[1] Univ Iowa, Carver Coll Med, Iowa City, IA USA
[2] UCL Queen Sq Inst Neurol, London, England
[3] Univ Wisconsin Madison, Madison, WI USA
[4] Univ Penn, Dept Neurol, Perelman Sch Med, Philadelphia, PA 19104 USA
[5] Fdn IRCCS Ist Neurol Carlo Besta, Milan, Italy
[6] Univ Rochester, Dept Neurol, Rochester, MN USA