Nature Reviews Neuroscience 9, 82 – 83 (February 2008)
One of the main cellular mechanisms assumed to underlie learning is long-term potentiation (LTP), an experimental form of synaptic plasticity that results in a long-lasting increase in the strength of synaptic transmission. However, prolonged synaptic stimulation in vitro eventually stops producing further LTP (also known as ‘LTP occlusion’). So, how does ongoing experience result in further learning? Clem et al. now show that the opposing actions of activated N-methyl-D-aspartate receptors (NMDARs) and metabotropic glutamate receptors (mGluRs) allow progessive synaptic strengthening during sensory-induced plasticity.