Figure 2: Melatonin treatment enhances cognitive function in Aβ1–42-induced AD rats. Spatial learning and memory activities were tested using the Morris water maze. (A) The latency of the navigation test measures the time taken to find the hidden platform. (B) The swimming distance of the navigation test. (C) The swimming speed over the 5 consecutive days of the navigation test. (D) The number of line crossings of the target quadrant in the exploration test. (E) The time spent in each quadrant in the exploration test. (F) Swimming paths during the exploration test. Data are expressed as the mean ± SEM (n = 6 per group). *P < 0.05, **P < 0.01, vs. sham group; #P < 0.05, ##P < 0.01, vs. AD group; & P < 0.05, vs. AD + melatonin group (two-way repeated measures analysis of variance followed by the least significant difference post hoc tests). A+M: AD + melatonin group; AD: Alzheimer’s disease; Aβ: AD group; Aβ1–42: amyloid-beta 1–42; M: melatonin group; NW: northwest quadrant; Opposite: southwest quadrant (SW), which was opposite the target quadrant; SE: southeast quadrant; Sham: sham group; Target: northeast quadrant (NE), the target quadrant.