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Fibre-specific white matter associations with spelling performance in typically developing children
Poster Session C, Thursday, October 1, 10:45 am - 12:45 pm, Wangari Maathai
cheyenne svaldi1,2, Xiangqi Luo1, Jo Taylor1; 1University College London, 2University of Groningen
Purpose: Spelling is a complex cognitive skill, involving both central (lexical, sub-lexical) and peripheral (motor planning, motor programming) orthographic processes. Similar to models of word reading, two potential routes may be used to retrieve orthographic representations during central orthographic processing (Rapp et al., 2002). On the one hand, the sub-lexical route, in which systematic phoneme-grapheme conversions are applied, is generally adopted at the initial stages of spelling development and when spelling pseudowords or unfamiliar words. When using the lexical route, on the other hand, familiar words are retrieved as a whole from orthographic long-term memory. This route may be employed as children get better at spelling and in particular for irregularly spelled words (e.g., “choir”). Although children spell words daily in school, little is known about the neurobiological basis of these different orthographic processes. Previous studies in adults suggest that a distributed network of dorsal (e.g., arcuate fasciculus), ventral (e.g., inferior longitudinal fasciculus), and cerebellar white matter pathways is associated with spelling performance. As the first to investigate similar white matter relations for sub-lexical and lexical orthographic processes in typically developing children, this study will advance our understanding of developmental cognitive models underlying different spelling processes. Method: We aim to recruit 60 9-to-10-year-old typically developing children who are right-handed and attending an English-speaking school. Children complete standardised tests, assessing lexical (irregular word spelling), sub-lexical (pseudoword spelling), and peripheral (handwriting) orthographic skills. Multi-shell diffusion-weighted imaging data are collected, which are used to reconstruct dorsal (e.g., arcuate fasciculus), ventral (e.g., inferior longitudinal fasciculus) and cerebellar white matter pathways using semi-automated tractography (TractSeg). Fibre-specific (i.e., fibre density, fiber cross-section and fiber density cross-section) properties will be derived from the tracts using fixel-based analysis. Linear models will be run across all fixels for each of the included tracts to investigate associations between these metrics and performance on the different sub-lexical and lexical spelling tasks, including sex and writing ability as covariates. Intracranial volume will also be included as a covariate for analyses involving fiber density and fiber density cross-section. Results: Data collection is currently ongoing and will be completed by the end of August. We hypothesise that scores for pseudoword spelling will relate more strongly to fibre metrics of dorsal white matter tracts, while irregular word spelling will relate more to ventral white matter pathways. More exploratory, we assume that cerebellar white matter will be associated with both central orthographic processes. Conclusions: As posited by cognitive models of spelling, we hypothesise that our results will confirm the distinction between central and peripheral orthographic processes. We propose that spelling assessment and intervention should target these processes independently.
Topic Areas: Writing and Spelling, Language Development/Acquisition