Poor decision-makers: motivation, working memory performance, and repartition across two inbred strains of rats

Abstract

A minority of healthy individuals (poor decision-makers, PD) exhibit a combination of behavioral traits reminiscent, at least in part, of addiction and predicting poor decision-making (DM), namely motor impulsivity, inflexibility, risk-taking, and higher motivation in Wistar Han rats. Two behavioral features, motivation and working memory (WM), play a role in DM capacities although the precise relationship is not entirely known. Additionally, we previously reported that neurotransmitters e.g., dopamine - modulation was tightly linked to the PD phenotype. The goal of the study was to investigate the detailed motivational functions in PD individuals including saccharin intake, reward-seeking or incentive behaviors under different internal states i.e., food-deprived or ad libitum. Maze-based spatial WM was also evaluated. Moreover, two inbred strains of rats, Lewis and Fisher 344 (F344) rats, known for modeling vulnerability to drug addiction and affected by substantial variations in the mesolimbic dopaminergic pathway, were run in the DM task (Rat Gambling Task, RGT). PD Wistar Han rats displayed higher saccharin intake levels and a drastic increased reward-seeking behavior on a fixed schedule. PD were more sensitive to the internal state in responding to saccharin delivery in fixed but not in progressive schedules. A few relationships were found within motivational functions, and with DM, that is a positive correlation between saccharin intake and reward-seeking behavior, and a negative correlation between saccharin intake and DM. PD were significantly not impaired in WM. Lewis and F344 rats displayed improved performance early in the task (exploration) and a higher proportion of PD was observed in Lewis as compared to F344 rats. Altogether, these findings complete the preclinical panel of behavioral functions that relate to poor DM and extend a presumed role of dopamine in such processes.