O uso lesivo de bebidas alcoólicas é o terceiro maior fator mundial de risco de doenças e incapacitação. O álcool pode causar várias alterações no Sistema Nervoso Central (SNC), dentre elas, a diminuição do processamento de informações visuais. Alguns estudos avaliam as alterações nos processos perceptuais durante a Síndrome de Abstinência do Álcool (SAA) por meio da ilusão visual da máscara côncava. Essa ilusão exemplifica o fenômeno ilusório de inversão visual da profundidade de uma máscara humana oca, que é percebida como convexa. Foi encontrado um possível desequilíbrio entre os componentes bottom-up e top-down da percepção visual provocado pelo álcool, capaz de prejudicar a capacidade do indivíduo de perceber essa ilusão. Entretanto, a presente pesquisa investiga uma hipótese alternativa, e sugere que a redução na frequência de respostas de inversão pode resultar de mudanças de critérios para emitir as repostas e não em alterações perceptuais. Para isso, foram utilizados os parâmetros da Teoria da Detecção de Sinal (TDS) aplicada à psicofísica. Participaram da pesquisa 20 indivíduos saudáveis, 20 com SAA leve e 20 com SAA moderada. Eles realizaram duas tarefas experimentais de observação monocular dos lados côncavo e convexo, alternadamente, de uma máscara da face humana de tamanho reduzido. Na tarefa de confidence rating, foram julgadas a concavidade ou convexidade da máscara e o grau de certeza nas respostas, com certeza ou com dúvida. Na tarefa de escolha forçada entre duas alternativas (2AFC), as máscaras foram apresentadas aos pares alternados e o participante identificava o lado côncavo. A análise dos resultados revelou que os indivíduos com SAA moderada apresentaram maiores escores para os índices de sensibilidade R-index, Az, e da, na tarefa de confidence rating, apontando para uma capacidade significativamente maior de identificação e discriminação dos lados côncavo e convexo da máscara. Isto reflete um prejuízo significativo na capacidade destes indivíduos em perceber a ilusão da máscara côncava. Não houve diferença entre os grupos de indivíduos saudáveis e com SAA leve. Entretanto, os grupos com SAA apresentaram um maior grau de certeza em seus julgamentos comparativamente ao grupo controle. Resultados semelhantes para o grupo com SAA moderada foram encontrados na tarefa de escolha forçada para os índices d e taxa de acerto, indicando maior capacidade desses indivíduos em discriminar os dois lados da máscara. Todos os participantes apresentaram critérios de decisão moderados na tarefa de confidence rating. Os indivíduos saudáveis, na tarefa de escolha forçada, se mostraram tão capazes quanto os com SAA moderada na discriminação dos dois lados da máscara. Os indivíduos saudáveis, na tarefa de escolha forçada, se mostraram tão capazes quanto os com SAA moderada na discriminação dos dois lados da máscara. Entretanto, supõe-se que esses resultados foram provenientes de estratégias inesperadas por esses indivíduos em seus julgamentos, prejudicando a validade interna dos resultados; e representam um viés de pesquisa importante. As análises apontam para um possível desequilíbrio, já relatado em estudos anteriores, entre os componentes bottom-up e top-down da percepção visual, provocado pelo álcool, que impede o SNC de corrigir hipóteses perceptuais ambíguas. / The harmful use of alcoholic beverages is the third largest worldwide risk factor for illness and disability. Alcohol can cause several changes in the Central Nervous System (CNS), among them, the decrease in the processing of visual information. Some studies evaluate changes in perceptual processes during Alcohol Withdrawal Syndrome (AWS) through the hollow face illusion. Its exemplifies the illusory visual depth inversion of a hollow human mask, which is perceived as convex. A possible imbalance was found between the bottomup and top-down components of visual perception caused by alcohol, which could impair the individual\'s ability to perceive the illusion. However, the present research investigates an alternative hypothesis, and suggests that the reduction in the frequency of inversion responses may result from changes in the criteria to issue responses rather than on perceptual changes. The parameters of the Signal Detection Theory (SDT) applied to psychophysics allow this analysis. Twenty healthy subjects, 20 with mild AWS and 20 with moderate AWS participated in the study. They performed two experimental tasks of monocular observation of concave and convex sides, alternately, of a reduced size human face mask. In the task of confidence rating, the concavity or convexity of the mask and the degree of certainty in the answers were judged: certainly or with doubt. In the task of forced choice between two alternatives (2AFC), the masks were presented in alternating pairs and the participant identified the concave side. The analysis of the results revealed that individuals with moderate AWS presented higher scores for the sensitivity index scores R-index, Az, and da, pointing to a significantly greater capacity of identification and discrimination of the concave and convex sides of the mask. This reflects a significant impairment in the ability of these individuals to perceive the hollow face illusion. There was no difference between healthy individuals and with mild AWS. However, all groups with AWS presented a greater degree of certainty in their judgments compared to the control group. Similar results for the group with moderate AWS were found in the task of forced choice to the indices d and hit rate, indicating a greater ability of these individuals to discriminate both sides of the mask. Healthy subjects, on the task of forced choice, showed themselves to be as capable as those with moderate AWS in discriminating both sides of the mask. However, it supposed that these results were from unexpected strategies used by these individuals in their judgments, impairing the internal validity of the results, and represented an important research bias. The analyzes point to a possible imbalance, already reported in previous studies, between the bottom-up and top-down components of visual perception, caused by alcohol, which inhibits the CNS from correcting ambiguous perceptual hypotheses.

