augmentation significative du signal BOLD au niveau du CPFDL dans les
contrastes des conditions de monitoring d’origine interne et monitoring
d’origine externe par rapport à la condition contrôle. De manière plus
importante, une augmentation significative de l’activité a été observée dans le
noyau caudé seulement dans les soustractions impliquant le monitoring
d’origine interne par rapport à la condition contrôle, et par rapport à la
condition de monitoring d’origine externe.
En deuxième lieu, des études ont montré une contribution spécifique des
régions fronto-striatales dans l’exécution d’un changement de règle. Toutefois,
l’effet d’un changement de règle sur l’activité cérébrale n’a jamais été étudié
sur les essais subséquents. À l’aide de l’IRMf, le cortex préfrontal ventrolatéral
(CPFVL) et le noyau caudé ont montré une augmentation significative de leur
activité lors des changements de règle continus et lors des changements de
règles sporadiques par rapport à la condition contrôle, et aussi lors des essais où
le maintien d’une même règle devait être effectué pour une courte durée par
opposition au contrôle. Cependant, aucune activité fronto-striatale n’a été
observée lorsqu’une même règle devait être appliquée pour une plus longue
période. De plus, une diminution significative de l’activité du noyau caudé a
été observée lors de la répétition de l’exécution d’une même règle suggérant
une meilleure intégration de cette dernière.
Finalement, plusieurs études ont montré une déactivation du RPD lors de
l’exécution de tâches. À l’aide de l’IRMf, nous avons posé l’hypothèse que le
RPD serait corrélé négativement avec les régions fronto-striatales lors de
l’exécution d’une tâche de changement de règle. Nos résultats montrent une
augmentation significative de l’activité des régions fronto-striatales lors d’une
augmentation du nombre d’essais de changement de règle consécutif, pendant
que le RPD montre une déactivation continue. De façon intéressante, pendant
que les régions fronto-striatales montrent une diminution de leur activité lors de
l’exécution d’une même règle pour une longue période, le RPD augmente son
activité de façon significative.
On conclut donc que le noyau caudé joue un rôle important dans la
planification d’une nouvelle action lorsque plusieurs possibilités doivent être
considérées en mémoire de travail, et ce en même temps. Finalement, le RPD
montre une corrélation négative avec les régions fronto-striatales suggérant sa
participation dans l’intégration d’une tâche devenant de plus en plus familière. / Recent studies have shown that the caudate nucleus interacts with the prefrontal
cortex, and that it is involved in executive processes. The goal of the thesis was
to investigate the role of the caudate nucleus in executive processes, and to
observe how the frontostriatal regions are interacting with the default mode
network (DMN).
Firstly, we studied the role of the caudate nucleus in self-ordered monitoring,
which consist of keeping track of which stimuli have been selected and which
remains to be selected, and externally-triggered monitoring, which refers to
keeping track of one’s selection when an external source is performing the
selection. It has been shown that de dorsolateral prefrontal cortex (DLPFC)
was particularly involved in both types of monitoring. Using functional
magnetic resonance imaging (fMRI), a significant increase of activity has been
observed in the DLPFC during both monitoring conditions vs control condition.
Importantly, significant increased activity in the caudate nucleus was observed
only in subtractions involving self-ordered monitoring (the self-ordered vs
control and self-ordered vs externally-triggered conditions).
Secondly, previous studies have shown a specific contribution of frontostriatal
regions during set-shifting. However, the effect of set-shifting on subsequent
trials had yet to be determined. Using fMRI, significant increase of activity was
observed in the ventrolateral prefrontal cortex (VLPFC) and the caudate
nucleus during shifting trials versus control and in trials where the same rule
was applied for a few trials before a set-shift occurred. However, no
frontostriatal activity was observed when the same rule was applied for a longer
period. Decreased activity in the caudate nucleus correlated with increasing
trial position in trials where no set-shift occurred, suggesting that the more a
rule is executed, the better it is established.
Finally, several studies have shown a deactivation of the DMN during the
execution of a goal-directed task. Using fMRI, we hypothesized that the DMN
was negatively correlated with the frontostriatal regions during the execution of
a set-shifting task. Our results showed a significant increase of activity in the
frontostriatal regions as more set-shifts are being performed while the DMN
gets more deactivated. Interestingly, as decreased activity was observed in the
frontostriatal regions during the execution of the same rule for a long period,
the DMN showed increasing activity.
