Striatal hyposensitivity to delayed rewards among cigarette smokers.

BACKGROUND Brain regions that track value (including the ventral striatum) respond more during the anticipation of immediate than delayed rewards, even when the delayed rewards are larger and equally preferred to the immediate. The anticipatory response to immediate vs. delayed rewards has not previously been examined in association with cigarette smoking. METHODS Smokers (n=35) and nonsmokers (n=36) performed a modified monetary incentive functional Magnetic Resonance Imaging (fMRI) task (Knutson et al., 2000) that included opportunities to win either immediate or delayed rewards. The delayed rewards were larger and equally preferred to the immediate rewards. RESULTS Across groups, greater activation was observed in regions previously shown to track value including bilateral ventral/dorsal striatum during the anticipation of immediate relative to delayed rewards. This effect was significantly greater among smokers than nonsmokers within the right ventral striatum. This group difference was driven particularly by low striatal activation among smokers during delayed reward trials. CONCLUSIONS The general tendency for striatal reward anticipatory activity to be attenuated when rewards are delayed is exaggerated among smokers relative to comparison participants. Among possible explanations of this relationship are that (1) low anticipatory response to delayed rewards is a phenotypic risk factor for smoking and (2) smoking-related neuroadaptations result in reduced recruitment during the anticipation of delayed rewards.