Agir de façon optimale dans un environnement incertain nécessite d'évaluer et de comparer les coûts et bénéfices des différentes alternatives. Cela implique aussi de réguler et de contrôler le comportement de façon flexible pour optimiser les périodes de recherche de gains ou de ressources et les périodes d'exploitation des acquis. Une des hypothèses actuelles sur les mécanismes neurobiologiques impliqués, propose que cortex cingulaire antérieur (CCA), associé à l’évaluation de l’action, et cortex préfrontal dorsolatéral (CPFdl), associé au contrôle cognitif, interagiraient pour réguler le comportement. Les travaux réalisés au cours de cette thèse ont permis de préciser le rôle joué par le CCA dans la détection et l’évaluation des performances ainsi que ses interactions avec le CPFdl au sein d'une boucle du contrôle cognitif. Menés grâce à des enregistrements électrophysiologiques chez le singe en comportement, ils apportent des précisions sur la séquence d’activation du CCA et du CPFdl dans la bande de fréquences gamma lors de l'adaptation du comportement. L’étude des potentiels de champs locaux de ces deux régions amènent à poser des hypothèses sur les mécanismes oscillatoires sous-jacents et notamment sur le rôle des communications basses fréquences entre le CCA et le CPFdl et leur implication différentielle entre recherche et exploitation. / Acting optimally in uncertain environments requires evaluating costs and benefits of choosing each alternative. It also requires to flexibly regulate between exploration for and exploitation of resources. One current hypothesis is that the anterior cingulate cortex (ACC), involved in action valuation, and dorsolateral prefrontal cortex (dlPFC), involved in cognitive control, interact to elaborate an optimal regulation of behaviour. Studies achieved during this thesis allowed to precise the role of ACC in the detection and valuation of action outcomes as well as to describe the interactions with dlPFC in a cognitive control loop. Thanks to neurophysiological recordings in behaving monkey our work give new clues on the sequential activation of ACC and dlPFC during adaptation. The analyses of local field potentials allowed us to suggest hypotheses on the underlying oscillatory mechanisms, in particular on low frequency communications between ACC and dlPFC, and their modulation during exploration and exploitation.

Agir de façon optimale dans un environnement incertain nécessite d'évaluer et de comparer les coûts et bénéfices des différentes alternatives. Cela implique aussi de réguler et de contrôler le comportement de façon flexible pour optimiser les périodes de recherche de gains ou de ressources et les périodes d'exploitation des acquis. Une des hypothèses actuelles sur les mécanismes neurobiologiques impliqués, propose que cortex cingulaire antérieur (CCA), associé à l'évaluation de l'action, et cortex préfrontal dorsolatéral (CPFdl), associé au contrôle cognitif, interagiraient pour réguler le comportement. Les travaux réalisés au cours de cette thèse ont permis de préciser le rôle joué par le CCA dans la détection et l'évaluation des performances ainsi que ses interactions avec le CPFdl au sein d'une boucle du contrôle cognitif. Menés grâce à des enregistrements électrophysiologiques chez le singe en comportement, ils apportent des précisions sur la séquence d'activation du CCA et du CPFdl dans la bande de fréquences gamma lors de l'adaptation du comportement. L'étude des potentiels de champs locaux de ces deux régions amènent à poser des hypothèses sur les mécanismes oscillatoires sous-jacents et notamment sur le rôle des communications basses fréquences entre le CCA et le CPFdl et leur implication différentielle entre recherche et exploitation.

