As a chronically relapsing brain disorder drug addiction places a major social and economic burden on society, not least on crime rate and health care provision. It is increasingly accepted that drug addiction results from complex interactions between pre-disposing behavioural variables or traits (e.g. sensation-seeking, impulsiveness), chronic drug exposure and environmental influences including learning experiences. Recently, ‘trait-like’ impulsivity in rats has been reported to be highly predictive of the development of compulsive (or habitual) cocaine-seeking behaviour that persists despite adverse consequences, a hallmark feature of addiction (Dalley et al., 2007; Belin et al., 2008). The proposed research aims to investigate the hypothesis that impulsive rats are more prone to habit-based behaviour than non-impulsive rats, a propensity postulated to depend on the prefrontal cortex (PFC) and impaired processing of contextual (environmental) attributes by the PFC and associated brain regions. The central objective of this research is to better understand the interaction between individual differences in impulsivity and contextual learning experiences and how this interaction facilitates the transition to habitual or compulsive patterns of drug-seeking. Specifically, this research will compare impulsive rats and non-impulsive rats in their sensitivity to outcome devaluation (OD), a test of habit-based learning and the role of the context in this process. This research will also investigate the role of PFC DA in the modulation of context-dependent OD by administering DA as well as selective DA receptor agonists and antagonists directly into the PFC of impulsive and non-impulsive rats. Overall, this research project integrates behavioural theories of learning (Bouton, 2002) with state-of-the-art drug addiction hypothesises (Everitt & Robbins, 2005) to elucidate how innate and environmental factors play a role in maladaptive behaviours relevant to drug addiction.
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