The cerebral cortex is able to undergo dramatic adaptive functional changes in response to a variety of challenges such as sensory experience, patterned vs. chaotic environmental cues, training, learning, and peripheral or central nervous system injury. The period of early postnatal development is particularly conducive to such changes although the adult cortex can also exhibit robust plasticity. A major site of these forms of adaptive changes is the cortical synapse. In this study, we examine the ability of cerebral cortical synapses, particularly in the visual cortex, to undergo changes in their functional strength in response to a particular model of synaptic learning-the covariance or BCM model. This model incorporates the demand for incoming synaptic activity and the level of activation of a target or postsynaptic neuron to correlate or covary. A dramatic switch in the underlying cellular signaling mechanism for this form of synaptic plasticity occurs during postnatal development. The neurotransmitter receptor mechanism that triggers the plasticity switches from one mediated by metabotropic glutamate receptors to a NMDA glutamate receptor-mediated process. The implications of this switch for developmentally regulated cortical synaptic plasticity are considered.
1999 Wiley-Liss, Inc.