A Large-Scale Investigation of White Matter Microstructural Associations with Reading Ability

Abstract

Reading involves the functioning of a widely distributed brain network, and white matter tracts are responsible for sending information between constituent network nodes. Several studies have analyzed fiber bundle microstructural properties to shed insights into the neural basis of reading abilities and disabilities. Findings have been inconsistent, potentially due to small sample sizes and varying methodology. To address this, we analyzed a large data set of 690 children ages 5-18 using state-of-the-art neuroimaging acquisitions and processing techniques. We searched for associations between fractional anisotropy (FA) and single-word and nonword reading skills in both typical and poor readers across multiple tracts previously thought to contribute to reading. Consistent with prior studies, FA increased with age across all tracts. There were significant correlations between better reading skills and higher FA in several fiber bundles among poor readers, but fewer and occasionally negative associations among proficient readers. The left superior longitudinal fasciculus and arcuate fasciculus unexpectedly exhibited higher FA within those diagnosed with reading disabilities compared to those without a diagnosis, while their right-hemisphere homologs exhibited higher FA in those with higher reading scores, regardless of diagnostic status. These results suggest a different relation between white matter pathways in children with typical reading ability versus those with reading disabilities.

White matter and literacy: a dynamic system in flux

“…These results are also generally in line with those reported by Meisler and Gabrieli(36) which did not find any significant relationship between FA and reading skills in a subset of the HBN dataset. Though the authors observed a relationship between FA and phonemic decoding in the right SLF and the left ICP in participants above age 9, their analysis focused on a different measure of reading skill (TOWRE) and relied on a different analytic pipeline (TractSeg(65)), which may explain the subtle differences between their findings and the present results.…”

“…For example, a recent cross-sectional analysis of the Healthy Brain Network (HBN) dataset (32), representing the largest study of white matter and reading to date, did not reveal any significant differences in FA between struggling and typical readers nor a significant relationship between FA and reading scores (35). These findings not only raise questions about the observed relationships between reading and the white matter in smaller, cross-sectional studies, but also about the impact of sample makeup on these brain-behavior correlations, as the HBN dataset is a much more diverse sample than those found in traditional single-lab studies.…”

The neocortical infrastructure for language involves region-specific patterns of laminar gene expression

“…As regards dyslexia, this disorder of reading is closely linked to linguistic cognition in many affected individuals, including reduced phonological awareness and sometimes language impairment (54)(55)(56). Dyslexia has also been linked to altered frontal-temporal structural connectivity via the arcuate fasciculus, although results on this have been inconsistent across studies (57,58). While reading is a cultural innovation, it recruits much of the neural circuitry that underpins the human capacity for oral language (59).…”

White matter connections of human ventral temporal cortex are organized by cytoarchitecture, eccentricity, and category-selectivity from birth

“…For example, it is unknown if lack of visual experience may lead to the preservation of connections between VTC and somatosensory cortex, which in turn, may enable VTC to respond to haptic inputs in individuals who are congenitally blind 100 . Critically, our framework enables measuring the fine-grained white matter connections of VTC in individual infants longitudinally 101 , increasing accuracy and precision in measuring the interplay between white matter connections, functional regions, and anatomy across development. Our framework opens new opportunities not only for evaluating development of white matter associated with functional regions in large infant datasets [74][75][76][77][78] but also for early identification and assessment of developmental disorders associated with VTC such as autism [102][103][104][105] , Williams syndrome 106 , congenital prosopagnosia 107,108 , and dyslexia 109,[102][103][104][105] .…”