PSEN1 and Alzheimer disease: The fact that familial cases of AD, which are caused by certain mutations in APP or presenilin 1 or 2, as well as transgenic mouse models overexpressing these transgenes do not show cognitive impairment and overt pathology till late in adult life led us to investigate the effect of P021 treatment during early development on cognition and AD pathology at adult age in 3xTg-AD mice.