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See Inside March / April 2011

A Stimulating Solution for Math Problems

A device that sends electric current through the brain improves numerical skills

People who struggle with basic arithmetic may get a boost from a tool that electrically stimulates the brain, according to a study that appeared November 23 in Current Biology.

Researchers at the University of Oxford and University College London studied people with normal math skills using a noninvasive technique called transcranial direct-current stimulation, in which scalp electrodes emit current that modulates neural activity. The team focused on the right parietal cortex because it contributes to spatial and math­ematical thinking. This brain region shows abnormal re­sponses in children with developmental dyscalculia, a learning disability that affects math skills.

Over the span of six days the inves­tigators applied current over the volunteers’ right parietal lobe for 20 minutes at the beginning of training sessions in which subjects learned to associate numbers with arbitrary symbols, such as triangles or cylinders. After practicing, subjects were rapidly presented with pairs of symbols of different visual sizes (using larger or smal­ler fonts), and they had to choose the physically larger one as quickly as they could. In some of the pairs, the physically larger item rep­resented a smaller magnitude—for in­stance, a huge symbol meaning “two” was paired with a tiny symbol representing “five”—­and that mismatch could cause a delay in reaction time because subjects must override their impulse to choose the greater number.

By the fourth day subjects who had their right parietal cortex stimulated became slower for mismatched trials as compared with matched trials, just as adults are when they respond to real digits. But participants who did not receive the same pattern of stimulation showed no difference between these trials, suggesting they had not internalized the symbols’ meaning. The results indicate that right-hemisphere stimulation helps people learn numerical symbols.

The superior performance lasted for six months—a long effect that suggests the method may someday benefit those with developmental dyscalculia, says study co-author Roi Cohen Kadosh, a cognitive neuroscientist at Oxford. “This was the first step in finding a way to improve numerical abilities,” he says.

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