Geon Short-Term Memory Trace: Postsynaptic AMPAR Memory

 

As discussed in the previous chapter, neuronal firing is determined by the summation of EPSPs and IPSPs that spread to the axon initial segment. A larger EPSP should facilitate neuronal firing. AMPA receptors (AMPARs) are the major contributor to EPSPs. Like NMDA receptors (NMDARs), they belong to ligand-gated ion channels. AMPARs can be activated by glutamate alone, but the opening of NMDARs requires both glutamate binding and the relief of Mg2+ block.

Long-term Potentiation

Long-term potentiation (LTP) refers to the enhancement of synaptic strength after associative learning. During learning process, the Ca2+ influx through NMDARs may activate CaMKII, resulting in the translocation of AMPARs to the postsynaptic site (Figure 3-1). Since the opening of AMPARs allows Na+ ions to enter the neuron, more AMPARs on the postsynaptic membrane should generate larger EPSP when glutamates are released from the presynaptic axon terminal. In this manner, the synaptic strength between two neurons is enhanced. The increased AMPAR number on the postsynaptic membrane represents a memory trace created by the learning process.

Image

Figure 3-1. LTP arises from the larger amount of AMPARs on the postsynaptic membrane. [Source: OpenStax College]

 

Author: Frank Lee
First Published: April 15, 2013
Last updated: September, 2017