Olfactory dysfunction is known to be one of the earliest symptoms of AD, and it has been shown that from OE to EC, all the olfactory network structures demonstrate pathology in AD; neurofibrillary tangles are observed in the OB at the early stages of AD (Braak and Braak, 1991; Price et al., 1991; Van Hoesen et al., 1991; Saiz-Sánchez et al., 2011; Kovács et al., 2001) as well as the tau pathologies in the OE (Lee et al., 1993). This evidence concerns the gene MAPT and Alzheimer disease.