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Brains compensate for age-related deterioration by recruiting other areas, Cambridge and Sussex scientists show

The strongest evidence yet that our brains can compensate for age-related deterioration by recruiting other areas to maintain cognitive performance has been found by scientists.

Our brain gradually atrophies as we age, meaning it loses nerve cells and connections, which can led to brain function declining.

An MRI scan of the brain. Picture: iStock
An MRI scan of the brain. Picture: iStock

Some people appear to maintain better brain function than others, but it is not understood why - nor do we understand how to protect ourselves from cognitive decline.

It has been widely accepted though that some people’s brains compensate for this deterioration in brain tissue by recruiting other areas to help perform tasks and brain imaging studies have supported this belief.

But it has not been clear whether it makes a difference to performance, or provides additional information on how to perform that task.

Now a team led by University of Cambridge scientists, in collaboration with the University of Sussex, have shown this recruitment improves performance in the brains of older people.

Study lead Dr Kamen Tsvetanov, an Alzheimer's Society dementia research leader fellow at Cambridge’s Department of Clinical Neurosciences, said: “Our ability to solve abstract problems is a sign of so-called ‘fluid intelligence’, but as we get older, this ability begins to show significant decline. Some people manage to maintain this ability better than others. We wanted to ask why that was the case – are they able to recruit other areas of the brain to overcome changes in the brain that would otherwise be detrimental?”

Brain imaging has shown fluid intelligence tasks engage a brain network known as the ‘multiple demand network’ (MDN), which involves regions at the front and rear of the brain, but its activity decreases with age.

The Cambridge team examined imaging data from 223 adults aged between 19 and 87 recruited by the Cambridge Centre for Ageing & Neuroscience (Cam-CAN).

They were asked to identify the odd-one-out in a series of puzzles of varying difficulty while lying in a functional magnetic resonance imaging (fMRI) scanner, so researchers could look at patterns of brain activity by measuring changes in blood flow.

In general, the ability to solve the problems decreased with age, as expected, and the MDN was particularly active, as were regions of the brain involved in processing visual information.

But using machine learning to analyse the images further, they found two areas of the brain that showed greater activity in the older people, which correlated with better performance on the task. These were the cuneus, at the rear of the brain, and a region in the frontal cortex.

Activity in only the cuneus region related to better performance in the older rather than younger volunteers, and contained extra information about the task beyond the MDN.

It is not clear what the cuneus is recruited, but the region is good at helping us stay focused on what we see.

Older adults can have a harder time briefly remembering information they have just seen, like the complex puzzle pieces used in the task. So increased activity in the cuneus might reflect a change in how often older adults look at these pieces, as a strategy to make up for their poorer visual memory.

Dr Ethan Knights from the Medical Research Council Cognition and Brain Sciences Unit at Cambridge, said: “Now that we’ve seen this compensation happening, we can start to ask questions about why it happens for some older people, but not others, and in some tasks, but not others. Is there something special about these people – their education or lifestyle, for example – and if so, is there a way we can intervene to help others see similar benefits?”

Dr Alexa Morcom, from Sussex’s School of Psychology and Sussex Neuroscience research centre, said: “This new finding also hints that compensation in later life does not rely on the multiple demand network as previously assumed, but recruits areas whose function is preserved in ageing.”

The research, published in the eLife journal, was supported by the Medical Research Council, the Biotechnology and Biological Sciences Research Council, the European Union’s Horizon 2020 research and innovation programme, the Guarantors of Brain, and the Alzheimer’s Society.

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