Due to abnormal functioning of the brain’s reward and prediction system patients with schizophrenia spectrum disorders are thought to assign salience to non-relevant objects and events and to form context-inappropriate associations. The brain’s ventral striatum is critical in the formation of associations, and aberrant associations are believed to create delusional content during psychosis. The study wanted to examine the neural response, particularly in the ventral striatum, combined with subjective reports as patients learn associations in an aversive Pavlovian conditioning paradigm. The stimuli were randomized and involved circles of different colors. The conditioned stimuli (CS+) was followed by an unconditioned stimuli (US), consisting of an unpleasant sound, in 50% of events. The unconditioned (CS-) stimuli was followed by a low, not unpleasant sound in 50% of events. The degree of striatal activation was thought to be associated with the severity of patient’s illness. Functional magnetic resonance imaging (fMRI) blood-oxygen-level dependent (BOLD) responses were examined in eleven unmedicated non-institutionalized patients with schizophrenia spectrum disorders and 15 matched healthy controls. No significant within group differences in neural or subjective response to the [CS+ > CS-] contrast were found. No significant associations between severity of illness and degree of striatal activation in response to CS+ or CS- were found. Significant differences in neural activation for the [CS+ > CS-] contrast were found in the ventral striatum, the right inferor frontal gyrus, and the right angular gyrus, with patients exhibiting stronger activation compared to controls. The results and implications are discussed along with suggestions for future research.

Kahneman and Tversky (1979) first demonstrated that when individuals decide whether or not to accept a gamble, potential losses receive more weight than possible gains in the decision. This phenomenon is referred to as loss aversion. We investigated how loss aversion in risky financial decisions is influenced by sudden changes to wealth, employing both behavioral and neurobiological measures. We implemented an fMRI experimental paradigm, based on that employed by Tom et al. (2007). There are two treatments, called RANDOM and CONTINGENT. In RANDOM, the baseline setting, the changes to wealth, referred to as wealth shocks in economics, are independent of the actual choices participants make. Under CONTINGENT, we induce the belief that the changes in income are a consequence of subjects' own decisions. The magnitudes and sequence of the shocks to wealth are identical between the CONTINGENT and RANDOM treatments. We investigated whether more loss aversion existed in one treatment than another. The behavioral results showed significantly greater loss aversion in CONTINGENT compared to RANDOM after a negative wealth shock. No differences were observed in the response to positive shocks. The fMRI results revealed a neural loss aversion network, comprising the bilateral striatum, amygdala and dorsal anterior cingulate cortex that was common to the CONTINGENT and RANDOM tasks. However, the ventral prefrontal cortex, primary somatosensory cortex and superior occipital cortex, showed greater activation in response to a negative change in wealth due to individual's own decisions than when the change was exogenous. These results indicate that striatum activation correlates with loss aversion independently of the source of the shock, and that the ventral prefrontal cortex (vPFC) codes the experimental manipulation of agency in one's actions influencing loss aversion.

Numerous social and educational psychologists propose that intrinsic motivation generated by personal interests and spontaneous satisfactions is qualitatively different from extrinsic types of motivation generated by external compensations and also that intrinsic motivation is more beneficial to learning than extrinsic types of motivation. However, in the field of neuroscience, intrinsic motivation has been little studied while extrinsic types of motivation (e.g., incentive motivation) have been thoroughly studied. The purpose of the present studies was to expand the neural understanding of motivation to include intrinsic motivational processes. To do so, a series of three event-related functional magnetic resonance imaging (fMRI) studies were conducted. Study 1 and Study 2 compared the neural activities when participants decided to act for intrinsic reasons (i.e., self-determined volitional and agentic behavior) versus when they decided to act for extrinsic reasons (i.e., non-self-determined volitional and agentic behavior). Both studies showed that the anterior insular cortex, known to be related to a sense of agency, was more activated during self-determined behavior associated with intrinsic reasons for acting while the posterior parietal regions (e.g., posterior cingulate cortex, angular gyrus), known to be related to a sense of a loss of agency, were more activated during non-self-determined behavior associated with extrinsic reasons for acting. These findings confirm the existence of neural-based intrinsic motivational processes, differentiate intrinsic motivation from incentive motivation, and document the important neural activities which function for generating self-determined agentic action. Study 3 examined these same neural activities as participants engaged in interesting and uninteresting versions of two experimental tasks. Results confirmed the results of the earlier two studies, as the anterior insular cortex was more recruited when participants performed the interesting, but not the uninteresting, version of the tasks. Results also extended the findings from Studies 1 and 2 in an important way in that the ventral striatum, a well-known brain region for reward processing, was more activated when participants performed the interesting, but not the uninteresting, version of the experimental tasks. These findings suggest that intrinsic motivation is generated based on the feeling of intrinsic need satisfaction (from anterior insular cortex activations) and the feeling of reward (from ventral striatum activations). Overall, the present research established three new findings: (1) the neural bases of intrinsic motivation lies largely in increased anterior insular cortical activities; (2) when people made decisions about self-determined intrinsically-motivated behavior, they show enhanced insular cortical activities and suppressed posterior parietal cortical activities; and (3) when people engaged in actual self-determined intrinsically-motivated behavior, they show enhanced insular cortical and ventral striatal activities. In establishing these new findings, the paper introduces a new area of study for motivational neuroscience--namely, intrinsic motivation.

