  Autapses are synapses that connect a neuron to itself in the nervous system.
Previously, both experimental and theoretical studies have demonstrated that
autaptic connections in the nervous system have a significant physiological
function. Autapses in nature provide self-delayed feedback, thus introducing an
additional time scale to neuronal activities and causing many dynamic behaviors
in neurons. Recently, theoretical studies have revealed that an autapse
provides a control option for adjusting the response of a neuron: e.g., an
autaptic connection can cause the electrical activities of the Hindmarsh-Rose
neuron to switch between quiescent, periodic, and chaotic firing patterns; an
autapse can enhance or suppress the mode-locking status of a neuron injected
with sinusoidal current; and the firing frequency and interspike interval
distributions of the response spike train can also be modified by the autapse.
In this paper, we review recent studies that showed how an autapse affects the
response of a single neuron.
