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The debate over how long our brains keep making new nerve cells heats up

A new study finds no signs of newborn neurons in adults’ memory-making region

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5:14pm, March 8, 2018
nerve cells

DWINDLING DOWN Young nerve cells (green) were spotted in the memory-related hippocampus of a newborn (left), but rarely in a sample from a 13-year-old (center). And none were seen in adults, including this sample from a 35-year-old (right).

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Adult mice and other rodents sprout new nerve cells in memory-related parts of their brains. People, not so much. That’s the surprising conclusion of a series of experiments on human brains of various ages first described at a meeting in November (SN: 12/9/17, p. 10). A more complete description of the finding, published online March 7 in Nature, gives heft to the controversial result, as well as ammo to researchers looking for reasons to be skeptical of the findings.

In contrast to earlier prominent studies, Shawn Sorrells of the University of California, San Francisco and his colleagues failed to find newborn nerve cells in the memory-related hippocampi of adult brains. The team looked for these cells in nonliving brain samples in two ways: molecular markers that tag dividing cells and young nerve cells, and telltale shapes of newborn cells. Using these metrics, the researchers saw signs of newborn nerve cells in fetal brains and brains from the first year of life, but they became rarer in older children. And the brains of adults had none.

There is no surefire way to spot new nerve cells, particularly in live brains; each way comes with caveats. “These findings are certain to stir up controversy,” neuroscientist Jason Snyder of the University of British Columbia writes in an accompanying commentary in the same issue of Nature.

Citations

S. F. Sorrells et al. Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults. Nature. Published online March 7, 2018. doi: 10.1038/nature25975

J.S. Snyder. Questioning human neurogenesis. Nature. Published online March 7, 2018. doi: 10.1038/d41586-018-02629-3

Further Reading

L. Sanders. Study casts doubt on whether adult brain’s memory-forming region makes new cells. Science News. Vol. 192, December 9, 2017. p. 10.

T. H. Saey. No new smell cells. Science News Online, May 23, 2013. 

T. H. Saey. New insights on new neuronsScience News. Vol. 174, September 27, 2008, p. 5.

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