UMD Theses and Dissertations
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Item RAPID ADAPTIVE PLASTICITY IN AUDITORY CORTEX(2010) Atiani, Serin; Shamma, Shihab A; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Navigating the acoustic environment entails actively listening for different sound sources, extracting signal from a background of noise, identifying the salient features of a signal and determining what parts of it are relevant. Humans and animals in natural environments perform such acoustic tasks routinely, and have to adapt to changes in the environment and features of the acoustic signals surrounding them in real time. Rapid plasticity has been reported to be a possible mechanism underling the ability to perform these tasks. Previous studies report that neurons in primary auditory cortex (A1) undergo changes in spectro-temporal tuning that enhance the discriminability between different sound classes, modulating their tuning to enhance the task relevant feature. This thesis investigates rapid task related plasticity in two distinct directions; first I investigate the effect of manipulating task difficulty on this type of plasticity. Second I expand the investigation of rapid plasticity into higher order auditory areas. With increasing task difficulty, A1 neurons' response is altered to increasingly suppress the representation of the noise while enhancing the representation of the signal. Comparing adaptive plasticity in secondary auditory cortex (PEG) to A1, PEG neurons further enhance the discriminability of the sound classes by an even greater enhancement of the target response. Taken together these results indicate that adaptive neural plasticity is a plausible mechanism that underlies the performance of novel auditory behaviors in real time, and provide insights into the development of behaviorally significant representation of sound in auditory cortex.Item Action, Perception, and the Living Body: Aristotle on the Physiological Foundations of Moral Psychology(2009) Russo, Michael P.; Singpurwalla, Rachel G. K.; Philosophy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this dissertation I show that Aristotle's moral psychology is grounded in his natural philosophy of the living body. Moral psychology studies the ways in which agency and moral responsibility are rooted in the functional structure of the psyche. For Aristotle, the psyche - that is, the soul (psychê) - is unified with the living body, and its functional structure is integrated with the dispositional propensities of the body's material constituents. On account of this, "the soul neither does anything nor has anything done to it without the body..." (DA I.1, 403a 5) Accordingly, Aristotle considers it an "absurdity" of the accounts of his predecessors that "they attach the soul to the body and set it into it, determining no further what the cause of this is or what the condition of the body is..." (DA I.3, 407b 14) However, most contemporary interpretations of Aristotle's moral psychology suffer from essentially this same problem: they interpret Aristotle's explanation of, say, voluntary action or lack of self-restraint (akrasia) in entirely psychological terms, and say nothing about the physiological processes that Aristotle takes to partially constitute, and to critically influence, these phenomena. Here I address this imbalance by exploring Aristotle's view of the somatic dimension of moral psychology. More specifically, I examine Aristotle's so-called "hylomorphism" - the view that a living thing's body and soul are its material and its form (respectively) - and his account of the physiological functions underlying "incidental perception" (roughly, "seeing as" or perceiving particulars under a description), voluntary action, practical reasoning and its role in moving us to act, lack of self-restraint, and moral development.Item CARDIOVASCULAR FITNESS MODIFIES THE RELATIONSHIP BETWEEN GENOTYPE AND NEUROCOGNITIVE FUNCTION DURING EXECUTIVE CHALLENGE IN LATE ADOLESCENCE(2008-11-06) Woo, Minjung; Hatfield, Bradley D; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Cardiovascular fitness and physical activity have been positively associated with executive cognitive functioning (i.e., planning, scheduling, coordinating, response inhibition, and working memory), which rely on the frontal region of the brain. Recent studies suggest that the benefit is particularly strong in middle-aged individuals who carry the Apolipoprotein (ApoE) e4 allele, a known genetic risk factor for Alzheimer's disease (AD). However, there have been no studies to determine this interactive relationship in adolescents. Therefore, the present study examined if cardiovascular fitness mediates the relationship between genotype and cerebral cortical responses in college-age males during a frontally-mediated executive challenge. Twenty nine e4 carriers (N=29; 15 high-fit, 14 low-fit) and thirty non-carriers (N=30; 15 high-fit, 15 low-fit) were stratified by cardiovascular fitness. Cognitive function was assessed by neuroelectric response, event-related potentials (ERPs) recorded at 11 sites (F3, Fz, F4, C3, Cz, C4, P3, Pz, P4, O1 and O2) to both an auditory Go-nogo executive task (ECF) and a non-executive Oddball task (non-ECF). The P300 amplitude, which is indicative of the recruitment of attentional resources, exhibited by the high-fit e4 carriers was higher relative