Doctor of Philosophy / Department of Psychology / Jerome Frieman / The present experiment investigated whether dwarf hamsters (Phodopus campbelli) demonstrate temporal discounting. This was investigated by comparing the behavior of dwarf hamsters and Sprague-Dawley rats (Rattus norvegicus) in an adjusting delay procedure and applying the theory of behavioral economics to explain the resulting behavior. Dwarf hamsters demonstrated temporal discounting and tolerated longer delays than did the more impulsive rats. There was not a statistically significant difference between these species concerning indifference points. There was a statistically significant difference in the slopes of their discounting functions and the delay at which the end criterion was met. Neither species exhibited sex differences with respect to these measures nor with storage of food. There were a number of differences between the species. Rats started responding quickly, whereas dwarf hamsters waited significantly longer. When faced with increasing delays, rats increased the number of pellets earned while dwarf hamsters earned the same amount. Finally, rats lost weight throughout the experiment while dwarf hamsters gained weight. There were also a number of similarities. When faced with an increasing delay, both rats and dwarf hamsters increased the number of responses made, and increased the number of times they timed out on Larger Later trials. Some of these findings disagree with previous research and predictions of the behavioral economic theory of demand, creating a need for further research.

abstract: People commonly make decisions and choices that could be delayed until a later time. This investigation examines two factors that may be especially important in these types of decisions: resource stability and comparison target. I propose that these two factors interact to affect whether individuals tend to adopt a delay strategy or whether they engage in more present-oriented strategy. Specifically, this thesis study tested whether picturing one’s ideal led to the adoption of a delay strategy to a greater extent when resources were stable and to a lesser extent when resources were unstable. Participants read a house-hunting scenario in which the market was stable or unstable, and either pictured their ideal house at the beginning of the task or did not. As expected, participants in the stable housing market were more willing to delay choosing a house, though the predicted interaction between resource stability and comparison target did not emerge. Contrary to the predictions, however, participants who pictured their ideal house were more willing to choose a house immediately and were more satisfied with the house they chose. Overall, these findings did not lend support to the main argument of this investigation that picturing one’s ideal would promote a delay strategy under stable resource conditions. The finding that participants preferred immediate choice after picturing their ideal may have interesting implications for persuasion and advertising. / Dissertation/Thesis / Masters Thesis Psychology 2015

The criminal justice system relies heavily on eliciting truthful information from suspects to solve crimes. A paramount problem with this approach involves the questioning of young suspects. Numerous studies support the conclusion that youth is a risk factor for providing false information during police questioning. The present study examined the influence of temporal discounting (the tendency for individual’s behavior to be influenced more strongly by proximal than distal factors; Berns, Laibson, & Loewenstein, 2007; Critchfield & Kollins, 2001) and other developmental factors (i.e., impulse control, future orientation, and sensation seeking) thought to underlie youths’ increased interrogative vulnerability. In line with previous research examining developmental differences in confession decisions, it was predicted that youth would be more likely than adults to provide false admissions to escape the immediate consequences of the situation. Furthermore, it was predicted that youth demonstrating lower impulse control, deficits in future orientation, and increased sensation seeking would be most likely to engage in this tendency. Using a randomized experimental design 205 adult and youth participants were questioned about their engagement in 20 criminal and unethical behaviors. Participants were told responding “yes” or “no” to these questions would have either immediate consequences (i.e., answering a series of repetitive questions) or future consequences (i.e., meeting with a police officer in a few weeks). Analyses revealed evidence of temporal discounting: Participants provided more admissions when denials, rather than admissions, were punished with immediate consequences. Contrary to hypotheses, age, impulse control, future orientation and sensation seeking did not moderate this relationship. Similarly, hypotheses regarding the relationship between age group, impulse control, and future orientation were unsupported. Compared to adults, adolescents did not exhibit less impulse control or future orientation. The current study was the first to experimentally examine factors thought to underlie youths’ increased proclivity to provide false information in interrogation. Justice system involved youth may differ from youth in the current study in key ways that help explain the lack of support for study hypotheses. Because of these differences, it is imperative that future research focuses on youth who are most at risk of encountering the justice system as suspects.

