Alzheimer’s disease is most often linked with memory loss. But for some people, the first signs are not memory problems at all. Instead, they begin to have trouble seeing things clearly, reading, or finding their way around.
A new study by researchers at University College London (UCL) may help explain why this happens. The answer may lie in where certain disease-related proteins build up in the brain.
This rare type of Alzheimer’s is called posterior cortical atrophy, or PCA. Unlike the more common form of Alzheimer’s, which mostly affects memory, PCA impacts the back part of the brain. This area is responsible for understanding and processing what we see.
People with PCA may have difficulty recognizing objects, reading words on a page, or knowing where they are. These problems usually start when people are in their 50s or 60s, which is younger than the typical age for Alzheimer’s to begin.
The researchers wanted to find out why PCA affects vision instead of memory. They studied the brains of people who had died and donated their brains to research. There were 26 people who had PCA and 27 who had the more typical, memory-led form of Alzheimer’s. All the brains came from the Queen Square Brain Bank at UCL.
The scientists looked at how two key proteins, called amyloid and tau, were spread across the brain. These proteins are known to play a role in Alzheimer’s disease. They also looked at microglia, which are special cells that help clean up damaged parts of the brain and fight off disease.
In people with PCA, the researchers found that amyloid and tau were mostly built up in the back of the brain, in an area called the parietal region. This part of the brain helps us process visual information. That explains why people with PCA have trouble with vision instead of memory.
Interestingly, the study also found that microglial activity—part of the brain’s immune response—was higher in people with PCA, especially in the areas of the brain that are usually affected in the more common type of Alzheimer’s.
This includes the sides of the brain, known as the temporal region. That’s the area usually linked with memory loss in regular Alzheimer’s cases.
In comparison, people with the typical memory-led form of Alzheimer’s had a lot of tau in the temporal region, but less microglial activity there. This difference in where the proteins and immune activity occur may help explain why some people first lose their memory, while others first lose their vision.
Dr. Zeinab Abdi, the lead researcher, said the study suggests that the location of protein build-up and inflammation in the brain might be the key to understanding why different people show different symptoms of Alzheimer’s disease. These findings could help scientists develop better treatments in the future—ones that are personalized to the type of symptoms a person has.
Dr. Richard Oakley, a senior researcher at the Alzheimer’s Society, explained that this kind of research is important because dementia is a complicated disease. Around one million people in the UK are living with dementia, and not everyone experiences the same symptoms.
Understanding rare types like PCA is important so that no one is left behind when new tests or treatments are created.
To sum up, this study shows that the differences in where harmful proteins and brain immune activity are located might explain why some people with Alzheimer’s disease lose their vision before their memory.
These findings not only help us understand the disease better but also show the importance of developing more personalized treatments for all types of dementia. It’s a reminder that Alzheimer’s disease is not the same for everyone, and treatment approaches need to reflect that.
If you care about Alzheimer’s, please read studies about the likely cause of Alzheimer’s disease, and new non-drug treatment that could help prevent Alzheimer’s.
For more information about brain health, please see recent studies about diet that may help prevent Alzheimer’s, and results showing some dementia cases could be prevented by changing these 12 things.
The research findings can be found in Neuropathology and Applied Neurobiology.
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