Alzhiemer's. (Image created using AI)
Researchers have now discovered the reason why some people seem to retain their mental sharpness despite the brain changes associated with Alzheimer's disease. According to a new study from the Netherlands Institute for Neuroscience (NIN) the answer may be as simple as the behaviour of rare brain cells called immature neurons which seem to help the brain resist damage rather than replacing damaged cells. The findings published in the journal Nature provide new clues to how the brain remains cognitively resilient despite the disease continuing to offer future treatments for Alzheimer's disease.
Why Alzheimer's disease affects individuals differently is one of the biggest mysteries about the disease. As the disease progresses many people have memory loss and dementia but everyone with Alzheimer's has memory loss and dementia even though they have the same changes in the brain.
"Around 30 per cent of older adults who develop Alzheimer's disease never experience its symptoms," says senior author Evgenia Salta of NIN. "We really don't know why. That's a big mystery and a very important one." The scientists believe that if they can figure out what makes these people resilient they can create treatments that will slow or halt dementia in the future.
To investigate, researchers analysed donated brain tissue from the Netherlands Brain Bank. The subjects consisted of healthy individuals as well as those diagnosed with Alzheimer's disease and those who had brain pathology associated with Alzheimer's disease but had never developed dementia.
The team focused on a small part of the memory centre in the brain one of the few places where new neurons can be formed in adulthood. Although the researchers were able to find immature neurons in all groups it was an extremely rare occurrence.
Talking about the findings, Salta said, "Even at an average age of over 80, we still found these immature neurons in all groups." One interesting aspect of this study is that researchers found no significant difference in the number of immature neurons in resilient people and people with Alzheimer's.
Following the research, scientists found that it was not the number of immature neurons that made a difference but rather their behaviour. The study also showed that immature neurons in cognitively resilient people expressed genes that promote cell survival and fewer genes that trigger inflammation and cell death.
Salta explains, "It might not be (only) about replacing lost neurons. 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."
The study concluded that no single factor is likely to account for cognitive resilience as the results are obtained from donated brain tissue and cannot be directly observed how these cells function in living people. Scientists are expected to conduct further research to explore the connections between immature neurons and other brain cells and how these connections contribute to preserving memory and thinking abilities throughout age.
Disclaimer: This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Always consult a qualified healthcare provider for any concerns about Alzheimer's disease or cognitive health.
