A recent finding indicates that inducible knockout of the NR1 NMDA receptor subunit promotes the loss of fear memories formed months earlier. One view is that posttraining NMDA receptor activation protects modified synapses from "synaptic drift." An alternative view is that NMDA receptors help maintain appropriate connectivity in memory-encoding networks.
Walker, D. L., & Davis, M. (2004, March 4). Are fear memories made and maintained by the same NMDA receptor-dependent mechanisms? Neuron. Cell Press. https://doi.org/10.1016/S0896-6273(04)00114-X