TARDBP and synucleinopathy: The general uncertainty regarding the etiology of the non-AD aMCI participants is consistent with previous studies showing that this group may consist of various entities, including the neurodegenerative ones (i.e., tauopathy, synucleinopathy, and TDP-43 pathology), that may fully manifest several years later (Villemagne et al., 2011; Ye et al., 2018).