UMD Theses and Dissertations
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Item EFFECTS OF AGE ON CONTEXT BENEFIT FOR UNDERSTANDING COCHLEAR-IMPLANT PROCESSED SPEECH(2024) Tinnemore, Anna; Gordon-Salant, Sandra; Goupell, Matthew J; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The number of people over 65 years old in the United States is rapidly growing as the generation known as “Baby Boomers” reaches this milestone. Currently, at least 16 million of these older adults struggle to communicate effectively because of disabling hearing loss. An increasing number of older adults with hearing loss are electing to receive a cochlear implant (CI) to partially restore their ability to communicate effectively. CIs provide access to speech information, albeit in a highly degraded form. This degradation can frequently make individual words unclear. While predictive sentence contexts can often be used to resolve individual unclear words, there are many factors that either enhance or diminish the benefit of sentence contexts. This dissertation presents three complementary studies designed to address some of these factors, specifically: (1) the location of the unclear word in the context sentence, (2) how much background noise is present, and (3) individual factors such as age and hearing loss. The first study assessed the effect of context for adult listeners with acoustic hearing when a target word is presented in different levels of background noise at the beginning or end of sentences that vary in predictive context. Both context sentences and target words were spectrally degraded as a simulation of sound processed by a CI. The second study evaluated how listeners with CIs use context under the same conditions of background noise, sentence position, and predictive contexts as the group with acoustic hearing. The third study used eye-tracking methodology to infer information about the real-time processing of degraded speech across ages in a group of people who had acoustic hearing and a group of people who used CIs. Results from these studies indicate that target words at the beginning of the context sentence are more likely to be interpreted to be consistent with the following context sentence than target words at the end of the context sentences. In addition, the age of the listener interacted with some of the other experimental variables to predict phoneme categorization performance and response times in both listener groups. In the study of real-time language processing, there were no significant differences in the gaze trajectories between listeners with CIs and listeners with acoustic hearing. Together, these studies confirm that older listeners can use context in a manner similar to younger listeners, although at a slower speed. These studies expand the field’s knowledge of the importance of an unclear word’s location within a sentence and draw attention to the strategies employed by individual listeners to use context. The results of these experiments provide vital data needed to assess the current usage of context in the aging population with CIs and to develop age-specific auditory rehabilitation efforts for improved communication.Item THE EFFECTS OF AGE, SARCOPENIA, AND RESISTANCE EXERCISE TRAINING ON MITOCHONDRIAL STRUCTURAL DYNAMICS IN SKELETAL MUSCLE(2024) Sapp, Catherine; Prior, Steven J; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Sarcopenia, the progressive, age-related loss of skeletal muscle mass, contributes to older adults’ risk of falls, hospitalization, and loss of independence. Mitochondrial dysfunction is a hallmark trait of aging and sarcopenia that may be mediated by changes to mitochondrial structure and location through the involvement of mitochondrial fusion, fission, and mitophagy (collectively referred to as mitochondrial quality control). Therefore, the purpose of this dissertation was to investigate whether mitochondrial quality control is altered by age or sarcopenia. The first study performed in a rat model of aging demonstrated that expression of proteins regulating fusion and mitophagy was higher in skeletal and cardiac muscle from old vs. young rats, and this was accompanied by reduced expression of fission proteins in skeletal muscle in the old rats. The second study included older humans and revealed no differences in mitochondrial quality control protein expression in skeletal muscle from sarcopenic vs. non-sarcopenic older adults. Furthermore, twelve weeks of resistance exercise training did not alter the expression of mitochondrial quality control proteins in the sarcopenic individuals. The third study investigated morphological differences in mitochondrial subpopulations and lipid droplets from the sarcopenic individuals from study two, both before and after resistance exercise training. Peripherally located and intermyofibrillar mitochondrial content and morphology did not change significantly after resistance exercise training. Lipid droplets from