# Adult hippocampal neurogenesis

Adult hippocampal neurogenesis (AHN) is how new neurons are born from neural stem and progenitor cells. They form in the subgranular zone of the hippocampal dentate gyrus (DG), then wire into granule-cell circuits. Those circuits handle pattern separation, episodic-memory encoding (forming the memories you keep), and mood. In rodents, newly born DG granule cells mature over roughly four to eight weeks, guided by Wnt, Notch, and BDNF, before they hook into the network.

Whether AHN keeps going in adult humans is one of the most hotly debated questions in neuroscience. Two widely cited 2018 post-mortem studies reached opposite answers. Sorrells et al. (Nature 2018) found immature-neuron markers (DCX, PSA-NCAM) undetectable in the human DG beyond early childhood. But Boldrini et al. (Cell Stem Cell 2018), using better tissue fixation, reported thousands of DCX-positive young neurons in donors up to 79 years old. The likely reasons for the clash: time since death, how long the tissue was fixed, and antibody sensitivity. Separately, radiocarbon birth-dating estimated about 1.75% of DG neurons turn over each year in adult humans (Spalding et al., Cell 2013).

Aerobic exercise reliably raises hippocampal BDNF and boosts DG neurogenesis in rodents. Whether the same causal link holds in adult humans is plausible but not yet proven. So exercise-driven AHN is an inferred mechanism behind the links between physical activity, preserved hippocampal volume, and slower cognitive decline.

## Sources

- Sorrells SF, Paredes MF, Cebrian-Silla A, et al.. (2018). Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults. Nature. https://doi.org/10.1038/nature25975
- Boldrini M, Fulmore CA, Tartt AN, et al.. (2018). Human Hippocampal Neurogenesis Persists throughout Aging. Cell Stem Cell. https://doi.org/10.1016/j.stem.2018.03.015
- Spalding KL, Bergmann O, Alkass K, et al.. (2013). Dynamics of Hippocampal Neurogenesis in Adult Humans. Cell. https://doi.org/10.1016/j.cell.2013.05.002
- Liu PZ, Nusslock R. (2018). Exercise-Mediated Neurogenesis in the Hippocampus via BDNF. Frontiers in Neuroscience. https://doi.org/10.3389/fnins.2018.00052

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_Canonical: https://longevity-switzerland.com/en/glossary/adult-neurogenesis · Part of Longevity Cities · Updated 2026-06-22_