Design. After being medically cleared and giving informed consent, each participant will complete several imaging visits (6 visits, on separate days) before and after taking varenicline. Two of these visits will take place before varenicline administration (baseline), two visits after a two-week varenicline dosing period (post-varenicline), and another two after a two-week placebo-pill period (post-placebo-pill). Each set of two scans will involve the randomized, double blind administration of a nicotine transdermal or placebo patch. fMRI and EEG data will be collected after patch application and will involve several tasks designed to probe brain regions in a corticolimbic circuit that may mediate aspects of reward-processing, learning, attention, goal-directed behaviors, and drug abuse.