We concluded that the caudate nucleus is specifically involved during the
planning of a novel action when several possibilities are available at the same
time. Finally, the DMN shows a negative correlation with the frontostriatal
regions suggesting its contribution to the execution of a more familiar task.
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Le plaisir et la santé dans la consommation alimentaire : activité cérébrale, motivation et simulation sensorielle / Health and pleasure in the self-regulation of food consumption : brain activity, motivation and sensorial simulationPetit, Olivia 17 March 2014 (has links)
L'autorégulation est une ressource essentielle pour ne pas succomber à la tentation de consommer des aliments fortement caloriques. Elle demande de la volonté et de contrôler ses émotions et sensations. Cependant, nous évoluons dans un environnement valorisant le plaisir alimentaire où les informations de santé sont mal prises en compte, entrainant des difficultés d'autorégulation. Ces difficultés se retrouvent notamment chez les personnes en surpoids et/ou au régime. Nous avons émis l'hypothèse que valoriser le goût des aliments sains pourrait aider ces personnes à s'autoréguler et nous avons conduit deux expériences pour la tester. Dans la première, les messages basés sur le plaisir de consommer des fruits et légumes se sont avérés plus persuasifs pour ces individus. De la même manière, dans la seconde étude lors de la prise de décision simuler le plaisir procuré par ces aliments augmente davantage le choix d'aliments sains pour ces individus. Par le recours à la neuro-imagerie fonctionnelle, nous montrons également des différences significatives d'activité cérébrale entre ces individus au moment du choix d'aliments sains dans cette condition. Il apparaît plus impulsif chez les sujets les plus sensibles à la récompense, se rapprochant du choix d'aliments fortement caloriques. Au contraire, il apparaît plus réfléchi chez les sujets ayant un IMC élevé, facilitant ainsi l'autorégulation. Au niveau théorique, cette recherche met en avant le rôle positif des émotions et sensations liées au plaisir dans l'autorégulation. Au niveau managérial, elle suggère l'importance d'adapter les stratégies de promotion des aliments sains au public ciblé. / Self-regulation is an essential resource for not succumbing to (junk) food. It requires willpower and control of emotions and sensations. However, individuals operate in an environment enhancing food pleasure where health informations are few and poorly considered, causing difficulties in self-regulation. These difficulties are found especially in overweight people and/or dieter. We hypothesized that value the taste of healthy foods could help people to self-regulate and we conducted two experiments to test it. In the first study, messages highlighting the pleasure of eating fruits and vegetables are more persuasive to subjects taking risks to health. Similarly, in the second study in decision making, focusing on the tatste of these foods increases more healthy food choices for these subjects. By using neuroimaging, we have shown brain activity distinctions between these subjects when choosing healthy food in this condition. Choosing healthy food is more impulsive for the most sensitive to reward subjects, approaching the choice of junk foods. Instead, it appears more reflective for subjects with a high BMI and choosing more junk foods, facilitating self-regulation. At the theoretical level this research highlights the positive role of emotions and sensations related to pleasure in self-regulation. At the managerial level, it suggests the importance of adapting strategies to the target audience in order to efficiently healthy food consumption.
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Avaliação funcional cerebral da velocidade de processamento por teste neuropsicológico adaptado para o ambiente de ressonância magnética / Brain functional assessment of the processing speed of information using a neuropsychological test adapted to the magnetic resonance environmentSilva, Pedro Henrique Rodrigues da 10 August 2017 (has links)
Muitas operações cognitivas requerem velocidade de processamento de informação (VPI) suficiente para serem executadas dentro do prazo permitido, sendo que VPI retardada geralmente está subjacente a déficits atencionais. A desaceleração no tempo de resposta é particularmente evidente em pacientes com traumatismo crânio-encefálico, doença de Parkinson, depressão, demência e esclerose múltipla (EM). A importância de compreender os déficits de VPI e o desenvolvimento de programas efetivos de reabilitação é, portanto, crítico. Devido à sua alta validade preditiva e à sua fácil administração, o Symbol Digit Modalities Test (SDMT) é um dos testes clínicos mais amplamente utilizados para a avaliação cognitiva de pacientes com menor VPI. No entanto, além de avaliar a presença e gravidade de seus déficits, é interessante determinar as regiões cerebrais responsáveis por essa função e sua integração. Devido à sua não invasividade e ao seu bom nível de confiabilidade, a técnica de Imagem de Ressonância Magnética Funcional Dependente do Nível de Oxigenação no Sangue (BOLD-fMRI) é a ferramenta mais apropriada para esse fim. Logo, o objetivo do presente estudo foi o mapeamento funcional cerebral de VPI durante o desempenho de uma tarefa (SDMT) adaptada para o ambiente da ressonância em um grupo de voluntários saudáveis jovens. 