Metaplasticity is a term originally coined by W.C. Abraham and M.F. Bear to refer to the
plasticity of
synaptic plasticity. Until that time synaptic plasticity had referred to the plastic nature of
individual synapses. However this new form referred to the plasticity of the plasticity itself, thus the term
meta-plasticity. The idea is that the synapse's previous history of activity determines its current plasticity. This may play a role in some of the underlying mechanisms thought to be important in
memory and
learning such as
Long-term potentiation (LTP),
Long-term Depression (LTD) and so forth. These mechanisms depend on current synaptic "state", as set by ongoing extrinsic influences such as the level of
synaptic inhibition, the activity of modulatory afferents such as
catecholamines, and the pool of
hormones affecting the synapses under study. Recently, it has become clear that the prior history of synaptic activity is an additional variable that influences the synaptic state, and thereby the degree, of LTP or LTD produced by a given experimental protocol. In a sense, then, synaptic plasticity is governed by an activity-dependent plasticity of the synaptic state; such plasticity of synaptic plasticity has been termed metaplasticity. There is little known about metaplasticity, and there is much research currently underway on the subject, despite its difficulty of study, because of its theoretical importance in brain and cognitive science. Most research of this type is done via
cultured hippocampus cells or hippocampal slices.
