Longevity Briefs: Charting The Structure Of The Brain, From Foetus To Centenarian

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

Why is this research important: It hardly needs to be stated that the brain is a vital organ, yet scientists know surprisingly little about how the brain normally develops throughout life. For a given age, height and sex, we have charts that give us a reasonably good approximation of what healthy weight and body composition should be. However, no such charts exist for brain development – it is not yet possible to look at a brain scan and say with confidence how old its owner is. For that, we need a large database of brain scans from people with a wide range of ages.

What did the researchers do:

Scientists have gathered brain scans from over 100 000 people – the largest collection of its kind – to create the first growth reference charts for brain development. The youngest brains scanned were from 16 week-old foetuses, while the oldest came from 100-year-old adults. They include brains from neurotypical people, from people with medical conditions like Alzheimer’s disease, and from those with neurocognitive differences such as autism.

The scale of the study is impressive – MRI scans are expensive, which limits scientists in the number of participants they can study. The researchers got around this issue by turning to already-completed neuroimaging studies. They reached out to researchers from all over the world, asking if they were willing to share their neuroimaging data, and were pleasantly surprised by the number of replies.

Key takeaway(s) from this research:

The charts show us how the human brain changes constantly throughout life, growing quickly in size when we’re young, then shrinking gradually with age. The thickness of the cortex (the outer layer of the brain associated with ‘higher’ functions like consciousness and emotion) and the grey matter (which contains most of the brain’s neuronal cell bodies) both reach their peak volumes before puberty. The volume of the white matter (composed mostly of fast-conducting nerve fibres to relay information between different brain regions) usually peaks in volume between ages 20 and 40.

After reaching their peak volume, the above regions of the brain decrease in volume at an accelerating pace throughout the rest of life. Only the ventricular system (the four cavities in which cerebrospinal fluid circulates) consistently grows in volume throughout life. Though the ventricles perform an important function, their expansion during adulthood is not a good thing – it is the result of other important brain structures shrinking.

The brain charts put together here are preliminary, but will hopefully one day see widespread clinical application. While this study is very large, it still suffers from a lack of diversity, looking primarily at the brains of Europeans and North Americans. MRI machines remain rare in many countries, which makes diverse data hard to find.