N-cadherin promotes dendritic spine stability. (A) Spines are dynamic and undergo formation and elimination, leading to spine turnover. These spines have relatively small postsynaptic densities and PSD-95 puncta. (B) Synaptic activity promotes the localization of N-cadherin to activated synapses. (C) Activated synapses expressing N-cadherin are stabilized, have large postsynaptic densities, and express large PSD-95 puncta.