Theses and Dissertations from UMD
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Item FACTORS AFFECTING RATES OF SOCIAL BUFFERING IN JUVENILE RHESUS MACAQUES (Macaca mulatta)(2010) Herman, Khalisa N.; Fox, Nathan A; Human Development; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The purpose of the current study was to investigate genetic and experiential contributions to social buffering between juvenile non human primates. A second aim was to investigate the role of behavioral displays during social buffering, in order to explain social buffering deficits in primates with a history of early social deprivation (Winslow et al., 2003). A total of 31 male rhesus macaques (mean age of 2 years) were videotaped during a Novel Cage Test with and without their homecage partner, and immediately following, blood samples were collected under anesthesia. Subjects were either reared with mothers and peers (mother reared, n=15) or without their mothers in the continuous presence of peers (peer reared, n =16). Cortisol concentrations and rh5-HTTLPR genotypes (long ( l ) and short ( s ) alleles) were generated from blood samples ( l/l =20, l/s =10, and s/s =1), and videos were coded for a variety of stress and affiliation behaviors. Genotype and rearing differences in social buffering of stress behaviors and neuroendocrine function were assessed. Rates of social buffering were also compared between a group of high display subjects that exhibited frequent behavioral displays (n =21) compared to a low display group (n=10). Additionally, the behavioral data were subjected to a lag sequential analysis to examine levels of contingent responsiveness, or the likelihood of behavioral displays occurring before affiliative responses (Bakeman et al., 1997). The results revealed social buffering deficits in the short allele, peer reared, and low display groups. Both the peer reared and low display groups were found to engage in less affiliative behaviors compared to the mother reared and high display groups respectively, while the short allele group appeared to receive less benefit from the presence of a familiar partner. Additionally, contingent responsiveness was identified as a feature of social buffering for the entire sample, but did not explain group differences in social buffering. Taken as a whole, this study identifies genetic and experiential vulnerability factors for social buffering. Furthermore, it adds to our knowledge of how behavioral displays are used during social buffering.Item Error Observation in Schizophrenia(2009) Mann-Wrobel, Monica Constance; Blanchard, Jack J.; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Despite the pervasive and impairing nature of social difficulties in schizophrenia, the causes of these problems are not fully understood. It has been suggested that problems with cognitive functioning contribute to the social deficits of schizophrenia. However, little is known about the neural mechanisms that underlie cognitive processes directly linked to social dysfunction in schizophrenia. Recent studies of the mirror neuron system have focused on the error-related negativity (ERN), a negatively-deflected event-related brain potential that is elicited following the commission of an erroneous response. This study examined ERN activity in schizophrenia patients and psychiatrically healthy controls during performance and observation of a confederate performing a computerized flanker task. The lateralized readiness potential (LRP) allowed for a direct comparison of brain activation reflecting response readiness verses error signaling. Correlations between ERN activity during flanker observation, social cognition (i.e., theory of mind), and community social functioning were explored. Finally, correlations between verbal memory, executive functioning, and social functioning were examined and social cognition was explored as a mediator between neurocognition and social functioning. Results indicated that controls produced a robust ERN during execution of the flanker task, whereas ERN activity among patients was comparatively attenuated in amplitude. During observation, there were no significant group differences and no identifiable observation ERN; however, there was greater negative activity following error than correct trials in this condition for all participants. LRP activity did not parallel that of the ERN, supporting the differentiation of motor activity and error-related processing during observation. The only significant correlation to emerge between ERN activity and social cognition and social functioning was between occupational status and execution ERN activity among controls only. Unexpectedly, neurocognition and social functioning were negatively correlated in the patient group. Expectedly, these variables were positively correlated among controls. Therefore, regression analyses were conducted separately by group; however, neither neurocognition nor social cognition predicted a significant proportion of the variance in social functioning. Despite limitations, this