16 controles saudáveis destros foram recrutados e submetidos à avaliação cognitiva com a versão oral do SDMT antes da aquisição de imagens. IRM foi adquirida em um sistema de 3T (Philips Achieva). Imagens funcionais (BOLD) foram adquiridas com uma sequência EPI. O experimento consistiu de seis blocos de 30 s de controle intercalados com cinco blocos de 30 segundos de tarefa (SDMT). Durante os blocos de tarefa, um símbolo foi apresentado a cada 2 segundos e ao participante foi requerido que associasse o número correspondente ao símbolo apresentado baseando-se em uma chave de resposta. Durante os blocos de controle, um número foi apresentado a cada 2 segundos e ao participante foi requerido que lesse silenciosamente o número em questão. Mapas paramétricos estatísticos foram obtidos para estudo de localização funcional utilizando o Modelo Linear Geral com um regressor boxcar convoluído com uma função de resposta hemodinâmica canônica (p-FDR < 0,01). Foi realizada a correlação bivariada entre as séries temporais médias das regiões associadas à tarefa para estudo de integração funcional (p-FDR < 0.0001). As informações de localização e integração funcionais foram inseridas em analise de conectividade efetiva. Ativações foram observadas na rede frontoparietal e no córtex occipital para análises individual e em grupo. Análise de conectividade efetiva para a arquitetura do sistema revelou o declive em posição serial com o giro lingual, o cúneo e duas regiões paralelas (pré-cúneo e lóbulo parietal superior), a partir do qual a informação converge para o giro frontal inferior e se bifurca para os giros frontais médios esquerdo e direito. Um modelo de rede envolvendo áreas relacionadas à VPI foi obtido e pode servir como referência para investigações futuras deste processo cognitivo em grupos clínicos, combinadas com estudos de neuroplasticidade cerebral. / Many cognitive operations require sufficient information processing speed (IPS) to be executed within the allowed time frame, with delayed IPS often underlining attentional deficits. The deceleration in response time is particularly evident in patients with traumatic brain injury, Parkinson\'s disease, depression, dementia and multiple sclerosis (MS). The importance of understanding IPS deficits and developing effective rehabilitation programs is therefore critical. Because of its high predictive validity and easy administration, the Symbol Digit Modalities Test (SDMT) is one of the most widely used clinical tests for the cognitive assessment of patients with lower IPS. However, in addition to evaluating the presence and severity of its deficits, it is interesting to determine the brain regions responsible for this function and its integration. Because of its non-invasiveness and its good level of reliability, the BOLD-fMRI technique is the most appropriate tool for this purpose. Therefore, the aim of the present study was the functional brain function mapping of IPS during the performance of a task (SDMT) adapted to the resonance environment in a group of healthy young volunteers. 16 healthy right controls were recruited and submitted to cognitive assessment with the oral version of SDMT prior to image acquisition. MRI was acquired in a 3T system (Philips Achieva). Functional images (BOLD) were acquired with an EPI sequence. The experiment consisted of six blocks of 30 s of control intercalated with five blocks of 30 seconds of task (SDMT). During the task blocks, a symbol was displayed every 2 seconds and the participant was required to associate the number corresponding to the displayed symbol based on a response key. During the control blocks, a number was displayed every 2 seconds and the participant was required to silently read the number in question. Statistical parametric maps were obtained for functional localization study using the General Linear Model with a boxcar regressor convolved with a canonical hemodynamic response function (p-FDR <0.01). The bivariate correlation between the mean time series of the regions associated with the task for functional integration study (p-FDR <0.0001) was performed. The functional location and integration information was inserted into effective connectivity analysis. Activations were observed in the frontoparietal network and in the occipital cortex for individual and group analyzes. Effective connectivity analysis for the system architecture revealed the declive in serial position with the lingual gyrus, the cuneus and two parallel regions (precuneus and superior parietal lobule), from which the information converges to the inferior frontal gyrus and bifurcates to the left and right middle turns. A network model involving areas related to IPS has been obtained and may serve as a reference for future investigations of this cognitive process in clinical groups, combined with studies of cerebral neuroplasticity.
