MAPT and Parkinson disease: It is notable that tau-related pathology was found in the bulbar component of the anterior olfactory nucleus only in patients of neurodegenerative disorders with marked loss of the sense of smell, such as AD, PD, and Lewy body dementia.34,35 Experimental studies further suggest that overexpression of tau may contribute to olfactory dysfunction in vivo.36,37 These findings indicate that overexpression or abnormal aggregation of tau may represent a common mechanism between olfactory dysfunction and several neurodegenerative diseases.