Not a lot of them but it adds up over time:
Just last year, two opposing papers appeared in leading journals, one claiming firm evidence of ongoing neurogenesis in the adult human dentate gyrus, while the other study came to the opposite conclusion. The fact that adult neurogenesis is reliably seen in rodents only adds to the confusion. Neuroskeptic, “A New Look at Neurogenesis in Humans” at Discover Magazine
Neuroskeptic also quotes an authority (Snyder): “Spalding et al. estimated that only 0.004% of neurons are added each day in adult humans [10]. While this would appear negligible under the microscope (1 cell in 25,000), it translates to ∼15% over a decade; a sizable fraction…”
It will be interesting to see if these nerves are unusually sensitive to changes, for example, epigenetic changes.
See also: Mechanosensing and mechanotransduction: How cells touch their world
and
Epigenetic change: Lamarck, wake up, you’re wanted in the conference room!
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