[1] UCL, UCL Inst Neurol, Sobell Dept Motor Neurosci & Movement Disorders, London WC1N 3BG, England
[2] Univ Med Ctr Hamburg Eppendorf UKE, Dept Neurol, Hamburg, Germany
[3] Hosp Badalona Germans Trias & Pujol, Dept Neurol, Badalona, Spain
[4] Hosp Mar, Dept Neurol, Barcelona, Spain
[5] Kings Coll Hosp NHS Fdn Trust, Dept Neurol, London, England
[6] Queen Elizabeth Hosp, Lewisham & Greenwich NHS Trust, Dept Neurol, London, England
[7] Univ London, Dept Psychol, London, England
[8] UCL, Inst Cognit Neurosci, London, England