Kindergarten characteristics and risk-taking behaviors in middle childhood = Caractéristiques à la maternelle et comportements de prise de risques en 6e année

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Leptin modulation of locomotor and emotional behaviors : the role of STAT3 signaling in dopamine neurons

La leptine circule en proportion de la masse graisseuse du corps et la transduction de son signal à travers la forme longue de son récepteur via un certain nombre de voies neurales , y compris MAPK, PI3-K ,AMPK et JAK2 - STAT3 . Il faut noter que STAT3 constitue une voie clée au récepteur de la leptine par laquelle la leptine module l'expression des gènes impliqués dans la régulation du bilan énergétique. La plupart des recherches ont porté sur la fonction du récepteur de la leptine au sein de l' hypothalamus, en particulier la fonction du récepteur de la leptine dans le noyau arqué. Toutefois, les récepteurs de la leptine sont également exprimés sur les neurones dopaminergiques de l'aire tégmentale ventrale et la leptine agit sur cette région du cerveau pour influencer la prise alimentaire, la motivation, la locomotion, l'anxiété et la transmission de la dopamine. De plus, la leptine active la STAT3 dans les dopaminergiques et GABAergiques populations neuronales. Bien que ces résultats contribuent à notre compréhension des multiples actions de la leptine dans le système nerveux central, il reste à résoudre les cellules et la signalisation du récepteur de la leptine qui sont responsables des effets neurocomportementaux de la leptine dans le mésencéphale. Visant à déterminer la contribution de la voie de signalisation STAT3 dans les neurones dopaminergiques du mésencéphale, nous avons généré une lignée de souris knockout conditionnel dans lequel l'activation du gène de STAT3 sur son résidu tyrosine 705 ( Tyr 705 ) est absent spécifiquement dans les neurones dopaminergiques. Avec l'utilisation de ce modèle de souris génétique, nous avons évalué l'impact de l'ablation de la signalisation STAT3 dans les neurones dopaminergiques sur un certain nombre de fonctions liées à la dopamine, y compris l'alimentation, la locomotion, les comportements liés à la récompense, l'émotion et la libération de dopamine dans le noyau accumbens. Fait intéressant, nous avons observé un dimorphisme sexuel dans le phénotype des souris STAT3DAT-KO. L'activation de la voie de signalisation STAT3 dans les neurones dopaminergiques est responsable de l'action de la leptine dans la réduction de la locomotion, récompense liée à l'activité physique, et de l'augmentation de la libération et de la disponibilité de la dopamine chez les souris mâles. Cependant, il ne module pas le comportement émotionnel. D'autre part, les souris femelles STAT3DAT-KO augmentent les niveaux d'anxiété et les niveaux plasmatiques de corticostérone, sans provoquer de changements de la dépression. Cependant, la perte d'activation de STAT3 dans les neurones dopaminergiques ne module pas le comportement locomoteur chez les souris femelles. Notamment, les actions de la leptine dans le mésencéphale pour influencer le comportement alimentaire ne sont pas médiées par l'activation de STAT3 dans les neurones dopaminergiques, considérant que les souris mâles et femelles ont un comportement alimentaire normal. Nos résultats démontrent que la voie de signalisation STAT3 dans les neurones dopaminergiques est responsable des effets anxiolytiques de la leptine, et soutient l'hypothèse que la leptine communique l'état d'énergie du corps (i.e. la relation entre la dépense et les apports énergétiques) pour les régions mésolimbiques pour atténuer les effets de motivation et de récompense de plusieurs comportements qui servent à réhabiliter ou à épuiser les réserves d'énergie. En outre, ce travail souligne l'importance d'étudier la modulation de la signalisation de la leptine dans différente types de cellules, afin d'identifier les voies de signalisation et les mécanismes cellulaires impliqués dans les différentes fonctions neuro-comportementales de la leptine.

Analysis and Implementation of Robust Grasping Behaviors

This thesis addresses the problem of developing automatic grasping capabilities for robotic hands. Using a 2-jointed and a 4-jointed nmodel of the hand, we establish the geometric conditions necessary for achieving form closure grasps of cylindrical objects. We then define and show how to construct the grasping pre-image for quasi-static (friction dominated) and zero-G (inertia dominated) motions for sensorless and sensor-driven grasps with and without arm motions. While the approach does not rely on detailed modeling, it is computationally inexpensive, reliable, and easy to implement. Example behaviors were successfully implemented on the Salisbury hand and on a planar 2-fingered, 4 degree-of-freedom hand.

Hybrid coordination of reinforcement learning-based behaviors for AUV control

This paper proposes a hybrid coordination method for behavior-based control architectures. The hybrid method takes advantages of the robustness and modularity in competitive approaches as well as optimized trajectories in cooperative ones. This paper shows the feasibility of applying this hybrid method with a 3D-navigation to an autonomous underwater vehicle (AUV). The behaviors are learnt online by means of reinforcement learning. A continuous Q-learning implemented with a feed-forward neural network is employed. Realistic simulations were carried out. The results obtained show the good performance of the hybrid method on behavior coordination as well as the convergence of the behaviors

Efficient learning of reactive robot behaviors with a Neural-Q_learning approach

The purpose of this paper is to propose a Neural-Q_learning approach designed for online learning of simple and reactive robot behaviors. In this approach, the Q_function is generalized by a multi-layer neural network allowing the use of continuous states and actions. The algorithm uses a database of the most recent learning samples to accelerate and guarantee the convergence. Each Neural-Q_learning function represents an independent, reactive and adaptive behavior which maps sensorial states to robot control actions. A group of these behaviors constitutes a reactive control scheme designed to fulfill simple missions. The paper centers on the description of the Neural-Q_learning based behaviors showing their performance with an underwater robot in a target following task. Real experiments demonstrate the convergence and stability of the learning system, pointing out its suitability for online robot learning. Advantages and limitations are discussed

