Center for Brain Imaging, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, 710071, China. State Key Laboratory of Cancer Biology, National Clinical Research Center for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, Shaanxi, 710032, China. Electronic address: jigang@fmmu.edu.cn. College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling, Shaanxi, 712100, China. Department of Psychology, Southwest University, Chongqing, 400715, China. Department of Radiology, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi, 710038, China. Depart of Psychiatry, Xijing Hospital, The Fourth Military Medical University, Xi'an, Shaanxi, 710032, China. State Key Laboratory of Cancer Biology, National Clinical Research Center for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, Shaanxi, 710032, China. Laboratory of Neuroimaging, National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD, 20892, USA. Section on Clinical Psychoneuroendocrinology and Neuropsychopharmacology, National Institute on Alcohol Abuse and Alcoholism and National Institute on Drug Abuse, Bethesda, MD, 20892, USA. Center for Brain Imaging, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, 710071, China. Electronic address: yizhang@xidian.edu.cn. Laboratory of Neuroimaging, National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD, 20892, USA. Electronic address: gene-jack.wang@nih.gov.