  In 1982 John Hopfield published a neural network model for memory retrieval,
a model that became a cornerstone in theoretical neuroscience. A key ingredient
of the Hopfield model was the use of a network dynamics that is governed by a
Lyapunov function. In a recent paper, Krotov and Hopfield showed how a Lyapunov
function governs a biological plausible learning rule for the neural networks'
connectivity. By doing so, they bring an intriguing approach to classification
tasks, and show the relevance of the broader framework across decades in the
field.
