For instance, Gomperts et al. (2012) discovered that the number of APOE4 alleles (0, 1, 2) was correlated with amyloid-beta protein within the precuneus (via [11C]-PiB PET) across their PD-MCI, PDD, DLB, and HC groups (Gomperts et al., 2012). This evidence concerns the gene APOE and Parkinson disease.