PSEN1 and Cognitive impairment: APP/PS1 mice start developing amyloid plaques between 5 and 6 months of age [20], and the onset of cognitive impairment is usually reported between 6 and 12 months of age [26], suggesting that the first three recording months represent a pre-symptomatic stage, although occasionally memory deficits are reported as early as 4 months of age [27].