The research suggests that teenagers with a particular genetic
variant have a thinner cerebral cortex, commonly known as grey matter, in
the left hemisphere of the brain. Teenagers with this genetic variant were
found to do less well in verbal and non-verbal reasoning tests. This is the
first time a genetic connection between intelligence and grey matter has been
Grey matter is the outermost layer of the human brain, and
plays a key role in memory, attention, perceptual awareness, thought, language
and consciousness. The thickness of the grey matter is closely related to a
person's intellectual ability.
Dr Sylvane DesriviÃ¨res, lead author, from King's College
London's Institute of Psychiatry, said: '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'.
Researchers analysed DNA samples and brain scans from 1,583
healthy 14-year-olds, who were also given a series of tests to determine their
verbal and non-verbal intelligence.
The researchers looked at more than 54,000 genetic variants
possibly involved in brain development, and found that the genetic variant affects
the expression of the NPTN gene. This gene encodes a protein affecting how
brain cells communicate.
The NPTN gene was found to have different activity in the
left and right hemispheres of the brain. The left hemisphere may be more
sensitive to the effects of NPTN mutations, and differences in intellectual
ability could be caused by the decreased function of the NPTN gene in parts of
the left hemisphere.
But Dr DesriviÃ¨res cautioned: 'Intelligence is influenced by
many genetic and environmental factors. 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"'.
Researchers hope that this finding will help explain the
biological basis of psychiatric disorders involving impaired cognitive ability such
as schizophrenia and autism.