MAPT and Alzheimer disease: Some studies have shown that memantine can (1) decrease the inhibition of PP2A activity by I2PP2A in PC12 cells [19]; (2) inhibit hyperphosphorylation of tau and associated neurodegeneration in hippocampal slices [12]; (3) protect rat cortical cultured neurons against Aβ-induced toxicity [16, 44]; and (4) significantly improve cognitive functions in some AD patients [45, 46].