PET scans reveal key Alzheimer’s changes in ageing brain

Posted on 2nd March 2016

Neuron: PET Imaging of Tau Deposition in the Aging Human Brain

Researchers at the University of California in Berkeley have used brain scans to study the build-up of two key Alzheimer’s proteins in older people.

The study uses PET scans for both the amyloid and tau protein, helping to build a clearer picture of what’s happening in the brain in ageing and in Alzheimer’s. The findings are published on 2 March in the journal Neuron.

PET scans are a type of brain scan that uses a radioactive ‘tag’ to highlight particular changes in the brain. Over the past few years advances in research have allowed doctors and researchers to use PET scans to detect the amyloid protein – known to build up abnormally in the brain in Alzheimer’s. However, these scans show that having amyloid in the brain doesn’t necessarily mean someone will show symptoms of the disease and so their use in making a diagnosis of Alzheimer’s has been limited.

Tau is another protein known to build abnormally in the brain in Alzheimer’s and this process is thought to map more closely to the development of symptoms than to the build-up of amyloid. In recent years, researchers have been working to develop and test PET scans that might also be able to detect the tau protein in the brain.

In this study, the researchers used PET scans for both amyloid and tau to study the brains of five people aged 20-26, 33 people aged between 64 and 90 with no memory problems, and 15 people aged between 53 and 77 who had Alzheimer’s disease. Participants were also given memory and thinking tests and 30 of the older adults had memory data available from around four years prior to their brain scan.

The researchers found that older participants had more tau in the brain, particularly in the medial temporal lobe – an area that contains the ‘memory centre’ of the brain. They also found that higher levels of tau in the medial temporal lobe were associated with poorer performance on memory tasks. When the tau protein was more spread out across the brain, a person’s memory and thinking was markedly worse and this was also linked to higher levels of amyloid in the brain.

Dr Simon Ridley, Director of Research at Alzheimer’s Research UK, said:

“One challenge for diagnosing and researching diseases like Alzheimer’s is that it’s hard to know exactly what’s happening inside the brain over time. Brains scans like PET scans provide a window into the brain that can transform our understanding of how diseases develop and potentially guide more accurate diagnosis.

“One important question that still remains in Alzheimer’s research is exactly where and when amyloid and tau proteins start to build in the brain and how this leads to the symptoms that people experience. It’s promising to see brain scan research now looking at both amyloid and tau in the brain in living people, but larger studies will need to validate these findings and explore whether they could have diagnostic value.

“While the findings add to evidence that tau is a key mediator of damage in Alzheimer’s, the results raise further questions about what triggers the most damaging events in the brain. Further research using PET scans to study tau will provide greater insight into how it interacts with amyloid and contributes to the disease, and whether this information could translate to meaningful improvements in diagnosis or treatments in the clinic.”

Posted in Science news