1. Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, United Kingdom;
2. Division of Neurological Pain Research and Therapy, Department of Neurology, University Hospital Schleswig-Holstein, Campus Kiel, 24105 Kiel, Germany
3. Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, United Kingdom