to that observed in the low-fit e4 carriers during both the ECF and non-ECF tasks. Importantly, the high-fit e4 carriers were also undifferentiated from both groups of the non-carriers. Furthermore, high-fit individuals, regardless of genotype, exhibited shorter P300 latency than did the low-fit individuals at sites Fz, Cz and Pz during ECF task and site Pz during non-ECF task. The current findings revealed genetic specificity in the relationship between cardiovascular fitness and the brain processes indexed by P300 amplitude function during late adolescence in response to both ECF and non-ECF challenge, with greater benefit incurred for the ECF task. The results suggest that cardiovascular fitness in e4 carriers is protective against the susceptibility to the liabilities (i.e., hypometabolism and cortical thinning) associated with this allele.Item Evaluating an Evidence-Based Intervention for Families and Survivors after Traumatic Brain Injury: The Brain Injury Family Intervention(2008-10-28) Stejskal, Taryn M; Epstein, Norman; Kreutzer, Jeffrey; Family Studies; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The long-term detrimental impact of traumatic brain injury (TBI) on individuals and their family members is well known. However, there have been few standardized family interventions or findings from treatment efficacy studies to guide clinical practice. The Brain Injury Family Intervention (BIFI) is an evidence-based, five-session, manualized clinical intervention, provided for both family members and the injured person. Guided by cognitive behavioral theory, the program provides education, skill building, and psychological support for both persons with brain injury and their family members. The objective of the present study was to test the efficacy of the BIFI as it was designed to improve the emotional well-being and life quality of persons with brain injury and their family members. Evaluation occurred in an outpatient neuropsychology department attached to a major academic medical center, with a sample of 53 family member caregivers of 53 TBI survivors. It was hypothesized that the BIFI would increase the proportion of caregivers' met needs, decrease their psychological distress, increase their perception that survivors' neurological functioning had improved, and reduce perceived obstacles to obtaining services. It also was hypothesized that the BIFI would result in improved neurological functioning for survivors. A secondary analysis of existing data using repeated measures mixed models was used to analyze four self-report measures for family members: (1) the Family Needs Questionnaire (FNQ); (2) the Service Obstacles Scale (SOS); (3) the Brief Symptom Inventory-18 (BSI-18); and (4) the Neurological Functioning Inventory (NFI). Survivors' neurological functioning was examined based on their own self-report data, also measured by the NFI. Data were collected at pre-treatment, immediate post-treatment and at a three-month follow-up after treatment. Statistical analyses revealed that, after participating in the BIFI program, caregivers reported significantly more met family needs, perceived fewer obstacles to receiving services, and rated the survivor as having reduced depression and somatic symptoms. No significant effects were observed for caregiver psychological distress or survivors' reports of their neurological functioning. Methodological limitations, implications for clinical intervention with families after TBI, and suggestions for future research are discussed.Item The response-monitoring mechanism: Influence of feedback and temperament(2008-05-06) Martin McDermott, Jennifer; 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 examine behavioral and physiological processes underlying response-monitoring and to document the manner in which these processes are expressed during early childhood. As well, this study examined two factors important in understanding individual differences in monitoring: performance feedback and temperament. A total of seventy-four children (mean age 7.5 years) were tested using a modified flanker paradigm administered in both no-feedback and feedback conditions. Accuracy and reaction time measures of behavioral performance were assessed as well as event-related potentials linked to response execution and feedback presentation. Data were also examined in relation to the temperamental dimensions of shyness and inhibitory control. The results indicate a strong impact of trial-by-trial feedback on both behavioral and physiological measures. Overall, feedback served to increase children's task engagement as evidenced by fewer errors of omission and faster reaction times. Similarly, the physiological measures also varied as a function of feedback such that the error-related Positivity (Pe) and the feedback-related negativity (FRN) were more pronounced on incorrect as compared to correct trials in the feedback condition. Larger FRN responses were also associated with fewer errors of commission. These findings were further moderated by individual differences in temperament. Specifically, feedback was particularly influential in increasing task involvement for children low in inhibitory control and enhancing performance accuracy for children low in shyness Overall these results confirm a strong impact of feedback on task engagement as assessed by children's behavioral performance and