By Philip Cohen
DO SPECIFIC chemicals in your brain play a key role in how clever you are?
Brain imaging specialists in New Mexico have found a link between variations in
the levels of two brain chemicals and the results of IQ tests. It's possible,
they say, that changing the balance of the chemicals with dietary supplements
could give your intelligence a boost.
Concentrations of the chemicals N-acetylaspartate (NAA) and choline
are known to change when people suffer from brain diseases or injuries. But the
new study reveals that in healthy people, levels of the chemicals account for a
large amount of the variation in people's IQs.
NAA is found only in neurons and is thought to contribute to their healthy
function. Choline is present in nerve cell membranes. When large numbers of
neurons are injured or killed, NAA levels drop and damaged cells release more
choline.
In patients with injured brains, this shift is linked to a loss of cognitive
function. But neuroscientist William Brooks of the University of New Mexico in
Albuquerque and his colleagues wondered how the chemicals fluctuate in people
with normal, healthy brains. "We really didn't know what to expect," says
Brooks. "But we were surprised by what we found."
From a local college, they selected 26 volunteers who had no history of brain
disease or psychiatric illnesses. They then used a technique called magnetic
resonance spectroscopy to measure levels of NAA and choline in a brain region
involved in a wide variety of cognitive functions. Within a week, the students
were given standard IQ tests.
The team found a strong link between levels of the chemicals and their
performance in the tests. Low levels of choline and high levels of NAA were
associated with high IQ. Statistical analysis showed NAA and choline levels
together could account for 45 per cent of the variation in the IQ tests. In
comparison, the level of a brain chemical called creatine showed no significant
link to IQ (Proceedings of the Royal Society B, vol 266, p 1375).
Brooks speculates that in healthy people, levels of NAA and choline may
indicate the rate at which neurons are being damaged, and thus the amount of
energy the brain is using up to maintain them. "If you have healthy neurons, but
you're struggling to keep them repaired, it makes sense you won't be as
cognitively sound," he says.
But there is another possible explanation, says Brooks: NAA and choline might
directly enhance and inhibit the function of neurons. If that's true, Brooks
says it might be possible to improve intellectual performance by manipulating
the level of these compounds with dietary supplements.
Howard Gardner, a psychologist at Harvard University warns that other
supposed biochemical indicators of intelligence have proved unreliable. And he
adds that performance in IQ tests can be affected by many factors, such as the
subject's health and their motivation. He suggests that Brooks's images may in
fact be tracking one of these other factors. "Beware the intelligence equals IQ
equation," says Gardner.
Brooks agrees that his results are preliminary. He and his colleagues hope to
examine more carefully what types of abilities NAA and choline best predict in a
larger group of volunteers.
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