It is amazing to think that if just one half of the cerebral cortex – the wrinkled outer layer of neural brain tissue – was unfolded and laid flat, it would have a surface area one and half times the size of an A4 paper (or 100,000mm-squared to be precise). This demonstrates the huge extent of cortical folding in the brain, which makes it look a bit like a walnut.
Now, new research by Newcastle University published in the journal PNAS has found that just like our skin over time, this folding is subject to ageing via a loss of elasticity. This ‘slackening’ was found to follow a ‘universal law’, giving us a way to spot those who deviate from the trend, such as people with Alzheimer’s disease. This could help in the earlier diagnosis and treatment of the disease in the future.
The expansion of the cerebral cortex has been essential in advancing our mental abilities in evolution, because unlike other brain regions, the cortex is associated with higher cognitive functions such as thought, perception and language. Understandably, this intricate cortical folding has remained a very difficult area to study. By mapping the brain folds of more than 1,000 people, the study discovered that cortical folding follows a universal law.
“We identified a parameter (of the law) that decreases with age, which we interpret as changing the tension on the cortical surface,” says lead author, Dr Yujiang Wang. “It would be similar to the skin. As we age, the tension drops and the skin starts to slacken.’’
The study also revealed that the size and degree of cortical folding differed between the genders, with males having larger, slightly more wrinkled brains, although both follow the same trend with regards to the law. This is contrasting to those diagnosed with Alzheimer’s disease, in which tension decreases premature to that of a normally aging cortex.
“This indicates that for the first time, we have a consistent way of quantifying cortical folding in humans,” says Dr Wang.
Mind over matter
This find has exciting potential for future applications as it provides an algorithm through which universal factors such as age, gender and disease, can be compared.
“More work is needed in this area,” concludes Wang, “but it does suggest that the effect Alzheimer’s disease has on the folding of the brain is akin to premature ageing of the cortex.”
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