Adults whose brains still have strong neuron production appear to have better memory and cognitive function than those whose ability declines, finds a study published today in Nature. The authors examined brain samples from deceased donors, ranging from young adults to “super-aged” people over 80 with exceptional memory.
They found that young and old adults with healthy cognition generated neurons, a process called neurogenesis, at high levels for their age. The team estimated that the new neurons made up only a small fraction – 0.01% – of those in the hippocampus, a brain region crucial for memory. In contrast, in people experiencing cognitive decline, including people with Alzheimer’s disease, neurogenesis appears to falter: the researchers discovered fewer developing or immature neurons in these brain samples.
Surprisingly, one group of “super-aged” had an even higher number of immature neurons than other groups, and significantly more than those with Alzheimer’s. However, the group sizes were small, so the findings were not all statistically significant.
On supporting science journalism
If you like this article, please consider supporting our award-winning journalism by subscribes. By purchasing a subscription, you help secure the future of impactful stories about the discoveries and ideas that shape our world today.
Maura Boldrini Dupont, a neuroscientist and psychiatrist at Columbia University in New York City, says the small size of the groups — each had ten or fewer individuals — is a reason to take the results with a grain of salt.
Understanding the tools the brain uses to generate neurons and maintain cognitive function in old age could help researchers develop drugs that induce neurogenesis in people with cognitive decline, said co-author Orly Lazarov, a neuroscientist at the University of Illinois Chicago.
Controversy over neurogenesis
The findings support the idea that people’s brains continue to generate neurons even into adulthood. But that idea has not always been accepted.
In the early 20th century, neuroscientist Santiago Ramón y Cajal proposed that the human brain could not form neurons after birth. Eventually, the researchers found that neurogenesis occurred in childhood, but still believed that it was the end point.
“That’s what they used to teach when I was in medical school,” says Dupont.
However, in recent decades, this dogma has been challenged by new evidence supporting neurogenesis in the adult hippocampus, fueling an ongoing debate in neurobiology.
Although scientists know that neurogenesis occurs in some adult animals, including mice and primates, they have not been able to agree on whether it occurs in the brain of adult humans. That’s mainly because there are more tools for studying neurogenesis in animals than in humans. In mice, for example, researchers can inject chemicals that track the birth and development of neurons. This cannot be done in living people, and research on human brain samples has been limited, says Lazarov.
One tool researchers have used to study neurogenesis in humans, however, is protein markers. Antibodies can be used to detect certain proteins expressed by neural stem cells – which can become neurons – and immature neurons in donated brain samples. But Lazarov points out the critics’ argument “that these proteins are not specific enough and can be expressed in other cell types, not only in neurogenesis”.
So researchers have turned to single-cell RNA sequencing to find more specific genetic markers for neural stem cells and immature neurons in the human hippocampus.
Into the future
Lazarov and her colleagues went a step further in their latest study. They not only used RNA sequencing to identify the genetic signatures of these cell types, but also uncovered their epigenetic signatures. Epigenetic markers are DNA modifications that control gene expression. The team used an assay that identifies parts of a cell’s DNA primed for expression to determine these signatures. Dupont says that the analysis is a strong point of the study.
Lazarov says the next step would be to understand the function of the neurons generated in the adult brain. “What we need is functional validation of these cells, to tell what they are doing in the human brain,” she says, adding that this will require new imaging techniques that are sensitive enough to detect this activity.
This article is reproduced with permission and var first published on 25 January 2026.
It’s time to stand up for science
If you liked this article, I would like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in its two-century history.
I have been one Scientific American subscriber since I was 12 years old, and it helped shape the way I see the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does for you too.
If you subscribe to Scientific Americanyou help ensure our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten laboratories across the United States; and that we support both budding and working scientists at a time when the value of science itself is too often not recognised.
In return, you receive important news, captivating podcasts, brilliant infographics, can’t-miss newsletters, must-see videos, challenging games, and the world of science’s best writing and reporting. You can even give someone a subscription.
There has never been a more important time for us to stand up and show why science is important. I hope you will support us in that mission.
