PSEN1 and Alzheimer disease: As there is increasing awareness for the importance of the pre-symptomatic phase in neurodegenerative diseases in the context of early diagnosis and of pathogenesis [reviewed in 37, 38], we investigated the temporal pattern of amyloid-beta plaque deposition in the hippocampus and analysed corresponding levels of adult hippocampal neurogenesis from very early prodromal to severe stages of amyloid-beta plaque formation in the APP Swedish PS1 dE9 mouse model and in the slower progressing Tg2576 AD mouse model.