MAPT and Alzheimer disease: To verify the causal role of MS tau accumulation in AD‐like spatial memory deficit, we infused stereotaxically AAV‐CAG‐hTau‐mCherry‐3flag or AAV‐CAG‐vector‐mCherry‐3flag (empty vector control) into the MS of 2‐month‐old C57 mice (Figure 3A).