NMDA Receptor as a Mediator of Activity-dependent Synaptogenesis in the Developing Brain

The synapses that exist in the adult vertebrate brain are the survivors of a rigorous, competitive sorting process that occurs during a discrete period of development and that uses activity patterns in convergent pathways. Numerous experiments have manipulated activity to demonstrate that the refined topographic projections and the segregated stimulus response properties of the mature central nervous system (CNS) are sculpted during development by a process that appears to stabilize converging synapses that cooperate in driving common target cells. That the local circuitry within each brain region may be organized by similar "Hebbian" rules has recently been suggested by a number of computational models of neural self-organization. Thus, activity, long relegated to the role of functional validator of other developmental interactions, is slowly emerging as a prominent structuring parameter in the complex process of neural circuit differentiation.