This study examined the effect of an 8-week, progressive exercise intervention on neural responses, specifically N2 amplitude as a measure of inhibitory control, to pictures of food. Healthy women ages 18-44 years were randomized to a morning (AM) exercise group or evening (PM) exercise group. The AM group did moderate-to-vigorous intensity exercise on 4 days per week between 6:30 and 9:30 a.m. while the PM group had the identical volume of exercise between 6:30 and 9:30 p.m. Neural responses, eating behaviors, cardiovascular fitness outcomes, and body weight/composition were measured at baseline and after the 8-week intervention. The N2 amplitude in response to pictures of high- and low-calorie foods was assessed using electroencephalography during a go/no-go task. Dietary restraint, emotional eating, and external eating were assessed using the Dutch Eating Behavior Questionnaire. VO2peak, HRmax, and time to completion were measured during a maximal treadmill test. Body weight was measured on a digital scale, and body composition was measured using dual-energy x-ray absorptiometry. There was not a significant task (go, no-go) × group (AM, PM) × period (baseline, 8 weeks) interaction (F = 0.18; p = 0.677), but there was a main effect of exercise over 8 weeks (F = 6.26; p = 0.017) with increased N2 amplitude following the intervention. There was not a significant interaction as a function of picture type (high-calorie, low-calorie), task, group, and period (F = 0.52; p = 0.478). Changes in body weight and neural outcomes were not significantly associated with changes in eating behaviors for either group (ps < 0.05). There was a significant group × period interaction for body weight (F = 4.90; p = 0.032). Body weight increased by 0.79 ± 1.16 kg in the AM group and decreased by 0.21 ± 1.46 kg in the PM group (effect size = 0.77; CI = 0.15-1.35). There was not a significant group × period interaction for body fat percentage, total body fat or fat-free mass (ps < 0.05). When examining the main effect of exercise on cardiovascular fitness outcomes, VO2peak was not different (F = 1.80; p = 0.187), time-to-completion on treadmill increased (F = 6.51; p = 0.014), and HRmax during the treadmill test was significantly lower (F = 5.49; p = 0.025). This study suggests that 8 weeks of exercise training may increase the inhibitory response to pictures of both high- and low-calorie foods. However, time of day of exercise did not influence this response. Eight weeks of exercise training did not change self-reported dietary restraint, external eating, or emotional eating, and there was no correlation between these eating behaviors and inhibitory control. However, evening exercise was more beneficial for body weight than morning exercise. Given the novelty of this study and its results, additional studies on the influence of time of day of exercise on weight management are needed.

Dans un monde régi par les lois physiques, notre cerveau est capable d'extraire des invariants et de générer des attentes pour préciser notre percept visuel. Pourtant, en éclairant une pièce, ou en naviguant à travers les chaînes de télévision, nous comprenons quasi-instantanément l'essence de ces nouvelles scènes naturelles. A quelle vitesse peut-on extraire une représentation sémantique globale des scènes? Quelle est l'influence du contexte sur la reconnaissance de l'objet d'intérêt? Quelles sont les informations visuelles nécessaires et la nature des traitements sous-jacents? Les deux premiers articles démontrent notre capacité à reconnaître la catégorie superordonnée du contexte d'une scène en moins de 400 ms tandis que l'accès au niveau basique nécessite 50 ms de traitement additionnel. Ils démontrent aussi que la présence d'objets saillants interfère sur la catégorisation rapide du contexte. Ces temps de traitements très similaires à ceux enregistrés dans la catégorisation rapide d'objets suggèrent un traitement global et parallèle de l'ensemble de la scène. Le troisième article montre que la congruence (incongruence) du contexte avec l'objet influence immédiatement le traitement de l'objet et le dernier précise les informations visuelles à la base de l'analyse du contexte. Je défends ainsi l'idée d'interactions bidirectionnelles précoces entre les traitements visuels ascendants et parallèles de l'objet et du contexte et recherche dans une dernière étude la latence minimale de ces interactions en remplaçant réponse manuelle par réponse oculaire. L'implication de ces résultats fondamentaux est discutée dans la perspective des recherches à venir.

