[1] Univ Rochester, Med Ctr, Rochester, NY 14627 USA
[2] Montreal Neurol Inst, Montreal, PQ, Canada
[3] Maimonides Hosp, Brooklyn, NY 11219 USA
[4] Inst Neurol, London WC1N 3BG, England
[5] Biogen Idec, Cambridge, MA USA
[6] Michigan Inst Neurol Disorders, Farmington Hills, MI USA