Theses and Dissertations at Montana State University (MSU)
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Item The impact of trait anxiety and psychosocial stress on sympathetic neural control in humans(Montana State University - Bozeman, College of Letters & Science, 2023) Bigalke, Jeremy Andrew; Chairperson, Graduate Committee: Cara A. Palmer; This is a manuscript style paper that includes co-authored chapters.Anxiety is highly prevalent, and while it is often adaptive, excessive stress and anxiety may predispose individuals to a heightened risk of cardiovascular disease. While excessive activity of the sympathetic nervous system (SNS) may underlie this association, direct measures of muscle sympathetic nerve activity (MSNA) indicate little, if any, alterations in resting sympathetic outflow in individuals with anxiety disorders. Assessment of the relationship between trait anxiety, MSNA, and blood pressure using a large cohort of healthy adults has not yet been conducted. Further, utilization of stress tasks within microneurographic settings that minimize the potential influence of breathing alterations, muscle movement, and other variables on the typically observed inter-individual variability in MSNA responsiveness to mental stress are needed to adequately assess the sole contribution of psychological stress on sympathetic neural activity. In Study 1, the association between trait anxiety, MSNA, and resting blood pressure was assessed in a population of 88 healthy adults, representing the largest study to date pairing trait anxiety with directly recorded sympathetic outflow to the periphery. Our findings indicate an independent relationship between trait anxiety, MSNA, and blood pressure when controlling for both age and sex. In Study 2, we utilized the trier social stress test (TSST) to assess the impact of anticipatory stress on MSNA and blood pressure in 28 healthy adults. Our findings showed that anticipatory stress is associated with increased blood pressure and reduced MSNA. Additionally, this appears to be baroreflex mediated as the magnitude of changes in blood pressure were directly proportional to reductions in MSNA, a relationship that was weakened or nonexistent during the active speech portion of the task. Lastly, anticipatory MSNA responsiveness accurately predicted reactivity to subsequent stress tasks. Together, these studies highlight a key relationship between both chronic, and acute psychological stress and anxiety on sympathoneural function in healthy adults.Item The influence of anxiety, age, and retrieval demands on memory(Montana State University - Bozeman, College of Letters & Science, 2021) Whillock, Summer Rain; Chairperson, Graduate Committee: Michelle L. MeadeThe present dissertation sought to determine if anxiety and hypervigilance can be activated outside the confines of specifically threatening stimuli by examining different situational pressures such as age and retrieval demands. In both experiments, participants studied categorized word lists and were randomly assigned to complete an initial recall test under free, forced, or warning (Exp. 2) recall instructions, followed by a second test under free recall instructions, and a final recognition test. For older adults, forced recall influenced the relationship between trait anxiety and memory such that heightened levels of trait anxiety were associated with greater correct recall and lower false recognition. In contrast, for younger adults, free recall influenced the relationship between memory-specific anxiety, hypervigilance, and memory such that heightened levels of memory-specific anxiety and hypervigilance were associated with lower levels of correct recognition. Further, warning recall influenced the relationship between memory-specific anxiety and memory in young adults, such that heightened levels of memory-specific anxiety were related to greater correct recall at test 1. Across two experiments, results show that it is possible for situational pressures to influence the relationship between anxiety and memory in the absence of specifically threatening stimuli. Additionally, the relationship between anxiety and memory depends on age, the type of anxiety being measured, and the retrieval demands of the task.Item Influence of alpha intrusion during sleep: psychological and physiological implications(Montana State University - Bozeman, College of Letters & Science, 2022) Greenlund, Ian Mark; Chairperson, Graduate Committee: Jason CarterPoor sleep quality is pervasive in developed societies from chronic sleep disturbances or self-imposed sleep curtailment. Sleep disorders like insomnia are associated with regular sleep difficulties including sleep initiation and maintenance. Anxiety and depression exhibit a bidirectional relationship with insomnia, potentially exacerbating poor sleep quality and altering sleep microarchitecture via high frequency electroencephalographic (EEG) intrusion. This includes wake EEG alpha and beta rhythms. An association between high frequency intrusion and psychological dysfunction is present, but little is known regarding alpha and beta frequency intrusion 1) presence with state and trait anxiety symptoms, 2) impact on nocturnal blood pressure regulation, and 3) exacerbation with binge alcohol consumption. In study 1, we examined the relationship between state and trait anxiety severity with alpha and beta intrusion during stage N2 sleep, slow wave sleep (SWS), and rapid eye movement (REM) sleep in 32 participants. We demonstrated that alpha and beta frequency intrusion was augmented in participants with higher state, but not trait anxiety. In study 2, we investigated whether alpha and beta frequency intrusion impacted nocturnal blood pressure regulation in 36 young, healthy adults. Overall, systolic arterial pressure (SAP) dipping and cardiovagal baroreflex sensitivity (cvBRS) were not related alpha and beta spectral power during sleep. In study 3, we explored whether binge alcohol consumption could further exacerbate alpha and beta intrusion during sleep in higher state and trait anxiety participants in 31 participants. A secondary aim of this study was to determine if high frequency spectral power was different between sexes following alcohol consumption. Following laboratory familiarization night (study 2), participants were tested twice, ~1 month apart in a randomized, crossover design consuming either an alcohol dose (study 3) based upon biological sex and body weight, or fluid control beverage (study 1) two hours prior to lights out. Alpha and beta spectral power was not different between lower and higher state and trait anxiety, but was