Cette thèse porte sur le traitement rapide des informations visuelles contenues dans les scènes naturelles. Elle s'articule en deux chapitres constitués chacun d'une revue de la littérature et d'articles présentant des travaux expérimentaux réalisés au cours de celle-ci.<br />Le chapitre 1 s'intéresse tout d'abord au degré de parallélisme dans le traitement des scènes naturelles.<br />Contrairement aux modèles sériels qui postulent que les objets sont analysés l'un après l'autre, une revue<br />détaillée de la littérature suggère une grande part de parallélisme dans le traitement visuel. Les deux<br />premiers articles de cette thèse portent sur la catégorisation d'objets dans les scènes naturelles et suggèrent que l'interférence entre représentations d'objets aurait lieu principalement au niveau décisionnel, probablement dans les aires frontales. La seconde partie du chapitre 1 s'intéresse au parallélisme de traitement qui permet d'extraire le sens du contexte général d'une scène. L'article 3 décrit l'efficacité du système visuel à extraire rapidement le sens global d'une scène et suggère que celui-ci pourrait interagir en parallèle avec la catégorisation des objets. L'article 4 tente de mieux cerner la participation des facteurs visuels ascendants et descendants dans l'analyse des scènes naturelles. Parmi toutes les catégories, les visages humains pourraient être traités de façon très particulière. <br />Le chapitre 2 discute certains arguments en faveur d'une spécificité des mécanismes impliqués. Des explications alternatives y sont proposées permettant d'envisager un modèle unique de traitement visuel pour toutes les catégories d'objets. L'article 5 montre qu'au niveau comportemental les visages d'êtres humains dans des scènes naturelles ne sont pas traités plus rapidement que d'autres catégories d'objets familiers. L'article 6 tente de déterminer le temps de traitement de ces stimuli au niveau électrophysiologique. Plusieurs hypothèses sont discutées. L'article 7 montre que la N170 n'est pas aussi spécifique des visages d'êtres humains que communément admis. Ce qui semble leur être spécifique est l'ampleur de l'effet d'inversion<br />au niveau comportemental et électrophysiologique. Tous ces résultats sont discutés dans le cadre des<br />modèles actuels du traitement visuel.

Reconnaître rapidement les visages familiers est une fonction fondamentale qui joue un rôle important dans nos interactions sociales. D'un point de vue évolutionniste, il semble en effet crucial de pouvoir rapidement déterminer si la personne qui nous fait face est amie ou ennemie pour adapter son comportement en conséquence. C'est sans doute pour cela que, dans l'opinion publique, mais également dans la littérature scientifique, la reconnaissance des visages est supposée être un processus très rapide, efficace et exécuté sans effort. Cependant, la reconnaissance des visages familiers est-elle réellement si rapide ? Ne serait-ce pas simplement une idée reçue ? Rapide, admettons, mais à quelle vitesse ? En adaptant des protocoles de catégorisation visuelle rapide (tâche de go/no-go) développés initialement pour étudier la rapidité du système visuel et en mettant en place de nouveaux protocoles de catégorisation ultra-rapide (" Speed and Accuracy Boosting procedure " ; SAB), nous avons pu déterminer les latences comportementales et électrophysiologiques les plus précoces pour reconnaître explicitement un visage célèbre. Nous nous sommes intéressés d'une part à la reconnaissance de type " bottom-up " (reconnaître plusieurs visages célèbres sans savoir au préalable de qui il s'agit) et d'autre part à la reconnaissance " top-down " (reconnaître une personne en particulier parmi des inconnus). Le temps de réaction minimum pour reconnaître des visages célèbres parmi des inconnus (reconnaissance " bottom-up ") est d'environ 360-390 ms, ce temps de réponse ne pouvant être amélioré ni par un apprentissage intensif des stimuli (Article 1), ni par un protocole de catégorisation ultra-rapide (Article 2). Ce temps de réaction est environ 100 ms plus tardif que lors d'une tâche de détection de visage (Article 1) ou de genre (Article 1). Ces latences sont très différentes lorsque la procédure SAB est appliquée à une reconnaissance de type " top-down ", descendant à environ 300 ms contre 270 ms dans une tâche de détection de visages (Article 3). De plus, en appliquant une méthode de MVPA (Multi-Variate Pattern Analysis) à des données d'EEG de surface, nous avons montré que l'activité neuronale liée à la reconnaissance des visages célèbres était disponible dès 230 ms après la présentation du stimulus (voire 200 ms pour le sujet les plus rapides) alors que l'activité neuronale liée à a détection d'un visage humain parmi des visages d'animaux était disponible dés 80 ms (Articles 4 et 5). L'activité neuronale était de plus fortement corrélée aux temps de réponses minimales en reconnaissance, confirmant ainsi son rôle dans la prise de décision. Nous discutons ces latences au regard des modèles de la voie visuelle ventrale et des modèles de la reconnaissance des visages. Nous distinguons trois modèles différents pouvant théoriquement être à l'origine de la familiarité et en favorisons un en particulier.

