Theses and Dissertations from UMD
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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
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Item MULTIMODAL ANALYSIS OF NEURAL SIGNALS RELATED TO SOURCE MEMORY ENCODING IN YOUNG CHILDREN(2024) Lei, Yuqing; Riggins, Tracy; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The emergence of source memory is an important milestone during memory development. Decades of research has explored neural correlates of source memory using electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). However, connections between findings from the two approaches, particularly within children, remain unclear. This dissertation identified fMRI-informed cortical sources of two EEG signals during memory encoding, the P2 and the late slow wave (LSW), that predicted subsequent source memory performance in a sample of children aged 4 to 8 years. Both P2 and LSW were source localized to cortical areas of the medial temporal lobe (MTL), reflecting MTL’s crucial role in both early-stage information processing and late-stage integration of memory, which also validated LSW’s suspected role in memory updating. The P2 effect was localized to all six tested subregions of cortical MTL in both left and right hemispheres, whereas the LSW effect was only present in the parahippocampal cortex and entorhinal cortex. P2 was additionally localized to multiple areas in the frontoparietal network, a cortical network known as the “attention network”, highlighting interactions between memory encoding and other cognitive functions. These results reflect the importance of considering both spatial and temporal aspects of neural activity to decode memory mechanism, and demonstrated the potential of combining multimodal measures in children, paving the way for future developmental research.Item Early emotional caregiving environment and associations with memory performance and hippocampal volume in adolescents with prenatal drug exposure(2023) Kohn, Brooke Hannah; Riggins, Tracy; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Early adversities, including prenatal drug exposure (PDE) and a negative postnatal emotional caregiving environment, impact children’s long-term development. The protracted developmental course of memory and its underlying neural systems offer a valuable framework for understanding the longitudinal associations of pre- and postnatal factors on children with PDE. This study longitudinally examines memory and hippocampal development in 69 parent-child dyads with PDE histories to investigate how the early emotional caregiving environment affects children with PDE’s neural and cognitive systems. Measures of physical health, drug exposure, and the emotional caregiving environment were collected between 0-24 months. At age 14 years, adolescents (N=69, 52.17% Female) completed multiple measures of episodic memory. at ages 14 (n=27) and 18 (n=17) years, a subset of adolescents underwent magnetic resonance imaging (MRI) scans. Latent constructs of episodic memory and the caregiving environment were created using Confirmatory Factor Analysis. Multiple regressions revealed a negative emotional caregiving environment during infancy was associated with poor memory performance and smaller left hippocampal volumes at 14 years. Better memory performance at 14 years predicted larger right hippocampal volume at 18 years. At 18 years, the association between the emotional caregiving environment and hippocampal volume was moderated by sex, such that a negative emotional caregiving environment was associated with larger left hippocampal volumes in males but not females. Findings suggest that the postnatal caregiving environment may modulate the effects of PDE across development, influencing neurocognitive development.Item ACUTE EXERCISE INDUCED MICROSTRUCTURAL AND FUNCTIONAL CHANGES IN THE HIPPOCAMPUS OF OLDER ADULTS(2023) Callow, Daniel; Carson, Jerome J; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Declining memory function is a common complaint of aging adults and a primary symptom of mild cognitive impairment (MCI) and Alzheimer’s disease (AD). The hippocampus is often the first brain area to exhibit noticeable deficits in age and pathologically-related cognitive decline and is a necessary structure for proper memory function. More specifically, the dentate gyrus (DG) and the third cornu ammonis area (CA3) of the hippocampus directly support mnemonic discrimination (MD), which is the process of reducing interference among new representations and distinctly encoding them as independent memories. Poor MD is associated with age and is a presymptomatic biomarker of cognitive decline and is believed to result from reduced neurogenesis, angiogenesis, and synaptogenesis within the DG/CA3 subregion of the hippocampus. While causes and treatments for memory decline remain elusive, lifestyle interventions, especially physical activity, have received attention as cost-effective and safe means of ameliorating and potentially preventing cognitive decline in a growing aging population. Animal and human studies suggest exercise benefits the hippocampal structure, preserving neurogenesis and angiogenesis in aging rodents and macrostructure and memory in older adults. However, the mechanisms by which exercise affects the human hippocampus remains a significant knowledge gap in the field and is a critical aspect in understanding the long-term impact exercise has on the aging hippocampus. To better address this gap, researchers have begun