Adult Neurogenesis in the Hippocampal Formation

Abstract

The dentate gyrus of the hippocampal formation continues to produce granule neurons throughout adulthood in many species, including humans. Although the functional significance of adult hippocampal neurogenesis is unknown, its magnitude and conservation across taxa suggest that this process may be fundamental to normal hippocampal function. Previous studies have demonstrated that the production and survival of neurons in the adult hippocampal formation are regulated by both experiential and neuroendocrine factors. Stress reduces the proliferation of granule cell precursors, in part, by increasing circulating levels of adrenal glucocorticoids. Conversely, estrogen increases the proliferation of granule cell precursors and is responsible for a sex difference favoring females in the production of immature granule neurons. Additionally, certain types of learning enhance the number of new neurons in the dentate gyrus of adult rats. Collectively, these findings suggest that adult-generated neurons are a substrate by which experiential and hormonal cues influence normal hippocampal function.