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How does the brain change with age? Part #3: MEG brain waves

How does the brain change with age? Part #3: MEG brain waves - 23 July 2013. BBSRC

A suite of videos explores a major BBSRC programme to study ageing and cognition in healthy adults.
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  How does the brain change with age? Part #3: MEG brain waves.

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In addition to fMRI (functional magnetic resonance imaging) brain imaging, the Cam-CAN Project (see below 'The resilience of the brain') uses another type of brain scanner, MEG (magnetoencephalography) to combine with data from fMRI. Again, MEG is a non-invasive procedure that is very quick, comfortable and safe.

MEG maps brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain's neurons. It can pinpoint sources of motor and sensory activity like fMRI, but with much less spatial precision. Its main advantage is speed – resolving events occurring over one thousandth of a second; in contrast to fMRI, which takes several seconds to do the same job because it relies on the brain's more sluggish blood flow response. fMRI does give better spatial resolution though, so combining the two can create 'real-time movies' of activity over the brain during cognitive tasks.

"MEG is a more recent technique that measures tiny magnetic fields caused by neural activity, rather than electrical fields (EEG) or blood oxygen changes (fMRI)," says Cam-CAN Assistant Director Professor Rik Henson. "Indeed, Cam-CAN is the only large project on ageing to have such MEG data available, which we expect will offer a unique perspective on the ageing process."

Henson adds that combining MRI and MEG data can help the researchers avoid a 'chicken-and-egg' conundrum. Because fMRI relies on blood supply, which changes with age, it can be difficult to differentiate age-related changes in the vessels that supply the brain from age-related changes in neural activity. "This is why we also use MEG, which measures neural activity more directly, offering a clearer window on functional changes," says Henson. "A complete picture of the ageing brain can only be obtained by combining all these different types of neuroimaging data."

The resilience of the brain

Ageing is an aspect of living common to every person, whether old or young, but what differs is how our brains and cognitive abilities change as we grow older. Some people's minds remain sharp and intact well into their 80s and 90s, whereas others can slide into early cognitive decline from their early 50s. Why such a divergence?

A major £5M grant from BBSRC has established the Cambridge Centre for Ageing and Neuroscience (Cam-CAN) team that seeks answers to these questions. By studying the brain and its cognitive functions using advanced brain imaging techniques and cognitive experiments the team of researchers, based at the University of Cambridge and the MRC Cognition and Brain Sciences Unit, hope to unravel the mechanisms and processes of healthy brain functions.

And it's not just about old people. The Cam-CAN project's full cohort of 3000 participants spans the full adult range of 18-88. This is because recent research suggests that the brain changes throughout our lifespan – not just when we are older. Important changes are happening in midlife that set the scene for how well our brains will work in retirement years.

"The changes that take place when we are older may only be a small piece of the puzzle," says Cam-CAN director Professor Lorraine Tyler from the University of Cambridge. "Individual brains may change at different rates at different ages, so a model of only the later years may be inadequate, and also would not help us to generate predictive models which may be needed to enable us to develop interventions early in life."

Hence, along with studying healthy rather than diseased states in all ages constitutes a novel and ambitious approach that could change our perspective of ageing processes, and reveal why abilities such as language are retained while others are lost.

In time, biomarkers for health can also be compared with the biomarkers from disease states, and interventions designed and implemented that in the future might restore the balance and well-being that every person wants.

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