When we performed a probe test at 24 h after the last training trial, the untreated APP/PS1 Tg mice showed no preference for the target quadrant, which indicated significant memory impairment, whereas the BDNF-treated APP/PS1 Tg mice performed better than the non-treated APP/PS1 Tg mice (Figure 4B). Here, BDNF is linked to memory impairment.