1. Medical Research Council Cyclotron Unit, Hammersmith Hospital, London, UK
2. Department of Neurology, Hǒpital Purpan, Toulouse, France
3. Cattedra di Neuropatologia e Psicopatologia, Dipartimento di Scienze Neurologiche, Universita degli Studi “La Sapienza,” Rome, Italy
4. Institute of Neurology, National Hospital for Nervous Diseases, London, UK