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13th February 2014

Scientists identify gene linking brain structure to intelligence

For the first time, scientists at King's College London have identified a gene linking thickness of the grey matter in the brain to intelligence. The study is published in Molecular Psychiatry and may help scientists understand biological mechanisms behind some forms of intellectual impairment.

 

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The researchers looked at the cerebral cortex – the outermost layer of the human brain. It is known as 'grey matter' and plays a key role in memory, attention, perceptual awareness, thought, language and consciousness. Previous studies have shown that the thickness of the cerebral cortex, or 'cortical thickness', strongly correlates with intellectual ability. However, no genes had been identified until now.

An international team of scientists, led by King's, analysed DNA samples and MRI scans from 1,583 healthy 14 year olds. These teenagers also underwent a series of tests to determine their verbal and non-verbal intelligence.

Dr Sylvane Desrivières, from King's College London's Institute of Psychiatry and lead author of the study: "We wanted to find out how structural differences in the brain relate to differences in intellectual ability. The genetic variation we identified is linked to synaptic plasticity – how neurons communicate. This may help us understand what happens at a neuronal level in certain forms of intellectual impairments, where the ability of the neurons to communicate effectively is somehow compromised.

"It's important to point out that intelligence is influenced by many genetic and environmental factors," she added. "The gene we identified only explains a tiny proportion of the differences in intellectual ability, so it's by no means a 'gene for intelligence'."

The researchers looked at 54,000 genetic variants possibly involved in brain development. They found that, on average, teenagers carrying a particular gene variant had a thinner cortex in the left cerebral hemisphere, especially in the frontal and temporal lobes, and performed less well on tests for intellectual ability. The genetic variation affects expression of the NPTN gene, which encodes a protein acting at neuronal synapses and therefore affects how brain cells communicate.

To confirm their findings, the NPTN gene was studied in both mouse and human brain cells. The scientists found that the NPTN gene had a different activity in the left and right hemispheres of the brain, which may cause the left hemisphere to be more sensitive to the effects of NPTN mutations. Their findings suggest that some differences in intellectual abilities can result from a decreased function of the NPTN gene in particular regions of the left brain hemisphere.

The genetic variation identified in this study only accounts for an estimated 0.5% of total variation in human intelligence. However, the findings may have important implications for the understanding of biological mechanisms underlying several psychiatric disorders, such as schizophrenia and autism, where impaired cognitive ability is a key feature of the disorder.

 

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