Posttraumatic Stress Disorder (PTSD) is an anxiety disorder characterised by disturbed arousal, altered attention, and fear processing, and a reduction in the ability to perform cognitive tasks. Predominant neurophysiological models of PTSD have been focused on alterations in fear-related regulation, and few incorporate broader changes in generic executive control which may underlie many of the clinical symptoms and cognitive deficits in PTSD. This thesis aimed to investigate the neurophysiology of executive inhibitory control in PTSD using a Go/NoGo response inhibition task and converging functional imaging, structural imaging and electrophysiological measures. The first series of studies aimed to elucidate a normative neural network model of inhibitory control, and are consistent with normative control involving the activation of a mainly right-lateralised ventral lateral prefrontal cortex (VLPFC) network. Inhibitory control-related activation was found to be affected by levels of anxiety and changes in underlying neural structure; alterations in frontal cortical maturation and volume were related to additional activation of bilateral frontal cortical regions and the dorsal striatum, with anxiety increasing the demand on inhibitory control-related activation. In contrast to healthy participants, PTSD was associated with reduced inhibitory control as indexed by inhibitory behaviour, diminished activation of the right VLPFC, and slowed inhibition-related information processsing. PTSD participants relied on the greater activation of a left fronto-striatal inhibition network to support control, with the activation affected by levels of PTSD severity and comorbid anxiety. This left fronto-striatal activation in PTSD was related to underlying increases in fronto-striatal neural structure. Further, the ability to efficiently engage a left fronto-striatal network in PTSD during inhibitory control predicted better response to cognitive behavior for PTSD, consistent with the proposal that an improved ability to flexibly engage control systems may facilitate the resolution of PTSD symptoms. Taken together, this program of research extends current neurophysiological model of PTSD to show that PTSD involves a fundamental disturbance in the function and structure of key fronto-striatal response control networks associated with inhibitory control.
| Identifer | oai:union.ndltd.org:ADTP/234998 |
| Date | January 2008 |
| Creators | Falconer, Erin Michelle, Psychology, Faculty of Science, UNSW |
| Publisher | Publisher:University of New South Wales. Psychology |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://unsworks.unsw.edu.au/copyright, http://unsworks.unsw.edu.au/copyright |
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