APOE and Alzheimer disease: PI deficits are evident in prodromal AD (Howett et al., 2019; Mokrisova et al., 2016), and in at-risk groups such as APOE-ε4 carriers (Kunz et al., 2015), together with reduced grid-like signals (Bierbrauer et al., 2020), volumes (Howett et al., 2019) and functional connectivity in the entorhinal region (Coughlan et al., 2020).