1. Institute of Basic Medical Science, Ningxia Medical University, Yinchuan, Ningxia 750004, P.R. China
2. School of Public Health and Management, Ningxia Medical University, Yinchuan, Ningxia 750004, P.R. China
3. Ningxia Key Laboratory of Cerebrocranial Diseases, Ningxia Medical University, Yinchuan, Ningxia 750004, P.R. China