Journal of Cerebral Blood Flow & Metabolism 35, 536–542; doi:10.1038/jcbfm.2014.240; published online 14 January 2015 Correspondence: Dr F Hua, Department of Neurology, Affiliated Hospital of Xuzhou Medical College, 99 West Huaihai Road, Xuzhou, Jiangsu 221002, PR China. E-mail: huafang@xzmc.edu.cn This work was supported by AHA National Program SDG 0830481N, National Natural Science Foundation of China , Jiangsu Specially Appointed Professor Program, and Jiangsu Six Major Talent Summit Programs to FH, and partly by NIH 5R01NS048451 and 1R01HD061971 to DGS.