Critical requirements for NMDA receptors in experience-dependent plasticity in the visual cortex

Abstract

NMDA receptors play an essential role in many forms of experience-dependent plasticity in the visual system. NMDA receptors support the ocular dominance (OD) shift, development of receptive field properties in cortical neurons, and learning tasks associated with the visual cortex, as well as the cellular correlates of such plasticity measurements, ie long-term potentiation (LTP) and long-term depression (LTD). Complete removal of NMDA receptors abolishes plasticity, while selective removal of NMDA receptors from distinct circuits in the visual system can reveal a more specific requirement and identify circuits required for plasticity. Using this approach, I aimed to delineate the brain circuits involved in two forms of experience-dependent plasticity. First, I determined a layer-specific requirement for NMDA receptors in stimulus-specific response potentiation (SRP), which is a model for the plastic changes that may underlie perceptual learning. SRP acquisition requires NMDA receptors in the cortex, and it can be supported by expression of NMDA receptors in only deep layer 4 and layer 5. In contrast, this minimal expression of NMDA receptors did not support a paradigm for OD plasticity in adult mice. The contrasting requirements for NMDA receptors in these two forms of experience-dependent plasticity suggest that distinct forms of plasticity can be supported in separate cortical circuits.