Steps Start to Add Up to a Math Path in the Brain

With functional MRI, researchers see that numbers trigger distinct activity patterns

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THURSDAY, Sept. 24, 2009 (HealthDay News) -- Careful observation and analysis of brain activity enables scientists to determine what number a person has just looked at or how many dots they've just been shown, a French study has found.

The researchers said their findings confirm the theory that numbers are encoded in the brain through detailed and specific activity patterns, something they say could help improve the investigation of humans' high-level numerical abilities.

While "number-tuned" neurons have been identified in monkeys, scientists previously had only been able to identify number-related brain regions in humans.

In the new study, the researchers used functional MRI to scan the brains of 10 volunteers as they were shown either number symbols or dots. They then used a multivariate analysis method to determine which number or how many dots the volunteers had seen.

The study was published online Sept. 24 in Current Biology.

"It was not at all guaranteed that with functional imaging it would be possible to pick this up," Evelyn Eger of Inserm, a biological, medical and public health research institute in France, said in a news release from the journal's publisher.

"In the monkey, neurons preferring one or the other numerosity appear highly intermixed among themselves as well as with neurons responding to other things, so it might seem highly unlikely that with [functional] MRI at 1.5 mm resolution -- where one voxel contains many thousands of neurons -- one would be able to detect differences in activity patterns between individual numbers," Eger said. "The fact that this worked means that there is probably a somewhat more structured layout of preferences for individual numbers that has yet to be revealed by neurophysiological methods."

"With these codes, we are only beginning to access the most basic building blocks that symbolic math probably relies on," she said. "We still have no clear idea of how these number representations interact and are combined in mathematical operations, but the fact that we can resolve them in humans gives hope that at some point we can come up with paradigms that let us address this."

More information

The U.S. National Institute of Neurological Disorders and Stroke has more about the brain.

SOURCE: Cell Press, news release, Sept. 24, 2009

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