Thesis (Ph. D.)--University of Wisconsin--Madison, 1984. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 216-254).

Thesis (M.A.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 28, 2007) Includes bibliographical references.

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Flora et al. (1992, 2003) found that aversive stimulation in the form of intense noise or cold water increased the number of impulsive responses when presented concurrently to a choice task. Hurtado-Parrado et al. (2023) systematically replicated Flora et al.’s (1992) study and found that adding a visual matching-to-sample task with images from the International Affective Picture System (IAPS; Lang et al., 2008) produced a higher number of responses on the impulsive option (Sooner-Smaller - SS) near indifference, as compared to a No-images group who showed preference for the self-controlled option (Larger-Later - LL). They also found that the overall rate of correct matching across all conditions was low. Hurtado-Parrado et al. proposed that the potential aversive or distractive effect of frequent failure during the matching task, and thus frequent point loss, could have had a similar effect of the cold pressor and aversive noise on impulsive responses (SS). The present study systematically replicated Hurtado-Parrado et al.’s (2023) experiment to evaluate the effects on SS responses of different rates of correct responses during the matching-to-sample component of the experimental task across four conditions: No-images, 0%, 60%, and 100% correct matching. Fourteen college students were exposed to all conditions in a within-subject design. The prediction that the number of SS responses would increase as the percentage of correct responses in the matching task decreased was not confirmed. Participants developed one of three choice patterns during the first no matching condition (No Images), namely preference for the self-control or impulsive option, or indifference. Subsequent changes in percentages of correct matching did not affect indifference or self-control preference, but contrary to the predicted effect, decreased impulsive responses towards indifference or self-control preference. These findings are discussed in terms of possible effects of (a) motivating operations (e.g., monetary compensation in the present study differed from previous studies by Flora et al., 1992, 2003 and Hurtado-Parrado et al., 2023); (b) extra-experimental contingencies (e.g., several students participated during the last days of the semester trying to complete course credits in small amount of time); (c) rule-construction and rule-following behavior (e.g., rule-construction during the No images condition could explain insensitivity to subsequent changes in percentage of correct matching), and (d) local and molar reinforcement rate variations across conditions (e.g., an increase in rates of point gain, and thus increase in their reinforcement value, could explain the reduction in initial impulsive preference of some participants when correct matching was later manipulated).

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Incidence of suicide has been shown to increase dramatically during adolescence. Despite an established pattern of depression and hopelessness leading to suicide in adults, no such pattern emerges in the adolescent literature. Recent investigations suggest that impulsivity may play a key role in adolescent suicide attempts. This study examined the role of impulsivity in adolescent suicidal gestures, as well as the relationships among demographic variables, anger expression, impulsivity, and suicidal behavior. A total of 100 participants (ages 11-17; 71 females and 29 males) were recruited from 2 inpatient crisis centers for children. The Children's Depression Inventory, Hopelessness Scale for Children, Adolescent Behavior Checklist, Pediatric Anger Expression Scale, and Suicide Intent Scale were administered to inpatients, and demographic information was obtained (age, gender, ethnicity, income, and structure of family). It was hypothesized that patterns of depression, anger, hopelessness, and impulsivity would vary by age, gender, ethnicity, and suicidality (e.g., suicidal gesture vs. no gesture). The large majority of hypotheses were not supported. Results are explained in terms of alternative theories for the role of impulsivity in adolescent suicidal gestures.

