Psychology of Reward and Punishment: Functional and Molecular Brain Imaging and Monoaminergic Correlates

Objective: This protocol will integrate functional brain imaging of reward processing, together with assessment of the response to oral dextroamphetamine (d-AMPH), monoaminergic genotyping, and evaluation of past exposure to stress, in order to examine: (1) the relationship between these factors (i.e. dopamine function, brain activity, reward processing, genetic profile and exposure to stress) in normal healthy adults; and (2) variation in these factors between normal healthy adults and individuals with current cocaine-dependence, and how this variation contributes to observed behavioral and functional differences between these populations. Study Population: The study populations will consist of adult (18-45 years old) healthy volunteers with no history of substance abuse or dependence and a matched group of individuals with current primary cocaine-dependence. Experimental Design and Method: After being medically cleared and giving informed consent, each participant will undergo fMRI (four sessions, on separate days) and PET scanning (two sessions, on separate days). All brain imaging sessions will take place after single-blind administration of either d-AMPH (0.43 mg/kg orally) or placebo. Functional MRI will commence after dosing and will include several measures (both cognitive and affective) designed to activate neural circuitry involved in the processing of reward and punishment. PET scanning will also take place after d-AMPH or placebo and will involve administration of the radioligand \[18F\] Fallypride to assess CNS dopamine function. Outcome Measures: This study is concerned with differences in the noted factors between experimental cohorts (controls vs. cocaine-dependent adults) and conditions (baseline vs. post d-AMPH). The primary outcome measures, used to ascertain these differences, will be: (1) the percentage change in fMRI BOLD signal during performance of measures of reward processing and cognitive function; (2) alterations or differences in the binding potential of \[18F\]Fallypride; (3) variations in genes related to DArgic function between individuals and groups, and the contribution of this variation to other outcome measures; and (4) history of exposure to stressful events and its role in behavioral and functional outcomes.