Faces de bebês são um estímulo emocional extremamente saliente para humanos. O objetivo deste estudo foi comparar a interferência emocional de faces de bebês e estímulos de ameaça (faces adultas com medo) na atenção automática de homens e mulheres com e sem filhos. Após estudo piloto, recrutou-se 61 homens e mulheres de 20 a 35 anos. Os participantes responderam a uma tarefa Go/No-Go na qual imagens de bebês com expressões de sofrimento, alegria ou neutra e imagens de adultos com expressões de medo, alegria e neutra, eram apresentadas. Foram calculados os vieses de atenção para faces de bebês em sofrimento, faces de adultos com medo e faces de bebês vs. adultos. Participantes com filhos, de ambos os sexos, apresentaram mais viés de cuidado (bebês vs adultos) do que os sem filhos. Os resultados indicaram que apenas status parental influenciou o viés para faces de bebês. / Babies are extremely salient emotional stimuli to human beings. The current study aimed to compare the emotional interference of baby faces and threat stimuli (adult fearful faces) on the automatic attention of men and women, parents and non-parents. A pilot study was conducted to adapt instruments and procedures. For the main study 61 men and women aged 20 to 35 years with minimum complete elementary school were recruited. Images of distressed, happy and neutral baby faces and fearful, happy and neutral adult faces were used in a Go/No-Go paradigm. Attentional bias indexes were calculated for biases towards baby distress, adult fear and baby vs. adult faces. Parents, regardless of sex, showed a higher nurturing attentional bias (baby vs. adult faces) in comparison to non-parents. This finding demonstrates that parental status influences the attentional bias to babies.

