Correspondence to: Dr. Tang Yunxiang, Faculty of Psychology and Mental Health, the Second Military Medical University of PLA, Shanghai 200433, China (Tel: 86-21-81871450. Email: tangyunxiang1973@tom.com); Chen Xingshi, Department of Electrophysiology, Shanghai Mental Health Center, Shanghai Jiao Tong University, Shanghai 200030, China (Tel:86-21-64387250. Emal: chenxingshi2008@ 163.com)