Examining the role of Dopamine D2 Receptors in cost-benefit decision making processes underlying motivated behavior in mice

Motivation is a process critical for the survival of organisms, directing and invigorating behavior. Recent human and animal studies have revealed that processing information about costs and benefits is important to adaptive goal-directed behavior, suggesting that cost-benefit decision making plays a crucial role in influencing motivated behavior. Current behavioral tasks which assay cost-benefit decision making often measure willingness to expend effort, but also manipulate reward value simultaneously. To study the distinct roles of effort and value, we develop two tasks in which we offered subjects either a choice between different types of work or a choice between different reward values. By giving subjects a choice between types of work, bar pressing or bar holding, or value, pellets and sucrose concentration, and parametrically altering the relative effort between them, the Concurrent Effort Choice (CEC) and Concurrent Value Choice (CVC) tasks create functions of choice behavior which represent the calculation of effort or value, respectively. Using pharmacological and genetic manipulations of the Dopamine D2 receptor (D2R), which has specifically been shown to be critically involved in dopamine’s modulation of motivated behavior, we address the hypothesis that D2R signaling affects the assessment of effort while leaving value representation unaltered. We first examine the effects of acute dopamine D2 receptor antagonism on cost-benefit decision making using these novel behavioral assays. We further characterize the role of the D2 receptor by examining a genetic model which overexpresses the D2 receptor specifically within the striatum