research is discussed as a starting point for integrating the study of psychophysiological activity with social behavior and functioning, particularly in a clinical population with pronounced social deficits.Item Susceptibility to Smoking and Nicotine Dependence in Schizophrenia(2009) Saperstein, Alice Meredith; Blanchard, Jack J; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Evidence suggests that high nicotine dependence observed in schizophrenia is related to its core neuronal deficits such as abnormalities in neural synchronization and sensory gating. Some of these neuronal deficits are shown to mark schizophrenia liability, raising the possibility that the increased nicotine dependence in schizophrenia is related to its etiological factors. This study sought to investigate mechanisms of increased vulnerability to smoking and nicotine dependence in schizophrenia. The individual and interacting effects of familial vulnerability factors, neurophysiological function, and resting cortical oscillatory activity (i.e. resting EEG power) were examined. The study sample was composed of four groups including outpatients with schizophrenia, first-degree relatives of patient index probands, healthy comparison control subjects from the community, and first-degree relatives of control probands. The resulting data demonstrated a pattern of more persistent nicotine use and greater dependence among those with schizophrenia relative to non-psychiatric comparison controls. Persistent smoking was also demonstrated to be highly heritable across groups with no discernable difference in the extent to which smoking is familial in those affected or unaffected by schizophrenia. With respect to resting oscillatory activity, analyses failed to find diagnostic group differences in EEG power for the alpha, beta, and gamma frequency bands and, unlike other substances of abuse, past and present nicotine use did not have a reliable effect on power in the beta frequency band. Rather, power in the gamma frequency band was significantly associated with smoking status. Furthermore, smoking was uniquely related to neurophysiological processes in probands with schizophrenia, suggesting that smoking status should be assessed in any study of information-processing dysfunction in this population. When all putative susceptibility factors were considered together, diagnosis of schizophrenia and family history of smoking best captured what may be characterized as an underlying (i.e. neurobiological) vulnerability to nicotine dependence, rather than circumscribed indices of electrophysiological functioning. Future studies might be implemented to refine the association between smoking and indices of electrophysiological function and, importantly, relate diagnostic or electrophysiological susceptibility factors to mediating processes and observable behaviors associated with aberrant patterns of nicotine use and dependence in persons with schizophrenia.Item The Relationship Between Physical Activity and Executive Control Functioning as Modified by Genotype(2007-08-03) Hearn, Joe W.; Hatfield, Bradley D.; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As we age, the structure of the brain deteriorates and cognitive functioning declines. The region of the brain that begins to age the fastest is the frontal lobe, in which the dorsal-lateral prefrontal cortex is involved in executive control functions such as planning, organizing, initiating behaviors, and working memory. For some individuals, the brain declines more rapidly with age because of genetic factors. Apolipoprotein E (APOE) is a gene that assists in the transport of cholesterol and repair of the brain when it is damaged. Presence of the ε4 allele impairs cholesterol transport and puts its carriers at risk for increased cognitive decline and possibly dementia of the Alzheimer's type (DAT). Physical activity can slow the aging process of the brain and delay the onset and severity of cognitive decline and DAT as it increases oxygenation and blood flow, neuronal growth and synaptogenesis, and it increases the expression of genes helpful to the functioning of the brain such as brain-derived neurotrophic factor (BDNF). Therefore, individuals at greater genetic risk for age-related cognitive decline (i.e., ε4 carriers) should receive increased benefit from physical activity. Accordingly, this study examined the relationship between physical activity and executive control functioning, assessed by the Wisconsin Card Sort Test (WCST) in middle-aged APOE ε4 carriers and non-carriers. High-active participants were predicted to perform better than their low-active counterparts, and this difference should be even greater among APOE ε4 carriers. While most research studies on this topic have focused on general cognitive performance, the present study is specific in its focus on executive control functioning. Sixty-seven cognitively normal middle-aged adults between the ages of 50 - 70 years were assessed on medical history, overall cognitive functioning, APOE genotype, level of