PMC

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.

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.

(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.

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.

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).

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.