APP and Alzheimer disease: Through quantitative analysis, we found that significantly fewer projection neurons in upstream areas, including the contralateral dHPC (Cont-dHPC), ENT and MSC, were labeled by AAV11 in APP/PS1 (AD) than those in the wild-type C57BL/6 mice (dHPC: 683.33 ± 73.11 vs 1098.67 ± 22.56, p = 0.0056; ENT: 201.00 ± 40.77 vs 350.67 ± 29.81, p = 0.0414; MSC: 17.33 ± 5.04 vs 54.33 ± 10.27, p = 0.0319) (Fig. 7d).