SV2A and Alzheimer disease: Principal component (PC) subject scores of synapse loss were favorably linked with performance in all cognitive domains within the AD group, with positive loadings contributing similarly across most ROIs (Pearson r = 0.24–0.40, P = 0.06–0.006). Aβ-amyloid deposition was significantly negatively correlated to synaptic density, which was demonstrated by bio-tracer depositions ([11C]PiB PET binds Aβ-amyloid, and [11C]UCB-J binds synaptic vesicle glycoprotein 2A (SV2A)). Illustration of PET [11C] PiB PET and [11C]UCB-J deposition demonstrated in Figure 4.