Separate lanes for math and reading in the white matter highways of the human brain

Abstract

Math and reading involve distributed brain networks and learning disabilities associated with these skills have a high rate of co-occurrence. However, it is unknown what are shared vs. dissociated white matter substrates of math and reading networks. Here we address this question using an innovative, multimodal approach applying functional MRI, diffusion MRI, and quantitative MRI to define these networks and evaluate structural properties of their fascicles. Results reveal that the superior longitudinal (SLF) and arcuate (AF) fascicles are shared between math and reading networks. Strikingly, within these fascicles, reading- and math-related tracts are segregated into parallel sub-bundles and show structural differences related to myelination. These novel findings: (i) open a new avenue of research enabling linkage of sub-bundles within fascicles to behavior and (ii) may explain both isolated and comorbid cases of math and reading disabilities, which may be associated with white matter abnormalities within sub-bundles or entire fascicles, respectively.