Impaired neural networks for approximate calculation in dyscalculic children: a functional MRI study

Abstract

Background: Developmental dyscalculia (DD) is a specific learning disability affecting the acquisition of mathematical skills in children with otherwise normal general intelligence. The goal of the present study was to examine cerebral mechanisms underlying DD.

Methods: Eighteen children with DD aged 11.2 +/- 1.3 years and twenty age-matched typically achieving schoolchildren were investigated using functional magnetic resonance imaging (fMRI) during trials testing approximate and exact mathematical calculation, as well as magnitude comparison.

Results: Children with DD showed greater inter-individual variability and had weaker activation in almost the entire neuronal network for approximate calculation including the intraparietal sulcus, and the middle and inferior frontal gyrus of both hemispheres. In particular, the left intraparietal sulcus, the left inferior frontal gyrus and the right middle frontal gyrus seem to play crucial roles in correct approximate calculation, since brain activation correlated with accuracy rate in these regions. In contrast, no differences between groups could be found for exact calculation and magnitude comparison. In general, fMRI revealed similar parietal and prefrontal activation patterns in DD children compared to controls for all conditions.

Conclusion: In conclusion, there is evidence for a deficient recruitment of neural resources in children with DD when processing analog magnitudes of numbers.

Figure 1

Paradigm. The paradigm used during fMRI examination consisted of approximate and exact calculation, approximate and exact control conditions as well as magnitude comparison. Each condition was presented in three blocks of 80 s.

Figure 2

Brain activation of children with DD and control children. Brain activation patterns of children with DD (N = 18) and control children (N = 20) during each condition are depicted on the SPM standard brain template. The activated brain regions shown had been subjected to a FWE or FDR correction with a minimum number of 10 voxels, with one exception in Figure 2C, where the shown cluster comprises only 5 voxels. A, B, C: approximate calculation – approximate control condition. D, E: exact calculation – exact control condition. F, G: magnitude comparison – rest.

Figure 3

Stronger activation in control children compared to children with DD. Control children exhibited stronger activation in the insula and parahippocampal gyrus on the right hemisphere during approximate calculation compared to children with DD. Activated brain regions were uncorrected at p < 0.001 with a minimum number of 10 voxels represented on the SPM glass brain.

Figure 4

ROI-analysis. Mean t-values in each defined ROI for approximate calculation in control children (black) and children with DD (striped) are shown. Significant group differences are marked with two stars (** p < 0.05) and trends with one star (* p < 0.1).