Life Sciences Commons^™

Neural Substrates Of Fear Generalization And Its Associations With Anxiety And Intolerance Of Uncertainty, Ashley Ann Huggins

Theses and Dissertations

Fear generalization - the tendency to interpret ambiguous stimuli as threatening due to perceptual similarity to a learned threat – is an adaptive process. Overgeneralization, however, is maladaptive and has been implicated in a number of anxiety disorders. Neuroimaging research has indicated several regions sensitive to effects of generalization, including regions involved in fear excitation (e.g., amygdala, insula) and inhibition (e.g., ventromedial prefrontal cortex). Research has suggested several other small brain regions may play an important role in this process (e.g., hippocampal subfields, bed nucleus of the stria terminalis [BNST], habenula), but, to date, these regions have not been examined …

Neural Correlates Underlying The Interactions Between Anxiety And Cannabis Use In Predicting Motor Response Inhibition, Richard Ward

Theses and Dissertations

The ability to effectively withhold an inappropriate response is a critical feature of cognitive control. Prior research indicates alterations in neural processes required for motor response inhibition in anxious individuals, including those with posttraumatic stress disorder (PTSD), and those who engage in regular cannabis use. However, thus far most research has examined how anxiety-related symptoms and cannabis use influence response inhibition in isolation of one another. The current study examined the interactions between anxious symptomology and recent cannabis use in a sample that recently experienced a traumatic event using functional magnetic resonance imaging (fMRI) during the completion of a Stop-Signal …

Data-Driven Approach To Dynamic Resting State Functional Connectivity In Post-Traumatic Stress Disorder, Carissa Weis

Theses and Dissertations

Posttraumatic stress disorder (PTSD) is a heterogenous psychological disorder that may result from exposure to a traumatic event. Using functional magnetic resonance imaging (fMRI), symptoms of PTSD have been associated with aberrations in brain networks that emerge in the absence of a given cognitive demand or task, called resting state networks. Most previous research in resting state networks and PTSD has focused on aberrations in the static functional connectivity among specific regions of interest (ROI) in the brain and within canonical networks constrained by a priori hypotheses. However, dynamic fMRI, an approach that examines changes in brain network characteristics over …

Neural Substrates Of Active Avoidance And Its Impact On Fear Extinction, Elizabeth Parisi

Theses and Dissertations

Models of anxiety suggest that avoidance of a conditioned fear stimulus prevents new safety learning, thereby serving to maintain fear. However, there is little empirical data in humans on the impact of avoidance of conditioned fear stimuli on subsequent fear extinction. In the present study I investigated the effect of avoidance of threat on neural activity during avoidance/control and a subsequent extinction phase using ultra high-resolution (7T) fMRI. Results indicated that active avoidance was associated with increased activity in regions involved in reward prediction, but this did not differentiate active avoidance from an active control condition. Neural activation during the …

Cannabis-Using Youth Demonstrated Blunted Rostral Anterior Cingulate Cortex Activation, But Normal Functional Connectivity, During An Emotional Go/No-Go Task, Kristin Elizabeth Maple

Theses and Dissertations

Cannabis use has been associated with deficits in self-regulation, including inhibitory control. Cannabis users have previously exhibited both structural and functional deficits in the rostral anterior cingulate cortex (rACC), a region involved in self-regulation of emotional response and inhibitory control. The present study aimed to examine whether abstinent cannabis users demonstrated abnormal functional activation and connectivity of the bilateral rACC during an emotional inhibitory processing task, and whether gender moderated these relationships. The study also aimed to examine whether bilateral rACC activation and connectivity in cannabis users was related to perceived stress. It was hypothesized that cannabis users would exhibit …

Hpa Axis Genetic Variation And Life Stress Influences On Functional Connectivity In Resting State Networks, Tara Ann Miskovich

Theses and Dissertations

Stressful or traumatic experiences are a key risk factor for developing psychopathology, primarily through the impact that chronic stress has on hypothalamic-pituitary-adrenal (HPA) axis functioning. The HPA axis regulates the stress response but can become dysregulated with chronic activation and impact brain functioning. In addition to environmental stressors, genetic variation in genes in the HPA axis appear to influence HPA axis functioning and is also related to disruption in brain functioning, particularly in the context of high life stress. The current study focused on examining potential mechanisms through which trauma and stress interacts with HPA axis genes to impact key …

Neural Correlates Of Memory Decisions Made In The Face Of Conflict, Elaine Mahoney

Theses and Dissertations

We’ve all experienced moments where, for some reason or another, we don’t want to reveal to others what we truly know. The current experiment investigated questions about the behavioral and neural correlates of these types of memory decisions made in the face of a conflicting goal. Participants in this experiment studied several scene-face pairs and were tested with three-face displays preceded by studied scene cues. They were instructed to indicate whether the three-face display contained the matching associate or not. Critically, half of the participants were instructed to simulate feigned memory impairment (i.e. simulators), while the remainder were instructed to …

Alcohol Use Disorders And An Fmri Stress Task: A Connectivity Analysis, Natasha E. Wright

Theses and Dissertations

Little research has been conducted on neuronal stress processing in individuals

with alcohol dependence (AD). The present study examined neural stress response in AD individuals compared to controls using an fMRI stress task, assessing amygdala

activation and its connectivity to the medial prefrontal cortex (mPFC). Further, the study

analyzed the impact of hormone levels and subjective stress on frontal-limbic

connectivity patterns.

Ten abstinent AD individuals and 11 controls were recruited. Subjects

participated in an fMRI stress task. A region of interest (amygdala) analysis was

conducted using area-under-the-curve. This activation was then examined in a whole brain functional connectivity analysis. Follow-up …