FIG. 10.

(a) Schematic diagram of the energy function landscape of the Hopfield network. (b) The potential landscape ${\varphi }_0(\mathit{x})$ of a symmetric neural network. (c) The potential landscape ${\varphi }_0(\mathit{x})$ as well as the corresponding force for an asymmetric neural circuit: the green arrows represent the flux, and the white arrows represent the force from the negative gradient of the potential landscape. Reproduced with permission from H. Yan et al., Proc. Natl. Acad. Sci. U. S. A. 110, E4185–E4194 (2013). Copyright 2013 the Authors.²³