Summary: Roughly 30% of older adults whose brains show Alzheimer’s-related pathology never develop noticeable dementia. This surprising degree of cognitive resilience is the focus of a new study that examines how the aged human brain retains young, immature neurons and how those cells behave differently in resilient versus symptomatic individuals.
Researchers using tissue from the Netherlands Brain Bank found that even in donors over 80 years old, the hippocampus continues to harbor immature neurons. The study shows that resilience is not simply a matter of producing more of these cells; it depends on how those cells respond to damage. In resilient brains, immature neurons engage survival programs, reduce inflammatory signals, and appear to support surrounding tissue, potentially preserving network function.
Key Facts
- Adult neurogenesis in advanced age: The study confirms that new, immature neurons persist in the aged human hippocampus, regardless of whether the brain shows Alzheimer’s pathology.
- Survival and anti-inflammatory programs: In brains that remained cognitively resilient, immature neurons showed lower signatures of cell death and inflammation and upregulated genes linked to coping with damage.
- The “fertilizer” idea: Rather than merely replacing lost neurons one-for-one, these young cells may act more like a support system, nurturing the health and function of nearby cells and networks.
- A new research focus: This work shifts attention from only studying how brains fail in Alzheimer’s to exploring how some brains resist and compensate despite widespread disease pathology.
Source: KNAW
Why do some people lose memory and cognition as Alzheimer’s pathology accumulates, while others stay mentally sharp?
That question drives growing interest in cognitive resilience—why some individuals maintain cognitive function despite the biological hallmarks of Alzheimer’s disease. The new study led by Evgenia Salta and colleagues explores one potential component of resilience: the presence and behavior of immature neurons in the aged human hippocampus.
“About 30 percent of older adults who have Alzheimer’s pathology never show its clinical symptoms,” says Evgenia Salta. “Understanding why some brains remain resilient is a major unsolved problem.” One hypothesis is that resilient brains are better at repairing or supporting damaged networks—possibly by adding or maintaining young cells that help preserve function.
Adult neurogenesis and the human brain
Adult neurogenesis—the generation of new neurons in an adult brain—has been well documented in animal models, but evidence in humans has been contentious. To investigate this in older adults, the team analyzed postmortem hippocampal tissue from the Netherlands Brain Bank, including samples from people without brain pathology, from those with Alzheimer’s disease, and from individuals with Alzheimer’s pathology who remained cognitively resilient.
Because immature neurons are rare and fragile, the researchers developed sensitive laboratory and computational methods to identify them without heavily relying on markers established in animal studies. They concentrated on a small hippocampal region where adult-born neurons are most likely to appear and applied single-nucleus RNA sequencing to profile gene expression in these cells.
Immature neurons persist but behave differently
The team detected persistent populations of immature neurons across all groups, even in donors averaging over 80 years old. Surprisingly, the resilient group did not simply have far more immature neurons. Instead, the critical difference lay in the cells’ molecular programs. In resilient brains, immature neurons activated gene networks associated with cell survival and stress resistance and showed reduced inflammatory and cell-death signatures.
This pattern suggests that these young neurons may help maintain the local environment and promote network stability rather than acting solely as direct replacements for lost neurons. The authors describe this as a “fertilizer” effect: immature cells could provide trophic or regulatory support that helps neighboring cells continue functioning despite ongoing pathology.
Salta cautions that the current data are correlational. The study provides a detailed molecular portrait of immature neurons and links their transcriptional state to resilience, but it cannot directly demonstrate the cells’ functional roles in living human brains. “This is one piece of a much larger puzzle,” she notes. “There will not be a single factor explaining resilience.”
Implications and next steps
The findings open new directions for Alzheimer’s research by emphasizing resilience mechanisms. Future work will probe how immature neurons interact with other cell types in the hippocampus, how those interactions change with disease, and whether boosting the survival programs seen in resilient brains could inform therapeutic strategies. Understanding why some immature neurons are better equipped to withstand Alzheimer’s-related stress could eventually point to ways to enhance brain resilience across aging populations.
Key Questions Answered:
A: It appears to be a matter of quality over quantity. While immature neurons persist in many aged brains, cells in resilient individuals display gene programs that favor survival and suppress inflammation, making them better adapted to hostile, disease-related conditions.
A: The data suggest an intrinsic potential for repair or support, but they do not prove that the brain can fully reverse dementia. In symptomatic Alzheimer’s, those endogenous mechanisms seem insufficient or impaired. A therapeutic goal might be to enhance the beneficial programs active in resilient brains.
A: These immature neurons are extremely rare and sensitive. The study combined targeted tissue sampling with high-resolution molecular profiling and new analytical approaches suited to aged human tissue, enabling reliable identification without over-reliance on animal-derived markers.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this Alzheimer’s disease and neurology research news
Author: Eline Feenstra
Source: KNAW
Contact: Eline Feenstra – KNAW
Image: Image credited to Neuroscience News
Original Research: Closed access.
“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. Cell Stem Cell. DOI: 10.1016/j.stem.2026.04.002
Abstract
Transcriptional profiles of immature neurons in aged human hippocampus track Alzheimer’s pathology and cognitive resilience
The presence and functional significance of immature neurons in the adult human hippocampus—especially in the context of neurodegeneration—remain open questions. While rodent models have demonstrated active roles for adult-born immature neurons under both healthy conditions and in models of Alzheimer’s disease, human evidence has been limited and lacked detailed molecular insights.
To fill this gap, the researchers performed single-nucleus RNA sequencing on aged human hippocampal samples from healthy donors, individuals with Alzheimer’s disease, and donors with Alzheimer’s pathology who were cognitively resilient. Using an integrated experimental and computational pipeline, they identified persistent populations of immature neurons across all groups and characterized transcriptional profiles indicative of juvenile cellular functions that are compromised in Alzheimer’s disease.
These findings suggest that immature neuronal populations may actively contribute to maintaining hippocampal homeostasis in aging and support cognitive resilience in the presence of Alzheimer’s pathology.