Activation
Silent synapses are activated via the insertion of AMPARs into the postsynaptic membrane, a phenomenon commonly called "AMPA receptor trafficking".
When glutamate binds to a strongly-depolarized postsynaptic cell (e.g., during Hebbian LTP), Ca2+ quickly enters and binds to calmodulin. Calmodulin activates calcium/calmodulin-dependent protein kinase II (CaMKII), which — among other things — acts on AMPAR-containing vesicles near the postsynaptic membrane. CaMKII phosphorylates these AMPARs, which serves as a signal to insert them into the postsynaptic membrane. Once AMPARs are inserted, the synapse is no longer silent; activated synapses no longer require simultaneous pre- and postsynaptic activity in order to elicit EPSPs.
Evidence suggests that dendrite arborization and synapse maturation 1 (Dasm1),an Ig superfamily member, is involved in the maturation of synapses, essentially "awakening" the silent synapses.
Read more about this topic: Silent Synapse