the intermyofibrillar region were similarly unchanged, but lipid droplets from the peripheral region had minor morphological changes after resistance exercise training. Together, this dissertation indicates that mitochondrial quality control proteins in skeletal and cardiac muscle are altered in response to aging and may contribute to mitochondrial dysfunction, but mitochondrial structural dynamics in skeletal muscle do not appear to be altered in older adults with a moderate degree of sarcopenia. This suggests that other, non-mitochondrial factors may play larger roles in the pathophysiology of sarcopenia. While the sarcopenic participants did improve muscular strength after resistance training, this was not accompanied by changes in mitochondrial content, morphology, or quality control. Therefore, resistance exercise training may not be an effective strategy to enhance mitochondrial structural dynamics in sarcopenia.Item "Get Dressed Up For The End Of The World!": The Reinvention of the Elder Goth Subculture During a Time of Crisis(2024) Bush, Leah J.; Corbin Sies, Mary; American Studies; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation is an ethnographic examination of relationships between subcultural identity and Gothic social worlds in the Elder Goth subculture in Baltimore, Maryland and Washington, D.C. Formed in Britain in the late 1970s, the Goth subculture is characterized by a distinct morbid aesthetic and an overwhelming emphasis on the color black. The subculture retains a relatively high number of Elder Goths who participate in the subculture beyond their youth. This interdisciplinary project draws from the lifespan perspective of age studies and aspects of performance studies and queer utopian theory. Individual identities and Gothic communities are built and sustained through subculturally specific fashion and embodied practices at nightclubs, outdoor gatherings, and the phenomenon of virtual streaming dance nights which emerged during the COVID-19 pandemic. The project also considers how meaning is made in subcultural places. Elder Goths draw on the subculture’s embrace of dichotomies in life, commitment to adaptation, and deepen their investment with the subculture at transitional points in their lives. Subculture is thus a fluid process of worldmaking which unfolds over the life course. This dissertation underscores the power of agency in making new and better worlds.Item THE WORST OF TIMES? AGING WITH LIMITED FAMILY TIES IN THE UNITED STATES(2024) Liu, Jingwen; Caudillo, Mónica L.; Sociology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The drastic demographic and family transitions since the 1970s have raised ongoing discussions about whether older adults fare well socially and psychologically when they are increasingly likely to age alone in the U.S. Based on the social convoy model, the three studies of this dissertation answer this question by extending the focus from the proximal kinship ties to nonkin networks and broader social participation. Particular attention is paid to gender and racial/ethnic differences as demographic and family transitions are experienced unevenly by different social groups. The first study examines how family instability and the deviation from “normative” family trajectories are associated with older adults’ mental health. It found different levels of importance of the structure and instability of family for men and women of different racial/ethnic groups. Moving beyond family and households, the second study explores the substitution effect of extended family, friends, and neighborhoods in the absence of proximal relations. It reveals the “double plight” of Black and Hispanic older adults who may suffer from both a disproportionate exposure to the declining marriage and a lack of supportive distant relations serving as buffer zones in the absence of core kinship ties. The third study disentangles the population-level age and cohort trends of social connectedness, a more comprehensive indicator of individuals’ social wellbeing. It finds distinct intercohort changes in both the overall level of social connectedness and intracohort gender and racial/ethnic disparities. These trends can be partially explained by cohort differences in socioeconomic resources and health. However, societal changes that emphasize the significance of intergenerational solidarity, friendship ties, digital communication, non-religious social participation, and volunteering may play a more significant role. Taken together, this dissertation depicts a mixed picture of different populations who demonstrate varying levels of vulnerability and resilience against the quickly developing society. Therefore, it calls for both the enhancement of social welfare regimes and more positive narratives about unique resilience and strengths for women, racial/ethnic minorities, and socioeconomically disadvantaged older adults.Item HIPPOCAMPAL GLUCOSE TRANSPORT AND OXIDATION IN RESPONSE