implementing acute exercise studies, which allow for greater control of non-exercise-related factors, are cheaper and more time efficient to conduct than training studies, and can predict and inform training-related adaptations. Unfortunately, limitations in the study designs, population tested, specificity of cognitive tasks, and spatial resolution of human imaging techniques have posed significant barriers to our understanding of how acute exercise relates to healthy brain aging at the functional and microstructural levels. Therefore, the objective of this dissertation was to expand our understanding of how acute aerobic exercise alters the function and microstructure of the aging hippocampus. Three within-subject studies were conducted comparing the relationship between a 30-minute bout of moderate to vigorous intensity aerobic exercise vs seated rest on MD performance, hippocampal microstructure, and high-resolution hippocampal-subfield microstructure and functional activity in healthy older adults. In study one, acute exercise preserved MD performance compared to decrements exhibited after seated rest in a pre and post-condition study design. In study two, a post-condition-only study design, acute exercise elevated microstructural diffusion within the hippocampus, indicative of a hippocampal neuroinflammatory response and upregulation of neurotrophic factors. Finally, in study three, a post-condition-only study design, we found that acute exercise resulted in lower MD, suppressed MD-related DG/CA3 network hyperactivity (indicative of healthier network function), and led to higher DG/CA3 extracellular diffusion. However, these neuroimaging-based correlates of hippocampal neuroplasticity and network function were not associated with differences in MD performance. These findings suggest that higher-intensity acute exercise can alter memory performance and stimulate neuroplasticity and neurotrophic cascades within the hippocampus and the DG/CA3 subfield, potentially via different mechanisms. Furthermore these results give insight into the immediate neurotrophic and behavioral effects of acute moderate to vigorous intensity aerobic exercise in older adults and provide new methods and tools for better understanding if and how exercise promotes healthy brain aging. Finally, these initial findings lay a foundation for optimizing exercise prescription and identifying future effective exercise treatments.Item SYSTEMS IMMUNOLOGY OF IMMUNE IMPRINTS INDUCED BY ACUTE VIRAL INFECTIONS(2023) Liu, Can; Johnson, Philip L.F.; Tsang, John S.; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Upon encountering perturbations such as viral infections, the immune system initiates a cascade of molecular and cellular responses. These alterations may persist even after recovery, resulting in enhanced or diminished response to subsequent stimuli compared to the naïve state. Such persistent changes, referred to as immune imprints or long-term non-specific memory, indicate an incomplete resolution from immunological perturbations. The primary focus of this dissertation is to systemically investigate the immune imprints resulting from acute infections and how they shape the baseline immune status to future heterologous challenges.First, we employed cutting-edge single-cell multi-omics and computational approaches to assess the immune response during the COVID-19 disease course and severity correlates at an unprecedented resolution. We identified gene expression profiles – apoptosis in plasmacytoid dendritic cells and IL-15-linked increase of fatty acid (FA) metabolism in CD56dimCD16hi NK cells – as primary correlates of disease severity. This increase of FA signature with disease severity was also concomitant with an attenuated inflammation, indicating a dysfunctional or exhaustion-like state of these NK cells. While the depressed inflammation signature in severe patients was also found in different cell types near hospitalization, it increased temporally at later time points, indicating a critical late-stage juncture in the disease course. Next, we took the opportunity of the period following the first wave of COVID-19 pandemic to study immune imprints in human cohorts who had recovered from COVID-19 before widespread vaccination and reinfection occurred. We demonstrated that individuals who recovered from mild COVID-19, exhibit distinct immune signatures through single-cell transcriptomic profiling. Male recoverees also showed heightened responses to the seasonal influenza vaccine compared to healthy individuals without a history of COVID-19 and female recoverees. These sex dimorphic imprints highlight the interplay between intrinsic factors like sex and non-intrinsic factors such as prior SARS-CoV-2 infection, in shaping an individual's immune system over time. Lastly, we also investigated the immune imprints after acute viral infection using a controlled experimental mouse model of influenza infection. After examining cellular and gene expression profiles in various organs after the infection, we found persistent changes in both adaptive and innate immune components across multiple organs. Moreover, these changes affected subsequent local IL-17 inflammatory response and secondary heterologous vaccinations in anatomically distinct organs. Together, both human and mouse studies here are important pieces toward an improved understanding of long-term immune imprints after perturbations, which can be leveraged to develop more effective and personalized vaccines and disease treatments.Item PAST AS PROLOGUE TO PEACE