Submitted by Cleide Dantas (cleidedantas@ufpa.br) on 2014-05-12T16:17:24Z No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_EstrategiasModelagemGoNoGo.pdf: 1054738 bytes, checksum: 598c8f9c11fa18aa9031a02edd37b946 (MD5) / Approved for entry into archive by Ana Rosa Silva (arosa@ufpa.br) on 2014-09-17T13:53:35Z (GMT) No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_EstrategiasModelagemGoNoGo.pdf: 1054738 bytes, checksum: 598c8f9c11fa18aa9031a02edd37b946 (MD5) / Made available in DSpace on 2014-09-17T13:53:35Z (GMT). No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_EstrategiasModelagemGoNoGo.pdf: 1054738 bytes, checksum: 598c8f9c11fa18aa9031a02edd37b946 (MD5) Previous issue date: 2010 / FAPESPA - Fundação Amazônia de Amparo a Estudos e Pesquisas / A aprendizagem de relações condicionais bidirecionais (simetria) tem sido raramente demonstrada em não-humanos. Recentemente três estudos apresentaram dados positivos de repertórios comportamentais de simetria em pombos. Estes estudos apontaram como possíveis variáveis determinantes da emergência de simetria: 1) O treino misto de relações arbitrárias e de identidade simultaneamente e com um mesmo conjunto de estímulos; 2) O sujeito não ter sido exposto a treino prévio de qualquer tipo de relação com os mesmos estímulos; e 3) A utilização do procedimento de discriminação condicional sucessiva (Go/No-go). O presente estudo buscou averiguar a necessidade do uso de Go/No-go, aplicando as demais variáveis (treino misto e não exposição prévia), para a obtenção da emergência de simetria. Este estudo avaliou em dois macacos-prego (Cebus apella) a aprendizagem de relações arbitrárias e de identidade de estímulos apresentados na mesma sessão experimental e a emergência de simetria, utilizando dois procedimentos. Um sujeito (M18) foi treinado em tarefa de Go/Nogo com tentativas mistas de relações arbitrárias e relações de identidade, com o mesmo conjunto de estímulos. O sujeito passou por dois treinos Go/No-go que não foram bem sucedidos em estabelecer controle condicional. Um outro sujeito (M27) foi treinado em uma tarefa de emparelhamento ao modelo com atraso zero com tentativas mistas de relações de identidade e arbitrárias, com mesmo conjunto de estímulos. Esse segundo procedimento buscou averiguar a necessidade do uso do procedimento Go/No-go para a obtenção da emergência de simetria. As sessões de treino eram compostas por oito tentativas de identidade (quatro relações) e oito tentativas de relações arbitrárias (duas relações), apresentadas em seqüência randômica. Todas as tentativas tinham três escolhas entre as comparações. Posteriormente, M27 foi submetido a três testes (todos com reforço programado para todas as tentativas). O treino de linha de base mista (identidade e arbitrária) ocorreu em 14 sessões. O primeiro teste foi de simetria, em uma sessão de oito tentativas para cada uma das quatro relações de identidade, duas arbitrárias e duas de teste, totalizando 64 tentativas, cujo critério de desempenho era acertar sete das oito tentativas de cada relação. M27 teve 2 erros em uma das relações de identidade e acertou todas as demais, inclusive as de simetria. Para averiguar se havia uma coerência do controle de estímulos, foi feito o segundo teste no qual as respostas de escolha entre as comparações não podiam mais ser condicionais ao modelo, uma vez que se utilizou um mesmo estímulo novo no lugar dos modelos para todas as tentativas, tanto de linha de base quanto de teste. M27 cometeu três erros ao todo. Esse resultado pode indicar que havia uma relação de controle, não prevista: como dois pares de estímulos se alternavam na função S- em todas as tentativas, M27 pode ter aprendido a rejeitar esses dois pares de estímulos independente do modelo apresentado. De modo a averiguar se de fato não havia controle por seleção de acordo com o modelo, foi feito um teste apenas com duas comparações com as mesmas outras configurações do primeiro teste. M27 errou seis das 32 tentativas de linha de base de identidade, seis das 16 arbitrárias e seis das 16 de simetria. Os acertos foram, portanto, acima da linha do acaso, o que confirma parcialmente a hipótese acima e pode indicar a presença de um controle misto condicional e discriminativo entre os estímulos de comparação. / The learning of bidirectional conditional relations (symmetry) has rarely been demonstrated in non-human. Recently, three studies presented positive data from behavioral repertoires of symmetry in pigeons. These studies indicated some variables as possible determinants of the emergence of symmetry: 1) Intermixed training of arbitrary and identity relations at the same time and with the same set of stimuli, 2) Non-exposition to prior training of any kind of relationship with same stimuli, and 3) The use of the successive conditional discrimination (Go/No-go). This study aimed to determine the need for the use of Go/No-go, using the other variables (intermixed training and no prior exposure), to obtain the emergence of symmetry. This study evaluated in two capuchin monkeys (Cebus apella) the learning of arbitrary and identity relations of stimuli presented in the same experimental session and the emergence of symmetry, using two procedures. One subject (M18) was trained in Go/No-go task with mixed arbitrary and identity trials, with the same set of stimuli. The subject went through two Go/No-go training that have not been successful in establishing conditional control. Another subject (M27) was trained in a 0-delayed matching-to-sample task with mixed arbitrary and identity trials, with the same set of stimuli too. This second procedure aimed to determine the need to use the procedure Go/No-go to obtain the emergence of symmetry. Training sessions were composed of eight identity trials (four relations) and eight arbitrary trials (two relations), presented in random sequence. All trials had three choices as comparisons. Subsequently, M27 was submitted to three tests (all of the trials had programmed reinforcement). The intermixed baseline training (identity and arbitrary) occurred in 14 sessions. The first test of symmetry was a session of eight trials for each of the four relations of identity, two arbitrary, and two test trials in a total of 64 trials, and the performance criterion was seven correct trials out of eight for each relation. M27 had 2 errors in a identity relation and reached the criterion for all the others, including those of symmetry. To determine whether there was a consistency of stimulus control, the second test was made in which the choices between the comparisons could no longer be conditional to the model, since was used one single new stimulus as sample at all time in both baseline and test trials. M27 made three errors global. This result may indicate that some kind of unprogrammed stimulus control, developed: as the same two pairs of stimuli alternated in the S- function in all trials, M27 may have learned to reject the two pairs of stimuli independently of the sample presented. In order to verify if indeed there was no control for selection according to the sample, it was ran a test with only two comparisons with the same settings of the first test. M27 made six errors in 32 identity baseline trials, six in 16 arbitrary trials and six in the 16 symmetry trials. The correct responses were therefore above chance level, which partly confirms the hypothesis above and may indicate the presence of a mixed stimulus control between conditional and discriminative stimuli for comparison.

