Basolateral amygdala - nucleus accumbens circuitry regulates optimal cue-guided risk/reward decision making

Abstract

Maladaptive decision making is a characteristic feature of substance use disorder and pathological gambling. Studies in humans and animals have implicated neural circuits that include the basolateral amygdala (BLA) and nucleus accumbens (NAc) in facilitating risk/reward decision making. However, the preclinical literature has focussed primarily on situations where animals use internally-generated information to adapt to changes in reward likelihood, whereas many real-life situations require the use of external stimuli to facilitate context-appropriate behavior. We recently developed the "Blackjack" task, to measure cued risk/reward decision making requiring rats to chose between Small/Certain and Large/Risky rewards, with auditory cues at the start of each trial explicitly informing that the probability of obtaining a large reward was either good (50%) or poor (12.5%). Here we investigated the contribution of the BLA and its interaction with the NAc in guiding these types of decisions. In well-trained male rats, bilateral inactivation of the BLA induced suboptimal decision making, primarily by reducing risky choice on good-odds trials. In comparison, pharmacological disconnection of the BLA and NAc-shell also induced suboptimal decision making, diverting choice from more preferred option by reducing or increasing risky choice on good vs. poor odds trials respectively. Together, these results suggest that the BLA-NAc circuitry plays a crucial role in integrating information provided by discriminative stimuli. Furthermore, this circuitry may aid in guiding action selection of advantageous options in situations to maximize rewards. Finally, they suggest that perturbations in optimal decision making observed in substance abuse and gambling disorders may be driven in part by dysfunction within this circuitry.

Keywords: Amygdala; Conditional discrimination; Decision making; Nucleus accumbens; Reward.