Official websites use. Share sensitive information only on official, secure websites. Adult-born hippocampal neurons are important for cognitive plasticity in rodents.
There is evidence for hippocampal neurogenesis in adult humans, although whether its extent is sufficient to have functional significance has been questioned. We have assessed the generation of hippocampal cells in humans by measuring the concentration of nuclear bomb test-derived 14 C in genomic DNA and we present an integrated model of the cell turnover dynamics.
We found that a large subpopulation of hippocampal neurons, constituting one third of the neurons, is subject to exchange. In adult humans, new neurons are added per day, corresponding to an annual turnover of 1. We conclude that neurons are generated throughout adulthood and that the rates are comparable in middle aged humans and mice, suggesting that adult hippocampal neurogenesis may contribute to human brain function. New neurons integrate throughout life in the hippocampus and olfactory bulb of most mammals.
The newborn neurons have enhanced synaptic plasticity for a limited time after their differentiation Ge et al. It has been long debated whether adult neurogenesis decreased during primate evolution and if there is sufficient generation of neurons in adult humans to contribute to brain function Kempermann, ; Rakic, A seminal study by Eriksson, Gage and colleagues provided the only direct evidence to date for adult neurogenesis in humans Eriksson et al.
To estimate the extent of adult neurogenesis in humans, recent studies have quantified the number of cells expressing the neuronal precursor neuroblast marker doublecortin in the subventricular zone, which gives rise to olfactory bulb neurons, and in the dentate gyrus of the hippocampus Knoth et al. The decrease in neuroblast numbers in the subventricular zone and their migratory path suggested that there is negligible, if any, adult olfactory bulb neurogenesis in humans Arellano and Rakic, ; Sanai et al.
