[1] Johns Hopkins Univ, Dept Neurol, Baltimore, MD 21218 USA
[2] Johns Hopkins Univ, Dept Elect & Comp Engn, Baltimore, MD 21218 USA
[3] North Shore Med Ctr, Dept Internal Med, Salem, MA USA
[4] Univ Texas Southwestern, Dept Neurol & Ophthalmol, Dallas, TX USA
[5] NYU, Dept Neurol, Langone Med Ctr, New York, NY 10016 USA