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Title: Schizophrenia, dopamine, and the prefrontal cortex : theory and computational models
Author: Reid, Alastair Gilmour
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2002
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I have suggested a possible mechanism for the action of DA in the PfCx and illustrated this with biologically plausible models which can be interpreted at cellular and pharmacological levels. I have then related this to schizophrenia. Dysfunctions between brain regions are also suggested to underly the symptoms of schizophrenia. This is the other theme of the thesis, where I have used a reinforcement learning based model to examine interactions between brain regions and the effects of variations in DA transmission on these interactions. More specifically, I will show how oscillations between pyramidal cells and GABA cells in the PfCx may arise (chapter 4), and how disruption of this information processing capacity can occur through multiple different pathologies. The existence of oscillations is shown through simulations and theoretically by modelling neurotransmitter interactions within the mesocortical and mesolimbic dopamine (DA) systems (chapter 5). This work reveals the conditions under which oscillations will occur, and shows how DA can act as a control parameter in initiating oscillations. Finally, I have modelled a high level cognitive process, the Tower of London task, using a rule-based model to represent PfCx function and a reinforcement learning model to represent NAcc function (chapter 6). The interaction between the two models is investigated and illustrations of the possible origins of the positive symptoms of schizophrenia are given. In all of these models, the role of DA has been crucial. One conclusion from this work is that the symptoms of schizophrenia may arise through inappropriate fluctuations in DA levels in the NAcc and the PfCx. The work is based on a large amount of neurobiological data and follows theories presented by Friston (1998) and Goldman-Rakic amongst others.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available