UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
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 given thesis/dissertation in DRUM.
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Item INSIGHTS IN ECOLOGY, BEHAVIOR, AND REPRODUCTION FROM VISUAL MODELS OF AFRICAN CICHLIDS(2024) Gonzalez, Zeke Martin; Carleton, Karen L; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Sexual selection has long been proposed to have played an important role in the explosive speciation of east African cichlids. Further, it is known that visual signals are the most salient ones to cichlids when it comes to reproduction. However, studies examining visual signals such as egg spots and size have been historically difficult to conduct due to the relationship between such phenotypes and confounding variables like age. In addition, the results from such studies often conflict and do not highlight clear patterns and hypotheses. In this dissertation, I use a receptor noise limited (RNL) visual model of increasing complexity to examine the discriminability of important visual signals in cichlid ecology, behavior, and evolution. In determining whether cichlid egg spots are truly mimics of cichlids eggs, I quantified fish and egg reflectance and found that two cichlid species are unable to distinguish the colors of eggs and egg spots in the lighting of their natural habitat. In order to bring together these quantitative methodologies with behavioral data, I tested the viability of using virtual stimuli displayed on a monitor to robustly examine how various visual signals affect conspecific male aggression. I found that although the cichlid Metriaclima zebra responds to virtual stimuli with equal aggression as towards live fish, it also responds with equal aggression towards virtual stimuli that differ in egg spot presence, body color, movement, and size. This suggests that virtual stimuli are not useful for behavioral tests in this species. Finally, in order to examine the salience of egg spots and body color in the wild, I calculated chromatic distance as a function of viewing distance for cichlid body colors against biologically-relevant backgrounds, conspecific body colors, and heterospecific body colors. The study shows that M. zebra body colors are discriminable from the space light at up to 5 m, but from the rocks at shorter distance, though distances that are comparable to the spacing of male territories. This suggests that males should be able to discriminate potential conspecific rivals on their breeding territories. Additionally, the visual model shows that M. zebra is highly discriminable from yellow heterospecifics but not so from blue heterospecifics. This dissertation emphasizes the importance of avoiding human biases in studies of cichlid color vision and behavior.Item The Way to Go: Considering Goals and Planned Behavior(2022) Factor, Adam; Kruglanski, Arie; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Theory of Planned Behavior offers a parsimonious and useful basis by which attitudes, subjective norms, and perceived behavioral control predict behavioral intentions and behavior. Often employed in fields across the social sciences, this model is highly influential for its relatively strong predictions and simple parsimony. On the other hand, there remain many limitations to the theory and directions for future improvement. Based on emerging theoretical work arguing for a new integrative TPB framework, three studies tested the impact of goal context on the TPB’s predictions. The first study examined two hypothetical scenarios in which goals relevant to a particular behavior were manipulated, finding that goals did impact the relationship between attitudes and behavioral intentions in one vignette but not the other. A second study found evidence that goal activation (in the form of an upcoming deadline) affected some of the TPB’s predictions, and that accounting for goal activation improved the overall utility of the model. Finally, a third study assessed the TPB variables for participant-generated behaviors. There was some evidence that commitment to goals and conflict between them helps predict behavior over time and may affect the relationship between intentions and behavior.Item 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.Item EVALUATING DIFFERENCES IN BODY WEIGHT, GUT MORPHOLOGY, IMMUNE RESPONSE, AND SICKNESS BEHAVIOR IN FAST- AND SLOW- GROWING BROILER CHICKENS WHEN INFECTED WITH SALMONELLA ENTERICA SEROVAR TYPHIMURIUM(2021) Snyder, Ashlyn Marie; Weimer, Shawna; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Fast growth rate in broilers comes with welfare concerns and research is needed to determine if fast- and slow-growing broilers differ in pathogen resistance. The objective of this study was to evaluate differences in fast- (FG) and slow-growing (SG) broilers when challenged with Salmonella Typhimurium or broth (control) 14 days post-hatch. Plasma IgA and IgG, jejunum and ileum histomorphology, and behaviors were measured. FG had greater d12 and d24 body weight and d7 jejunum measures, indicating better absorption, and earlier increases in plasma IgA and IgG, indicating earlier immune development. SG had greater d7 IgG, indicating stronger maternal immunity. Post-challenge, FG gut morphology was more impaired, and SG had greater IgA and reduced