When You're At Rest, Your Brain's Right Side Hums

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There's plenty of brain activity even when people are thinking nothing at all. But it's the brain's right side — for most people the less-dominant half — that stays busiest while you're at rest, according to surprising new findings.

Researchers found that during periods of wakeful rest, the right hemisphere of the brain chatters more to itself than the left hemisphere does. It also sends more messages to the left hemisphere than vice versa. Surprisingly, this remains true whether the owner of the brain is left- or right-handed. That seems odd, because in right-handed people the left hemisphere is the dominant one, and in left-handed people the right is usually more dominant.

Andrei Medvedev of Georgetown University Medical Center's Center for Functional and Molecular Imaging asked 15 study participants to sit peacefully and let their minds drift while they wore a cap that measured brain activity.

This resting state, previously found to improve memory, "is a special state when the brain tries to deal with information that was acquired during previous active states," Medvedev told LiveScience.

The cap, which was covered with optic fibers, shone infrared light into the scalp. The light waves reached the outermost brain layers and bounced back. The amount of light that reflected back told researchers how much oxygenated and deoxygenated blood was in a specific brain region. Changes in blood oxygenation tell the researchers which brain areas are using more oxygen and are thus more active.

Medvedev was interested in communication within and between brain regions. He found that the right hemisphere was interacting more with itself and with its counterpart than the left hemisphere was.

"I did not expect that," he said. "I actually was expecting that the left hemisphere would be more important, more integrated, but it appears the right hemisphere during this resting state is more connected." [7 Reasons to Meditate]

So far Medvedev and his colleagues don't know why the right hemisphere is so busy. Because the brain goes into a sort of "housecleaning" mode during resting states, it's possible the right hemisphere works as something like an outside housekeeper, organizing and integrating as well as sending that information to the usually dominant left hemisphere, he said.  

The research highlights the need to get more lefties into scientific studies, Medvedev said.

"Most brain theories emphasize the dominance of the left hemisphere, especially in right-handed individuals, and that describes the population of participants in these studies. Our study suggests that looking at only the left hemisphere prevents us from a truer understanding of brain function," he said in a statement. 

Medvedev reported his findings today (Oct. 17) in New Orleans at the annual meeting of the Society for Neuroscience.

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