Scientists have uncovered new evidence that certain immature brain cells may help some people resist the symptoms of Alzheimer’s, even when the disease is already present. The findings hint at previously unknown mechanisms that could shape how the brain ages.
Why do some people develop memory loss and cognitive decline as Alzheimer’s disease progresses, while others remain mentally sharp despite similar brain changes? Researchers are increasingly focused on this question through the study of “cognitive resilience,” an area drawing growing attention in neuroscience.
“Around 30 percent of older adults who develop Alzheimer’s disease never experience its symptoms,” Evgenia Salta, last author, begins. “We really don’t know why. That’s a big mystery, and a very important one.”
Can the Brain Repair Itself During Alzheimer’s?
One possible explanation is that resilient brains may be better at repairing damage caused by Alzheimer’s disease. “Perhaps they can add new brain cells to a network that is degenerating,” Salta says.
This theory is connected to adult neurogenesis, the process by which new neurons form in the adult brain. Scientists have confirmed this process in several animal species, but whether it occurs in humans has remained controversial for years.
To investigate, Salta and her colleagues analyzed donated human brain tissue from the Netherlands Brain Bank. The study included healthy control brains, brains from Alzheimer’s patients, and brains from people who had Alzheimer’s-related brain pathology but never developed dementia symptoms.
Scientists Discover Immature Neurons in Aging Brains
The researchers examined a small region of the brain involved in memory, one of the few areas where these new neurons may develop. “These cells are extremely rare, so we had to develop new ways to find them,” Salta says. “We really zoomed in on the exact spot where we expected them to be.”
The team also applied advanced analysis techniques designed to identify the cells more accurately without depending too heavily on assumptions based on animal research.
Their search revealed the presence of so-called “immature” neurons, which resemble young, developing brain cells. “Even at an average age of over 80, we still found these immature neurons in all groups,” Salta says.
However, the researchers were surprised that resilient individuals did not have dramatically higher numbers of these cells compared to Alzheimer’s patients, as they had initially expected.
How Resilient Brains Protect Themselves
Instead, the major difference appeared to involve how the immature neurons functioned. “In resilient individuals, these cells seem to activate programs that help them survive and cope with damage,” Salta says. “We also see lower signals related to inflammation and cell death.”
The findings suggest the cells may do more than replace lost neurons. “It might not be (only) about replacing lost neurons,” Salta explains. “It could be that these cells support the surrounding tissue and help the brain stay functional and ‘youthful’. They may act as a sort of fertilizer in a garden that has started falling apart.”
Salta cautions against drawing firm conclusions too quickly, particularly given recent media attention surrounding the topic. Although the data provide clues about how these cells may behave, the researchers cannot directly confirm their exact function in this type of study. “We assume the cells’ function based on the data, but we cannot confirm it in this type of study,” she says.
“This is one piece of a very large puzzle,” she concludes. “There will never be just one factor that explains resilience.”
Cognitive Resilience Could Shape Future Alzheimer’s Treatments
The research also raises broader questions about why brains age differently from one person to another. “Somewhere along this trajectory, there’s a kind of decision point,” Salta explains. “Some people remain stable, others develop dementia. We want to understand what drives that difference.”
Future studies will examine how these immature neurons interact with other brain cells and whether those interactions help protect cognitive function.
Although the findings do not yet explain why these cells behave differently in resilient individuals and Alzheimer’s patients, they reflect a growing shift in Alzheimer’s research. Scientists are increasingly studying not only how the disease progresses but also what allows some people to resist its effects.
“Cognitive resilience is extremely exciting,” Salta says. “If we understand what protects these brains, it could eventually lead to new therapeutic strategies.” For now, the research suggests the aging brain may be far more adaptable and complex than previously believed.
Reference: “Transcriptional profiles of immature neurons in aged human hippocampus track Alzheimer’s pathology and cognitive resilience” by Giorgia Tosoni, Dilara Ayyildiz, Sarah Snoeck, Elena P. Moreno-Jiménez, Amber Penning, Estibaliz Santiago-Mujika, Olmo Ruiz Ormaechea, Hyunah Lee, Suresh Poovathingal, Kristofer Davie, Julien Bryois, Will Macnair, Jasper Anink, Luuk E. De Vries, Sahand Farmand, Erik Nutma, Dick F. Swaab, Eleonora Aronica, Jinte Middeldorp, Sandrine Thuret, Laurent Roybon, Onur Basak, Carlos P. Fitzsimons, Paul J. Lucassen and Evgenia Salta, 24 April 2026, Cell Stem Cell.
DOI: 10.1016/j.stem.2026.04.002
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