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Aplicação de técnicas de aprendizado de máquina para apoio ao diagnóstico do transtorno de déficit de atenção e hiperatividade por meio da análise de padrões de conectividade cerebralSiqueira, Anderson dos Santos January 2014 (has links)
Orientador: Prof. Dr. João Ricardo Sato / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia da Informação, 2014. / O transtorno do déficit de atenção e hiperatividade (TDAH) é um transtorno de neurodesenvolvimento, associado a fatores genéticos e ambientais, compreendendo a sintomatologia: desatenção, hiperatividade e impulsividade. Neste estudo, utilizou-se a teoria dos grafos e a ressonância magnética funcional (fMRI) para obtenção de um método de distinção entre pacientes e controles para o suporte ao diagnóstico do TDAH. O objetivo deste trabalho foi a comparação das medidas de conectividade cerebral de pacientes (TDAH) com sujeitos controle (desenvolvimento típico) por meio da fMRI, medidas de centralidade e o Support Vector Machine (SVM). Utilizou-se a base de dados ADHD-200. Construiu-se um classificador a partir das características extraídas das redes de conectividade cerebral na tentativa de se distinguir entre sujeitos controle e pacientes. O método envolveu o uso do SVM em características de imagens de fMRI, em dois pares de grupos: controle vs pacientes
(TDAH) e TDAH subtipos. Foram modelados grafos ponderados e não ponderados e
calculadas algumas medidas de centralidade. Na análise por site dos sujeitos controle versus TDAH desatento foram observadas diferenças na conectividade das regiões cerebrais intermediárias, com escore de 63% no limiar 0,25 da centralidade betweenness no site 4. Com grafo ponderado, outras diferenças de conectividade cerebral foram observadas, com escore de 73% para a medida betweenness entre as regiões cerebrais no site 6. A análise dos portadores de TDAH subgrupo desatento versus combinado, no site 6 foram observadas distinções na medida betweenness e no degree das conexões das regiões cerebrais, no limiar de 0,15, com escores de 73% e 77% respectivamente. Em face aos resultados apresentados
é possível encontrar algumas distinções nas conexões cerebrais, principalmente entre os sujeitos portadores de TDAH desatento versus TDAH combinado, a partir da extração das características cerebrais, com utilização de algumas medidas de centralidade como variáveis preditoras para o algoritmo SVM. / The Attention Deficit and Hyperactivity Disorder (ADHD) is a neurodevelopmental
disorder associated with genetic and environmental factors, including the symptoms:
inattention, hyperactivity and impulsivity. In this study, we used graph theory and
functional magnetic resonance imaging (fMRI) to obtain a method for distinguishing
between patients and controls to support the diagnosis of ADHD. The aim of this
study was to compare measures of brain connectivity between patients (ADHD) and
control subjects (typically developing). We used through fMRI, measures of centrality,
support vector machines (SVM) and the database ADHD-200. We built a classifier
based on the features extracted from the brain connectivity networks in an attempt to
distinguish between patients and control subjects. The method involved the use of
SVM in connectivity features in two sets of groups: Control vs. patients (ADHD) and
inattentive ADHD vs Combined. Measures of weighted and unweighted graphs were
modeled and some measures of centrality were extracted. In the unweighted graph
analysis by site and inattentive ADHD vs control subjects comparison, differences
were found in the connectivity pattern, with a score of 63% for betweenness centrality
in site 4. In weighted graph, further differences in brain connectivity were observed,
with a score of 73% also in betweenness in site 6. In this same site, the analysis of
patients with ADHD inattentive versus combined subgroup, achieved scores of of
73% (betwenness) and 77% (degree) in unweighted graph analysis. In conclusion,
we found some differences in brain connectivity patterns, especially between
subjects with ADHD inattentive versus combined ADHD. By using some measures of
centrality as predictors for the SVM algorithm, we found moderate classification
accuracy in individual groups¿ prediction.
