The Role of Dorsal and Ventral White Matter Tracts in Phonological and Semantic Processing of Language in Pre-Readers and Beginning Readers

Abstract

This preregistered Diffusion Tensor Imaging (DTI) study aims to investigate the functional dissociation between left dorsal and ventral white matter tracts during reading development. We examine the unique relations of dorsal tracts (Superior Longitudinal Fasciculus, Arcuate Fasciculus) to phonological processing and ventral tracts (Inferior Longitudinal Fasciculus, Inferior Fronto-Occipital Fasciculus) to semantic processing, and whether phonological specialization in dorsal tracts is evident in pre-readers and semantic specialization in ventral tracts is evident in beginning readers. Automatic Fiber Quantification was performed on DTI scans of 81 pre-readers (5-year-olds) and 164 beginning readers (7-year-olds) to map and segment white matter tracts. Partial correlation analysis was conducted to assess the relationship between language scores and the white matter integrity (measured via fractional anisotropy) of tracts at node-level. In pre-readers, the results revealed that the tract integrity of the dorsal AF tract (nodes 68-87) showed a unique positive relation with phonological processing, measure with Elision. In beginning readers, the tract integrity of the ventral IFOF (nodes 41-57) showed a unique positive relation with semantic processing, measure with Word Classes. These findings suggest the importance of phonological processing during early language development (age 5); while during later stages of development (age 7), semantic mechanisms become more prominent in language processing. This study provides conclusive DTI evidence for a shift from phonological to semantic processing in pre-readers to beginning readers, which support the connectionist model in developmental context.