These findings confirm the notion that numbers are encoded in the brain via detailed and specific activity patterns and open the door to more sophisticated exploration of a human’s high-level numerical abilities.
Although “number-tuned” neurons have been found in monkeys, scientists hadn’t managed before now to get any farther than particular brain regions in humans.
“It was not at all guaranteed that with functional imaging it would be possible to pick this up,” said Evelyn Eger of INSERM (Institut national de la sant et de la recherche mdicale) in
Researchers presented 10 study participants with either number symbols or dots while their brains were scanned with a MRI. They then devised a way of decoding the numbers or the number of dots people had observed.
Although the brain patterns corresponding to number symbols differed somewhat from those for the same number of objects, the numerosity of dot sets can be predicted above chance from the brain activation patterns evoked by digits, the researchers show. That doesn’t work the other way around, however.
At least for small numbers of dots, the researchers did find that the patterns change gradually in a way that reflects the ordered nature of the numbers — allowing one to conclude that six is between five and seven, for instance.
The methods used in the new study may ultimately help to unlock how the brain makes more sophisticated calculations, the researchers say, according to an INSERM release.
“With these codes, we are only beginning to access the most basic building blocks that symbolic math probably relies on,” Eger said.
These findings were published online in Current Biology.