Another research indicates that (1) β-amyloid deposition and abnormal tau processing occur very early in the AD continuum [67, 68]; (2) elevated CSF p-tau/β-amyloid ratio may drive longitudinal atrophy of nbM and subsequent volume loss in the entorhinal cortex [12], potentially via reduced cholinergic tone; (3) the Ch4 region of the basal forebrain shows a very early accumulation of phosphorylated tau [4]; and (4) early β-amyloid deposition may contribute to basal forebrain degeneration due to the structure’s high sensitivity to amyloid-related loss of trophic factors [69]. Here, MAPT is linked to Alzheimer disease.