Aged wild-type littermates and APPswe+PS1/ΔE9 mice present similar deficits in associative learning and spatial memory independent of amyloid load

APPswe+PS1/AE9 transgenic (Tg) mice with Aβ plaque formation in neocortex and hippocampus were evaluated in tests measuring exploratory activity, anxiety, and memory ability using open field test (OFT), Y-maze, contextual fear conditioning (CFC), and Morris water maze (MWM). Wild type (WT) and Tg mice over eight months old showed same locomotion activity and anxiety level in novel stimulation, open field, and Y-maze contexts. In other experiments that measured associative memory and spatial memory in Tg mice and their litter-mates, the subjects also presented similar deficiencies in memory acquisition. These two aged groups showed abnormal freezing level variance especially in CFC test. In comparison to that in non-Tg 8-week-old mice group, the acquisition of spatial memory in MWM task was impaired in aged WT and bigenic Tg mice. Taken together, aged WT littermates and Tg mice present similar deficits in associative learning and spatial memory independent of amyloid plaques.