augmented in females compared to age-matched males. Collectively, these studies are the first investigate alpha intrusion presence with state and trait anxiety symptoms, impact on nocturnal blood pressure regulation, and sex specific exacerbation following alcohol consumption.Item On life and death: vitality, mortality salience, and worldview defense(Montana State University - Bozeman, College of Letters & Science, 2018) Sanders, Courtney Suzanne; Co-Chairs, Graduate Committee: Jessi L. Smith and Ian HandleyHuman experience is most notably characterized by feeling or being 'alive.' However, according to Terror Management Theory (TMT), humans possess the awareness of their own mortality, and the resulting potential for existential anxiety produced by mortality salience might interact with vitality, or the subjective experience of enthusiasm and aliveness. The construct of vitality includes attributes such as resilience and self-esteem, which is why vitality was predicted to be a more holistic approach to dealing with the potential death anxiety triggered by mortality salience. TMT operates under the notion that anxiety from the realization of one's mortality is managed in part by embracing cultural worldviews, or psychological systems that provide life with meaning. When one fails to employ such a psychological buffer in the face of mortality concerns, this results in an increased defensiveness toward those who threaten or violate cultural worldviews. As such, Study 1 hypothesized that, under mortality salience, those low in a self-report measure of vitality would react more defensively to a moral transgressor than those high in vitality. To test this prediction, 176 individuals completed a self-report measure of vitality and were randomly assigned to provide a written response to two open-ended questions about their own death or to two parallel questions about watching television. Then, following a necessary delay, all participants provided judgments of moral transgressors; previous work shows that reminders of death lead to harsher judgments on this scale. No evidence for buffering was found in the results of Study 1, and findings failed to replicate past TMT research. To better understand vitality as a construct, Study 2 randomly assigned 90 individuals to view photos of either natural, outdoor scenes, or photos of built, outdoor scenes and were subsequently measured on vitality. Results of Study 2 conceptually replicated findings of previous work illustrating that those exposed to photos of nature reported higher levels of vitality than those exposed to photos of built environments. These findings strengthen evidence of the vitalizing effects of nature and supports contact with nature as a potential factor in future studies on vitality. Alternative explanations and implications are discussed.Item The search for moderation: does anxiety enhance the unconscious thought advantage?(Montana State University - Bozeman, College of Letters & Science, 2017) Whillock, Summer Rain; Chairperson, Graduate Committee: Ian M. HandleyWhen people face a large amount of information on which to base a decision, common sense suggests that they should slowly and deliberatively think about that information. However, Unconscious Thought Theory (UTT) suggests that a slow yet unconscious mechanism can process complex information and output decisions that rival, and perhaps exceed, the quality of decisions that result from deliberative thought (Dijksterhuis & Nordgren, 2006). However, this idea is controversial and research into UTT reveals that an unconscious thought advantage (UTA) over conscious thinking is small and manifests unreliably (Nieuwenstein et al., 2015; Strick et al., 2011). The aim of this thesis was to identify and test a potential moderator of the UTA. Logically, situations that hinder conscious thought but leave unconscious thought relatively unaffected should enhance the UTA. The Attentional Control Theory (ACT) offers one such situation, that anxiety compromises conscious processes that rely upon attentional control and working memory (Eysenck, Derakshan, Santos, & Calvo, 2007). Because conscious thought relies heavily on working memory relative to unconscious thought, experiencing anxiety may lead the two thought processes to diverge. Specifically, anxiety should negatively influence conscious thought but not significantly influence unconscious thought. In the present study, participants viewed information about roommate candidates and made judgments after a period of either distraction or focused deliberation, while under calm or anxious conditions. Results did not support the hypothesis that the experience of anxiety would increase the UTA; participants performed comparably in the conscious thought and unconscious thought conditions. Further, participants in the conscious thought condition performed better under anxious compared to calm conditions. Exploratory analyses and future directions are discussed.Item Evaluation of innate anxiety in Ta1tubulin-cre/Ikbkap -/- mice : the effects of the IKAP protein deletion from the central nervous system(Montana State University - Bozeman, College of Letters & Science, 2014) Kujawa, Katharine Jacobs; Chairperson, Graduate Committee: A. Michael BabcockFamilial Dysautonomia (FD) is a hereditary sensory and autonomic neuropathy (Type III) marked by a mutation within the Ikbkap gene encoding the IKAP protein. This mutation is prevalent in 99% of the clinical FD population (Shobhat & Halpern, 2010). Symptoms include emotional labiality, cardiovascular instability, vomiting crises and decreased pain and temperature sensation. One clinical symptom associated with FD is increased anxiety in response to stressful situations (Axelrod, 2006). Dr. Lefcort in the department of Biology and Neuroscience at Montana State University has generated a novel mouse model of FD in which Ikbkap is selectively deleted from CNS neurons. The present study characterized the expression of anxiety behaviors in this mouse model using a standard elevated plus maze task. It was observed that FD mice spent significantly more time in the open arms relative to control mice. These mice exhibited significantly greater instances of unprotected head-dipping and fewer protected head-dipping compared to controls. The FD mice also traveled slower than controls but time immobile and distances traveled were found to be similar. These data suggest that the FD mice presented as less anxious, an observation that is inconsistent from observations in the clinical population. Additional research aimed at characterizing the behavioral phenotype of these mice is under investigation.