Experience-Dependent Plasticity and the Maturation of Glutamatergic Synapses

Glutamatergic synaptic currents undergo a characteristic pattern of maturation during early development. This pattern involves changes in the kinetics of N-methyl-D-aspartate (NMDA) receptor currents and, possibly, the formation of “silent” synapses that express only NMDA receptor currents and are later made functional by the addition of α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate (AMPA) receptor currents. These maturational changes in glutamatergic synapses have implications for the early development of neural networks (Cline et al. 1996) and for the mechanisms underlying long-term potentiation (LTP) of synaptic efficacy (Malenka and Nicoll 1997). Here, we suggest that this pattern of synaptic maturation also has important implications for understanding how already functional networks are adaptively modified by the experience of the individual animal during later stages of development and possibly into adulthood.