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 An international team of scientists analyzed 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 intelligence.
The researchers looked at the cerebral cortex — the outermost layer
of the brain that is also known as "grey matter" and plays a key
role in memory, attention, perceptual awareness, thought, language
and consciousness.
They then analyzed 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 intellectual ability.
"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 Psychiatry.
"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.
The findings, published on Tuesday 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.
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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.
(Editing by Andrew Heavens)
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