Neural stem cell of the hippocampus: development, physiology regulation, and dysfunction in disease

The formation of the hippocampus is generated during embryonic development, but most neurons within the structure are produced after birth. The hippocampus is a primary region of neurogenesis within the adult mammalian brain. Adult-born neurons have to integrate into the established neural circuitry throughout life. Although the function of neurogenesis in the adult hippocampus, particularly in humans, remains unclear, experimental data suggest that adult-born neurons are involved in some forms of memory, as well as in diseases. Adult hippocampal neurogenesis is dynamic, responding to physiological and pathological stimuli that may promote brain function or contribute to diseases such as epilepsy. Here, we review some of the mechanisms and signaling pathways involved in the development of the hippocampus, as well as in adult neurogenesis. We discuss some recent findings suggesting heterogeneity within the hippocampal stem cell pool and the regulation of activation of quiescent stem cells. Finally, we discuss some of the issues relating neurogenesis to pathophysiology and aging.