Decision making mechanisms underlying choice in an animal model of addiction.

décembre 2014 Directeur(s) de thèse : Serge AHMED Résumé de thèse

Drug addiction is defined as a psychiatric disorder involving compulsive drug use, despite negative consequences, and is increasingly conceptualized as resulting from poor decision making with a preference bias towards the drug at the expense of other socially-valued behaviors. The most important challenge in current addiction research is to understand the physiopathology of this disorder. Animal models are important tools in addiction research, since they are less ethically and technically limited than human studies.

However, preclinical research on drug addiction is typically performed in laboratory rats that are given ready access to drugs for intravenous self-administration but without other options. The lack of choice during drug access limits its validity for understanding the physiopathology of addiction. A series of studies from our laboratory has previously shown that when offered a mutually exclusive choice between pressing a lever to get sweet water or an alternative lever to receive an intravenous dose of cocaine or heroin, most rats prefer sweet water.
Only a minority of rats persists in drug taking despite the availability of an alternative reward, and thus, appears to be more vulnerable to drug addiction. During my thesis, my main objective was to determine the psychological and behavioral determinants of choice between drugs of abuse (cocaine and heroin) and sweet water.

This research allowed us to determine the decision-making processes underlying this choice, by testing the predictive validity of different decision-making models. Additionally, we evidenced a strong interaction between the choice setting, the drug’ direct effects and rats’ specific cognitive abilities that reliably influences drug choices in rats.
This finding should lead to a novel interpretation of drug choice studies in rats and also raises important issues regarding the relative validity of choice procedures for modelling drug addiction.