Global cerebral ischemia (GCI) in rats has been shown to promote exploration of anxiogenic zones of the Elevated-Plus Maze (EPM) and Open Field Test (OFT). This study investigated changes in impulsive choice and/or defensive responses as possible contributors of heightened anxiogenic exploration observed after ischemia. Impulsivity was assessed using delay discounting (DD) paradigms, while the Predator Odour Test (PO) served to assess changes in defensive responses towards a naturally aversive stimulus. Male Long Evans rats underwent 9 days of autoshaping training and 24 days of DD training prior to GCI or sham surgery (n= 9/group). Post-surgery, rats completed the OFT, EPM, and PO, followed by 6 days of DD sessions. Blood droplets served to evaluate corticosterone secretion associated with PO exposure. With impulsivity being regulated through mesocorticolimbic monoaminergic pathways, we also characterized post-ischemic changes in the expression of dopamine D2 receptors (DRD2), dopamine transporters (DAT), and ΔFosB in the basolateral amygdala (BLA), nucleus accumbens core (NAcC) and shell (NAcS), and ventromedial prefrontal cortex (vmPFC) using immunohistofluorescence. Our findings revealed no impact of GCI on delay discounting rates, while PO approach behaviours were minimally affected. Nonetheless, GCI significantly reduced DRD2 and ΔFosB-ir in the NAcS and NAcC, respectively, while DAT-ir was diminished in both NAc subregions. Collectively, our findings refine the understanding of cognitive-behavioural and biochemical responses following stroke or cardiac arrest. They support significant alterations to the dopaminergic mesocorticolimbic pathway after ischemia, which are not associated with altered impulsive choice in a DD task but may influence locomotor exploration of the OFT and EPM.

Mathematical modeling of dynamical systems plays a central roll in science and engineering. This thesis is concerned with the process of finding a mathematical model, and it is divided into two parts - one that concentrates on nonlinear system identification and another one where an impulsive model of testosterone regulation is constructed and analyzed. In the first part of the thesis, a new latent variable framework for identification of a large class of nonlinear models is developed. In this framework, we begin by modeling the errors of a nominal predictor using a flexible stochastic model. The error statistics and the nominal predictor are then identified using the maximum likelihood principle. The resulting optimization problem is tackled using a majorization-minimization approach, resulting in a tuning parameter-free recursive identification method. The proposed method learns parsimonious predictive models. Many popular model structures can be expressed within the framework, and in the thesis it is applied to piecewise ARX models. In the first part, we also derive a recursive prediction error method based on the Hammerstein model structure. The convergence properties of the method are analyzed by application of the associated differential equation method, and conditions ensuring convergence are given. In the second part of the thesis, a previously proposed pulse-modulated feedback model of testosterone regulation is extended with infinite-dimensional dynamics, in order to better explain testosterone profiles observed in clinical data. It is then shown how the analysis of oscillating solutions for the finite-dimensional case can be extended to the infinte-dimensional case. A method for blind state estimation in impulsive systems is introduced, with the purpose estimating hormone concentrations that cannot be measured in a non-invasive way. The unknown parameters in the model are identified from clinical data and, finally, a method of incorporating exogenous signals portraying e.g. medical interventions is studied.

Master of Science / Department of Psychological Sciences / Kimberly Kirkpatrick / Obesity is associated with impaired decision making across a range of choice behaviors including impulsive choice behavior and incentive value. Given that people make approximately 200 food choices each day (Wansink & Sobal, 2007), it is essential to better understand this relationship between obesity and impaired decision making. As such, the current study sought to understand how long-term exposure to diets high in processed fat and sugar affected impulsive choice behavior, devaluation, and food preferences. The results suggested that diet affects impulsive choice behavior. Rats exposed to diets high in processed fat or sugar were more sensitive to changes in delay, a marker of impulsivity. Results from the bisection task indicated that the diet-induced impulsivity could be a result of poor time discrimination. In addition, there were differences in incentive value. All rats successfully devalued rewards, but the high-fat and high-sugar group showed lower overall levels of responding. Further, diet-induced impulsivity could lead to overconsumption of high-fat and high-sugar foods due to differences in food preference. After 9 months on the diets, rats fed a chow and high-sugar diet displayed a sugar preference, while the rats fed a high-fat diet displayed a fat preference. Together, the results suggest that the alterations in impulsive choice and incentive valuation induced by diet could make individuals vulnerable to overeating, and thus obesity, as well as other disorders that are characterized by impulsive choice and deficits in incentive valuation.