Alzheimer’s is often associated with a progressive loss of memory and cognitive function. However, the disease does not progress the same way in everyone. While some people with the disease have increasing difficulty remembering things, understanding contexts, or managing their daily lives independently, others remain cognitively capable for a long time despite noticeable changes in the brain. Why is that? Why does a similar biological burden lead to significant impairments in some people, while others develop comparatively few symptoms?
This question has occupied Alzheimer’s researchers for years. A research team at the Netherlands Institute for Neuroscience has now discovered a possible clue: Certain immature nerve cells in the hippocampus appear to exhibit different patterns of biological activity in people who remain mentally healthy despite Alzheimer’s-related changes than in people with dementia. The results were published in 2026 in the journal Cell Stem Cell. They do not provide a definitive explanation for the brain’s resilience, but they do show that the pathological changes themselves may not be the only decisive factor. The response of the remaining cells to this stress also appears to play a role.
When Alzheimer’s-Related Changes Do Not Necessarily Mean Dementia
Alzheimer’s is a neurodegenerative disease in which, among other things, pathological deposits of amyloid-beta and changes in the tau protein can develop in the brain. These processes are associated with increasing damage to nerve cells and their connections. However, such changes cannot always be directly equated with the extent of mental impairment. In some older adults, postmortem examinations reveal clear evidence of changes typical of Alzheimer’s, even though they exhibited no or only minor cognitive impairments during their lifetime.
This phenomenon is referred to as cognitive resilience. It refers to the brain’s ability to maintain its performance relatively well despite pathological changes or other stresses. This should be distinguished from cognitive reserve. Put simply, this term describes how flexibly the brain can use existing networks and abilities to cope with damage. Education, mental activity, and complex experiences are frequently studied in this context. However, they do not alone explain why some people are more resilient than others. Rather, cognitive resilience likely arises from several factors, including the structure of neural networks, genetic influences, the health of blood vessels, and the response of various brain cells to damage.
Another study published in Nature Medicine in 2026 underscores the importance of this resilience. The researchers followed 3,119 older adults over a median period of 13.7 years. Their findings show that both changes typical of Alzheimer’s disease and cognitive resilience are associated with the risk of developing dementia later in life. This supports the notion that it is not only the pathological changes in the brain that are decisive, but also how well the brain can cope with them.
Immature Neurons in the Brain’s Memory Center
The new Dutch study draws attention to another possible factor: immature neurons in the hippocampus. The hippocampus is one of the key structures involved in the formation of new memories and spatial memory. It is also one of the brain regions that are often affected early on in Alzheimer’s disease. The researchers examined a rare group of nerve cells there that exhibit characteristics of immature neurons. Such cells have not yet fully developed all the properties of mature nerve cells.
It is particularly interesting that the researchers also found these cells in the brain tissue of older adults. They were detectable in all three groups studied: in people without detectable Alzheimer’s-typical changes, in people with Alzheimer’s dementia, and in individuals whose brains showed such changes but whose cognitive function had largely remained intact.
However, this alone does not prove that new nerve cells are continuously being formed in old age. Cellular characteristics that indicate an immature stage of development are not clear evidence that the cells in question were formed only recently. Whether and to what extent new neurons are formed in adults remains a subject of scientific debate. For the current study, therefore, another question was particularly crucial: Do these cells differ in their biological activity between people whose brains function comparatively well despite Alzheimer’s changes and people who have developed dementia?
It May Not be the Number Alone that is Decisive
Initially, the researchers might have expected that people with preserved cognitive function would have significantly more immature nerve cells. After all, a larger number of such cells could theoretically help to compensate for damaged neural networks. However, the differences in cell count were smaller than expected. This led to another consideration: Perhaps what matters most is not how many of these cells are present, but how they respond to the stress caused by pathological changes.
To investigate this more closely, the team analyzed the activity patterns of the genes in the cells. These so-called gene expression profiles provide clues as to which biological programs are particularly active in a cell. The analysis revealed differences between the groups. In the immature nerve cells of people with cognitive resilience, patterns were found that are consistent with better coping with cellular stress and protection against damage. At the same time, certain signals associated with inflammatory processes and cell death were less pronounced.
