Brain activation during language task contrasts in children with and without dyslexia: Inferring mapping processes and assessing response to spelling instruction

Abstract

In the summer following grades 4 to 6, 18 children with dyslexia, who were randomly assigned to orthographic or morphological spelling treatment, and 21 controls, who were good readers and spellers, performed four sets of language tasks while their brain was scanned before and after the dyslexics received treatment. A paradigm with sequential steps for analysing effects of treatment on individual fMRI brain response is introduced and illustrated with contrasts beyween four sets of language tasks (morpheme mapping with and without phonological shifts, phoneme mapping and orthographic mapping). Results for controls showed (a) reliable brain activation associated with contrasting sets of the language tasks; (b) unique activation for morphological, phonological and orthographic word forms; and (c) evidence of cross-word form mapping. Results for dyslexics demonstrated that (a) dyslexics and controls activated some of the same and some different brain regions; (b) sometimes dyslexics underactivated and sometimes they overactivated in regions where controls reliably did or did not activate; (c) following treatment, dyslexics showed significant changes in some of the regions where they initially differed from controls and sometimes normalised by activating previously inactivated regions and sometimes by deactivating previously activated regions; and (d) treatment-specific brain responding occurred for both orthographic and morphological treatment but primarily for orthographic treatment. Normal controls were equally adept at morpheme mapping involving phonological transformations, but dyslexics had more difficulty with morpheme processing involving phonological transformations; dyslexics were impaired not only in phoneme mapping but also in orthographic mapping. Inferior frontal gyrus and cerebellum appeared to be involved in cross-word form mapping. Taken together the results support the view that phonological, orthographic and morphological processes should be assessed and taught in the dynamic assessment of typically developing readers and spellers and dyslexics.