Variants of the back-propagation algorithm as well as unsupervised methods by Geoff Hinton and colleagues at the University of Toronto can be used to train deep, highly nonlinear neural architectures,[29] similar to the 1980 Neocognitron by Kunihiko Fukushima,[30] and the "standard architecture of vision",[31] inspired by the simple and complex cells identified by David H. Hubel and Torsten Wiesel in the primary visual cortex.