Your brain maps out numbers, including integers and fractions

From learning to count to solving complex calculations, math requires an inherent organization of information. A team of researchers led by Stanislas Dehaene, Ph.D. and Daniela Valério, Ph.D. at the INSERM-CEA Cognitive Neuroimaging Unit (Unicog) Lab in France took dynamic brain scans of adults presented with fractions and integers. Their findings, published on October 22^nd in the open access journal PLOS Biology, revealed a map of brain activity that underlies how we arrange numerical information.

One of the biggest questions in neuroscience is how does the brain represent complex, abstract concepts? One theory is that the brain organizes related concepts together, with similar concepts represented by nearby patterns of brain activity, and the network of these distances is called a “semantic map.” Numbers present an excellent case for testing the semantic map hypothesis, because these values have a universally understood arrangement.

In this study, 20 native French speakers were shown a series of integers and fractions and asked whether each number was bigger or smaller than the previous. Meanwhile, the researchers measured their brain activity with functional MRI (fMRI) to examine how patterns of brain activity changed as participants compared numbers of different sizes.

The scans revealed an organized pattern of activity in the intraparietal sulcus, a region of the brain known to be involved in numerical processing. As participants compared numbers, the patterns of activity changed in a structured way, suggesting that this region contains a spatial map of numerical magnitude ranging from smaller to larger numbers.

Analyses of individual participants also determined that integers and fractions were processed differently. However, when comparing different types of numbers, the neural scans demonstrated numerical magnitude within a shared, organized system. The participants also made more errors in number ordering (from low to high values) when fractions were involved and they were slower when two fractions were close together.

The authors add, “Our study shows that when we focus on the magnitude of numbers, the brain organizes quantities into a highly structured internal map. This map brings fractions and integers together along a shared mental number line, allowing us to represent and compare different kinds of numbers within the same system. This organization may help us process quantities and make mathematical decisions more efficiently.” 

In your coverage, please use this URL to provide access to the freely available paper in PLOS Biology: https://plos.io/4AzeOLD 

Citation: Valério D, Debray S, Karami A, Cauté M, Gravel N, Dehaene S (2026) A cortical semantic map integrates fractions and integers in the human brain. PLoS Biol 24(10): e3003820. https://doi.org/10.1371/journal.pbio.3003820

Author countries: France

Funding: This work was supported by the European Research Council (ERC; https://erc.europa.eu/) under the ERC grant “MathBrain” to SD (grant number ERC-2022-ADG 101095866). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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