Structural brain connectivity differences between children with developmental dyscalculia and typically developing peers.

Objective: Developmental dyscalculia (DD) is a specific learning disability that negatively affects individual's arithmetic learning. Difficulties often continue from childhood through adulthood. Underlying neurobiological mechanisms of DD, however, have not been fully understood. The purpose of this study was to investigate possible structural brain connectivity differences between children with DD and typically developing (TD) peers. Methods: After screening 2058 third grade students in elementary schools with mathematical tests, we assigned children to DD and TD groups according to the screening results. After two years later, we invited children for detailed neuropsychological assessments. We obtained pure DD and TD children sample excluding comorbidities. Volunteer children were familiarized with a mock MRI-scanner. We acquired Diffusion Tensor Imaging (DTI) data with a Siemens Magnetom-Trio-Tim 3Tscanner with 60-different phase-encoding directions. Results: After preprocessing, we evaluated 10 children with pure DD (11.3±0.7 years) and 16 TD peers (11.2±0.6 years). We first assessed white matter microstructure with tract-based spatial statistics. Then we used probabilistic tractography to evaluate tract lengths and probabilistic connectivity maps in specific ROIs (Regions-of-Interest). At whole-brain level, we found no significant microstructural differences in white matter between DD children and TD peers. Also, seed-based connectivity probabilities showed no differences between groups. However, we found significant differences in ROI-tracts which had previously been related to math ability in children. The major findings of our study were reduced white matter integrity and shorter fiber lengths of the left superior longitudinal/arcuate fasciculus and left anterior thalamic radiation in the DD group. Conclusion: These results from regional analyses indicate that learning, memory and language-related pathways in the left hemisphere might underlie DD. Further studies are needed to implement with larger data sets, using longitudinal and/or interventional designs to confirm these findings. (This study was supported by TÜB‹TAK under the project code 214S069). [ABSTRACT FROM AUTHOR]