Brain food

 作者:隗雷     |      日期:2019-03-08 03:20:00
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,