Predictors of Attitudes toward Cosmetic Surgery among U.S. and Colombian College Women: The Roles of Eating Behaviors and Demographic Variables

Cross-cultural studies on eating behaviors and related constructs can identify cultural and social factors that contribute to eating disorder symptomatology. Eating disorders (EDs) are a major cause for concern in the U.S., and recent studies in Colombia have shown growing rates among their female population. In addition, cosmetic surgery procedures have been increasing rapidly in both the U.S. and Colombia, and preliminary research suggests a positive relation between disordered eating and endorsement of plastic surgery. In samples of college women from Colombia and the U.S., we investigated patterns of association between disordered eating variables and cosmetic surgery acceptance. Our approach utilized separate analyses for various subcomponents of disordered eating (to determine their unique associations with cosmetic surgery acceptance) while adjusting for potentially relevant covariates and examining cross-cultural patterns. Participants were students at an urban, public college in the U.S. (n=163) and an urban, private college in Colombia (n=179). Overall, our findings suggested that participants from Colombia with greater disordered eating were more likely to endorse cosmetic surgery for social reasons, while those from the U.S. were more likely to consider undergoing cosmetic surgery for personal reasons. Differing findings between the two samples may be due to cultural and social factors, which we delineate. These findings also have potential implications for presurgical counseling of cosmetic surgery candidates.

Psychometric properties of the Spanish version of the Controlling Coach Behaviors Scale in the sport context

Resumen tomado de la publicaci??n

The development of language and communicative behaviors in deaf/hearing twins

This paper examines language development in twins--one that is hearing and the other that is hearing impaired.

Influence of vegetation on the nocturnal foraging behaviors and vertebrate prey capture by endangered Burrowing Owls

Restrictions in technology have limited past habitat selection studies for many species to the home-range level, as a finer-scale understanding was often not possible. Consequently, these studies may not identify the true mechanism driving habitat selection patterns, which may influence how such results are applied in conservation. We used GPS dataloggers with digital video recorders to identify foraging modes and locations in which endangered Burrowing Owls (Athene cunicularia) captured prey. We measured the coarse and fine-scale characteristics of vegetation at locations in which owls searched for, versus where they caught, vertebrate prey. Most prey items were caught using hover-hunting. Burrowing Owls searched for, and caught, vertebrate prey in all cover types, but were more likely to kill prey in areas with sparse and less dense vegetative cover. Management strategies designed to increase Burrowing Owl foraging success in the Canadian prairies should try to ensure a mosaic of vegetation heights across cover types.

Is speeding a "real" antisocial behavior? A comparison with other antisocial behaviors

The relationship between speed and crashes has been well established in the literature, with the consequence that speed reduction through enforced or other means should lead to a reduction in crashes. The extent to which the public regard speeding as a problem that requires enforcement is less clear. Analysis was conducted on public perceptions of antisocial behaviors including speeding traffic. The data was collected as part of the British Crime Survey, a face-to-face interview with UK residents on issues relating to crime. The antisocial behavior section required participants to state the degree to which they perceived 16 antisocial behaviors to be a problem in their area. Results revealed that speeding traffic was perceived as the greatest problem in local communities, regardless of whether respondents were male or female, young, middle aged, or old. The rating of speeding traffic as the greatest problem in the community was replicated in a second, smaller postal survey, where respondents also provided strong support for enforcement on residential roads, and indicated that traveling immediately above the speed limit on residential roads was unacceptable. Results are discussed in relation to practical implications for speed enforcement, and the prioritization of limited police resources. (c) 2006 Elsevier Ltd. All rights reserved.

Imbalanced functional link between executive control network and reward network explain the online-game seeking behaviors in Internet gaming disorder

Literatures have shown that Internet gaming disorder (IGD) subjects show impaired executive control and enhanced reward sensitivities than healthy controls. However, how these two networks jointly affect the valuation process and drive IGD subjects' online-game-seeking behaviors remains unknown. Thirty-five IGD and 36 healthy controls underwent a resting-states scan in the MRI scanner. Functional connectivity (FC) was examined within control and reward network seeds regions, respectively. Nucleus accumbens (NAcc) was selected as the node to find the interactions between these two networks. IGD subjects show decreased FC in the executive control network and increased FC in the reward network when comparing with the healthy controls. When examining the correlations between the NAcc and the executive control/reward networks, the link between the NAcc - executive control network is negatively related with the link between NAcc - reward network. The changes (decrease/increase) in IGD subjects' brain synchrony in control/reward networks suggest the inefficient/overly processing within neural circuitry underlying these processes. The inverse proportion between control network and reward network in IGD suggest that impairments in executive control lead to inefficient inhibition of enhanced cravings to excessive online game playing. This might shed light on the mechanistic understanding of IGD.

Do online hotel rating schemes influence booking behaviors?

Travelers’ hotel booking behaviors increasingly depend on peers' opinions and online ratings. This study investigates the effects of online hotel ratings on travelers' attitudes toward the hotel and booking intentions, using a 2 × 2 experimental research design. The results suggest that online rating lists are more useful and credible when published by well-known online travel communities (e.g., TripAdvisor). More favorable attitudes toward a hotel and higher booking intentions emerge when the hotel appears in best hotels lists. Finally, for the entries on best hotels lists, better attitudes and higher booking intentions result if the list is published on a well-known online travel community (Tripadvisor), whereas for entries on a worst hotel list, attitudes and booking intentions decrease even further if the list appears on TripAdvisor.