Affiliation: | 1. Intramural Research Program of the National Institute on Drug Abuse, Baltimore, MD 21224, USA;2. Princeton Neuroscience Institute and Department of Psychology, Princeton University, Princeton, NJ 08544, USA;3. Department of Anatomy and Neurobiology, Maryland School of Medicine, Baltimore, MD 21201, USA;4. Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA |