Hypometabolism predicts cognitive decline from normal aging6,23,28 and is associated with memory deterioration in AD.29-31 Consistent with a model where tau and hypometabolism drive neurodegeneration before clinical symptoms, Aβ accumulation alone does not explain cognitive impairment in AD.15,32,33 Yet, conflicting findings pertaining to the role of tau in these associations cast doubt on whether cognitive correlates of hypometabolism are independent of34 or mediated by tau pathology.35 This evidence concerns the gene MAPT and Alzheimer disease.