Researchers have found a gene linking
intelligence to the thickness of so-called "gray matter" in the
brain, and say their discovery could help scientists understand how and why
some people have learning difficulties.
An international team of scientists
analysed DNA samples and brain scans from more than 1 500 healthy 14-year-olds
and gave them a series of tests to establish their verbal and non-verbal
The researchers looked at the cerebral cortex – the outermost layer of the brain that is also known as "gray
matter" and plays a key role in memory, attention, perceptual awareness,
thought, language and consciousness.
They then analysed more than 54 000 genetic
variants possibly involved in brain development and found that, on average,
teenagers with a particular gene variant had a thinner cortex in the left half
of their brains – and were the ones who performed less well on tests for
"The genetic variation we identified
is linked to synaptic plasticity – how neurons communicate," said Sylvane
Desrivieres, who led the study at King's College London's Institute of
"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."
She stressed, however, that their
finding did not amount to a discovery of a "gene for
intelligence". "It's important to point out that intelligence is
influenced by many genetic and environmental factors. The gene we identified
only explains a tiny proportion of the differences in intellectual
ability," she said.
Mechanisms of several psychiatric disorders
The findings, published in the
journal Molecular Psychiatry, could help scientists gain more insight into the
biological mechanisms underlying several psychiatric disorders, such as
schizophrenia and autism, since people with these conditions often have
impaired cognitive ability.
The genetic variation that Desrivieres'
team found affects a gene known as NPTN, which encodes a protein acting on
neuronal synapses and therefore affects how brain cells communicate.
To confirm the finding, the team studied
the NPTN gene more closely in mouse and human brain cells in the lab and found
it had a different activity in the left and right hemispheres of the brain.
This, they said, suggests the left
hemisphere may be more sensitive to the effects of NPTN mutations, and that
some differences in intellectual ability are due to decreased NPTN function in
particular regions of the left brain hemisphere.
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