Appetitive cue exposure increases neural reward responses without modulating temporal discounting

Abstract

When given a choice, humans and many animals prefer smaller but sooner over larger but later rewards, a tendency referred to as temporal discounting. Alterations in devaluation of future rewards have been reported in a range of maladaptive behaviors and clinical conditions. Although temporal discounting is highly stable over time and testing environments (e.g., laboratory vs. virtual reality), it is partly under contextual control. For example, highly appetitive cues such as erotic images might increase preferences for immediate rewards, although overall evidence remains mixed. Dopaminergic circuit activity and striatal dopamine concentrations are often assumed to drive increases in temporal discounting following appetitive cue-exposure, yet this was never explicitly tested. Here we examined cue-reactivity effects (erotic vs. neutral pictures) on subsequent temporal discounting in a pre-registered within-subjects study in healthy male participants (n=38). Functional magnetic resonance imaging (fMRI) assessed neural cue-reactivity, value-computations and choice-related effects. Preregistered analyses replicated previous findings of value coding in ventromedial prefrontal cortices, striatum and cingulate cortex. Likewise, as hypothesized, lateral prefrontal cortex activity increased during choices of delayed rewards, potentially reflecting cognitive control. As predicted, erotic vs. neutral cue exposure was associated with increased activity in attention and reward circuits. Contrary to our preregistered hypotheses, temporal discounting was largely unaffected by cue exposure. Likewise, cue-reactivity in key areas of the dopaminergic reward circuit (Nacc, VTA) was not significantly associated with changes in behavior. Our results indicate that behavioral effects of erotic cue exposure on temporal discounting might not be as unequivocal as previously thought and raise doubt on the hypothesis of an upregulated dopaminergic ramping mechanism, that might support myopic approach behavior towards immediate rewards.