Strictly speaking, an autapse is a synapse from the axon of a neuron to one of its dendrites, that is, from its output to its input. However, structures have been found via Eyewire formed as a looped branch in a dendrite that may be either autapses or self-touches (i.e. not a synapse at all). In EyeWire's 2D view, these generally appear to be branches that move away from the main branch, approach it again, but only touch again along a cell membrane.
Autapses have been known since at least 1972.
- Seung, HS; Lee, DD; Reis, BY; Tank, DW (2000). "The Autapse: A Simple Illustration of Short-Term Analog Memory Storage by Tuned Synaptic Feedback", J. Computational Neuroscience 9:171-185. doi: 10.1023/A:1008971908649.
- Seung, Sebastian (March 20, 2012) Loops, Eyewire Forums
- Van der Loos, H; Glaser EM (1972). "Autapses in neocortex cerebri: synapses between a pyramidal cell's axon and its own dendrites", Brain Research 48:355-60. doi: 10.1016/0006-8993(72)90189-8. Paywalled.