TO DISRUPTED BLOOD FLOW IN AN AGING RAT MODEL OF HEART FAILURE(2023) Pena, Gabriel Santiago; Smith, J. Carson; Kuzmiak-Glancy, Sarah; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The primary objective of this dissertation was to investigate, in a rodent model of cardiovascular disease promoted by transverse aortic constriction (TAC), whether cerebral hypoperfusion stemming from chronic high pulsatile blood flow, and cerebral hypoperfusion stemming from low cerebral blood flow differentially affected hippocampal glucose transport and hippocampal mitochondrial function. We first, characterized the changes in right and left carotid hemodynamics and diameter in response to TAC and in a SHAM control group at three different time points (20-, 30-, and 40 weeks) post-surgery. Then, right, and left hippocampal mitochondrial content and substrate oxidation were investigated, and protein expression of glucose transporters and mitochondrial quality control markers were quantified. In this study, both the SHAM and TAC conditions included male and female rats to address possible sex differences. We report that all time points within TAC, right carotid blood flow velocities and pulsatility were greater than the left, but did not worsen over time. No differences in mitochondrial content were found within TAC nor between TAC and SHAM, but within TAC animals there were impairments in right hippocampal coupled and uncoupled respiration when compared to the left. When compared to the SHAM controls, right and left hippocampi of TAC animals had higher protein expression of mitochondrial quality control markers, but no differences in glucose transporter expression were found. Thus, while both high blood flow and/or pulsatility as well as low cerebral blood flow may lead to brain hypoperfusion, the metabolic consequences of the two may not be the same. The results from this dissertation contribute to the expanding literature characterizing the intersection between cardiovascular disease and neurodegeneration.Item Age in Place: Design for Dignity(2024) Perkins, Abigail Corinne; Bennett, Ralph; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The senior population in the United States is rapidly growing. As a result, there is a growing need for more affordable housing options for seniors. Assisted living centers can be a wonderful community for seniors to live in when they can no longer maintain their homes or if they need additional care. These apartments provide excellent opportunities for socialization, exercise, and travel. However, a variety of factors including cost, availability of specific care facility, and a desire for independence can cause a senior to not receive the help that they need in a timely manner. For seniors with additional care needs, such as a form of dementia, the need for flexible care is paramount. Current care options often lead to seniors with dementia having to move to facilities that are not designed for residents with dementia and hire additional care aids. The lifetime cost of dementia is a huge burden to the patient and their family. Affordable senior housing is needed for seniors who cannot afford memory care and choose to live in assisted living facilities in order to improve a senior’s quality of life. The thesis will explore how we can use findings of environmental psychology to improve the design of assisted living facilities for seniors dealing with rapid memory loss from dementia.Item Metabolic Profiling of Brain Microvascular Endothelial Cells: Investigating the Role of Sex, Stress, APOE Genotype, and Exercise in Alzheimer's Disease Risk(2024) Weber, Callie; Clyne, Alisa M; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Alzheimer’s disease (AD) is the 7th leading cause of death in the United States, yet there are still no effective treatments to prevent or slow the progression of the disease. AD develops from a combination of genetic and lifestyle risk factors including female sex, elevated stress hormone exposure, the apolipoprotein (APOE) ε4 genotype, and a sedentary lifestyle. In order to better identify the manifestations of AD, it is vital to understand how each of these risk factors impact brain health and lead to neurological dysfunction associated with AD. Brain microvascular endothelial cells (BMEC) line the blood vessels of the brain and have specialized tight junctions designed to strictly regulate nutrient and waste transfer between the blood and the brain. Two of the early indicators of AD development are breakdown of the tight junctions and whole brain glucose hypometabolism. Since BMEC form the first line of defense for the brain against neurotoxic compounds in the blood and are responsible for glucose transport to the rest of the brain, the overarching goal of this thesis is to understand how female sex, elevates stress hormone exposure, the APOE ε4 genotype, and a sedentary lifestyle induce breakdown of tight junction proteins and glucose hypometabolism in