Enhanced preference for delayed rewards requires the basolateral amygdala and retrosplenial cortex

Sunk or irrecoverable costs imposed on a subject can impact reward-based decisions. However, it is not known if these incurred costs elicit a sustained change in reward value. To address this, we examined if sunk temporal costs subsequently alter reward consumption and reward preference in rats. We first identified the relative preference between different flavored food pellets during a free-feeding consumption test. Animals were then trained to experience the initial less preferred reward after long delays and the initial preferred reward after short delays. This training regimen enhanced the consumption and preference for the initial less desirable food reward. We probed whether this change in reward preference involved neural systems that contribute to reward valuation. Pharmacological manipulations and site-specific lesions were performed to examine the potential involvement of the dopamine system, the orbitofrontal cortex (OFC), the basolateral amygdala (BLA), and the retrosplenial cortex (RSC). The change in reward preference was unaffected by systemic dopamine receptor antagonism or OFC lesions. In contrast, lesions of the BLA or the RSC prevented the enhanced consumption and preference for the initial less desirable reward. These findings demonstrate that both the BLA and RSC participate in how sunk temporal costs alter reward value and reward preference. Significance StatementFrom an economic standpoint, only future costs should factor into ones decisions. However, behavioral evidence across species illustrates that past costs can alter decisions. The goal of this study was to identify the neural systems responsible for past costs influencing subsequent actions. We demonstrate that delivering an initially less desirable reward after long delays (high temporal costs) subsequently increases the consumption and preference for that reward. Furthermore, we identified the basolateral amygdala and the retrosplenial cortex as essential nuclei for mediating change in reward preference elicited by past temporal costs.