Figure 6. Scheme of microglia functions during synaptogenesis.

(a) Sequence of proposed cellular events during synapse formation: Microglial contact initiates a rise in local [Ca²⁺]_i resulting in actin accumulation and filopodia formation. Some filopodia find presynaptic partners and mature into functional synapses. (b) Schematic graph depicting a change in microglia phenotype and function, from immature or activated microglia inducing filopodia formation and enhancing specific circuit synapse formation during early synaptogenesis, followed by a putative role in synapse elimination by more mature, quiescent microglia in the latter period of circuit formation.