Crucially for detection of Alzheimer’s disease prior to symptom onset, performance on the 4MT correlates with dementia risk score in asymptomatic 40–59 year olds (Ritchie et al., 2018), while young adult APOE ɛ4 carriers at increased risk of Alzheimer’s disease exhibit reduced grid-cell like representations and activation of the EC during a functional MRI navigation task (Kunz et al., 2015). Here, APOE is linked to early-onset autosomal dominant Alzheimer disease.