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Working memory—our ability to store pieces of information temporarily—is crucial both for everyday activities like dialing a phone number as well as for more taxing tasks like arithmetic and accurate note-taking. The strength of working memory is often measured with cognitive tests, such as repeating lists of numbers in reverse order or recalling sequences of dots on a screen. For children, performance on working memory assessments is considered a strong predictor for future academic performance.
Yet cognitive tests can fail to identify children whose brain development is lagging in subtle ways that may lead to future deficits in working memory and, thus, in learning. Doctors give the tests periodically and plot the results along a development curve, much like a child’s height and weight. By the time these tests reveal that a child’s working memory is below average, however, it may be too late to do much about it.
But in a new study, published January 29 in The Journal of Neuroscience, scientists demonstrated that they could predict the future working memory of children and adolescents by examining brain scans from two different types of magnetic resonance imaging (MRI), instead of looking only at cognitive tests. Henrik Ullman, a PhD student at the Karolinska Institute in Stockholm and the lead author on the paper, says that this was the first study attempting to use MRI scans to predict future working memory capacity. “We were pretty surprised when we found what we actually found,” Ullman says.
In the project the researchers ran standard cognitive tests on and scanned 62 subjects ranging in age from six to 20 years old. The MRI scans measured the density of various brain structures and also measured brain activity during one of the working memory tests. Two years later the subjects were given the cognitive tests again—but not scanned—to see how their working memory capacity had changed over time.
Researchers then looked for correlations between the results of the first round of tests and scans and the results of the cognitive tests two years later. Although the first-round cognitive test results were good predictors of future working memory, the researchers also found that including the MRI results improved their ability to predict future working memory better than the cognitive test results alone did.
By looking at the brain activity results, researchers were also able to figure out which specific regions of the brain were associated with current and future working memory. While the subjects were taking the cognitive tests, researchers saw high activity in the frontoparietal cortex, which is known to be important to working memory as well as attention and perception. But that activity did not strongly predict future working memory results; rather, the results two years on were best predicted by activity in the thalamus and basal ganglia. Ullman says that although these regions are “very central parts of the nervous system,” they’re not normally thought of as being directly involved in working memory. The thalamus is best known for processing sensory information, such as sound and touch; the basal ganglia are involved in a variety of mental processes, including movement control. Some studies have reported activation in these areas during working memory tasks, Ullman says, but they are not areas most commonly reported to participate.
The results of the study don’t explain why those particular regions of the brain might affect future working memory capacity. But Ullman says that the main importance of the study is proof in principle that brain imaging can in fact predict future cognitive function. He thinks that similar brain scans may one day help to diagnose learning and cognition problems earlier in life. If you know which children are more likely to develop these problems, Ullman says, “then you can mobilize support for them earlier.”
Nico Dosenbach, a researcher and instructor of pediatric neurology at Washington University in Saint Louis who was not involved in the study, agrees that the research has future applications. He says, however, it is far too early say when that might happen. Still, if scans can predict future problems before they are picked up by cognitive tests, the technology could prove useful for early detection of such disorders as Alzheimer’s disease. To make a real difference in combatting Alzheimer’s-related cognitive decline, Dosenbach says, doctors must “intervene as early as possible.”
