Intrinsic plasticity is the continuous modification of intrinsic electrical properties of a neuron by synaptic or neuronal activity. It can affect diverse processes as synaptic integration, sub-threshold signal propagation, spike generation, spike back-propagation, and meta-plasticity as it is mediated by changes in the expression level or biophysical properties of ion channels in the membrane. The function of intrinsic plasticity in behaving animals is uncertain but there is experimental evidence for several distinct roles: as part of the memory engram itself, as a regulator of synaptic plasticity underlying learning and memory, and as a component of homeostatic regulation.
Intrinsic plasticity is distinct from synaptic plasticity, which involves changes at the synapse between two neurons rather than changes in the electrical properties within a single neuron. There are some closely related phenomena that can affect a neuron's excitability – such as neuromodulation, structural plasticity, short-term plasticity due to channel kinetics, and neural development – but are generally excluded from the term intrinsic plasticity.