Weak task-related modulation and stimulus representations during arithmetic problem solving in children with developmental dyscalculia

Abstract

Developmental dyscalculia (DD) is a disability that impacts math learning and skill acquisition in school-age children. Here we investigate arithmetic problem solving deficits in young children with DD using univariate and multivariate analysis of fMRI data. During fMRI scanning, 17 children with DD (ages 7-9, grades 2 and 3) and 17 IQ- and reading ability-matched typically developing (TD) children performed complex and simple addition problems which differed only in arithmetic complexity. While the TD group showed strong modulation of brain responses with increasing arithmetic complexity, children with DD failed to show such modulation. Children with DD showed significantly reduced activation compared to TD children in the intraparietal sulcus, superior parietal lobule, supramarginal gyrus and bilateral dorsolateral prefrontal cortex in relation to arithmetic complexity. Critically, multivariate representational similarity revealed that brain response patterns to complex and simple problems were less differentiated in the DD group in bilateral anterior IPS, independent of overall differences in signal level. Taken together, these results show that children with DD not only under-activate key brain regions implicated in mathematical cognition, but they also fail to generate distinct neural responses and representations for different arithmetic problems. Our findings provide novel insights into the neural basis of DD.

Fig. 1

(A and B) Behavioral performance in the DD and TD groups. Both groups showed strong differences between addition problem type, with Simple problems being performed faster and more accurately than Complex problems. There were no group differences in either accuracy or RT. However, the interaction between problem type and group was marginally significant (p = .06) indicating weaker performacne for Complex problems in the DD group.

Fig. 2

Arithmetic complexity effects in the TD and DD groups. Brain response related to arithmetic complexity obtained by contrasting Complex and Simple addition problems. Coronal slices show significant activation (Complex > Simple, red scale) and significant deactivation (Simple > Complex, blue scale) in each group. (A) TD children showed greater complexity-related activation in multiple dorsal and ventral stream areas as well as the prefrontal cortex, including left intraparietal sulcus (IPS), right IPS and superior parietal lobule (SPL), bilateral precuneus, bilateral dorsolateral prefrontal cortex (middle frontal gyrus), bilateral insula, left inferior and middle temporal gyrus (MTG) and bilateral fusiform gyrus. (B) In contrast, no brain areas showed greater complexity-related activation in children with DD. Instead, they showed greater activation to Simple problems in left MTG and in the ventromedial prefrontal cortex (vmPFC).

Fig. 3

Comparison of dorsal and ventral visual stream responses in the DD and TD groups. (A) Surface rendering of brain areas that showed reduced complexity-related responses in the DD, compared to the TD, group. (B) The DD group showed reduced activation in the right superior parietal lobule (SPL, 44, −60 58), right supramarginal gyrus (SMG, 60, −52, 34), and the right intraparietal sulcus (IPS, 32, −74, 54). (C) The DD group also had reduced responses in the lateral occipital (LOC, 54, −74, 6), right fusiform gyrus (50, −62, −20), and left middle temporal gyrus (MTG, −60, −28, 14). Plots of signal levels in regional peaks shows that the TD group showed incresed activtity on Complex, compared to Simple, problems. In contrast, children with DD had simlar activation levels for Simple and Complex problems.

Fig. 4

Comparison of prefrontal cortex responses in the DD and TD groups. (A) Surface rendering of prefrotnal areas that showed reduced complexity-related brain responses in the DD, compared to the TD, group. (B) The DD group showed lower activation in the left middle frontal gyrus (MFG, −52, 30, 30), right premotor cortex (PMC, 56, 16, 40) and adjoining MFG, and in the right inferior frontal gyrus (IFG, 30, 28, −20) and adjoining MFG. Plots of signal levels in regional peaks shows that the TD group had increased activtity on the Complex, compared to Simple, problems. In contrast, children with DD had similar activation levels for Simple and Complex problems.

Fig. 5

ROI analysis in bilateral cytoarchitectonically defined subdivisions of the IPS. In all three subdivisions (hIP2, hIP1, hIP3) of the bilateral IPS, TD children showed greater activation for Complex, compared to Simple, problems. In contrast, children with DD showed similar activation levels for Complex and Simple problems in all three subdivisions of the left and right IPS; *p < .05.

Fig. 6

Representational similarity analysis in cytoarchitectonically defined subdivisions of the IPS. Children with DD showed greater similarity of multi-voxel brain responses to Complex and Simple problems in the anterior most subdivision (hIP2: −44, −40, 48) of the left and right IPS; *p < .05.