BMEC. I first demonstrate that female sex exacerbates endothelial dysfunction in response to high levels of a stress hormone, Angiotensin II (AngII). Specifically, I show that in response to AngII, female endothelial cells increase oxidative stress and inflammatory responses while male endothelial cells do not. Next, I used CRISPR/Cas9 to generate a set of induced pluripotent stem cells (iPSC) homozygous for the APOE ε3 and ε4 genotype and differentiated them into BMEC (hiBMEC). Using the hiBMEC I showed the APOE ε4 genotype induces barrier deficiencies that are partially mediated through reduced levels of protein deacetylase Sirtuin 1 (SIRT1), and that the APOE ε4 genotype causes glucose hypometabolism through decreased insulin signaling. Finally, by adding serum from sedentary and exercise trained individuals to genotype-matched hiBMEC, I show that APOE ε3 and ε4 hiBMEC have divergent responses to treatment with serum from sedentary and exercise trained individuals. Treatment with exercise trained serum increases SIRT1 and glycolytic enzymes compared to sedentary serum, while exercise trained serum decreases SIRT1 and glycolytic enzymes in APOE ε4 hiBMEC compared to sedentary serum. The work described in this thesis gives a fundamental, mechanistic understanding to the roles of female sex, stress hormone exposure, the APOE ε4 genotype, and a sedentary lifestyle in BMEC dysfunction and hypometabolism, giving insight into how these factors contribute to AD development and progression.Item EVALUATING THE EFFECTS OF MODIFIABLE LIFESTYLE AND CARDIOVASCULAR HEALTH FACTORS ON DIABETES LIFE EXPECTANCY IN NHANES AND BRAIN AGING IN UK BIOBANK(2024) Feng, Li; Lei, David K.Y. DL; Ma, Tianzhou TM; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation explored the impact of lifestyle and cardiovascular health factors on aging, particularly focusing on individuals with diabetes, the effects of blood pressure on brain aging, and the influence of cardiovascular health and genetic predispositions on brain white matter aging.The first study examined the trends in lifestyle quality among US adults with type 2 diabetes from 1999 to 2018 using NHANES data, involving 7,410 participants. A healthy lifestyle score encompassing smoking, drinking, physical activity, and diet showed a slight increased over the years. Notably, disparities remained significant by socioeconomic groups. The study found that adherence to low-risk lifestyle factors was associated with a 55%-57% lower risk of all-cause mortality, emphasizing the importance of lifestyle modification in diabetes management, and it was independent of cardiovascular risk control. The second study investigated the causal effect of elevated blood pressure on white matter brain aging in a cohort of 228,473 European ancestries aged 40-69 from the UK Biobank by using two-sample Mendelian randomization. Our result revealed that high blood pressure, particularly diastolic, accelerated the machine-learning-derived white matter brain age gap, based on white matter microstructure integrity measured by fractional anisotropy derived from diffusion tensor imaging data, with a causal effect evidence found in late middle-aged women. This underscores the importance of blood pressure control in preventing brain aging, especially in post-menopausal women. Lastly, the impact of Life's Essential 8 (LE8), a comprehensive measure of cardiovascular health (lifestyle part: diet, smoke, physical activity, sleep; health part: BMI, blood sugar, blood pressure, blood lipid), on white matter brain aging was assessed, with a particular focus on how the APOE4 genotype modifies the relationship. Analyzing data from 18,817 European ancestries aged 40-60 from the UK Biobank, the study revealed that higher LE8 scores correlated with a younger brain age. Interestingly, the effect varied significantly with APOE4 status, highlighting the need for personalized health strategies based on genetic profiles. In conclusion, these studies collectively highlight the crucial role of modifiable lifestyle and health factors in managing chronic diseases, controlling blood pressure, and maintaining brain health, with an emphasis on the integration of genetic profiles for personalized healthcare.Item CORTICAL REPRESENTATIONS OF INTELLIGIBLE AND UNINTELLIGIBLE SPEECH: EFFECTS OF AGING AND LINGUISTIC CONTENT(2023) Karunathilake , I.M Dushyanthi; Simon, Jonathan Z.; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Speech communication requires real-time processing of rapidly varying acoustic sounds across various speech landmarks while recruiting complex cognitive processes to derive the intended meaning. Behavioral studies have highlighted that speech comprehension is altered by factors like aging, linguistic content, and intelligibility, yet the systematic neural mechanisms underlying these changes are not well understood. This thesis aims to explore how the neural bases are modulated by each of these factors using three