Heterosynaptic plasticity

Heterosynaptic plasticity is a subtype of synaptic plasticity, referring to a chemical synapse's ability to undergo changes in strength, or efficacy of signal transmissions. More broadly, synaptic plasticity can be defined as molecular changes providing the mechanism for learning and memory to occur, by altering neuronal firing frequency. Modern synaptic plasticity theory, built off the work of Santiago Ramón y Cajal, separates plasticity into two more broadly defined categories, Hebbian plasticity, also known as homosynaptic plasticity, and heterosynaptic plasticity. Synaptic plasticity is typically input-specific, meaning that the activity of a postsynaptic neuron, is altered by a neuron or neurons' release of neurotransmitters, transmitting a stimuli. In homosynaptic plasticity, only the input from a presynaptic neuron synapsing with a specific postsynaptic neuron can undergo plasticity. However, in the case of heterosynaptic plasticity, plasticity can result from either activity in a presynaptic neuron or from a separate modulatory interneuron, creating synaptic depression or strengthening. Thus, Hebbian or homosynaptic plasticity is often referred to as activity dependent, while heterosynaptic plasticity is referred to as modulatory dependent. A number of distinct forms of heterosynaptic plasticity have been found in a variety of brain regions and organisms. These different forms of heterosynaptic plasticity contribute to a variety of neural processes including associative learning, the development of neural circuits, and homeostasis of synaptic input.