The increase in synapse density at the apical dendrite was not maintained in aged APP/PS1 animals (WT 5.13 ± 0.22 vs. AD 4.95 ± 0.26 puncta/μm, p = 0.599; Figures 6E–6H), suggesting that Aβ-associated synapse loss might be mitigated by early synapse gain in some dendritic compartment(s). Here, PSEN1 is linked to Alzheimer disease.