 On the other hand, some neural networks are more biologically realistic (Buckner and Garson 2019; Illing, Gerstner, and Brea 2019). For instance, there are neural networks that replace backpropagation with more realistic learning algorithms, such as a reinforcement learning algorithm (Pozzi, Bohté, and Roelfsema 2019, Other Internet Resources) or an unsupervised learning algorithm (Krotov and Hopfield 2019). There are also neural networks whose nodes output discrete spikes roughly akin to those emitted by real neurons in the brain (Maass 1996; Buesing, Bill, Nessler, and Maass 2011).