O’Dell et al. evaluated, in a cross-sectional study with [11C]UCB-J and [11]C-labelled Pittsburgh Compound-B ([11C]PiB) PET radiotracers, the spatial association between Aβ deposition and SV2A synaptic density in the living human brains of patients with AD-associated aMCI or with AD mild dementia. This evidence concerns the gene SV2A and Alzheimer disease.