Dyscalculics have abnormal pulses of activity in a brain furrow called the right intraparietal sulcus, find Nicolas Molko of INSERM, the French Institute of Health and Medical Research in Paris, and his colleagues. The fissure helps the mind to conjure spatial images.
It was also unusually shallow and short in the 14 women that Molko's team scanned with functional magnetic resonance imaging. The women had a genetic condition called Turner's syndrome, which is linked with dyscalculia.
The finding supports the idea that dyscalculics have difficulty conceiving arrangements of numbers, such as a line stretching from one to 100. 'It goes very well with what has been found before,' says neuropsychologist Monica Rosselli of Florida Atlantic University in Boca Raton.
Molko hopes that brain imaging could eventually diagnose dyscalculics better than today's cognitive tests. The finding might also inform educational schemes that encourage affected children to use different strategies to number lines, say.
All very nice to know. Now if they could just tell me how to deepen my right intraparietal sulcus a tad...