Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Social behaviours have been widely studied in behavioural economics and psychology. However, the origins of these behaviours in the brain are poorly understood. In this dissertation I will discuss two main avenues of study which constituted separate projects during my PhD candidacy. The first section contains experiments in which I collaborated with Dr Raymundo Báez-Mendoza on the topic of inequity. The second part includes a study on coordination and cooperation behaviour in macaques. Inequity is a concept ubiquitous in daily life. It is the difference between one’s own reward and that of another. There have been several studies that have suggested inequity affects brain activity. However, few studies have touched upon how this parameter is incorporated in neuronal activity. In the experiments that will be described here, monkeys (Macaca mulatta) performed actions to obtain rewards for both themselves and another. The level of inequity in these rewards was manipulated by varying the magnitude of own and other’s rewards. We then proceeded to study neuronal activity by means of single neuron recordings in the striatum of two macaques. We found that inequity modulated task related activity in about 32% of recorded striatal neurons. In addition to this study on inequity we also recorded some sessions in which one of the animals made choices with varying rewards for self and other. From these results, I attempted to characterise behaviour with regards to own reward and inequity in choice situations. Inequity has been considered a contributing factor in explaining cooperation behaviour. Coordination and cooperation are important and frequently observed behaviours. To study coordination and cooperation, I designed an experiment in which the combination of two monkeys’ choices determined the rewards for both animals. In this dissertation I attempt to address how the animals perform combined choices (playing together vs. alone) as well as the nature of their behaviour (e.g. pro-social vs. self-interested). The aim of this work was to characterise what type of information the animals use to solve these tasks. This is vital if one is to study these concepts in the brain using macaques as a model. In summary, this work contributes to a better understanding of social behaviour and provides an example of how this social behaviour is computed in the brain.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 76-84).

The ability to infer the invisible displacement of objects has long been thought to elude most species with the exception of humans and great apes. However, in recent years, a number of researchers have proposed that this elusive capacity, rather than reflecting profound differences in the conceptual abilities of monkeys and other nonprimates, may instead reflect differences in processing capacities (such as inhibition and working memory). This thesis investigated knowledge of occluded object movements involving gravity, in rhesus and stumptail macaques (Macaca mulatta and arctoides), and two- and three-year-old children (Homo sapiens). In the first part of the thesis, using manual search tasks, a behavioural analysis revealed a number of biases that influence search on invisible displacement tasks, but also showed that contrary to the contentions of some authors, these biases do not mask the existence of correct representations. One study did reveal how seemingly mundane differences between tasks might lead to markedly different patterns of search and emergence of biases. In the second part of the thesis, in the first direct test of the prediction-postdiction hypothesis, an analysis of anticipatory eye gaze suggested that an inability to predict the location of an object does not account for the looking-searching dissociation that has become so prevalent in both the developmental and comparative literature. In attempting to bring together the findings from all the chapters, a framework is suggested in which representations are viewed as differing in strength such that the strength of a representation may determine whether or not a pre-existing bias surfaces in behaviour.

This thesis deals with two main issues: personality (stable individual differences in behavior) and behavioral endocrinology (or socioendocrinology) in nonhuman primates. The first part of the thesis comprises of two primate personality studies of two species: Hanuman langurs and Barbary macaques. Two basic methods of animal personality research (behavioral coding and trait rating) were compared. Stability of personality assessments has been demonstrated. Social rank of individuals was used to validate the questionnaire ratings as well as to illustrate the independence and stability of personality assessment. The second part of the thesis is based on two studies investigating hormone levels in female Barbary macaques. The relationship between cortisol, testosterone, dominance hierarchy and behavior was investigated. And the possible effect of maternal hormone levels around the time of conception on the sex of an infant was evaluated.