physiological reactivity. Findings are presented in the framework of individual differences in cognitive control and variations in children's physiological measures of response-monitoring are discussed. Several avenues for future research are provided which emphasize the need for investigations of response-monitoring in young children and also highlight the importance of exploring the applicability of these assessments across various cognitive and social contexts.Item Age-related Difference in Kinematics and Cerebral Cortical Processes during Discrete Drawing Movements in Children and Adults(2007-06-06) Pangelinan, Melissa Marie; Clark, Jane E; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Research has shown developmental improvements in drawing movements during childhood. These changes may be related to protracted structural development and myelination of cortical brain structures underlying motor planning and control. However, no study to our knowledge has examined the relationship between cortical development and the emergence of accurate visuomotor behavior. This thesis characterized age-related differences in kinematics and cerebral cortical processes during the performance of discrete drawing movements in children, as compared to adults. Three groups were included in the study: young girls (6- to 7-year-olds), older girls (9- to 11-year-olds), and adult females (n=15, each). Participants performed 5cm center-out drawing movements with the dominant hand (right hand), while electroencephalography (EEG) was recorded. All participants exhibited similar task-related cortical communication (coherence) and activation (relative spectral power) in several frequency bands. Activation of motor neural resources (motor cortical potentials) in the midline pre-motor and motor regions was also similar across age groups. The similarity of the brain activation patterns for these measures may contribute to the comparable behavioral performance among all groups for root mean squared error (straightness) and movement length. However, other features of the young children's brain activation patterns and motor control were different than the older children and/or adults. Specifically, the young children showed increased activation of frontal (executive process) areas, whereas the older children and adults exhibit increased relative activation in task-relevant sensorimotor areas (as measured by spectral power) in frequencies related to sensorimotor processes and attention. Similarly, increased coherence in the lower beta and gamma bands, indicative of local networking, was found in the adults between the frontal and central regions, and the frontal and parietal areas. Moreover, the adults show increased activation of the contralateral sensorimotor areas time-locked to the onset of movement, compared with the young children. The increased activation of the motor areas and visuomotor networks during movement planning may contribute to faster, smoother, and more consistent behavioral performance for the older children and adults, not evident in the young children.Item Individual Differences in Emotional and Physiological Responses to Televised Sports Violence: A Test of Sensation Seeking Theory(2007-04-26) Lee, Shu-Chen; Hatfield, Bradley D.; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Purpose: To test sensation-seeking theory as an explanation for individual differences in emotional and physiological responses to violence in televised sports and account for sex differences in those responses. Methods: One hundred ten non-smoking subjects prescreened for the personality trait of sensation seeking were selected for the experiment. Subjects viewed two videos of plays from professional football games; one featuring violent action, the other showing little or no violence, and a video of natural scenery (neutral content) as a distraction between the two treatment videos to minimize any carry-over effects. Participants' emotional responses (levels of pleasure and arousal) were subjected to two separate 2 (sensation seeking) x 2 (biological sex) x 3 (video treatment) x 2 (order of video treatment) ANOVAs, while participants' physiological reactions (heart rate, skin conductance, and respiration) were subjected to three separate 2 (sensation seeking) x 2 (biological sex) x 3 (video treatment) x 2 (viewing period) x 2 (order of video treatment) ANOVAs to test the study's main hypotheses. Results: Emotional (self-reported levels of pleasure and arousal) and physiological responses (heart rate, skin conductance, and respiration) were not different between high and low sensation seekers for either high- or low-violence televised sports. However, high sensation seekers did report higher levels of pleasure (for both sexes) and exhibit faster mean respiration (for males only) when watching high-violence televised sports than neutral content, and the pleasure level was significantly higher for high sensation seekers (for both sexes) when watching low-violence televised sports than neutral content. Significant sex differences in self-reported levels of pleasure and arousal were observed; males reported higher levels of pleasure than females when watching high-violence televised sports, and males reported less arousal than females when watching low-violence televised sports. Sex differences in physiological responses were also found; however, the direction