1. Department of Geriatrics, Xijing Hospital, Medical University of the Air Force, Xi`an, 710032, China
2. Department of Rehabilitation, Affiliated Hospital of Yan`an University, Yan`an, 716000, China
3. Department of Anatomy and Histology and Embryology, K.K. Leung Brain Research Centre, China
4. Department of Clinical Aerospace Medicine, Medical University of the Air Force, Xi`an 710032, China