Department of Neurology, Jinling Hospital, Nanjing University School of Medicine, 305# East Zhongshan Road, Nanjing, Jiangsu Province, People's Republic of China; Department of Psychological Studies and Center for Psychosocial Health and Aging, The Hong Kong Institute of Education, China. Department of Psychological Studies and Center for Psychosocial Health and Aging, The Hong Kong Institute of Education, China. Bioinformatics and Imaging Programmatic Cores, The Methodist Hospital Research Institute, Weill Cornell Medical College, Houston, TX, USA. Department of Radiology and Organ Imaging, The Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region, China. Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region, China. Department of Neurology, Jinling Hospital, Nanjing University School of Medicine, 305# East Zhongshan Road, Nanjing, Jiangsu Province, People's Republic of China. Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region, China. Electronic address: vctmok@cuhk.edu.hk.