4-5 Day inpatient study. Participant will have scanned pictures (MRI & PET scans) taken of their brain after being injected with a small amount of WIN, a radioactive substance. Participants give daily urine samples and fill out health related questionnaires. It is important to determine whether the alterations characterized within one week of last drug use persist over a longer time period. Based on results of the studies from aims 1 & 2, we will decide which of the 2 probes, WIN or FDOPA-PET is the more sensitive index of stimulant-dependency-induced changes.