For instance, besides α-syn depositions, decreased levels of β-amyloid1–42 (Aβ1–42) and increased microtubule-associated protein tau concentrations have been shown to correlate with PD cognitive decline, thus proposing Aβ1–42 and tau as prognostic markers for cognitive deficits in PD (Sengupta et al., 2015). This evidence concerns the gene MAPT and Parkinson disease.