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EEG and fMRI studies of the effects of stimulus properties on the control of attentionMugruza Vassallo, Carlos Andrés January 2015 (has links)
In this dissertation the effects of variations in stimulus properties and CTOA, in auditory attention tasks were explored using recently developed approaches to EEG analysis including LIMO. The last experiment was structured using information theory, designing an effective experiment. Four studies were carried out using a number parity decision task, that employed different combinations of cueing Tone (T), Novel (N) and the Goal (G) stimuli. In the first EEG study, contrary to previous findings (Polich 2002, 2007) in control participants, no correlation between the time of a novel condition to the next novel condition and P300 amplitude was found. Therefore single trial across-subject averaging of participants’ data revealed significant correlations (r > .3) of stimulus properties (such as probability, frequency, amplitude and duration) on P300, and even r > .5 was found when N was an environmental sound in schizophrenic patients. In the second EEG study, simultaneously with fMRI recordings, the participants that showed significant behavioural distraction evoked brain activations and differences in both hemispheres (similar to Corbetta, 2002, 2008) while the participants, as a whole, produced significant activations mainly in left cortical and subcortical regions. A context analysis was run in distracted participants contrasting the trials immediately prior to the G trials, resulting in different prefrontal activations, which was consistent with studies of prefrontal control of visual attention (Koechlin 2003, 2007). In the third EEG study, the distractor noise type was manipulated (white vs environmental sounds) as well as presence or absence of scanner background noise in a blocked design. Results showed consistent P300, MMN and RON due to environmental noise. In addition, using time constants found in MEG results (Lu, Williamson & Kaufman, 1992) and adding the CTOA to the analysis, an information theory framework was calculated. After the simulation of the information of the experiment, a saddle indentation in the curve of the information measure based on the states of the incoming signal at around 300 ms CTOA was found. This saddle indentation was evident in more than 60 novel trials. In the fourth study, the CTOA and stimulus properties were manipulated in a parametric experiment. Based on the three studies, reducing complexity if the task (first study), using more than 60 stimuli in the novel conditions (third study). The CTOA randomly varying between 250 ms or 500 ms. Thirty-eight ANCOVA with 2 categorical and 1 continuous regressors were conducted and determined which time and channels elicited reliably signatures (p <.05) in the whole participants at short CTOA. Results revealed differences for the waveforms of current condition by depending on which condition appeared previously as well in terms of frequency and duration in scalp frontal electrodes (such as the second study). These results were interpreted as a consequence of switching between modes of attention and alerting states which resulted in the activation of frontal areas. Moreover, contextual analyses showed that systematic manipulation of stimulus properties allowed the visualization of the relationships between CTOA, executive function and orienting of attention.
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Le Connectome du Langage dans le cerveau humain : étude structurelle et foncionnelle en tractographie par Imagerie tensorielle de diffusion, IRM fonctionnelle et stimulation électrique peropératoire. / The human brain language connectome : Structural and fonctional study using DTI tractography, functional MRI and intraoperative electrical stimulationVassal, François 27 June 2016 (has links)
Si les régions cérébrales du langage ont étélargement explorées grâce à l’IRM fonctionnelle (IRMf) et la stimulation électrique directe (SED)peropératoire, leur connectivité reste encore incomplètement documentée. Il n’est pas seulement débattuquels faisceaux de SB contribuent au langage, mais également quelle est leur anatomie précise et leur rôlefonctionnel spécifique. Une meilleure compréhension du connectome du langage est requise pourdiminuer la morbidité postopératoire en neurochirurgie et développer de nouveaux traitements cibléspour la rééducation des aphasies. Notre objectif était de cartographier structurellement etfonctionnellement, in vivo, la connectivité du langage. Dans une première étude préclinique portant sur 2Oadultes sains, nous avons combiné des informations structurelles axonales révélées par la tractographieavec des informations fonctionnelles corticales dérivées de l’IRMf (tâche de lecture compréhensive). Huitfaisceaux de SB ont été explorés —i.e. faisceau arqué, faisceau longitudinal supérieur, faisceau frontooccipitalinférieur, faisceau unciné, faisceau longitudinal inférieur, faisceau longitudinal moyen, faisceauoperculo-prémoteur, faisceau frontal transverse—, dont le rôle fonctionnel a été analysé en recherchantune connexion entre leurs terminaisons corticales et les activations IRMf. Les caractéristiquesanatomiques des faisceaux (i.e. volume, longueur, terminaisons corticales), leurs asymétries interhémisphériqueset leurs variations interindividuelles ont été colligées. Ce protocole a permis deconstruire le connectome du langage et d’étudier en détails son organisation structurelle macroscopique.Dans