Dynamics of hippocampal neurogenesis in adult humans.
Level 4 - case-series / case-control
Cross-sectional postmortem observational study using retrospective isotopic birth dating.
PubMed 23746839 · doi:10.1016/j.cell.2013.05.002
What was done
The authors assessed hippocampal cell generation in humans by measuring concentrations of nuclear-bomb-test-derived 14C in genomic DNA from postmortem brain tissue. They applied mathematical modeling of cell turnover dynamics to quantify the rate and extent of adult hippocampal neurogenesis.
What was found
A subpopulation consisting of one-third of hippocampal neurons is subject to turnover. In adult humans, approximately 700 new neurons are added to each hippocampus per day, corresponding to an annual turnover rate of 1.75% within the renewing population, with only a modest decline during aging. These rates were comparable between middle-aged humans and mice.
Why it matters
It demonstrates that substantial hippocampal neurogenesis continues throughout human adulthood at rates comparable to rodents, supporting the possibility that adult-born neurons contribute to human brain function.
Limits
The abstract does not disclose the sample size (number of postmortem brains analyzed), donor ages, medical histories, or postmortem intervals. The functional impact on human cognition is inferred from rodent analogies rather than directly measured.
Cited by
- contradicts Adults have approximately 100 billion neurons in their brain and they are the exact same neurons present at birth because neurons are never replaced.