Critical period control in sensory cortex.

The search continues for factors whose regulation during development accounts for the end of the critical period for experience-dependent cortical plasticity. Recent studies suggest that NMDA receptors and neurotrophins may be involved either individually or in concert. NMDA receptor subunits are developmentally regulated in a way that affects the kinetic properties of the NMDA receptor. The expression of mRNAs for neurotrophins and their receptors is regulated by developmental factors and by neuronal activity, and exogenous neurotrophins block critical period plasticity in the visual cortex.