An autapse is a chemical synapse from a neuron onto itself. It can also be described as a synapse formed by the axon of a neuron on its own dendrites, in vivo or in vitro.
Discovered in 1972, autapses were originally thought to be a biological curiosity. In 1998, they had been commonly found in some circuits of the cat's visual cortex, which suggested a functional role. In 2000, they were first modeled as supporting persistence in recurrent neural networks. In 2004, they were modeled as providing oscillatory behavior to a neuron. By 2006, their presence and operation in multiple areas in the brain were described. in 2009, they were associated with sustained activation. In 2014, a regulation role was added. In 2015, they were described as enabling self-describing neural circuits. In 2016, a model of resonance was offered.