Neurogenesis in human hippocampus: Implications for Alzheimer disease pathogenesis

Hippocampal neurogenesis, the innate capacity of stem cells in the hippocampus to generate new neurons throughout life, is attracting interest in neurodegenerative disease research as an indicator of neuroplasticity and therefore treatment. Conditions that improve cognitive output and increase neurogenesis are associated with a decreased incidence of Alzheimer disease (AD), and conditions that lead to reduced cognition and neurogenesis are associated with increases in the incidence of AD. Therefore, hippocampal neurogenesis may be of particular relevance in the development of AD, and the modulation of this process can afford an important therapeutic avenue. Nevertheless, apparent contradictions across studies examining all factors of hippocampal neurogenesis in AD have led to a confusing state of affairs regarding the role of this process in the disease, as aberrant cell cycle activation has been advanced as an early pathogenic factor in the development of AD. The objective of this review is to critically examine these contradicting reports and provide additional and alternative insights into the function of hippocampal neurogenesis in AD.