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Anhedonia and other reward-related deficits in animal models of psychiatric disorder

Wright, Rebecca 2015. Anhedonia and other reward-related deficits in animal models of psychiatric disorder. PhD Thesis, Cardiff University.
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New insights have revealed the complex and heterogeneous nature of reward-related behaviours: not only are different aspects of reward (e.g. reward 'liking' and 'wanting') subserved by dissociable neural mechanisms, but they are differentially expressed across major psychiatric disorders. The aim of this thesis was to investigate discreet reward-related processes, pertaining to the hedonic and cognitive processing of rewards, in relation to schizophrenia and depression preclinical models. The Methylazoxymethanol acetate (MAM) neurodevelopmental model of schizophrenia and the Wistar Kyoto (WKY) inbred depression model were chosen based on their good face and construct validities to the clinical conditions. Microstructural analysis of licking in simple drinking and contrast situations were used to investigate the constructs of consummatory and anticipatory anhedonia in these models. Whilst MAM-treated rats showed no behaviours indicative of consummatory or anticipatory anhedonia, WKY rats showed generally lower consummatory and palatability responses to sweet solutions and failed to suppress their palatability responses to a contrasted solution (when a preferred solution was expected). Therefore, WKY rats demonstrated behaviours analogous to deficits in both consummatory and anticipatory aspects of hedonic processing. To investigate cognitive processing of rewards, outcome devaluation and differential outcome paradigms were adopted, but no impairments on either task were found for the MAM model. In contrast, WKY rats were insensitive to post-conditioning changes in reward value and did not benefit from stimulus-correlated outcomes during the acquisition of a conditional discrimination task. Therefore, WKY rats do not appear to use the nature and /or value of rewards to guide their behaviours in the same manner as controls. In short, MAM-treated animals did not display the hedonic deficits or impaired instrumental behaviours expected for a comprehensive schizophrenia model. In contrast, the WKY inbred rat strain appears to be suitable in investigating manifestations of clinical depression in respect to reward-processing deficits.

Item Type: Thesis (PhD)
Date Type: Publication
Status: Unpublished
Schools: Psychology
Subjects: B Philosophy. Psychology. Religion > BF Psychology
Uncontrolled Keywords: Schizophrenia; Depression; Methylazoxymethanol acetate; Wistar Kyoto; Reward; Anhedonia; Licking microstructure; Goal-directed action; Habits; Differential outcomes effect
Date of First Compliant Deposit: 18 May 2016
Date of Acceptance: 18 May 2016
Last Modified: 07 Jun 2017 10:32

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