Genetic Differences in Limbic Activation Associated With Nicotine Withdrawal

Objectives: * To evaluate neural correlates associated with emotional processing during nicotine withdrawal preferentially involving the amygdala and associated areas within the corticolimbic and mesolimbic circuitry. We hypothesize that relative to a pre-quit baseline, post-quit nicotine withdrawal will result in increased activity to negative emotional cues, in contrast to other cues, in one or more areas of interest, and particularly in the right cerebral hemisphere. * To determine if bupropion and varenicline moderate patterns of brain activation during post-quit nicotine withdrawal. We hypothesize that relative to placebo, bupropion and varenicline will attenuate the effects of post-quit nicotine withdrawal on emotional processing, reducing activation to negative emotional cues, relative to other cues, in one or more areas of interest, and particularly in the right cerebral hemisphere. * To determine if genotype (DRD2 TaqA2 allele and the ins variant of the -141C ins/del DRD2) moderates patterns of brain activation during post-quit nicotine withdrawal.