1. V. Kostic, V. Jackson-Lewis, S. Przedborski, Department of Neurology, Columbia University, 650 West 168 Street, BB-307, New York, NY 10032, USA.
2. F. de Bilbao and M. Dubois-Dauphin, Hôpitaux Universitaires de Genève, Division of Neuropsychiatry, 2 Chemin du Petit Bel Air, 1225 Geneva, Switzerland.