In a study published in the Proceedings of the National Academy of Sciences, researchers from the University of Cambridge and University College London (UCL) used magnetic resonance imaging (MRI) to study the brain structure of almost 300 individuals aged 14-24 years old.
By comparing the brain structure of teenagers of different ages, they found that during this important period of development, the outer regions of the brain, known as the cortex, shrink in size, becoming thinner. However, as this happens, levels of myelin – the sheath that ‘insulates’ nerve fibres, allowing them to communicate efficiently – increase within the cortex.
Previously, myelin was thought mainly to reside in the so-called ‘white matter’, the brain tissue that connects areas of the brain and allows for information to be communicated between brain regions. However, in this new study, the researchers show that it can also be found within the cortex, the ‘grey matter’ of the brain, and that levels increase during teenage years. In particular, the myelin increase occurs in the ‘association cortical areas’, regions of the brain that act as hubs, the major connection points between different regions of the brain network.
Dr Kirstie Whitaker from the Department of Psychiatry at the University of Cambridge, the study’s first author, says: “During our teenage years, our brains continue to develop. When we’re still children, these changes may be more dramatic, but in adolescence we see that the changes refine the detail. The hubs that connect different regions are becoming set in place as the most important connections strengthen. We believe this is where we are seeing myelin increasing in adolescence.”
The researchers compared these MRI measures to the Allen Brain Atlas, which maps regions of the brain by gene expression – the genes that are ‘switched on’ in particular regions. They found that those brain regions that exhibited the greatest MRI changes during the teenage years were those in which genes linked to schizophrenia risk were most strongly expressed.
Image: Teenager
Credit: Bob Bradburn
Reproduced courtesy of the University of Cambridge
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