Non-motor symptoms such as the presence of Lewy bodies and neurites that consist of aggregated forms of the 140 amino acid protein α-synuclein were also found in post-mortem brain studies and therefore considered to be one of the histological hallmarks of PD (Fearnley and Lees, 1991; Spillantini et al., 1998; Braak et al., 2003). This evidence concerns the gene SNCA and Parkinson disease.