[1] Johns Hopkins Univ, Sch Med, Dept Neurol, Baltimore, MD 21205 USA
[2] Johns Hopkins Univ, Sch Med, Dept Neurosurg, Baltimore, MD 21205 USA
[3] Johns Hopkins Univ, Whiting Sch Engn, Baltimore, MD USA
[4] Johns Hopkins Univ, Sch Med, Dept Radiol, Baltimore, MD 21205 USA
[5] Johns Hopkins Univ, Sch Med, Dept Phys Med & Rehabil, Baltimore, MD 21218 USA
[6] Johns Hopkins Univ, Dept Cognit Sci, Baltimore, MD 21218 USA