MAPT and Alzheimer disease: We used ~6 months-old 3xTg-AD mice, at this age 3xTg-AD mice are characterized by increased levels of intracellular Aβ peptide in the hippocampus, but absence of amyloid plaques or hyperphosphorylated tau protein (Oddo, 2003; Billings et al., 2005), while we detected relatively mild memory deficits and a profound impairment of adult neurogenesis on these mice.