Group for Neural Theory, Laboratoire des Neurosciences Cognitives, École Normale Supérieure, Paris, France.|Wolfson Institute for Biomedical Research and Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom.|Wolfson Institute for Biomedical Research and Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom.|Group for Neural Theory, Laboratoire des Neurosciences Cognitives, École Normale Supérieure, Paris, France.|Wolfson Institute for Biomedical Research and Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom.