All ETDs from UAB

Advisory Committee Chair

David C Knight

Advisory Committee Members

Edwin W Cook

Rajesh K Kana

Adrienne C Lahti

Kristina M Visscher

Document Type

Dissertation

Date of Award

2013

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

Successful regulation of the emotional response to a threat allows one to react more effectively under threatening conditions. The prefrontal cortex (PFC) and amygdala are key brain regions that mediate the regulation and expression of emotion. We employed Pavlovian fear conditioning to investigate the neural mechanisms that influence the emotional response to a threat. These procedures were designed to investigate conditioned diminution of the unconditioned response (UCR). The specific aims were to better understand the role of associative learning, expectation, controllability, and predictability in modulating UCR expression. This project employed functional magnetic resonance imaging (fMRI) to assess the magnitude of the threat-related response within the PFC, cingulate cortex, inferior parietal lobule, insula, amygdala, and hippocampus. We also investigated the peripheral expression of emotion indexed via skin conductance response (SCR) and startle eye-blink electromyography (EMG) during differential fear conditioning. To assess the effect of expectation of an impending threat, volunteers provided a continuous self-report measure of UCS expectancy throughout the conditioning sessions. We also examined whether individual differences in anxiety level influenced the emotional response to a threat. In general, we observed a relationship between anxiety level and the threat-related neurophysiological response. Conditioned UCR diminution within the neurophysiological response was also observed. More specifically, the threat-related fMRI signal response and SCR expression was diminished on predictable vs. unpredictable trials. However, the opposite pattern was observed in the EMG data. An enhanced startle-eyeblink response was observed for predictable compared to unpredictable trials. Further, controllability affected the threat-related fMRI signal response within the ventromedial PFC and hippocampus. The unconditioned SCR elicited by the threat paralleled the fMRI signal response within several brain regions that showed UCR diminution. A negative relationship was observed between UCS expectancy and the threat-related response within several brain regions that showed conditioned UCR diminution. In summary, we observed learning-related changes in the emotional response to a threat within regions of the PFC, amygdala, and hippocampus. The current findings suggest that these brain areas support learning-related processes that modulate the emotional response to a threat.

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