neurogenesis

Neurogenesis is the production of new neurons from neural stem and progenitor cells. Developmental neurogenesis shapes the brain, while a limited amount persists in adulthood in select regions. In mammals, the main adult niches are the subgranular zone of the dentate gyrus in the hippocampus and the subventricular zone along the lateral ventricles, from which new neurons migrate to the olfactory bulb via the rostral migratory stream. In humans, evidence supports ongoing hippocampal neurogenesis into adulthood, though the extent and significance remain subjects of debate.

The process includes activation of quiescent neural stem cells, proliferation of intermediate progenitors, differentiation into neuroblasts, and maturation into granule cells or interneurons. New neurons migrate short distances, form synapses, and become functionally integrated, influenced by neuronal activity and the surrounding environment.

Molecular signals regulate neurogenesis. Brain-derived neurotrophic factor (BDNF), Wnt signaling, and Notch pathways influence proliferation, differentiation, and survival. Inflammation and aging tend to suppress neurogenesis, whereas physical activity, environmental enrichment, learning, and some antidepressants can enhance it.

Measurement and relevance: researchers use markers such as doublecortin and Ki-67 in tissue studies, and carbon-14 dating has been used to study humans. The role of adult neurogenesis in learning and mood is an active area of research, with potential implications for neurodegenerative diseases and brain injury, but practical therapies remain experimental.