Memory  >   Long-Term Potentiation and Depression

Long-Term Potentiation

Long-term potentiation (LTP) refers to the enhancement of synaptic strength which, as discussed in Chapter 3, is determined by synaptic AMPARs. Experimentally, LTP can be induced by several different protocols. However, in the physiological system, the associative learning is thought to induce LTP by activating NMDARs to trigger Ca2+ influx, which in turn may activate CaMKII, resulting in the translocation of AMPARs to the postsynaptic site (Figure 5-1).


Figure 5-1. LTP arises from the increase of synaptic AMPARs. [Source: OpenStax College]

Long-Term Depression

Long-term depression (LTD) refers to the weakening of synaptic strength, resulting from the decrease of synaptic AMPARs. Like LTP, LTD is also induced by Ca2+ influx through NMDARs. However, in the case of LTD, the Ca2+ influx activates calcineurin to dephosphorylate AMPARs, leading to AMPAR endocytosis (removal from the membrane) (Figure 5-2).


Figure 5-2. LTD is caused by AMPAR endocytosis. [Source: OpenStax College]

How can Ca2+ influx through NMDARs induce two opposite memory processes? Its underlying mechanism is explained in this chapter.


Author: Frank Lee
First Published: January, 2018