L'attention est une fonction au cœur de la cognition qui, à tout moment, nous permet de sélectionner les informations pertinentes à traiter, tout en ignorant les autres. Cette sélection de l’information qui s’opère à la fois dans l'espace et dans le temps résulte de l’intégration des informations sensorielles et d’un contrôle de "haut niveau" en fonction de nos buts. Cette fonction dépend d’un réseau cérébral incluant le système fronto-pariétal et est sous l’influence de différents neuromodulateurs, en particulier la noradrénaline, dont l’action reste encore mal connue. Mon travail de thèse consistait à comprendre le rôle de la noradrénaline sur les processus attentionnels. Mes objectifs étaient d’une part de vérifier notre hypothèse selon laquelle la noradrénaline modulerait les différentes facettes de l’attention (attention spatiale et attention soutenue) et d’autre part d’élucider les mécanismes d’action par lesquelles la noradrénaline exercerait ces effets. Pour répondre à ces questions, nous avons testé l’impact d’une augmentation de la transmission noradrénergique (administration intramusculaire d'atomoxétine) chez le singe, dans des tâches comportementales nécessitant une sélection de l’information visuelle soit dans l’espace (tâche d'attention avec indice et exploration spontanée d'images) soit au cours du temps (tâche de discrimination go/nogo). Nos résultats démontrent que l’atomoxétine facilite les processus attentionnels à la fois dans l’espace et au cours du temps. Dans l’espace, l’atomoxétine module l’orientation de l’attention visuo-spatiale en fonction du contexte, en ajustant le taux d’accumulation sensorielle ou l’impact de la saillance des images sur l’orientation de l’attention. Au cours du temps, l’atomoxétine ajuste la relation entre la sensibilité à discriminer la cible parmi des distracteurs et le biais de réponse des animaux. En résumé, mes résultats démontrent que la noradrénaline influence les deux facettes, spatiale et temporelle de l’attention et suggèrent une action via un ajustement des processus de traitement de l’information sensorielle et un ajustement du contrôle de l’attention au contexte / Attention is a function at the heart of cognition that, at any given moment, enables us to select some information for further processing, while setting aside others. This selection of information that operates both in space and time, results from the integration of sensory information and higher-level control according to our goals. This function depends on a cerebral network including the fronto-parietal system. It is also under the influence of different neuromodulators, in particular norepinephrine, the action of which is still poorly understood.The aim of my PhD work was to understand the role of norepinephrine on attentional processes. My objectives were, on the one hand, to test our hypothesis that norepinephrine is capable of acting on the different facets of attention (spatial attention and sustained attention) and, on the other hand, to elucidate the mechanisms of action by which noradrenaline exerts its action. To answer these questions, we tested the impact of an increase in noradrenergic transmission (intramuscular administration of atomoxetine) in monkeys, using behavioral tasks requiring a selection of visual information in space (cued attentional task and spontaneous image exploration) or over time (go/nogo discrimination task). Our results demonstrate that atomoxetine facilitates attentional processes both in space and over time. In space, atomoxetine modulates the orientation of visuospatial attention according to the context, adjusting the rate of sensory accumulation or the impact of image saliency on attention orientation. Over time, atomoxetine adjusts the relationship between the sensitivity to discriminate a target among distractors and the animal’s response bias.In summary, my results demonstrate that norepinephrine influences both the spatial and temporal facets of attention and suggests an action through an adjustment of sensory information processing and an adjustment of attention control to the context