sham foraging, indicating a stronger immune response to challenge. The results illustrate fast- and slow-growing broilers differ in Salmonella resistance, which can help breeders make selection decisions to prevent Salmonella transmission into the human food supply.Item SURVIVING THE DEAD ZONE: INTERACTIONS AMONG JELLYFISH, COPEPODS, AND FISH IN THE CHESAPEAKE BAY(2020) slater, wencheng katherine; Pierson, James J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The oxygen-deficient areas (dissolved oxygen < 2 mg L-1) in oceans and estuaries have been increasing worldwide in recent decades and are especially common in populated and developed areas due to eutrophication and warming. The objectives of this dissertation were to understand the effects of hypoxia on zooplankton and the plankton foodweb in the Chesapeake Bay. The study focused on copepod (Acartia tonsa) and its major predators bay anchovy (Anchoa mitchilli), comb jellyfish (Mnemiopsis leidyi), and bay nettle (Chrysaora chesapeakii) with data collected during six cruises in 2010 and 2011 and an individual-based model. Oxygen deficiency was evaluated with both dissolved oxygen concentration (DO < 2 mg L-1) and the oxygen supply and demand of the copepod (pO2 < Pcrit). The effects of hypoxia on zooplankton concentrations were estimated with net tows, and the impact of hypoxia on the plankton foodweb were quantified by comparing copepods’ nonpredatory mortality (estimated with neutral red experiments) and predatory mortality (estimated with gut contents of comb jellyfish and bay anchovy). A copepod behavior model was also built to examine how stress-induced behavior affected copepod vertical distributions and the tradeoffs between avoiding both hypoxia and predation. The results indicated the impact of oxygen deficiency could be underestimated using solely the metric of dissolved oxygen, especially under warm and saline conditions. Both copepod and planktivorous fish concentrations were lower under hypoxic conditions, but gelatinous zooplankton concentrations were higher. Both nonpredatory and predatory mortality of copepods were higher under hypoxic conditions, suggesting a direct linkage between hypoxia and decreasing copepod abundance. Most importantly, the source of copepod mortality changed with both hypoxic severity and season: the relative importance shifted from nonpredatory in spring to a combination of predatory and nonpredatory in summer and autumn, and the dominant predators shifted from juvenile bay anchovies under moderate hypoxia to comb jellyfish under warm and severely hypoxic conditions. The model demonstrated how enhancing stress avoidance would result in aggregating at a shallower depth and thus increasing predation risk, supporting the hypothesis that behavior change under hypoxia may increase predatory mortality. Overall my research has shown that hypoxia directly decreases zooplankton abundance and increases predation impact, and avoiding hypoxia could contribute to higher predation impact.Item LOCAL FIELD POTENTIAL ANALYSIS OF BEHAVIORAL TASK INDUCED PLASTICITY IN HIGHER-ORDER AUDITORY CORTEX(2016) Locastro, Michael; Shamma, Shihab; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Previous studies have shown attention related transient changes induced during auditory discrimination behavioral tasks in primary auditory cortex (A1). This study involved awake, behaving ferrets performing similar auditory tasks with negative reinforcement; however, recordings were focused on higher-order cortical areas to understand what, if any, plastic effects exist and how they compare with A1. Although neurons in the posterior ectosylvian gyrus (PEG) exhibit similar tuning properties and conform to a tonotopic mapping consistent with prior findings, these areas enhance selectivity to target stimuli. The neurophysiological recordings from A1, PEG, and frontal cortex were then compared using the local field potential (LFP). This analysis focused on the response-power changes within these recordings and findings were consistent with single unit trends.Item THE ASSOCIATION OF SOCIAL ANHEDONIA WITH ROMANTIC RELATIONSHIP PROCESSES(2016) Assaad, Lily; Lemay, Edward; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Social anhedonia is a deficiency in the capacity to experience pleasure from social interactions. This study examined the implications of social anhedonia for romantic relationship functioning, including the association of social anhedonia with sentiments towards romantic partners that are central to relationship functioning (satisfaction, commitment, regard, and care), analogous perceptions of the partner’s sentiments, hostile behavior during relationship conflict, and perception of the partner’s hostile behavior. Data were collected from 281 participants who were involved in romantic relationships. Support was found for social anhedonia’s hypothesized negative association with satisfaction, regard, and care, as well as all four perceived partner sentiments. These associations were independent of attachment anxiety and avoidance. Additionally, attachment avoidance mediated social anhedonia’s relationship with commitment. However, no support was found for social anhedonia’s hypothesized positive association with actual and perceived partner hostile behavior. Results suggest that social anhedonia