Problem with arithmetic? Blame it on white matter

If you are not able to add or multiply quickly and accurately, that's not exactly your fault - it's the quality of the white matter in your brain that decides it.

A study led by Bert De Smedt, a professor from University of Leuven in Belgium, has discovered that healthy 12-year-olds - who score well in addition and multiplication - have higher-quality white matter.

But this correlation does not appear to apply to subtraction and division.

Neural pathways are comparable to a bundle of cables. These cables are surrounded by an isolating sheath - myelin or 'white matter'.

"The thicker the isolating sheath and the more cables there are, the more white matter. And the more white matter, the faster the signals are transferred," explained Bert de Smedt.

In this study, the researchers asked 25 children to solve a series of different arithmetic operations while undergoing a brain scan.

They then compared the quality of the children's white matter tracts with their arithmetic test performance.

"We found that a better quality of the arcuate fasciculus anterior - a white matter tract that connects brain regions often used for arithmetic - corresponds to better performance in adding and multiplying, while there is no correlation for subtracting and dividing," they said.

The arcuate fasciculus anterior (green) is a neural pathway connecting brain regions often used for arithmetic.

'Grey' cells process information in the brain and are connected via neural pathways, the tracts through which signals are transferred.

A possible explanation for this is that this white matter bundle is involved in rote memorisation, whereas when we subtract and divide, such memorisation plays less of a role.

"When subtracting and dividing, we are more likely to use intermediary steps to calculate the solution, even as adults," added Bert de Smedt.

These findings also add insight into the link between reading and arithmetic, said De Smedt.

"Reading proficiency and arithmetic proficiency often go hand-in-hand. This also might explain why we often see arithmetic problems in children with dyslexia," stressed de Smedt.

Next step would be to investigate how white matter tracts can be strengthened through extra arithmetic training.