MAPT and Mental deterioration: Longitudinal studies from the Parkinson’s Progression Markers Initiative (PPMI) have shown that patients with worse olfactory function at baseline exhibit greater cognitive decline, higher tau/Aβ1-42 ratios (Fullard et al., 2016), and more pronounced cerebral atrophy in regions such as the parahippocampal gyri and transverse temporal gyrus (Kawabata et al., 2024).