In later disease stages—including PD dementia—local cortical Lewy body and tau pathology, local pathology in thalamo‐cortical circuits (Freunberger, Werkle‐Bergner, Griesmayr, Lindenberger, & Klimesch, 2011; Steriade, Gloor, Llinas, Da Silva, & Mesulam, 1990), and degeneration of the cholinergic nucleus of Meynert (Bosboom, Stoffers, Stam, et al., 2009; Hepp et al., 2017) may contribute to cortical neurophysiological changes in PD. This evidence concerns the gene MAPT and Parkinson disease.