Die Fähigkeit, Zustände in der Außenwelt zu beurteilen und zu kategorisieren, wird unter dem Oberbegriff „perzeptuelles Entscheiden“ zusammengefasst. In der vorliegenden Arbeit wurde funktionelle Magnetresonanztomografie mit multivariater Musteranalyse verbunden, um offene Fragen zur perzeptuellen Entscheidungsfindung zu beantworten. In der ersten Studie (Hebart et al., 2012) wurde gezeigt, dass der visuelle und parietale Kortex eine Repräsentation abstrakter perzeptueller Entscheidungen aufweisen. Im frühen visuellen Kortex steigt die Menge entscheidungsspezifischer Information mit der Menge an verfügbarer visueller Bewegungsinformation, doch der linke posteriore parietale Kortex zeigt einen negativen Zusammenhang. Diese Ergebnisse zeigen, wo im Gehirn abstrakte Entscheidungen repräsentiert werden und deuten darauf hin, dass die gefundenen Hirnregionen unterschiedlich in den Entscheidungsprozess involviert sind, je nach Menge an verfügbarer sensorischer Information. In der zweiten Studie (Hebart et al., submitted) wurde gezeigt, dass sich eine Repräsentation der Entscheidungsvariable (EV) im fronto-parietalen Assoziationskortex finden lässt. Ferner weist die EV im rechten ventrolateralen präfrontalen Kortex (vlPFC) einen spezifischen Zusammenhang mit konfidenzbezogenen Hirnsignalen im ventralen Striatum auf. Die Ergebnisse deuten darauf hin, dass Konfidenz aus der EV im vlPFC berechnet wird. In der dritten Studie (Christophel et al., 2012) wurde gezeigt, dass der Kurzzeitgedächtnisinhalt im visuellen und posterioren parietalen Kortex, nicht jedoch im präfrontalen Kortex repräsentiert wird. Diese Ergebnisse lassen vermuten, dass der Gedächtnisinhalt in denselben Regionen enkodiert wird, die auch perzeptuelle Entscheidungen repräsentieren können. Zusammenfassend geben die hier errungenen Erkenntnisse Aufschluss über den neuronalen Code des perzeptuellen Entscheidens von Menschen und stellen ein vollständigeres Verständnis der zugrundeliegenden Prozesse in Aussicht. / Perceptual decision-making refers to the ability to arrive at categorical judgments about states of the outside world. Here we use functional magnetic resonance imaging and multivariate pattern analysis to identify decision-related brain regions and address a number of open issues in the field of perceptual decision-making. In the first study (Hebart et al., 2012), we demonstrated that perceptual decisions about motion direction are represented in both visual and parietal cortex, even when decoupled from motor plans. While in early visual cortex the amount of information about perceptual choices follows the amount of sensory evidence presented on the screen, the reverse pattern is observed in left posterior parietal cortex. These results reveal the brain regions involved when choices are encoded in an abstract format and suggest that these two brain regions are recruited differently depending on the amount of sensory evidence available. In the second study (Hebart et al., submitted), we show that the perceptual decision variable (DV) is represented throughout fronto-parietal association cortices. The DV in right ventrolateral prefrontal cortex covaries specifically with brain signals in the ventral striatum representing confidence, demonstrating a close link between the two variables. This suggests that confidence is calculated from the perceptual DV encoded in ventrolateral prefrontal cortex. In the third study (Christophel et al., 2012), using a visual short-term memory (VSTM) task, we demonstrate that the content of VSTM is represented in visual cortex and posterior parietal cortex, but not prefrontal cortex. These results constrain theories of VSTM and suggest that the memorized content is stored in regions shown to represent perceptual decisions. Together, these results shed light on the neuronal code underlying perceptual decision-making in humans and offer the prospect for a more complete understanding of these processes.

