1. From the Neurophysiology Laboratory (I.A.A., Y.S., C.S.O., K.I.M.), Neurosurgical Service, Massachusetts General Hospital and Harvard Medical School, Boston, Mass; the Department of Neurosurgery (T.M.), Kochi Medical School, Kochi, Japan; and the Division of Neurosurgery (E.-J.L.), Department of Surgery, National Cheng Kung University Medical Center and Medical School, Tainan, Taiwan.