Chinese brain researchers find evolutionary clue in elderly who stay sharp and have higher quality of life in old age

https://www.scmp.com/news/china/science/article/3200943/chinese-brain-researchers-find-evolutionary-clue-elderly-who-stay-sharp-and-have-higher-quality-life?utm_source=rss_feed

A group of Chinese researchers has found that having more developed frontal lobes keeps the mind sharp in some people as they age, and is possibly a result of natural selection in human evolution.

Their study looked at how the brain structure of older adults with superior cognitive performance differed from those with mild cognitive impairment (MCI).

The study, which was published in the peer-reviewed Chinese journal Science Bulletin on November 11, found that people who had successful cognitive ageing (SCA) had a better preserved brain structure in the frontal region, while those with mild cognitive impairment showed structural deterioration in another part, the temporal region.

The authors further proposed a “frontal preservation, temporal impairment (FPTI)” hypothesis to explain the neural basis of the differences in individuals’ cognitive ageing.

The frontal regions, or frontal lobes, are associated with higher cognitive functions, such as decision-making, problem-solving and attention. The frontal lobes mark one of the biggest differences between human beings and animals. In humans they are larger proportionally than in other creatures.

Chen Yaojing, study corresponding author and a researcher at Beijing Normal University, said the human frontal lobe evolved the most recently and it exhibited age-related decline sooner than other abilities.

“There’s a theory called ‘last in, first out’. The newest part in evolution will decline first because human beings tend to save their survival abilities to the end,” she said.

“So for most elderly people, the functions of their frontal lobes decline early. But for people with successful cognitive ageing, their frontal lobes are preserved well.”

The temporal lobes are mainly responsible for processing auditory information and preserving memory. Pathological cognitive ageing and its associated diseases, such as dementia, have been linked to structural abnormalities in the region, according to the researchers.

The study recruited three groups of older adults aged between 70 and 88, including 64 successful cognitive ageing individuals, 68 mild cognitive impairment patients, and 66 cognitively normal controls.

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The SCA group is defined as showing superior performance on one of the two cognitive tests and higher than 1.5 standard deviations of the mean. The MCI group is defined as having cognitive impairment in at least one domain and lower than 1.5 standard deviations of the mean.

“Our team initiated the Beijing Ageing Brain Rejuvenation Initiative in 2008, which focused on elderly people with cognitive impairment because they needed more attention. But during our community-based research, we found there was a group of elderly people who aged more slowly and had a higher quality of life,” Chen said.

“We want to learn from them and find out ways to keep our brain in a healthier state.”

Chen and her colleagues assessed different tissue types in the brain and compared grey matter volume, grey matter networks and white matter network properties of the three groups.

Grey matter consists primarily of neuronal cell bodies and largely functions to process information in the brain. White matter, which is largely composed of axons, serves to conduct and send nerve signals to other regions of the brain and the spinal cord.

They found that compared to the other two groups, the SCA group had larger grey matter volume, enhanced grey matter integrity and networks and improved white matter network nodal efficiency in the frontal regions.

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In contrast, the MCI group had decreased grey matter integrity and white matter network connections in the temporal regions.

They also discovered the three groups had different levels of grey matter integrity and white matter network efficiency in the right hippocampus region, with the SCA group performing best.

“If our hypothesis is proven true, in the future we can develop the frontal lobes or slow the ageing of temporal lobes,” Chen said. “This is a multidisciplinary effort.”