IN POST-GENOCIDE CAMBODIA: A STUDY OF MEMORY CONSTRUCTION AND MEMORY EDUCATION BY THE EXTRAORDINARY CHAMBERS IN THE COURTS OF CAMBODIA AND CAMBODIAN CIVIL SOCIETY(2022) Rappeport, Annie; Lin, Jing; Education Policy, and Leadership; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Genocides demonstrate the worst of humanity manifest and created difficult pasts for future generations to contend with. What societies choose to remember is one of the most crucial choices made in the aftermath of mass atrocities. Looking to the Khmer Rouge regime and genocide from 1975-1979, the role of transitional justice and civil society is pioneering new ways to educate and remember the genocidal past. Recently, memory and education relation to memory have been an emphasized part of transitional justice processes including prioritization set by the Extraordinary Chambers in the Courts of Cambodia (ECCC) which was established in 2003 after much negotiation. The hybrid tribunal allocated significant funding and staffing towards outreach, education and survivor participation opportunities as a means to address and contend with the Khmer Rouge genocide. The following study centers the experiences of those on the frontlines of the work being done at the intersections of transitional justice (ECCC), civil society and education. The research features 25 in-depth interviews with key informants combined with a complementary document analysis. The key informants represent leaders in Cambodian scholarship, the tribunal process, education, NGO and civil society memory and peace work. The findings show many relevant lessons learned in relation to outreach programs, victim-centered transitional justice, culturally competent modes of reconciliation and education, participant centered archiving, the benefits of using performing arts and the function of moral and symbolic reparations in the Cambodian context. Keywords: Cambodia, Reconciliation, Transitional Justice, Peace Studies, Memory Studies, Genocide, Peace Education, Civil SocietyItem GENRES OF MEMORY AND ASIAN/AMERICAN WOMEN’S ACTIVISM(2022) Bramlett, Katie; Enoch, Jessica; English Language and Literature; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As human rights and racial inequality dominate public discourse, it has become increasingly clear that Americans are invested in conversations of public memory. The removal of confederate monuments and demands for equity in memorialization for people of color underscore the point that who is remembered and how they are honored is important. Further, the growing awareness of violence against Asian/Americans and the hate crime against Asian/American women in Atlanta has emphasized the need to understand the history of violence against Asian/Americans, Asian/American gendered stereotypes, and the Asian/American activists who fight for equal rights. This dissertation examines three distinct memorial genres—a statue, a traveling exhibit, and a documentary—created by Asian/Americans about Asian/American women activists. My interdisciplinary research engages feminist memory studies, Asian/American studies, and cultural rhetorics to investigate how public memory activists leverage the affordances of different memorial genres to recover Asian/American women’s activism. I consider the ways Asian/American women’s memorials contest the past and navigate the politics of memorialization to influence the present. Each chapter considers how memorials not only remember past activism, but also work to reframe current conversations about Asian/American women in more just and equitable frameworks. I claim that my chosen memorials are created by memorial activists and each seek to expand U.S. memory beyond traditional gendered stereotypes that are pervasive in the United States.Item Black Gay and Bisexual Men, Internet Access, Memory, and Visual Culture(2021) Jiles, Robert De Von; Bruce, La Marr J; Farman, Jason; American Studies; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Drawing from the fields of visual culture, black queer studies, black feminist theory, internet studies, and affect theory, “Black Gay and Bisexual Men, Internet Access, Memory, and Visual Culture” focuses on black gay and bisexual men who have internet access to create, view, and circulate visual representations about their own experiences and how they challenge, subvert, and reify negative and one-dimensional representations about their lived experiences. The cultural objects analyzed in the dissertation include two episodes from playwright and screenwriter Donja R. Love’s independent scripted web series Modern Day Black Gay and Darius Clark Monroe’s short film Slow. Both cultural objects were released for online viewing and can be accessed for free. As Black queer visual culture, Slow and MDBG trouble a racial and heteronormative visual field that renders black gay and bisexual men as excess. Tapping into affects such as desire, intimacy, love and pleasure, Love and Monroe use memory in the cultural objects to create visual images from the excess. In turn, the cultural objects stimulate black gay and bisexual viewers’ memories, and activate affective encounters occur Slow and MDBG use visual images to interrogate and reinscribe notions about black sexuality, black masculinity, black family and community, black love, same-sex romance, and black religion. This dissertation investigates the relationship between artists, the art objects, and the viewers and look for meaning in their creation, representation and interpretations of gay online hookup culture, gender and sexual stereotypes, and conservative homophobic Christian beliefs and practices. In addition to a textual analysis of the cultural objects, methods in the dissertation include interviews, self-ethnography, several small group screenings of the cultural objects by black gay and bisexual male participants, and group discussions following the screenings about the participants' interpretations of the material and how their experiences relate to the cultural texts.Item Is nap status related to memory, sleep physiology, and the hippocampus in early childhood?