1 Department of Psychological and Brain Sciences, Krieger School of Arts and Sciences, Johns Hopkins University, Baltimore, MD, 21218, USA. patricia.janak@jhu.edu.
2 Department of Neuroscience, Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, MD, 21205, USA. patricia.janak@jhu.edu.
3 Behavioral Neuroscience Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, Baltimore, MD, 21224, USA.