1 Group for Neural Theory, Laboratoire de Neurosciences Cognitives et Computationnelles, Département d'Etudes Cognitives, École Normale Supérieure, Université Paris Sciences et Lettres, Paris, France.
2 Department of Physics and Astronomy, and Centre for Vision Research, York University, Toronto, Ontario, Canada. joelzy@yorku.ca.
3 Learning in Machines and Brains Program, Canadian Institute for Advanced Research (CIFAR), Toronto, Ontario, Canada. joelzy@yorku.ca.