abstract: Intermittent social defeat stress induces psychostimulant cross-sensitization, as well as long-lasting social avoidance behavior. Previous data reveal heightened expression of AMPA receptor (AMPAR) GluA1 subunits in rat ventral tegmental area (VTA), which occurs concurrently with social stress-induced amphetamine (AMPH) cross-sensitization. These studies described herein examined whether VTA GluA1 AMPARs are important for the behavioral consequences of social stress and investigated the role of the infralimbic (IL) to VTA pathway in the induction of these responses. Functional inactivation of GluA1 in VTA DA neurons prevented stress-induced AMPH sensitization without affecting social avoidance behavior, while GluA1 overexpression in VTA DA neurons mimicked the effects of stress on AMPH sensitization. Female rats were more sensitive to the effects of stress on AMPH administration than males, specifically during proestrus/estrus, which is characterized by higher circulating estradiol. Fluorescent immunohistochemistry revealed that females expressed higher GluA1 in VTA DA neurons as a result of intermittent social defeat stress, independent of estrus stage; by contrast, females during proestrus/estrus displayed higher tyrosine kinase receptor type 2 (TrkB) expression, which is the receptor for brain derived neurotrophic factor (BDNF), in VTA DA neurons, independent of stress exposure. Functional inactivation of GluA1 in VTA DA neurons prevented stress-induced AMPH sensitization and overexpression mimicked the effects of stress on AMPH sensitization. This suggests that BDNF-TrkB signaling may work concomitantly with GluA1 signaling in the VTA to drive sex-dependent differences in stress-induced locomotor sensitization effects. Optogenetic inhibition of the IL-VTA pathway in male rats prevented stress-induced AMPH sensitization compared to control animals. In addition, fluorescent immunohistochemistry displayed less Fos labeling in the nucleus accumbens (NAc) of rats with IL-VTA light inhibition compared to control animals. This suggests that the IL-VTA pathway plays a critical role in the induction of stress-induced sensitivity to AMPH, and blocking this pathway prevents mesolimbic DA signaling to the NAc. We conclude that IL glutamate projections onto GluA1-homomeric AMPA receptors in VTA DA neurons play a critical role in driving the stress-induced sensitization response in males and females. Therefore, GluA1 VTA DA neurons could potentially be a therapeutic target to prevent stress-induced drug susceptibility in the future. / Dissertation/Thesis / Doctoral Dissertation Neuroscience 2020

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Cette thèse présente une approche probabiliste de la modélisation de la mécanique des matériaux et des structures. Le dimensionnement est influencé par l'incertitude des paramètres d'entrée. Le travail est interdisciplinaire et les méthodes décrites sont appliquées à des exemples de biomécanique et de génie civil. La motivation de ce travail était le besoin d'approches basées sur la mécanique dans la modélisation et la simulation des implants utilisés dans la réparation des hernies ventrales. De nombreuses incertitudes apparaissent dans la modélisation du système implant-paroi abdominale. L'approche probabiliste proposée dans cette thèse permet de propager ces incertitudes et d’étudier leurs influences respectives. La méthode du chaos polynomial basée sur la régression est utilisée dans ce travail. L'exactitude de ce type de méthodes non intrusives dépend du nombre et de l'emplacement des points de calcul choisis. Trouver une méthode universelle pour atteindre un bon équilibre entre l'exactitude et le coût de calcul est encore une question ouverte. Différentes approches sont étudiées dans cette thèse afin de choisir une méthode efficace et adaptée au cas d’étude. L'analyse de sensibilité globale est utilisée pour étudier les influences des incertitudes d'entrée sur les variations des sorties de différents modèles. Les incertitudes sont propagées aux modèles implant-paroi abdominale. Elle permet de tirer des conclusions importantes pour les pratiques chirurgicales. À l'aide de l'expertise acquise à partir de ces modèles biomécaniques, la méthodologie développée est utilisée pour la modélisation de joints de bois historiques et la simulation de leur comportement mécanique. Ce type d’étude facilite en effet la planification efficace des réparations et de la rénovation des bâtiments ayant une valeur historique. / This thesis presents a probabilistic approach to modelling the mechanics of materials and structures where the modelled performance is influenced by uncertainty in the input parameters. The work is interdisciplinary and the methods described are applied to medical and civil engineering problems. The motivation for this work was the necessity of mechanics-based approaches in the modelling and simulation of implants used in the repair of ventral hernias. Many uncertainties appear in the modelling of the implant-abdominal wall system. The probabilistic approach proposed in this thesis enables these uncertainties to be propagated to the output of the model and the investigation of their respective influences. The regression-based polynomial chaos expansion method is used here. However, the accuracy of such non-intrusive methods depends on the number and location of sampling points. Finding a universal method to achieve a good balance between accuracy and computational cost is still an open question so different approaches are investigated in this thesis in order to choose an efficient method. Global sensitivity analysis is used to investigate the respective influences of input uncertainties on the variation of the outputs of different models. The uncertainties are propagated to the implant-abdominal wall models in order to draw some conclusions important for further research. Using the expertise acquired from biomechanical models, modelling of historic timber joints and simulations of their mechanical behaviour is undertaken. Such an investigation is important owing to the need for efficient planning of repairs and renovation of buildings of historical value.

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京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19272号 / 医博第4036号 / 新制||医||1011(附属図書館) / 32274 / 京都大学大学院医学研究科医学専攻 / (主査)教授 高橋 淳, 教授 村井 俊哉, 教授 渡邉 大 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20076号 / 医博第4169号 / 新制||医||1018(附属図書館) / 33192 / 京都大学大学院医学研究科医学専攻 / (主査)教授 影山 龍一郎, 教授 斎藤 通紀, 教授 高橋 淳 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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