À la frontière entre neurosciences et intelligence artificielle, les neurosciences computationnelles tentent de comprendre les formidables capacités de calcul du cerveau, notamment l'efficacité du traitement de l'image par le système visuel. Mon travail est un double travail expérimental et de modélisation. Dans la partie expérimentale, je tente de déterminer les raisons qui font la précision et la rapidité des processus visuels. On présente brièvement (20-30 ms) des photographies contenant ou non des animaux au sujet qui doit relâcher un bouton quand l'image contient un animal. Le singe macaque réalise cette tâche avec une précision légèrement inférieure à celle de l'homme mais avec une plus grande rapidité. Je tente ensuite de contraindre la catégorisation pour déterminer le rôle à la fois des propriétés intrinsèques des images - couleur, luminance, nombre d'animaux présents, parties visibles de leurs corps, espèce de l'animal... - mais aussi de leurs propriétés extrinsèques - condition de présentation, effet de séquence, familiarité du stimulus, consigne... Bien que certaines conditions accélèrent la catégorisation, les réponses les plus précoces (dont on montre qu'elles ne sont pas spécifiques de certaines images), et les enregistrements EEGs correspondant au traitement de l'image ne sont que très peu affectés. Cela implique donc un traitement rapide massivement parallèle - quasiment automatique - des informations visuelles, où chaque neurone du système visuel peut difficilement émettre plus d'une décharge. À partir de ces contraintes, et de celles imposées par la structure du système visuel, j'ai construit un simulateur biologiquement plausible (SpikeNET) qui permet de simuler le comportement des neurones réels (de la détection de barres orientées jusqu'à la reconnaissance de visages). Les performances de ces modèles sont étonnantes du point de vue du traitement d'image et rivalisent avec les approches classiques en intelligence artificielle.

The purpose of this thesis was to explore the potential of near-infrared spectroscopy (NIRS) as an access channel by establishing reliable signal detection to verify the existence of signal differences associated with changes in activity. This thesis focused on using NIRS to measure brain activity from the prefrontal cortex during an auditory Go-No-Go task. A singular spectrum analysis change-point detection algorithm was applied to identify transition points where the NIRS signal properties varied from previous data points in the signal, indicating a change in brain activity. With this algorithm, latency values for change-points detected ranged from 6.44 s to 9.34 s. The averaged positive predictive values over all runs were modest (from 49.41% to 67.73%), with the corresponding negative predictive values being generally higher (48.66% to 78.80%). However, positive and negative predictive values up to 97.22% and 95.14%, respectively, were achieved for individual runs. No hemispheric differences were found.

The purpose of this thesis was to explore the potential of near-infrared spectroscopy (NIRS) as an access channel by establishing reliable signal detection to verify the existence of signal differences associated with changes in activity. This thesis focused on using NIRS to measure brain activity from the prefrontal cortex during an auditory Go-No-Go task. A singular spectrum analysis change-point detection algorithm was applied to identify transition points where the NIRS signal properties varied from previous data points in the signal, indicating a change in brain activity. With this algorithm, latency values for change-points detected ranged from 6.44 s to 9.34 s. The averaged positive predictive values over all runs were modest (from 49.41% to 67.73%), with the corresponding negative predictive values being generally higher (48.66% to 78.80%). However, positive and negative predictive values up to 97.22% and 95.14%, respectively, were achieved for individual runs. No hemispheric differences were found.

Faces de bebês são um estímulo emocional extremamente saliente para humanos. O objetivo deste estudo foi comparar a interferência emocional de faces de bebês e estímulos de ameaça (faces adultas com medo) na atenção automática de homens e mulheres com e sem filhos. Após estudo piloto, recrutou-se 61 homens e mulheres de 20 a 35 anos. Os participantes responderam a uma tarefa Go/No-Go na qual imagens de bebês com expressões de sofrimento, alegria ou neutra e imagens de adultos com expressões de medo, alegria e neutra, eram apresentadas. Foram calculados os vieses de atenção para faces de bebês em sofrimento, faces de adultos com medo e faces de bebês vs. adultos. Participantes com filhos, de ambos os sexos, apresentaram mais viés de cuidado (bebês vs adultos) do que os sem filhos. Os resultados indicaram que apenas status parental influenciou o viés para faces de bebês. / Babies are extremely salient emotional stimuli to human beings. The current study aimed to compare the emotional interference of baby faces and threat stimuli (adult fearful faces) on the automatic attention of men and women, parents and non-parents. A pilot study was conducted to adapt instruments and procedures. For the main study 61 men and women aged 20 to 35 years with minimum complete elementary school were recruited. Images of distressed, happy and neutral baby faces and fearful, happy and neutral adult faces were used in a Go/No-Go paradigm. Attentional bias indexes were calculated for biases towards baby distress, adult fear and baby vs. adult faces. Parents, regardless of sex, showed a higher nurturing attentional bias (baby vs. adult faces) in comparison to non-parents. This finding demonstrates that parental status influences the attentional bias to babies.