physical activity, and executive control functioning (WCST). Using hierarchical regression, seven WCST variables were regressed on age, genotype, physical activity, and the interaction between genotype and physical activity. Analysis revealed that as level of physical activity increased, performance significantly improved on all seven WCST variables for APOE ε4 carriers, but not for non-carriers. These results reveal that the benefits of physical activity to cognitive performance in this age group are specific to those who are genetically at-risk for cognitive decline.Item Perceptual Consequences of Early-Onset Hereditary Hearing Loss in the Belgian Waterslager Canary (Serinus Canarius)(2006-05-30) Lauer, Amanda M; Dooling, Robert J; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Belgian Waterslager canaries (BWS) are bred for a distinctive low-pitched song that includes sounds that are thought to resemble water. This strain of canary has been used in multiple neurobiological and behavioral studies of song learning. These birds have a permanent hereditary hearing loss associated with missing and abnormal hair cells. The hearing deficit develops after hatch, but is present when the birds learn their song. The manner in which these birds process complex sounds indisputably affects the content of their vocalizations; however, no studies have looked at BWS canaries' ability to detect and discriminate sounds other than detection of pure tones in quiet. Thus, the BWS canary provides a unique opportunity to investigate the relationship between the form and function of an auditory system involved in vocal learning. Here I describe a series of psychoacoustic experiments that investigate differences in masking, discrimination, temporal processing, and perception of song elements in BWS canaries and normal-hearing non-BWS canary strains. Spectral and temporal studies of masking showed that frequency resolution and the phase response of the basilar papilla are impaired in BWS canaries. Frequency discrimination was superb at low frequencies, but worse than normal at high frequencies in BWS canaries. Duration and intensity discrimination was not adversely affected by the hearing loss. Temporal resolution was normal or better than normal under some conditions in BWS canaries. Despite the hearing loss, BWS canaries are able to accurately discriminate among strain-specific song syllables as well as syllables of other canary strains. In fact, BWS canaries are actually better than non-BWS canaries at discriminating among BWS canary syllables. These perceptual predispositions in BWS canaries are presumably related to the structural abnormalities of the inner ear, and are likely to play a role in song learning and song maintanence by enhancing the birds' ability to attend to important acoustic features that are characteristic of BWS vocalizations.Item Bee-ing There: The Systematicity of Honeybee Navigation Supports a Classical Theory of Honeybee Cognition(2006-04-27) Tetzlaff, Michael James; Rey, Georges; Philosophy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Classical theory of cognition proposes that there are cognitive processes that are computations defined over syntactically specified representations, "sentences" in a language of thought, for which the representational-constituency relation is concatenative. The main rival to Classicism is(Nonimplementational, or Radical, Distributed) Connectionism. It proposes that cognitive processes are computations defined over syntactically simple, distributed representions, for which the constituency relation is nonconcatenative. I argue that Connectionism, unlike Classicism, fails to provide an adequate theoretical framework for explaining systematically related cognitive capacities and that this is due to its necessary reliance on nonconcatenative constituency. There appears to be an interesting divergence of attitude among philosophers of psychology and cognitive scientists regarding Classicism's language of thought hypothesis. On one extreme, there are those who argue that only humans are likely to possess a language of thought (or that we at least have no evi- dence to the contrary). On the other extreme, there are those who argue that distinctively human thinking is not likely to be explicable in terms of a language of thought. They point to features of human cognition which they claim strongly support the hypothesis that human cognitive-state transition functions are computationally intractable. This implicitly suggests that the cognitive processes of simpler, nonhuman minds might be computationally tractable and thus amenable to Classical computational explanation. I review much of the recent literature on honeybee navigation. I argue that many capacities of honeybees to acquire various sorts of navigational information do in fact exhibit systematicity. That conclusion, together with the correctness of the view that Classicism provides a better theoretical framework than does Connectionism for explaining the systematicity of the relevant cognitive