Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    CORTICAL AND STRIATAL MECHANISMS OF VALUE-BASED DECISION-MAKING AND THEIR DISRUPTION IN ADDICTION
    (2022) Hadfield, Heather; Roesch, Matthew R; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    For decisions both great and small, the brain utilizes an extensive network that integrates value assessment, reward prediction, and motivation to quickly and efficiently select the most beneficial option while minimizing aversive consequences for ourselves. Numerous psychiatric conditions, in particular drug addiction, can disrupt this network and impair decision-making behavior. It is therefore important to understand the neural underpinnings of decision-making and how neural activity and its associated behavior are disrupted by drugs of abuse. My dissertation will expand on current studies of this circuitry by examining epigenetic and neurophysiological mechanisms of value-based decision-making within two regions of the brain. In my final aim, I explore a new behavioral assay that may be used to study these and other regions relevant for value-based decision-making in the context of another complex behavior.In my first aim, I have recorded from single neurons in the rat dorsal lateral striatum (DLS) after overexpressing histone deacetylase 5 (HDAC5), an epigenetic enzyme implicated in incubation of craving, in the dorsal striatum (DS). In my second aim I used pharmacological lesion and single-neuron recording combined with cocaine self-administration techniques to study anterior insula, a region well-known for combining internal and external experience but largely under-studied in the context of higher cognitive processes. These studies were conducted while rats performed an odor-guided decision-making task in which the value of rewards were manipulated by either the delay to or the size of the reward across a series of trial blocks. I have found overexpression of HDAC5 in DS promoted inflexible, faster, and automatic behavior in the decision-making task while increasing DLS’s response to reward cues- similar to previous studies examining DLS activity and behavior after cocaine self-administration. In my studies of insula, I found recording from this region novel, global signals of reward value that seemed to reflect the overall structure of the behavioral task. Following cocaine-exposure, these signals were diminished while immediate rewards were over-represented on a trial-by-trial basis, leading to steeper discounting of delayed rewards. Additional studies lesioning this region promoted faster reaction times and increased goal-directed behavior. Together, these results provide insights into how drugs of abuse may impair behavioral flexibility and the tracking of long-term changes in reward from multiple mechanisms. However, it is still unknown how these changes in value assessment give rise to complex impairments of behavior. As a first step to addressing this issue, I used a new task to examine how chronic drug use- which disrupts both neural signals in the corticostriatal circuit and epigenetic enzymes- also impairs the complex ability to delay gratification. This final study replicated well-established findings of drug-induced reversal-learning impairment, but surprisingly did not alter decision-making. This collection of work demonstrates the complexity with which drug exposure alters neural circuitry and value-based decision-making, and additionally shows the importance of utilizing complex behavioral assays to explore the relationship between brain and behavior.
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    Sleep throughout the alcoholism recovery process: a mixed methods examination of individuals' experiences transitioning from an inpatient research facility providing rehabilitation treatment to the community
    (2015) Brooks, Alyssa Todaro; Beck, Kenneth; Public and Community Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Despite research establishing the relationship between sleep disturbances and alcohol use, there is no clear understanding or model for what occurs once individuals who seek inpatient alcoholism treatment are discharged from rehabilitation facilities and attempt to integrate back into their homes and communities. This study used a mixed methods approach to assess individuals' perceptions of and experiences with sleep throughout the process of alcohol rehabilitation and to explore associations between sleep-related beliefs/behavior, sleep quality, and relapse. The Social Cognitive Theory (SCT), which posits that personal factors, the environment, and human behavior exert influence upon each other through reciprocal determinism, was used as the underlying theory for this study. Constructs from the SCT were measured directly in this study using both quantitative and qualitative approaches in a convergent parallel design to study the following aims: a) to assess perceptions of and experiences with sleep during alcohol rehabilitation, b) to describe sleep patterns, perceptions, and beliefs among individuals who are alcohol-dependent throughout the transition from a clinical research facility providing rehabilitation treatment back to the community, and c) to assess whether sleep-related beliefs and/or behavior are associated with sleep quality or alcohol relapse. Data were collected from a cohort of clinical research participants enrolled on an inpatient alcohol treatment protocol (n=32). Sleep was assessed quantitatively and qualitatively within one week of discharge from the inpatient facility and again four to six weeks post-discharge. Results indicated a prevalence of sleep disturbances throughout the process of rehabilitation. Self-efficacy for sleep was associated with better sleep quality at both time points. Thematic analyses of interview transcripts yielded overarching themes of sleep-related beliefs/behavior, sleep environments, stress related to transitions, and self-medication. This study demonstrates a prevalence of sleep disturbances among individuals undergoing alcohol treatment and relationships between SCT constructs and sleep quality. The period of transition from inpatient to outpatient represents a time of change, thus future behavioral sleep intervention efforts in this population may benefit from addressing underlying sleep-related beliefs and behaviors to improve sleep quality and encourage healthy and sober living.
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    The Issue of Mirrors
    (2011) Sowash, Shenandoah; Weiner, Joshua; English Language and Literature; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This collection is, more than anything, a series of self-portraits. It attempts to depict how various speakers move through suffering, madness, addiction, lust, heartbreak, and settings ranging from rural Ohio to Brooklyn. The diction and syntax suggest both pathos and comedy, often within a single line. The ordinary experience becomes an opportunity for exploration and discovery, and sites of tragedy are not sites of victimhood, but spaces for productive play.