Made available in DSpace on 2016-03-15T19:39:42Z (GMT). No. of bitstreams: 1 Ricardo Rafael de Araujo.pdf: 639007 bytes, checksum: 913741be473f0be64fda69ad9172445d (MD5) Previous issue date: 2011-02-25 / Fundo Mackenzie de Pesquisa / Attention can be understood as a set of neural mechanisms that enhance the processing of relevant information, thoughts or actions while ignoring irrelevant or scattered stimuli. Thus, attention allows the organism to interact in a proper way with the environment. Among the brain structures associated with the control of attention, the Dorsolateral Prefrontal Cortex (DLPFC) has a remarkable role in current literature as a region associated with behavioral control. Transcranial Direct Current Stimulation (TDCS) is based on the application of a low intensity electric current through electrodes placed in the scalp, aimed at modulating the activity of different brain areas. This technique has been used to study brain functions. This study has the objective of verifying how attention can be modulated through the application of bilateral tDCS on DLPFC using measures of reaction time (RT) in tasks of temporal and spatial orientation. To accomplish that, two experiments were planned and executed. In the first one, which focused on the voluntary orienting of spatial attention, each participant had to orient attention to the position indicated by an arrow; in the second, on voluntary orienting of temporal attention, each participant had to orient attention to the most frequent time interval of visual targets. In both cases, participants had to respond as fast as possible when the target was displayed by pressing a joystick key. RTs were registered. The sample was composed of 18 undergraduate students, age range 19-25 years old (12 for the first experiment and 6 more for the second). In each experiment, subjects were submitted to three tDCS conditions (anodal, cathodal and sham) on the DLPFC during the undertaking of tests. Analyses of variance were made, in order to compare the involved factors. For the experiment of spatial orientation, the anodal condition produced lower RTs, when compared to sham. For the temporal orienting experiment it was observed that, in the anodal modulation, RTs were increased for the less frequent interval (500 ms), indicating that the anodal tDCS can have influenced in a more effective way attentional orienting to the most frequent intervals. Therefore it is possible to postulate the existence of a facilitating effect of anodal tDCS in the modulation of DLPFC, which generated an impact in attentional orienting, lowering RTs to the valid condition (spatial) when compared to sham tDCS. / A atenção pode ser compreendida como um conjunto de mecanismos neurais que facilitam o processamento de informações, pensamentos ou ações relevantes enquanto ignoram outros irrelevantes ou dispersos. Deste modo a atenção permite que o organismo interaja de maneira adequada com o ambiente. Dentre as estruturas cerebrais associados ao controle da atenção, o Córtex Prefrontal Dorsolateral (CPFDL) tem tomado papel de destaque na literatura atual como uma região associada ao controle comportamental. A Estimulação Transcraniana por Corrente Contínua (ETCC) se baseia na aplicação de corrente elétrica de baixa intensidade por meio de eletrodos posicionados no escalpe com o objetivo de modular a atividade de diferentes regiões cerebrais e tem sido utilizada como modo de estudo da função cerebral. Esse trabalho tem como objetivo verificar como a atenção pode ser modulada a partir da aplicação ETCC bilateral sobre o CPFDL, utilizando medidas de tempo de reação (TR) em tarefas de orientação temporal e espacial. Para Tanto foram planejados e executados dois experimentos. No primeiro experimento, relativo à orientação voluntária da atenção espacial, cada participante deveria orientar a atenção para a posição do espaço indicada por uma seta. O segundo experimento, relativo à orientação voluntária da atenção temporal, cada participante deveria orientar a atenção para o intervalo temporal de maior recorrência. Em ambos os casos os participantes deveriam responder o mais rapidamente possível ao aparecimento do alvo pressionado uma tecla de joystick registrando-se assim o seu TR. Participaram desse estudo 18 alunos de graduação (12 no primeiro desenho experimental, e para o segundo desenho experimental foram adicionados mais 6 colaboradores) na faixa etária de 19 à 25 anos. A cada sessão os colaboradores deveriam responder a ambos os experimento enquanto eram submetidos a diferentes polaridades de ETCC (anódica, catódica e placebo) sobre o CPFDL. Foram feitas análises de variância para comparar os fatores estudados. No experimento de orientação espacial a condição anódica produziu TR menores em comparação à condição placebo. No caso do experimento de orientação temporal foi observado que na modulação anódica houve um aumento nos TR no intervalo menos recorrente de 500 ms, indicando que a ETCC anódica pode ter influenciado de modo mais efetivo o direcionamento atencional aos intervalos mais freqüentes. Neste sentido é possível sugerir a existência de um efeito facilitatório da ETCC anódica na moducalçao do CPFDL, o que gerou um impacto no direcionamento atencional, diminuindo os TR para a condição valida (orientação espacial) quando comparados a ETCC placebo.