of the effect was inconsistent. In addition, viewers' self-reported pleasure and arousal increased with the degree of violence; nevertheless, this relationship was more pronounced in males than in females. Conclusions: Sensation-seeking theory failed to account for individual and sex differences in emotional and physiological responses to sports violence; however, the data support the notion that high sensation seekers enjoyed arousing and exciting media content (both high- and low-violence football plays) more than milder themes (neutral content). Although previous studies have found that the preference for violent televised sports, such as football, is associated with sensation seeking, the results indicated there might be other characteristics besides violent content that account for sensation seekers attraction to football. Biological sex was found to be a strong predictor of spectators' responses to sports violence. In addition, this study provides support for previous research suggesting that violence contributes to viewers' arousal and enjoyment of televised sports, especially for male viewers.Item Sensory Integration During De-adaptation to Visuomotor Distortions(2006-08-31) King, Bradley Ross; Clark, Jane E.; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Previous research has demonstrated that adults can adapt to novel sensorimotor perturbations, a process thought to be achieved by the gradual update of an adaptive internal representation. However, few research studies have investigated the persistence of a newly acquired representation, as assessed by the reduction of performance errors after the perturbation has been removed (i.e., de-adaptation). The primary objective of this thesis was to determine if the central nervous system (CNS) could flexibly utilize visual and proprioceptive afference to de-adapt to novel sensorimotor perturbations. It has been previously demonstrated that the CNS relies more heavily on visual information for hand localization in the azimuthal direction whereas proprioception is more heavily weighted for hand localization in the radial direction. Seventy-two right-handed adults executed reaching movements during exposure to either an incremental visuomotor rotation or gain distortion. Visual feedback provided during post-exposure was manipulated. Results indicate that the CNS predominantly utilized visual afference to de-adapt to both perturbations, despite the fact that rotation adaptation resulted in movement errors in the azimuthal direction whereas gain adaptation resulted in movement extent errors. These data suggest that the CNS did not flexibly re-weight proprioceptive afference in the absence of visual feedback during a center-out drawing task.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 A Role for the Superior Colliculus in the Control of Sonar Vocal Production in the Echolocating Bat, Eptesicus fuscus(2005-03-28) Sinha, Shiva; Moss, Cynthia F; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Microchiroptera have evolved a biological sonar system that enables aerial foraging in total darkness. These echolocating bat species emit sequences of ultrasonic vocalizations and use the returning echoes to create acoustic images of the environment. Bats orient their gaze in space by adjusting their sonar vocalizations, flight dynamics, and head aim in a coordinated manner when approaching targets. Insectivorous species of echolocating bats have been shown to actively modulate the features of sonar vocalizations with changing target distance. Therefore, variations in the time-frequency structure and temporal patterning of sonar calls produced by foraging bats reflect adaptive goal directed behaviors. The bat's heavy reliance on sound production and processing is reflected in neural specializations of auditory and motor structures. The experiments described in this dissertation probe the midbrain superior colliculus (SC), a vertebrate sensorimotor nucleus mediating orienting behaviors, and they specifically explore adaptations in the SC of the insectivorous bat, Eptesicus fuscus, for acoustic orienting. The anatomical experiments conducted demonstrate that the bat SC has projections to pre-vocal motor control regions in the brainstem: paralemniscal tegmentum area, cuneiform nucleus, and midbrain reticular formation. Further insights were gained by developing chronic neural recording techniques to study SC neuronal activity in actively echolocating bats. These are the first chronic recordings in unrestrained, freely behaving bats. The physiological experiments reveal two bouts of neural activity prior to each sonar vocalization, and suggest a relationship between the timing of pre-vocal activity and sonar call duration. Based on the anatomical findings and the functional pre-motor activity identified here, along with previous electrical and chemical microstimulation studies in the bat midbrain, a conceptual model is proposed for the SC of bats that suggests its role in orienting acoustic gaze along the range axis. This role of the bat SC is similar to that proposed for primate and feline SC in controlling the visual depth of focus via vergence eye movements. The parallel between the visuomotor and echolocation systems for orienting gaze to objects at different distances suggests that the computations performed by the SC serve common functions across modalities and effort organs.