1. Center for Studies of Addiction, Department of Psychiatry, University of Pennsylvania Perelman School of Medicine , Philadelphia, Pennsylvania , USA
2. University of Pennsylvania Perelman School of Medicine, Department of Radiology , Philadelphia, Pennsylvania , USA
3. National Institute on Alcohol Abuse and Alcoholism , National Institutes of Health, Bethesda, Maryland , USA
4. National Institute on Drug Abuse, National Institutes of Health , Baltimore, Maryland , USA