Mean and standard error of the mean of total number of synaptophysin-immunoreactive presynaptic boutons (A–C; SIPB), total neuron numbers (D–F; NN) and SIPB-to-neuron number ratio (G–I; SIPB-to-NN) in the DG (A, D, G), CA3 (B, E, H), and CA1–2 (C, F, I) in the hippocampus of either 2-month-old (M2; black bars) or 10-month-old (M10; open bars) APPSL mice (APPSL), PS1ho KI mice (PS1ho) and APPSL/PS1ho KI mice (APPSL/PS1ho). Results of general linear model univariate analysis of variance are summarized in Table 2; results of post-hoc Bonferroni tests for pairwise comparisons between animals in groups M2 and M10 of the same genotype are indicated in the graphs. *, p < 0.05; **, p < 0.01.