une seconde partie, ces données ont été transposées à la clinique pour le traitement chirurgical depatients souffrant de tumeurs cérébrales (gliomes) en régions du langage. Pendant la résection tumorale,des images de tractographie intégrées à un système de neuronavigation ont été systématiquementcombinées à la SED au cours d’un test de dénomination orale d’images. Ce protocole opératoire a permisd’optimiser les résultats chirurgicaux en termes de qualité d’exérèse et de préservation du langage, et aconstitué une opportunité unique d’étudier en temps réel les corrélations structure – fonction. Encouplant la localisation anatomique précise où chaque SED a été délivrée —obtenue grâce aux images detractographie naviguées— et la sémiologie des paraphasies induites par la SED —colligée par unorthophoniste présent au bloc opératoire—, nous avons déterminé le rôle spécifique de 5 faisceaux tantcortico-corticaux (faisceau arqué, faisceau fronto-occipital inférieur, faisceau frontal transverse) quecortico-sous-corticaux (fibres prémotrices orofaciales, faisceau fronto-striatal) dans différentes souscomposantesdu langage, i.e. traitement phonologique, traitement sémantique, contrôle moteur,planification articulatoire, contrôle exécutif/cognitif de la réponse verbale. Considérés de façon globale,nos résultats permettent d’envisager une meilleure compréhension de l’organisation anatomofonctionnelledes réseaux cérébraux du langage. Au-delà de l’intérêt scientifique, la possibilité deconstruire le connectome du langage spécifique à chaque individu ouvre la voie vers d’importantesapplications en neurochirurgie, dans une perspective de médecine personnalisée. Aujourd’hui, la chirurgiedes tumeurs cérébrales guidée par l’image. Demain, le développement de nouveaux traitements pour larééducation des aphasies, e.g. la déposition ciblée d’agents pharmacologiques, de cellules souches ou deneuromodulations, interagissant directement avec la connectivité résiduelle épargnée par la lésion. / The langage connectome is defined as the neuronal networks that subserve languagefunctions. Anatomically, it comprises specialized cortical areas and modulatory subcortical areas (i.e. deepgray nuclei and cerebellum), as well as their interconnections trough white matter (WM) fascicles.Although brain regions involved in language have been largely explored thanks to functional MRI (fMRI)and intraoprative electrical stimulation (IES), the underlying WM connectivity is still not mastered. It isnot only unknown which WM fascicles specifically contribute to language, but there is also much debateabout their precise anatomy and the functions they subserve during language processing. Betterunderstanding of the structural and functional organization of the language connectome is requisite toreduce postoperative morbidity in neurosurgery and develop targeted treatments for aphasiarehabilitation. Herein, our objective was to map structurally and functionally, in vivo, the subcorticalconnectivity of language. First, we conducted a preclinical study in 20 healthy subjects, combining DTItractography and fMRI (reading comprehension task) to yield connectivity associated with language. Weexplored 8 WM fascicles that have been proposed as putative candidates for language —i.e. arcuatefascicle, superior longitudinal fascicle, inferior fronto-occipital fascicle, uncinate fascicle, inferiorlongitudinal fascicle, middle longitudinal fascicle, operculopremotor fascicle, frontal aslant tract—, towhich we assigned functionality by tracking their connections to the fMRI-derived clusters. We generateda normative database of anatomical characteristics for each WM fascicle, such as volume, length, corticalterminations and their interhemispheric and interindividual variations. By using this construct, weprovided in explicit details the structural map of the language connectome. Second, this body ofknowledge was transposed to brain tumor surgery. Patients suffering of gliomas located close to languageregions were operated on under local anesthesia (i.e. awake surgery) in order to perform intraoperativelanguage mapping (object naming task). Essential language sites were localized through IES andanatomically characterized thanks to navigated tractography images. This intraoperative protocol allowedmaximum tumor resection while preserving language functions. Furthermore, it gave us a uniqueopportunity to perform reliable, real-time structure – function relationships, determining the role of 5WM fascicles (arcuate fascicle, inferior fronto-occipital fascicle, frontal aslant tract, orofacial premotorfibers, frontostriatal fascicle) in different subcomponents of language, i.e. phonological processing,semantic processing, articulatory planning, motor control and executive/cognitive control of verbalresponse. Globally considered, our results allow a better understanding of the anatomo-functionalorganization of the language network in the human brain. Beyond the scientific interest, the possibility toconstruct the individual (patient-specific) connectome paves the way for major applications inneurosurgery, in the perspective of personalized medicine. Today, the maximum safe resection of braintumors located in eloquent language areas, guided by navigated, multimodal images. Tomorrow, thedevelopment of new treatments for rehabilitation of post-stroke aphasia patients, such as the targeteddelivery of drugs, stem cells, or neuromodulation devices, fitting with the residual functional connectivityspared by the lesion.
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