neurogenese

Neurogenesis, occasionally referred to as neurogenese in some languages, is the process by which new neurons are generated from neural stem and progenitor cells. During embryonic development, neurogenesis shapes nearly all brain structure; in most mammals, a more limited form persists in adulthood in a few regions. The best-established sites of adult neurogenesis are the hippocampal dentate gyrus and the subventricular zone along the lateral ventricles, where cells can migrate to the olfactory bulb in rodents. In humans, the extent and functional significance of adult neurogenesis are actively debated.

Neurogenesis proceeds through stages: proliferation of neural stem cells, lineage commitment to neural progenitors and neuroblasts, migration to appropriate cortical or hippocampal layers, and maturation into functionally integrated neurons that form synaptic connections. In the hippocampus, newborn granule neurons in the dentate gyrus undergo maturation over several weeks and contribute to hippocampal circuits involved in pattern separation and learning.

Regulation

Intrinsic factors such as transcription regulators Notch, SOX2, ASCL1, and NeuroD1 interact with extrinsic signals including brain-derived neurotrophic factor (BDNF), Wnt signaling, and Notch pathways to control proliferation and differentiation. External stimuli—physical exercise, environmental enrichment, learning, and stress hormones—modulate neurogenesis up or down. Inflammation and aging generally reduce the rate of new neuron formation.

Function and clinical relevance

Animal studies link ongoing adult neurogenesis to memory formation, mood regulation, and recovery from injury. Altered neurogenesis has been proposed to contribute to depression, age-related cognitive decline, and some neurodegenerative conditions, though causal relationships and therapeutic potential remain under investigation.

Measurement and human debate

Researchers use markers such as BrdU incorporation, doublecortin (DCX), and NeuN to identify newborn neurons, along with imaging approaches. In humans, evidence for significant adult hippocampal neurogenesis is mixed; recent work suggests low levels persisting into adulthood, while others report limited or region-specific activity. Ongoing research aims to resolve methodological differences and clarify functional impact.