[1] Natl Hosp Neurol & Neurosurg, Inst Neurol, London WC1N 3BG, England
[2] Inst Neurol, Sobell Dept Motor Neurosci, London WC1N 3BG, England
[3] Inst Neurol, Wellcome Trust Ctr Neuroimaging, London WC1N 3BG, England
[4] Univ Calif Los Angeles, Los Angeles, CA 90024 USA
[5] NINDS, NIH, Bethesda, MD 20892 USA
[6] Univ Kansas, Med Ctr, Lawrence, KS 66045 USA
[7] Emory Univ, Atlanta, GA 30322 USA
[8] Univ Edinburgh, Edinburgh EH8 9YL, Midlothian, Scotland
[9] Kings Coll London, London, England
[10] Univ Newcastle, Callaghan, NSW 2308, Australia
[11] UCL, Inst Cognit Neurosci, London WC1E 6BT, England