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L’impulsivité décisionnelle est une des multiples dimensions de l’impulsivité. Elle est définie comme la préférence d’une petite récompense immédiate à une grande récompense différée, et dérive du fait que la valeur que l’on attribue à une récompense diminue avec le temps. Quand la dévaluation temporelle est excessive, l’impulsivité de choix devient un symptôme présent dans de nombreuses pathologies. Le striatum, structure cérébrale profonde composée de trois sous-territoires, le noyau caudé, le striatum ventral et le putamen, est un élément clé dans le traitement de l’impulsivité décisionnelle. En effet, il constitue la principale cible de la dopamine, connue pour être un modulateur de l’impulsivité. En lien avec le cortex, le striatum antérieur est impliqué dans les processus de prise de décision, de motivation liée à la récompense, et de sélection de l’action. Nous avons étudié le rôle spécifique des territoires du striatum dans l’impulsivité de choix chez le singe réalisant une tâche de dévaluation temporelle. En utilisant une approche comportementale et d’imagerie, nous avons montré que le noyau caudé était impliqué dans l’impulsivité de choix induite par le Pramipexole, un agoniste dopaminergique des récepteurs D2/3. Dans une seconde étude, nous avons montré que le Méthylphénidate, un inhibiteur de recapture de la dopamine utilisé comme traitement du trouble du déficit attentionnel/hyperactivité, diminuait l’impulsivité décisionnelle en passant par une action sur le striatum ventral. En résumé, ces résultats confirment le rôle de la dopamine dans l’impulsivité décisionnelle et montrent les rôles spécifiques du noyau caudé et du striatum ventral dans les processus décisionnels liés à la dévaluation temporelle / Temporal discounting is the process by which future rewards are subjectively devalued by the decision maker. Impulsive choices, defined as the tendency to prefer small immediate rewards over larger but delayed ones, derive from a high temporal discounting. This particular dimension of impulsivity is a trait of personality, but also a symptom in many neuropsychiatric disorders. It has been shown many times that impulsive choices can be modulated by dopaminergic agents. The dopamine targets the striatum, a cerebral structure linked to cortex, subdivided into three territories – the Ventral Striatum (VS), the Caudate Nucleus (CdN) and the Putamen - and involved in motivation, goal directed behaviors, decision making and action selection. All these functions are involved in impulsive behaviors, although the specific role of each territory in impulsivity remains unknown. Here, using pharmacologic and imaging approaches, we aimed to study the role of the anterior striatum in impulsive choices using the delay discounting task in non-human primates. First, we showed that the CdN supports impulsive choices triggered by Pramipexole, a D2/3 agonist suspected to produce impulsive control disorders. In a second study, we used Methylphenidate, a blocker of dopamine transporter used in attention deficit hyperactivity disorder, and we demonstrated that the VS supports Methylphenidate therapeutic effects on impulsive choices expressed in temporal discounting task. Together, our results show that dopaminergic modulation plays a specific role on the CdN and the VS in the processes of impulsive choices, and suggest a dual action between ventral and dorsal striatal territories

Cette thèse est composée de deux parties. Dans la première partie, nous proposons une théorie pour l'interaction entre l'apprentissage par renforcement et les processus de régulation homéostatique. En fait, la régulation efficace de l'homéostasie interne et la défendre contre les perturbations a besoin des stratégies comportementales complexes pour obtenir des ressources physiologiquement épuisés. À cet égard, il est essentiel que les processus cérébraux de régulation homéostatique et les processus d'apprentissage associatifs travaillent de concert. Nous proposons une théorie computationnelle normative pour régulation homéostatique par l'apprentissage associatif, où la stabilité physiologique et l'acquisition de récompense s'avèrent les mêmes objectifs, réalisables simultanément. En théorie, le cadre résout la question de longue date de la façon dont le comportement manifeste est modulée par l'état interne, et comment les animaux apprennent à agir de manière prédictive pour empêcher des défis homéostasie potentiels (répondre par anticipation). Il fournit en outre une explication normative pour choix intertemporel, aversion au risque, la concurrence entre les systèmes de motivation, et le manque de motivation pour l'injection intraveineuse de produits alimentaires. Neurobiologiquement, la théorie suggère une explication pour le rôle de l'interaction par orexine entre les circuits hypothalamiques et les noyaux dopaminergiques du mésencéphale, comme une interface entre les états internes et les comportements motivés. Dans la deuxième partie de la thèse, nous utilisons le modèle présenté dans la première partie, comme base du développement d'une théorie de la dépendance à la cocaïne. Nous soutenons que la dépendance à la cocaïne provient du système de régulation homéostatique être détourné par les effets pharmacologiques de la cocaïne sur le cerveau. Nous démontrons que le modèle réussit à expliquer une variété des aspects comportementaux et neurobiologiques de la dépendance à la cocaïne , à savoir la grandissant de l’administration de cocaine sous les conditions de long accès a cocaïne, fonction dose-réponse pour la cocaïne , rechute à l'addiction à la cocaïne provoquée par amorçage, et l'interaction entre la disponibilité du récepteur de la dopamine D2 et dépendance à la cocaïne. / This thesis is composed of two parts. In the first part, we propose a theory for interaction between reinforcement learning and homeostatic regulation processes. In fact, efficient regulation of internal homeostasis and defending it against perturbations requires complex behavioral strategies to obtain physiologically-depleted resources. In this respect, it is essential that brains homeostatic regulation and associative learning processes work in concert. We propose a normative computational theory for homeostatically-regulated reinforcement learning (HRL), where physiological stability and reward acquisition prove to be identical objectives achievable simultaneously. Theoretically, the framework resolves the long-standing question of how overt behavior is modulated by internal state, and how animals learn to predictively act to preclude prospective homeostatic challenges (anticipatory responding). It further provides a normative explanation for temporal discounting of reward, and accounts for risk-aversive behavior, competition between motivational systems, taste-induced overeating, and lack of motivation for intravenous injection of food. Neurobiologically, the theory suggests a computational explanation for the role of orexin-based interaction between the hypothalamic circuitry and the midbrain dopaminergic nuclei, as an interface between internal states and motivated behaviors. In the second part of the thesis, we use the HRL model presented in the first part, as the cornerstone for developing an Allostatic Reinforcement Learning (ARL) theory of cocaine addiction. We argue that cocaine addiction arises from the HRL system being hijacked by the pharmacological effects of cocaine on the brain. We demonstrate that the model can successfully capture a wide range of behavioral and neurobiological aspects of cocaine addiction, namely escalation of cocaine self-administration under long- but not short-access conditions, U-shaped dose-response function for cocaine, priming-induced reinstatement of cocaine seeking, and interaction between dopamine D2 receptor availability and cocaine seeking.

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