The role of the left intraparietal sulcus in the relationship between symbolic number processing and children's arithmetic competence

Abstract

The neural foundations of arithmetic learning are not well understood. While behavioral studies have revealed relationships between symbolic number processing and individual differences in children's arithmetic performance, the neurocognitive mechanisms that bind symbolic number processing and arithmetic are unknown. The current fMRI study investigated the relationship between children's brain activation during symbolic number comparison (Arabic digits) and individual differences in arithmetic fluency. A significant correlation was found between the numerical ratio effect on reaction times and accuracy and children's arithmetic scores. Furthermore, children with a stronger neural ratio effect in the left intraparietal sulcus (IPS) during symbolic number processing exhibited higher arithmetic scores. Previous research has demonstrated that activation of the IPS during numerical magnitude processing increases over the course of development, and that the left IPS plays an important role in symbolic number processing. The present findings extend this knowledge to show that children with more mature response modulation of the IPS during symbolic number processing exhibit higher arithmetic competence. These results suggest that the left IPS is a key neural substrate for the relationship between the relative of precision of the representation of numerical magnitude and school-level arithmetic competence.

Fig. 1

(a) Correlation between reaction time behavioral ratio effect and math fluency raw scores. (b) Correlation between accuracy ratio effect and math fluency raw scores. Note: RT, reaction time ratio effect (large ratio RT-small ratio RT/mean of large and small ratio RTs); INACC, accuracy ratio effect (mean incorrect responses for large ratios – mean incorrect responses for small ratios/mean of large and small ratios incorrect responses). Note: two participants had the same data points and are overlapping in (b).

Fig. 2

(a) Schematic illustration of the defined ROIs superimposed on a high resolution anatomical image from one of the participants. The size of the square represents the dimensions of the ROI. The Talairach coordinates for the right inferior frontal gyrus, left intraparietal sulcus and the left superior frontal gyrus are the following: x = 43, y = 28, z = 23; x = −26, y = −61, z = 34; x = −22, y = 3, z = 58, respectively. (b) The bar chart illustrates the mean values for large and small ratio conditions during the numerical comparison task in each region. The error bars represent two standard error estimates from the mean. Note: ** denotes a significant difference at p < .01. The error bars represent two standard errors from the mean.

Fig. 3

Correlation between math fluency raw scores and the neural ratio effect in the left IPS.

Fig. 4

(a) Correlation between the neural ratio effect in the left IPS and the reaction time behavioral ratio effect. (b) Correlation between the neural ratio effect in the left IPS and the accuracy behavioral ratio effect.

Fig. 5

(a) An illustration of the whole brain analysis revealing an effect of numerical ratio on the left IPS. The superimposed blue area represents the region from the Houdé meta-analysis used in the main results. (b) Parameter estimates for small and large ratios obtained from the left IPS cluster revealed by the whole brain analysis. (c) Partial correlation (controlling for chronological age) of the ratio effect in the left IPS (extracted from the regions identified through the whole brain analysis) and math fluency raw scores. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)