Further research is needed to clarify how early spatial pattern separation deficits emerge in the course of AD, especially in preclinical AD, and whether they are caused directly by accumulation of amyloid-β, spread of the tau pathology from the PrC and alEC to the pmEC and posterior-medial cortical regions, which is facilitated by amyloid-β deposition (Jacobs et al., 2018), or by combination of both pathologies. This evidence concerns the gene MAPT and Alzheimer disease.