1. Wellcome Department of Cognitive Neurology, Institute of Neurology, London WC1N 3BG, UK
2. Neuropsychology Unit, University Department of Clinical Neurology, The Radcliffe Infirmary, Oxford OX2 6HE, UK
3. Rivermead Rehabilitation Centre, Oxford OX1 4XD, UK
4. Royal Free Hospital School of Medicine, Roland Hill Street, London NW3, UK