Inclusion Criteria:  Must be right-handed Must be illicit drug-free at the time of scanning as appropriate (verified by negative urine drug screen) Must be healthy (without medical, neurological, psychiatric illness) Must be psychotropic medication free (≥ 14 days)  Exclusion Criteria:  Must not be a smoker Females must not be pregnant or nursing Must not suffer from claustrophobia Must not meet exclusion criteria for MRI scanning (i.e., non-fixed magnetizable objects) Must not have ongoing, chronic, or relapsing/remitting medical, psychiatric,or neurological illness as determined by a combination of history, medical record, and/or examination.