In the aged human brain, we have observed a continuum of active caspase-3 phenotypes, such that most of the neurologically normal control individuals demonstrated some, albeit typically low, levels of active caspase-3 in dopamine neurons (Figure 8A-C), while in prePD and PD cases dopamine neurons displayed more intense fluorescence of active caspase-3 (Figure 8D-I). This evidence concerns the gene CASP3 and Parkinson disease.