These observations are noteworthy because chronic inflammatory processes and the loss of nerve cells can play a significant role in neurodegenerative diseases. If certain cells are better able to cope with harmful conditions, this could potentially help the surrounding neural networks remain functional for longer. However, these are findings derived from the analysis of human brain tissue. The researchers were therefore unable to directly prove that the observed gene activity patterns actually protect cognitive function.
Could these Cells Protect the Brain from Damage?
One particularly interesting hypothesis is that immature nerve cells might do more than simply provide potential replacement building blocks for lost neurons. Nerve cells depend on a functioning environment. They communicate with other cells, receive signals, and require adequate nourishment to perform their tasks. Other cell types in the brain, such as astrocytes and microglia, also influence this environment and respond to injury or inflammation.
The researchers suspect that immature nerve cells might also influence their environment. It is conceivable that they emit signals or support processes that promote the survival of neighboring cells. This would represent a different approach than the notion that the brain compensates for damage primarily by having new nerve cells replace old ones. Instead, certain cells could help ensure that existing networks continue to function for longer.
However, it is not yet clear whether this hypothesized protective function actually exists. The study reveals differences in the cells’ molecular properties, not their specific effects in the living brain. Further experiments are needed to investigate how these cells interact with their environment and whether they actually contribute to cognitive resilience.
What does this Discovery Mean for Alzheimer’s Research?
For a long time, much of Alzheimer’s research focused on understanding the processes that damage nerve cells. These include the accumulation of pathological proteins, changes in immune responses in the brain, and the loss of neural connections. Increasingly, however, scientists are also interested in the other side of the disease: What mechanisms enable some brains to function comparatively well despite such stresses?
This shift in perspective could prove important in the long term. If we can identify the biological characteristics that distinguish resilient brains, this could lead to new approaches for protecting nerve cells or maintaining the functionality of neural networks for longer. The current study is a potential starting point for this. It identifies molecular characteristics of immature nerve cells that are associated with cognitive resilience. However, it remains to be seen whether therapeutic strategies can one day be developed from these findings.
It would therefore be premature to infer a new treatment for Alzheimer’s from the results. Nor can it be concluded that the number of immature nerve cells can be specifically increased through certain activities, dietary supplements, or other measures, thereby preventing dementia.
Can the Brain’s Resilience be Strengthened in Everyday Life?
The study itself did not examine lifestyle measures. It therefore does not provide any new recommendations for specifically activating the cellular mechanisms described. Nevertheless, independent of this research, there is evidence that overall brain and vascular health is important for reducing the risk of cognitive decline. Regular exercise, treating high blood pressure and diabetes, not smoking, getting enough sleep, and engaging in social and mental activities are among the factors being studied in dementia prevention.
It is crucial to have realistic expectations. No single habit can guarantee that someone will not develop Alzheimer’s disease. Even people who live healthy lives can develop the disease. Conversely, a diagnosis or an increased risk does not necessarily mean that the course of the disease will be the same for everyone affected. Rather, research on cognitive resilience underscores how differently brains can respond to age-related changes. A better understanding of these differences could help tailor prevention and treatment more individually in the future.
Why Some Brains are More Resilient Remains an Important Research Question
The new study from the Netherlands provides an interesting clue as to why some people can maintain their mental performance for longer despite changes typical of Alzheimer’s disease. The focus is on immature nerve cells in the hippocampus, whose molecular activity patterns differed between people with and without cognitive impairments. The results suggest that it may not be solely the number of certain cells that is decisive. Their ability to cope with stress and harmful conditions could also play a role.
It has not yet been proven that these cells actively protect the brain or that their properties can be exploited therapeutically. Further research is needed to determine this. However, the study opens up an important perspective: To better understand Alzheimer’s, researchers must not only investigate how the brain is damaged; they must also identify the biological mechanisms that help some brains remain functional for as long as possible despite these changes.
