APOE and Alzheimer disease: One method of improving brain-behavior models is to examine how variation in AD biology (e.g., levels of Aβ), demographic characteristics (e.g., sex) or variation in genes (e.g., carriage of the apolipoprotein e4 allele [APOE ε4) can influence the memory decline that occurs in early AD (Buckley, et al., 2018; Lim, et al., 2014b; Lim, et al., 2017b).