[1] HARVARD UNIV, SCH MED, DEPT PHYSIOL, BOSTON, MA 02115 USA
[2] MASSACHUSETTS EYE & EAR INFIRM, EATON PEABODY LAB, BOSTON, MA 02114 USA
[3] MIT, DEPT ELECT ENGN & COMP SCI, CAMBRIDGE, MA 02139 USA
[4] MASSACHUSETTS GEN HOSP, NEUROL SERV, BOSTON, MA 02114 USA