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(医科学) / 甲第21693号 / 医科博第97号 / 新制||医科||7(附属図書館) / 京都大学大学院医学研究科医科学専攻 / (主査)教授 中川 一路, 教授 朝長 啓造, 教授 西渕 光昭 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Typically, rhesus mothers begin rejecting their infants' attempts to nurse when the infants are approximately three months of age in order to begin the process of weaning. A small subgroup of mothers begin rejecting their infants earlier, at one or two months of age, typically before infants seek and maintain independence from their mother. The effects of this early maternal rejection on the development of infants and some potential factors that contribute to premature maternal rejection were explored in this study. Infants who were rejected early were hypothesized to subsequently spend less time in positive contact with their mother, have lower activity levels, were groomed less by their mother and, as a consequence of the maternal rejections, display a higher frequency of aggression toward other group members when compared to infants experiencing maternal rejection after the age-typical, three months of age. Mothers who were primiparous and/or had a poor early-rearing experience were hypothesized to be more likely to reject their infants prematurely. Consistent with these hypotheses, infants who were rejected early spent less time on their mother's ventrum and were groomed less by their mother, suggesting that early maternal rejection may lead to less positive mother-infant interactions and a more distant mother-infant relationship. Infants rejected early were also more likely engage in aggression. Given the punitive nature of the maternal rejection, the results suggest that aggression is transmitted from mother to infant through their interactions. Prematurely rejected infants were found to spend significantly more time in a passive, withdrawn behavioral state. When assessing the causes of premature rejections, primiparous mothers were not more likely to prematurely reject their infants, indicating that premature rejection was not simply a lack of experience with an infant. There was evidence that the mothers engaging in early rejection had poor early-rearing experiences, with surrogate-peer-reared mothers showing more early rejections than those who were reared by an adult female, and with mothers who were peer-reared having higher rates of rejection overall. The present results suggest that early rejection is associated with more difficult mother-infant relationships and may lead to increased likelihood of aggression in infants.

As we interact with the world, we must decide what to do next based on previously acquired and incoming information. The study of perceptual decision-making uses highly controlled sensory stimuli and exploits known properties of sensory and motor systems to understand the processes that occur between sensation and action. Even these relatively simple decisions invoke operations like inference, integration of evidence, attention, appropriate action selection, and the assignment of levels of belief or confidence. Thus, the neurobiology of perceptual decision-making offers a tractable way of studying mechanisms that play a role in higher cognitive function. The controlled nature of perceptual decision-making tasks allows an experimenter to infer the latent processes that give rise to a decision. For example, many decisions are well-described by a process of bounded evidence accumulation, in which sensory evidence is temporally integrated until a terminating threshold is exceeded. This thesis improves our understanding of how these latent processes are implemented at the level of neurobiology. After an introduction to perceptual decision-making in Chapter 1, Chapter 2 focuses on the behavioral observations that corroborate whether a subject’s decisions are governed by bounded evidence accumulation. Through simulations of multiple decision-making models, I show that several commonly accepted signatures of evidence accumulation are also predicted by models that do not posit evidence accumulation. I then dissect these models to uncover the features that underlie their mimicry of evidence accumulation. Using these insights, I designed a novel motion discrimination task that was able to better identify the decision strategies of human subjects. In Chapter 3, I explore how the accumulation of evidence is instantiated by populations of neurons in the lateral intraparietal area (LIP) of the macaque monkey. Recordings from single LIP neurons averaged over many decisions have provided support that LIP represents the accumulation of noisy evidence over time, giving rise to diffusion dynamics. However, this diffusion-like signal has yet to be observed directly because of the inability to record from many neurons simultaneously. I used a new generation of recording technology—neuropixels probes optimized for use in primates—to record simultaneously from hundreds of LIP neurons, elucidating this signal for the first time. Through a variety of analyses, I show that the population’s representation of this signal depends on a small subset of neurons that have response fields that overlap the choice targets. Finally, in Chapter 4, I discover a neural mechanism in the midbrain superior colliculus (SC) involved in terminating perceptual decisions. I show that trial-averaged activity in LIP and SC is qualitatively similar, but that single-trial dynamics in each area are distinct. Unlike LIP, SC fired large bursts of activity at the end of the decision, which were sometimes preceded by smaller bursts. Through simultaneous recordings, I uncover the aspects of the diffusion signal in LIP that are predictive of bursting in SC. These observations led me to hypothesize that bursts in SC are the product of a threshold computation involved in terminating the decision and generating the relevant motor response. I confirmed this hypothesis through focal inactivation of SC, which affected behavior and LIP activity in a way that is diagnostic of an impaired threshold mechanism. In total, this work improves our ability to identify the hidden, intermediate steps that underlie decisions and sheds light on their neural basis. All four chapters have been published or posted as separate manuscripts (Steinemann et al., 2022; Stine et al., 2020; Stine et al., 2022; Stine et al., 2019).

No description available.