MAPT and Mental deterioration: 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).