The association of dorsal and ventral white matter tracts with phonological and semantic processing of language in 5- to 7-year-old children

This preregistered Diffusion Tensor Imaging (DTI) study aims to investigate the functional dissociation between left dorsal and ventral white matter tracts during language development. We examine the unique relations of dorsal tracts, including the Superior Longitudinal Fasciculus, Arcuate Fasciculus, to phonological processing and ventral tracts, including the Inferior Longitudinal Fasciculus and Inferior Fronto-Occipital Fasciculus, to semantic processing. Automatic Fiber Quantification was performed on DTI scans of 81 5-year-olds and 164 7-year-olds to map and segment white matter tracts. Partial correlation analysis was conducted to assess the relationship between language skill and white matter integrity (measured via fractional anisotropy) of tracts at the node-level. In 5-year-olds, the results revealed that the tract integrity of the dorsal Arcuate Fasciculus tract (nodes 68-87) showed a unique positive relation with a standardized measure of phonological processing (i.e. Elision). In 7-year-olds, the tract integrity of the ventral Inferior Fronto-Occipital Fasciculus (nodes 41-57) showed a unique positive relation with a standardized measure of semantic processing (i.e. Word Classes). These findings suggest the importance of phonological processing during early language development (age 5) while during later stages (age 7), semantic mechanisms become more prominent.