A decision making model of Obsessive Compulsive Disorder: A neuropsychological and functional neuroimaging investigation

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Copyright: Olley, Amanda
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Abstract
Obsessive Compulsive Disorder (OCD) is a debilitating illness characterised by chronic doubt and indecision, and yet traditional models of OCD do not adequately account for these clinical manifestations. The current thesis therefore proposed a conceptual shift in OCD research towards an integrated decision making model to account for these behavioural phenomena and also encapsulate the neuropsychological profile and neurobiological differences reported in OCD. To determine the utility of decision making as a potential endophenotypic marker for OCD, and provide empirical support for the model, the current thesis explored decision making style, confirmed the neuropsychological profile of OCD and its potential impact on decision making, determined the extent and nature of decision making and response inhibition deficits in OCD, and employed functional magnetic resonance imaging (fMRI) paradigms to ascertain the neurobiological underpinnings of decision making. A distinct decision making style was identified in OCD characterised by elevated hyper vigilance, avoidant tendencies and reduced decision making confidence. Moderate neuropsychological deficits were observed largely within the domains of information processing and visual memory. Using a dynamic gambling task based on regret theory and a risk-taking task, both novel to the OCD population, OCD participants tended to make slower, sub-optimal, risk-averse decisions, particularly under conditions of uncertainty or when regret was a potential consequence. fMRI investigation of these tasks identified distinct neuronal dysfunction in each stage of the decision making process. The behavioural and neuroimaging studies supported a disruption in visuoperceptual systems, associated with the underactivity of the temporal, parietal and occipital regions, with unique contributions of the orbitofrontal cortex, dorsolateral and ventromedial prefrontal cortex. Evidence of clinical, cognitive and neurobiological dysfunction was amalgamated into a revised neuropsychobiological decision making framework that accounted for the heterogeneous clinical features of OCD as well as chronic doubt and indecision. Central to the model were the notions of regret and risk-aversion, concepts that require further research and validation. Importantly, the model not only provides further understanding of this uniquely complex disorder, but provides a framework upon which to base and evaluate novel or adjunctive treatments.
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Author(s)
Olley, Amanda
Supervisor(s)
Sachdev, Perminder
Malhi, Gin
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Publication Year
2015
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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