PSEN1 and Alzheimer disease: In the 5XFAD AD mouse model, OPC proliferation and the numbers of pre‐myelinating and newly matured oligodendrocytes were increased as well (Kedia et al. 2024) Despite such increases in OPC activity—likely driven by OPCs' response to local demyelination—the overall myelin levels in the cortex and hippocampus of APP/PS1 mice, as well as in postmortem tissues of AD patients, have been shown to be significantly decreased, and myelin structural changes have been observed in APP/PS1, J20, and 5XFAD mice (Chen et al. 2021) (Behrendt et al. 2013) (Ferreira et al. 2020) (Kedia et al. 2024).