Because we could not observe a significant difference between the 13-month-old wt and Tg2576 mice and evidence of neurogenesis was difficult to detect in the aged mice, 7-week-old SD rats (which are easier to handle for stereotaxic injection than are mice) were used to evaluate the effects of neuritin on neurogenesis rather than to investigate the effects of neuritin on the neurogenesis in the context of AD. This evidence concerns the gene NRN1 and Alzheimer disease.