different experiments, by comparing speech representation in the cortical responses, measured by Magnetoencephalography (MEG). We use neural encoding (Temporal Response Functions (TRFs)) and decoding (reconstruction accuracy) models which describe the mapping between stimulus features and the cortical responses, which are instrumental in understanding cortical temporal processing mechanisms in the brain.Firstly, we investigate age-related changes in timing and fidelity of the cortical representation of speech-in-noise. Understanding speech in a noisy environment becomes more challenging with age, even for healthy aging. Our findings demonstrate that some of the age-related difficulties in understanding speech in noise experienced by older adults are accompanied by age-related temporal processing differences in the auditory cortex. This is an important step towards incorporating neural measures to both diagnostic evaluation and treatments aimed at speech comprehension problems in older adults. Next, we investigate how the cortical representation of speech is influenced by the linguistic content by comparing neural responses to four types of continuous speech-like passages: non-speech, non-words, scrambled words, and narrative. We find neural evidence for emergent features of speech processing from acoustics to linguistic processes at the sentential level as incremental steps in the processing of speech input occur. We also show the gradual computation of hierarchical speech features over time, encompassing both bottom-up and top-down mechanisms. Top-down driven mechanisms at linguistic level demonstrates N400-like response, suggesting involvement of predictive coding mechanisms. Finally, we find potential neural markers of speech intelligibility using a priming paradigm, where intelligibility is varied while keeping the acoustic structure constant. Our findings suggest that segmentation of sounds into words emerges with better speech intelligibility and most strongly at ~400 ms in prefrontal cortex (PFC), in line with engagement of top-down mechanisms associated with priming. Taken together, this thesis furthers our understanding on neural mechanisms underlying speech comprehension and potential objective neural markers to evaluate the level of speech comprehension.Item ASSESSING THE IMPACT OF POLYPHARMACY ON THE ELDERLY USING NATIONALLY REPRESENTATIVE SURVEY DATA(2023) Eschenlauer, Adam; Franzini, Luisa; Health Services Administration; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Background: Polypharmacy is a growing issue that affects individuals of all ages yet is most prevalent among patients aged 65 and older with chronic comorbidities. Although integral to most treatment plans, pharmaceutical intervention may negatively impact one’s health when five or more medications are taken daily. Given the concurrent rise in elderly population and polypharmacy prevalence, it is vital that we better understand the impact that concomitant medication use has on this vulnerable segment of population.Purpose: This research examines the factors leading to polypharmacy among the elderly population and explores its various impacts on healthcare utilization. Data and Methods: This study uses Medical Expenditure Panel Survey (MEPS) Data. Fixed-Effects regression analyses examine relationships between predictive factors and polypharmacy, polypharmacy and expenditures, and polypharmacy and utilization. Classification models assess the ability of machine learning to correctly predict utilization within the sample population. Key Results: Aside from clinical indicators, demographic and socio-economic factors play a role in determining polypharmacy status. Polypharmacy risk is higher for women (1.088, p < 0.001), high income individuals (1.107, p < 0.01), and those covered by Medicaid (1.110, p < 0.001). Conversely, married individuals (0.930, p < 0.001) and non-Hispanic Blacks (0.864, p < 0.001) have reduced risks of polypharmacy. We find polypharmacy to be associated with higher total (p < 0.001), inpatient (p < 0.01), outpatient (p < 0.01), and prescription medical expenditures (p < 0.001) when holding other predictors constant. We find the risk of hospitalization to be higher for polypharmacy patients (RR: 1.592, p < 0.001) than nonpolypharmacy patients after controlling for multimorbidity and medication class. Lastly, machine learning algorithms classify admissions with an overall accuracy of 84.9%; however, a low true positive rate (TPR) of 41.7% and high true negative rate (TNR) of 96.5% indicate best performance is achieved in predicting non-admissions. Conclusion: Polypharmacy is associated with several non-clinical factors and has a statistically significant impact on medical expenditures and admissions. Though imperfect, predictive analysis methods improve our ability to identify patients at risk for admissions and present a potential opportunity for future applications aimed at reducing utilization and costs.