MAPT and Parkinson disease: Pathological changes underlying the development of dementia in Parkinson’s disease relate to accumulation of α-synuclein (Spillantini et al., 1997), as well as amyloid-β, and tau (Irwin et al., 2017) with a synergistic relationship seen between these proteins (Compta et al., 2011; Swirski et al., 2014).