Electric Currents Boost Brain Power

By Jim Giles
www.Nature.com

Connecting a battery across the front of the head can boost verbal skills, says a team from the US National Institutes of Health.

A current of two thousandths of an ampere (a fraction of that needed to power a digital watch) applied for 20 minutes is enough to produce a significant improvement, according to data presented this week at the annual meeting of the Society for Neuroscience, held in San Diego. And apart from an itchy sensation around the scalp electrode, subjects in the trials reported no side-effects.

Meenakshi Iyer of the National Institute of Neurological Disorders and Stroke in Bethesda, Maryland, ran the current through 103 initially nervous volunteers. "I had to explain it in detail to the first one or two subjects," she says. But once she had convinced them that the current was harmless, Iyer says, recruitment was not a problem.

The volunteers were asked to name as many words as possible beginning with a particular letter. Given around 90 seconds, most people get around 20 words. But when Iyer administered the current, her volunteers were able to name around 20% more words than controls, who had the electrodes attached but no current delivered. A smaller current of one thousandth of an amp had no effect.

Iyer says more work needs to be done to explain the effect, but she speculates that the current changes the electrical properties of brain cells in the prefrontal cortex, the brain region through which it passes. She believes that the cells fire off signals more easily after the current has gone by. That would make the brain area, a region involved in word generation, generally more active, she suggests.

Iyer's group, which is led by Eric Wassermann, was prompted to run the tests after considering problems facing researchers who were studying the effect of magnetic fields on the brain. Some neuroscientists hope that magnetic fields could have a therapeutic effect, perhaps by boosting activity in areas of the brain that have suffered cell loss owing to dementia. But magnetic fields can cause seizures and also require bulky equipment to generate them.

Iyer hopes that low electric currents will offer a safer and more portable alternative. After running further safety tests, she plans to test the effect of the current on patients with frontal temporal dementia, a brain disease that causes speech problems. "This won't be a cure," Iyer cautions. "But it could be used in addition to drugs."

The idea of using electrical current to boost brain activity dates back to experiments on animals in the 1950s. The early work showed some potential, but fell from favour because of a perceived link to electroconvulsive therapy, a controversial technique in which patients with depression are treated by having short but intense pulses of electricity applied to the brain.

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