capacities, gives one reason in support of the claim that sophisticated navigators like honeybees have a kind of language of thought. At the very least, it provides one reason in support of the claim that the constituency relation for the mental representations of such navigators is concatenative, not nonconcatenative.Item EXERCISE BEHAVIOR AND MAINTENANCE OF CEREBRAL CORTICAL ACTIVITY DURING COGNITIVE CHALLENGE IN MIDDLE-AGED MEN AND WOMEN GENETICALLY AT RISK FOR DEMENTIA: A MEGNETOENCEPHALOGRAPHIC STUDY(2005-04-20) Deeny, Sean Patrick; Hatfield, Brad D; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Exercise is known to protect and enhance cognitive function in normal aging through increased blood flow and upregulation of neurotrophic factors in the brain. One recent study suggests that carriers of a known genetic risk factor for Alzheimer's disease (AD), the apolipoprotein E (APOE) E4 allele, may exhibit a more profound benefit of exercise on neurocognitive function relative to non-E4 carriers. Brain imaging studies in cognitively normal, middle-aged E4 carriers have revealed deficits in temporal and parietal cortical function even in the absence of clinical symptoms of dementia. As exercise has been shown to protect these regions in normal aging, and even enhance cortical functioning, the current study employs magnetoencephalographic (MEG) measures of cortical activation during the Ericksen flanker task and the Sternberg working memory task to examine whether highly physically active 50-70 year old E4 carriers and non-carriers, who are free from dementia, exhibit greater cortical activation in task-related regions relative to their low-active counterparts. The results revealed that high-active participants, regardless of genotype, exhibited greater activation on the Ericksen flanker task in the right frontal and right temporal regions relative to low-active participants, while performing similarly on accuracy and reaction time (RT). On the Sternberg working memory task high-active E4 carriers exhibited greater activation than low-active E4 carriers in the right temporal region, while being undifferentiated from both the high-active and low-active non-E4 carriers. This effect was most pronounced in the 150-200 ms post-stimulus time window. All groups performed similarly on accuracy and RT. The results suggest that high-resolution brain imaging methods are sensitive to differences in brain function in populations at different genetic risk for dementia prior to any signs of clinical impairment. Furthermore, the relationships between physical activity and brain function are measurable and distinguishable between groups of different genetic susceptibility on tasks and brain regions specific to AD-related neurocognitive decline. The findings support the notion that populations genetically at risk for dementia who remain sedentary may be at greater risk for decline in brain function relative to those who are physically active.Item Brain Electrical Activity in Infants of Depressed and Anxious Mothers(2005-05-09) VanMeenen, Kirsten; Wigfield, Allan; Human Development; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Numerous studies suggest that positive and negative emotions are associated with different patterns of cerebral hemisphere activation and that specific patterns of electroencephalographic (EEG) asymmetry may indicate risk for depression and anxiety. The extant developmental psychopathology literature has examined patterns of EEG asymmetry in the offspring of parents with affective disorders and such research has reported linkages between frontal EEG asymmetry and depression, suggesting that measures of EEG asymmetry may be important neurological markers of risk for affective disorders. Despite the greater prevalence of anxiety disorders than depressive disorders and the literature suggesting that resting EEG asymmetry may serve as an index of both depression and anxiety, no research has yet examined patterns of EEG asymmetry in the offspring of parents with anxiety disorders. The purpose of the present study was to examine early markers of risk for psychopathology in the biological domain (e.g., patterns of EEG asymmetry) in an attempt to elucidate some of the precursors of anxiety and depression in children so that we might gain a better understanding of the development of these disorders. The present investigation examined the relation between maternal history of depression and anxiety and patterns of EEG asymmetry in infant offspring. EEG measures of alpha power (4-6 Hz) in the right and left hemisphere were recorded in infants (four to eight months of age) of mothers with a documented history of major depressive disorder (n = 39), anxiety disorder (n = 22), and comparison subjects (n = 38) during a resting baseline task. Results suggest that maternal depression and maternal anxiety was statistically unrelated to patterns of infant asymmetry. The results suggested that fewer infants of mothers with specific phobia (with and without depression) had right mid-parietal asymmetry than infants of control mothers. Perceived social support was related to patterns of infant EEG asymmetry. These findings provide modest support for the hypothesis that maternal diagnostic history may be related to patterns of infant asymmetry in various regions of the brain during a resting state.Item Use of Multiple Cues for Navigation by the Leaf-cutter Ant Atta cephalotes.