Cette thèse porte sur la façon dont les individus prennent des décisions en présence de risque et d'incertitude. Elle est composée de quatre essais qui étudient théoriquement et expérimentalement la prise de décision.Les deux premiers essais étudient des situations où un décideur doit décider si un événement a eu lieu en utilisant des informations incertaines. Le fait d'identifier correctement que cet événement s'est produit est plus rémunéré que le fait d'identifier correctement qu'il ne s'est pas produit. Ce problème de décision induit une divergence entre deux qualités d'une décision : l'optimalité et l'exactitude. Les deux essais reproduisent de telles situations dans une expérience de laboratoire basée sur des tâches perceptuelles et analysent les décisions en utilisant la théorie de la détection du signal pour étudier l'arbitrage optimalité-exactitude. Le premier essai confirme l'existence d'un tel arbitrage avec un rôle dominant de la recherche de l'exactitude. Il explique l'existence de cet arbitrage par utilité non-monétaire associée au fait d'avoir raison. Le deuxième chapitre montre que présenter les informations perceptuelles en dernier contribue à l'existence de l'arbitrage optimalité-exactitude.Le troisième essai étudie comment les préférences vie-à-vie d'autrui interagissent avec l'attitude face à l'ambiguïté. Il présente les résultats d'une expérience où les sujets doivent faire des dons à des associations caritatives. Les dons peuvent avoir des coûts ou des bénéfices ambigus. Nous constatons que l'ambiguïté a pour effet de rendre les individus plus égoïstes. En d'autres termes, nous montrons que les individus utilisent l'ambiguïté comme une excuse pour ne pas donner. Ce comportement d’auto-justification est plus marqué pour les coûts ambigus que pour les avantages ambigus.Le quatrième essai examine la validité externe des mesures de préférence pour le risque en laboratoire en utilisant des décisions dans d'autres tâches expérimentales risquées et des décisions prisent sur en dehors du laboratoire. Nous constatons que les mesures de préférence pour le risque permettent d'expliquer les premières, mais qu'elles n'expliquent pas les secondes. / This thesis investigates how individuals make decisions under risk and uncertainty. It is composed of four essays that theoretically and experimentally investigate decision-making.The first two essays study situations where a decision maker has to decide whether an event has occurred using uncertain evidence. Accurately identifying that this event has occurred is more rewarded than accurately identifying that it has not occurred. This decision problem induces a divergence between two qualities of a decision: optimality and accuracy. Both essays reproduce such situations in a laboratory experiment based on perceptual tasks and analyze behavior using Signal Detection Theory to study the optimality-accuracy trade-off. The first essay confirms the existence of the trade-off with a leading role of accuracy. It explains the trade-off by the concern of individuals for being right. The second chapter finds that presenting perceptual evidence last contributes to the existence of the optimality-accuracy trade-off.The third essay studies how other-regarding preferences interact with attitude toward ambiguity. It reports the results of an experiment where subjects have to make donations to charities. Donations may have either ambiguous costs or ambiguous benefits. We find that other-regarding preferences are decreased under ambiguity. In other terms, we highlight that individual use ambiguity has an excuse not to give. This excuse-driven behavior is stronger for ambiguous costs than ambiguous benefits.The fourth essay challenges the external validity of laboratory risk preference measures using behavior in experimental risk tasks and naturally occurring behavior under risk. We find that risk preference measures are related with the former but that they fail to explain the latter.

[pt] Nesta tese estudamos o potencial que terão a próxima geração de detectores de neutrinos (JUNO, Hyper-Kamiokande e DUNE) para a detecção dos efeitos da matéria da Terra através da identificação das modulações no espectro de energia dos neutrinos de supernovas de colapso de núcleo em nossa galáxia, assumindo a possibilidade do decaimiento invisível de v2 após os neutrinos terem deixado a estrela, caminho da Terra. Simulações recentes do colapso gravitacional (e subsequente explosão) de estrelas com massa maior do que ~ 8Mo mostram que durante a fase de esfriamento as energias médias (Eve) e (Evx) tornam-se muito semelhantes e os fluxos tendem a se igualar, tornando difícil observar os efeitos da matéria da Terra usando um único detector. Neste trabalho mostramos que a inclusão do decaimiento dos neutrinos também cria a possibilidade de observar os efeitos em consideração no canal de detecção de neutrinos se o ordenamento de massa for normal e no canal anti-neutrino se o ordenamento for invertido, o que não é esperado na ausência de decaimento. Em particular, se a taxa de decaimento for maior do que ~ 70%, descobrimos que o decaimento invisível de v2 pode aumentar as possibilidades de observação dos efeitos da matéria da Terra, mesmo para supernovas a uma distância de 10 kpc de nós. / [en] In this thesis we studied the potential that the next-generation neutrino detectors (JUNO, Hyper-Kamiokande and DUNE) will have to the detection of the Earth matter effects through the identification of the modulations in the energy spectrum of neutrinos from core-collapse supernovae in our galaxy, assuming the possibility of the invisible decay of v2 after the neutrinos have left the star, on their way to Earth. Recent simulations of gravitational collapse (and subsequent explosion) of stars more massive than ~ 8Mo show that during the cooling phase the average energies (EVe) and (Evx) become very similar and the fluxes tend to equalize, making it difficult to observe the Earth matter effects using a single detector. In this work we show that the inclusion of neutrino decay creates also the possibility of observing the effects under consideration in the neutrino detection channel if the mass ordering is normal and in the anti-neutrino channel if the ordering is inverted, which is not expected in the absence of neutrino decay. In particular, if the decay rate is more than ~ 70%, we find that the invisible neutrino decay of v2 can enhance the observation possibilities of Earth matter effects even for supernovae at a distance of 10 kpc from us.