Author:

Keywords:

White Matter, DTI, Spherical Deconvolution, Arithmetic

Abstract:

Structural brain connectivity is integral to efficient cognitive processing. Therefore, understanding the role of structural pathways in arithmetic may further clarify the neural mechanisms of arithmetic abilities. Previously, in numerical cognition, these white matter (WM) pathways have been examined by means of Diffusion Tensor Imaging (DTI) and the associated fractional anisotropy (FA) index (Matejko & Ansari, 2015 for a review). Despite the availability of the technique, however, (developmental) DTI research in arithmetic is scarce. Furthermore, the available DTI studies in children have major shortcomings, such as the fact that data were often collected from children with wide age ranges, and that classical DTI is subject to various methodological limitations. These limitations include that DTI only estimates the direction of one fiber per voxel, which leads to an oversimplification of the underlying anatomy (i.e., DTI will make it seem as if only one fiber runs through voxels with fiber crossings). This is problematic, as many crossing fibers are situated around the inferior parietal lobe, an area associated with individual differences in mathematics. Secondly, the interpretation of the FA index is not clear-cut, as it provides a quantitative measure per voxel, determined by micro- and macrostructural properties. These methodological limitations can be resolved by more complex non-tensor models, such as Spherical Deconvolution (SD), which has the asset of characterizing the orientation of more than one fiber per voxel. Furthermore, to resolve FA-issues, the hindrance modulated orientational anisotropy (HMOA) index can be derived from SD, which provides information about the diffusion properties along each fiber orientation, even in regions with fiber crossings. In our own data, a comparison between DTI and SD of WM in the inferior parietal lobe revealed not only visual differences (e.g., fibers reached further into the cerebral cortex), but showed an increased number of fibers and volume for SD. The current study investigates how WM tracts relate to arithmetic abilities, in 9- to 10-year-old children, and is the first to compare both DTI and SD to do so. The results of this study are not yet final, but will be presented at the conference.