Braak et al. categorized AD into 6 stages on the basis of tau protein aggregation according to the autopsy results of AD patients, which starts from the transcortical internal olfactory cortex (stage I), sequentially involving the internal olfactory cortex and hippocampus (stage II), the neocortex (stage III), the associative cortex (stages IV and V), and finally the cortex (stage VI) to develop into a whole-brain lesion [77, 78]. The gene discussed is MAPT; the disease is Alzheimer disease.