(2020) Allard, Tamara L; Riggins, Tracy; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Research suggests there may be links between developmental changes in sleep (e.g., transition out of a nap), memory, and brain (specifically, hippocampus). The purpose of this investigation was to explore differences in sleep physiology, visuospatial memory, and hippocampal volume based on nap status. Participants were 3 to 5-year-old children (n=51) who were habitual nappers (napping >5 days/week), semi-habitual nappers (3–4 days/week), or non-nappers (<2 days/week). Participants completed a memory task before and after a wake and nap session. Polysomnography (PSG) and hippocampal volumes were also assessed. Findings demonstrated that, regardless of nap status, children performed better on a memory task following a nap. PSG revealed that habitual nappers spent marginally more time in nREM2 sleep and less time in SWS compared to semi-habitual nappers. Finally, non-nappers demonstrated a larger hippocampus than the other groups. These findings support the suggestion that developmental differences in these domains are related during childhood.Item The Unhealed Wound: Contemporary Black Diasporic Literature and the Continuing Memory of the Duvalier Dictatorship(2019) Edwards, Norrell F; Orlando, Valerie K; Mallios, Peter; English Language and Literature; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In the 1990s, as Haiti continued to withstand the aftershocks of the end of a 29 year father-son dictatorship, the United States and France hovered in the periphery to “help” Haiti’s transition to democracy. World systems theory dictates that a country like Haiti would be relegated to the periphery while countries like the United States and France inhabit the core. The Unhealed Wound: Contemporary Black Diasporic Literature and the Continuing Memory of the Duvalier Dictatorship inverts this dynamic. This work places Port-au-Prince at the core, while New York and Paris—secondary homes to Haitian exiles and emigres—becomes the periphery. Traversing national borders, politics and disciplines, this study investigates how memory, history and literature shape the physical and imagined cityscapes of New York, Port-au-Prince and Paris. Bringing together authors such as Edwidge Danticat, Lyonel Trouillot and Shay Youngblood, Edwards questions and explores dynamics of the Black immigrant body and Haitian body in these cities in the 1980’s, 1990’s and early 2000’sItem Understanding and remembering pragmatic inferences(2018) Kowalski, Alix; Huang, Yi Ting; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation examines the extent to which sentence interpretations are incrementally encoded in memory. While traditional models of sentence processing assume that comprehension results in a single interpretation, evidence from syntactic parsing indicates that initial misinterpretations are sometimes maintained in memory along with their revised counterparts (e.g., Christianson, Hollingworth, Halliwell & Ferreira, 2001). However, this evidence has largely come from experiments featuring sentences that are presented in isolation and words that are biased toward incorrect syntactic analyses. Because there is typically enough sentential context in natural speech to avoid the incorrect analysis (Roland, Elman, & Ferreira, 2006), it is unclear whether initial interpretations are incrementally encoded in memory when there is sufficient context. The scalar term “some” provides a test case where context is necessary to select between two interpretations, one based on semantics (some and possibly all) and one based on pragmatic inference (some but not all) (Horn, 1989). Although listeners strongly prefer the pragmatic interpretation (e.g., Van Tiel, Van Miltenburg, Zevakhina, & Geurts, 2016), prior research suggests that the semantic meaning is considered before the inference is adopted (Rips, 1975; Noveck & Posada, 2003; Bott & Noveck, 2004; Breheny, Katsos, & Williams, 2006; De Neys & Schaeken, 2007; Huang & Snedeker, 2009, 2011). I used a word-learning and recall task to show that there is evidence of the semantic meaning in the memory representation of sentences featuring “some,” even when the pragmatic interpretation is ultimately adopted. This raises two possibilities: first, the memory representation was of poor quality because both interpretations were available during encoding, or the semantic meaning was computed and encoded first and lingered even after the pragmatic interpretation was computed and encoded. Data from a conflict-adaptation experiment revealed a facilitating effect of cognitive control engagement. However, there was still a delay before the pragmatic inference was adopted. This suggests that only the semantic meaning is available initially and the system failed to override it in memory when the pragmatic interpretation was computed. Taken together, these findings demonstrate the incrementality of memory encoding during sentence processing.