A significant interaction effect of APOE-ε4 × group was observed bilaterally in the NBM (P < 0.0005) and amygdala (P < 0.0005) for LMCI vs. CN subjects and in the NBM (P = 0.007 and 0.004 for left and right NBM, respectively) for AD vs. CN subjects. This evidence concerns the gene APOE and Alzheimer disease.