(2005-04-13) Vick, Kyle; Jeka, John; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In the first chapter, there is a brief introduction to ant navigation and a review of previous literature as well as a summary chapters 2-7. In chapter 2, I examine orientation of Atta cephalotes workers in the laboratory. Laden nest-bound foragers were moved from a "bridge" with or without trail pheromone present and placed on a parallel bridge with or without pheromone. In chapter 3, I continue to examine orientation of A. cephalotes foragers in the laboratory. Foragers walked on a single bridge and I altered various cues and contexts and recorded which manipulations caused the ants to reverse course. In chapter 4, I put orientation cues into direct conflict by letting the ants forage on a Y-maze. Foragers that were returning to a food source preferred visual cues to odor cues while recruited foragers consistently used odor cues. In chapter 5, I use a vertical T-maze to investigate the role that gravity plays in A. cephalotes navigation. The gravitational cue was put in direct conflict with odor cues and light cues. There was an asymmetry to the ants' response to the gravity cue in that ants returning to a food source had a tendency to go up regardless of the previous position of the food source or the position of the odor trail. Introducing a light cue changed the angle required to make the ants respond to the gravitational cue. In chapter 6, I investigate the anatomy of A. cephalotes eyes and brains. Based on tissue sections, I measured the angles between adjacent ommatidia in the eyes, and the volumes of sub-compartments of the brain. In chapter 7, I use the results from the other chapters to inform my speculations about the nature and neural basis of A. cephalotes navigation. I develop an hypothesis of navigation in the wild and a simple model of its neural underpinnings.Item CHOLINERGIC CONTRIBUTIONS TO EMOTION REGULATION(2004-12-17) Benson, Brenda Ellen; Cohen, Avis H; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Theories based on clinical and neuroanatomical studies implicate the muscarinic cholinergic system in normal and pathological emotion regulation. Emotional and sensory experiences can be induced with intravenous administration of the local anesthetic procaine hydrochloride, which selectively activates limbic regions in humans and animals. Procaine has a high affinity for muscarinic cholinergic receptors in vitro. This research tests three hypotheses: (1) procaine binds to muscarinic receptors in vivo; (2) procaine alters functional connectivity among cholinergic brain regions and their targets; and (3) procaine-induced emotions are related to core cholinergic regions. In Experiment I, anesthetized rhesus monkeys underwent positron emission tomography (PET) studies before and after administration of six doses of procaine on separate days using a radioligand with preferential binding to muscarinic M2 receptors ([18F]FP-TZTP). Procaine blocked [18F]FP-TZTP in a dose-response fashion uniformly across the brain, while significantly increasing tracer flow in limbic compared with non-limbic regions. In Experiment II, behavioral and physiological measures were assessed at baseline and following procaine in 32 healthy controls and 15 patients with bipolar disorder undergoing [15O] PET yielding regional cerebral blood flow (rCBF). Procaine selectively increased rCBF in anterior paralimbic regions in healthy controls, but to a lesser degree in patients. Regions connected via cholinergic pathways showed significantly different functional connectivity in both groups with procaine, however, prefrontal regions showed differential functional connectivity with cholinergic brain regions in patients compared with controls. Changes in activity of cholinergic regions explained the variance in anxiety ratings in an opposite manner in each group, and in euphoria ratings only in patients. In conclusion, procaine binds directly with muscarinic receptors in vivo while selectively increasing limbic activity in anesthetized monkeys. Two key findings herein procaine-induced alterations in functional connectivity of core cholinergic regions in humans, and the association of core cholinergic regional activity with emotional experience support theories implicating cholinergic contributions to emotion regulation. Decreased anterior paralimbic activity and altered functional connectivity of cholinergic regions in patients with bipolar illness compared with controls revealed by procaine offers additional insight into the regional neurobiology of the disease, and may ultimately be targeted in therapeutic approaches to bipolar disorder.