During recent years, it has become increasingly evident that early aggregates or “soluble oligomers” of α-synuclein play an important role in the pathogenesis of α-synucleinopathies rather than the late aggregates or “amyloid fibrils.” Thus, high levels of soluble α-synuclein oligomers are present in the brain homogenates of patients with PD and DLB [18,19]. This evidence concerns the gene SNCA and Parkinson disease.