Overview
- A peer-reviewed, open-access paper published Oct. 22 reported 7-tesla fMRI evidence that the anterior intraparietal sulcus builds a continuous topographic map of numerical magnitude.
- Researchers measured brain activity in 20 native French-speaking adults doing a magnitude-comparison task and used voxel-level pattern analysis to reveal orderly shifts in cortical activity corresponding to number size.
- Whole numbers and fractions were projected onto the same cortical coordinates according to their quantitative value, showing a unified ‘mental number line’ rather than separate format-specific maps.
- Behavioral data showed a clear cost for fractions: participants were slower and made more errors when comparing fractional values, especially when the numbers were close in magnitude.
- The authors note key limits—the small, adult, single-language sample—and call for developmental and cross-cultural studies before applying the finding to classroom strategies or diagnosing learning disorders such as dyscalculia.