may undermine the functioning of interpersonal relationships.Item Neuromodulation in the Olfactory Bulb(2015) Smith, Richard Scott; Araneda, Ricardo C; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Neuromodulation of olfactory circuits by acetylcholine (ACh) plays an important role in odor discrimination and learning. Early processing of chemosensory signals occurs in two functionally and anatomically distinct regions, the main and accessory olfactory bulbs (MOB and AOB), which receive significant cholinergic input from the basal forebrain. Here we explore the regulation of AOB and MOB circuits by ACh, and how this modulation influences olfactory mediated behaviors. Surprisingly, despite the presence of a conserved circuit, activation of muscarinic ACh receptors revealed marked differences in cholinergic modulation of output neurons: excitation in the AOB and inhibition in the MOB. Granule cells (GCs), the most abundant intrinsic neuron in the OB, also exhibited a complex muscarinic response. While GCs in the AOB were excited, MOB GCs exhibited a dual muscarinic action, a hyperpolarization and an increase in excitability uncovered by cell depolarization. Furthermore, ACh had a different effect on the input/output relationship of MCs in the AOB and MOB, showing a net effect on gain in MCs of the MOB, but not in the AOB. Interestingly, despite the striking differences in neuromodulatory actions on output neurons, chemogenetic inhibition of ACh release produced similar perturbations in olfactory behaviors mediated by these two regions. Decreasing ACh in the OB disrupted the natural discrimination of molecularly related odors and the natural investigation of odors associated with social behaviors. Thus, the distinct neuromodulation by ACh in these circuits could underlie different solutions to the processing of general odors and semiochemicals, and the diverse olfactory behaviors they trigger.Item Designing to Engage Users in Sustainable Buildings(2015) Grzywa, Ashley; Draper, Powel; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis is an investigation of how buildings can be designed to encourage pro-environmental behavior by engaging users in a sustainable built environment. By engaging users in sustainability building design can reestablish a cultural understanding of humanity’s interdependence with the natural environment. The basis for investigation is a brief analysis of how cultural perceptions of the natural environment have changed over time and an understanding of what motivates pro-environmental behavior. Understanding of the types of work done and spaces used by building occupants throughout a work day informs opportunities for user engagement in the production, consumption, recycling and monitoring of energy, water and waste. Insights revealed through this research culminate in a design proposal for an office building that integrates user engagement with sustainable building performance and puts us on a path toward cultural transition to sustainable behavior and symbiosis with the natural environment.Item ADAPTIVE FLIGHT AND ECHOLOCATION BEHAVIOR IN BATS(2015) Falk, Ben; Moss, Cynthia F; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bats use sonar to identify and localize objects as they fly and navigate in the dark. They actively adjust the timing, intensity, and frequency content of their sonar signals in response to task demands. They also control the directional characteristics of their sonar vocalizations with respect to objects in the environment. Bats demonstrate highly maneuverable and agile flight, producing high turn rates and abrupt changes in speed, as they travel through the air to capture insects and avoid obstacles. Bats face the challenge of coordinating flight kinematics with sonar behavior, as they adapt to meet the varied demands of their environment. This thesis includes three studies, one on the comparison of flight and echolocation behavior between an open space and a complex environment, one on the coordination of flight and echolocation behavior during climbing and turning, and one on the flight kinematic changes that occur under wind gust conditions. In the first study, we found that bats adapt the structure of the sonar signals, temporal patterning, and flight speed in response to a change in their environment. We also found that flight stereotypy developed over time in the more complex environment, but not to the extent expected from previous studies of non-foraging bats. We found that the sonar beam aim of the bats predicted flight turn rate, and that the relationship changed as the bats reacted to the obstacles. In the second study, we characterized the coordination of flight and sonar behavior as bats made a steep climb and sharp turns while they navigated a net obstacle. We found the coordinated production of sonar pulses with the wingbeat phase became altered during navigation of tight turns. In the third study, we found that bats adapt wing kinematics to perform under wind gust conditions. By characterizing flight and sonar behaviors in an insectivorous bat species, we find evidence for tight coordination of sensory and motor systems for obstacle navigation and insect capture. Through these studies, we learn about the mechanisms by which mammals and other organisms process sensory information to adapt their behaviors.