Hope remains for those who passed the baby-formula stage long ago. Although the adult brain isn’t as malleable as a young brain, and is therefore less easily influenced by environmental factors, evidence is growing that the adult brain is still remarkably plastic. Scientists haven’t yet studied white matter enough to know how to improve it directly, especially in healthy people. But exercise, diet, and mental activity have all been shown to boost brain health and decrease the risk of dementia, a disorder that has been linked to white-matter damage. And other studies have shown that just a few months of practicing a new skill can enlarge certain parts of the brain, including parts of the frontal cortex involved in motor planning and parts of the temporal lobes that integrate visual, auditory, tactile, and internal physiological information. Similar studies on ways to improve the quality of white matter are under way.
Although looking at images of my own white matter was fascinating, it was not deeply illuminating. The scan gave me no indication of how efficient or flexible my mental processes are. And, the researchers told me, not even the most astute neuroanatomist would be able to glean a general sense of my cognitive capabilities from my brain scan.
Learning more about the role of white matter in intelligence will give scientists a fuller picture of how brain anatomy influences cognition. It could help explain how differently structured brains might produce the same IQ, or whether particular patterns–thick white matter here, a large chunk of gray matter there–are linked to particular cognitive strengths and weaknesses. “One of the key findings that has come out of the last decade of studies of intelligence is the fact that the brain can generate the same IQ score a number of ways,” says Haier. Intelligence is characterized by “individual differences in learning, memory, and attention and how they are integrated in any one individual.” Haier envisions a day when brain scans could alert teachers to the cognitive strengths and weaknesses of each student, so that lessons could be individually tailored. It might be possible to derive much the same information from extensive cognitive testing, but such testing is rare because it’s expensive and time consuming. A 15-minute brain scan, on the other hand, might be applied much more broadly.
Although it’s not yet possible to estimate someone’s IQ from a brain scan, some scientists say that day may not be far off. “For a very simple example,” says Haier, “suppose the total amount of gray matter in several areas is a good correlate of IQ, and this correlation gets better if we add additional scan information–perhaps the amount of white matter in other areas or the amount of activation in certain areas while a problem is solved. We don’t yet know which combination of brain parameters will be most predictive of psychometric IQ or other intelligence factors or mental abilities, but we know how to find out. Once funding is available to scan very large samples with multiple techniques and test everyone with a battery of psychometric measures, it’s just a matter of time.”
That could be a boon for physicians working with Alzheimer’s patients or others suffering from diseases that cause cognitive damage. Some experts, however, fear it will create the sense that people’s abilities are completely predetermined. Scientists working in the field argue that using a brain scan to quantify intelligence is really no different from using a standardized test like the SAT. But because a brain scan measures a physical property, it’s likely to arouse even more concern than today’s testing methods. “If you can estimate someone’s IQ from a brain scan, even if it isn’t any more predictive than an SAT [score], it gives the illusion that his or her future is fixed,” says Karama.
In truth, it’s not yet clear that brain scans would be any better than SAT scores at predicting an individual’s cognitive function–or success in school, career, or life. Their value will depend on what we do with them. Perhaps, as with the SAT, training courses will be developed to help people improve their scores–to make better use of the network of connections in their brains. Says UCLA’s Frew, “It’s not just the tool. It’s how well we are using it.”
Emily Singer is Technology Review’s senior editor for biomedicine.