Poster D24, Friday, August 17, 4:45 – 6:30 pm, Room 2000AB

Relationship between functional connectivity and spelling behaviour in individuals with dyslexia

Kulpreet Cheema1, Dr. William Hodgetts1,2, Dr. Jacqueline Cummine1;1Faculty of Rehabilitation Medicine, University of Alberta, Canada, 2The Institute for Reconstructive Sciences in Medicine, Canada

Background. Writing skills are imperative to successful academic and social functioning in today’s literate society. These skills are even more challenging for individuals with dyslexia who face lifelong impairments with reading and spelling. Although spelling acquisition is one of the most emphasized goals in schools, literature exploring the underlying neural mechanisms associated with spelling is surprisingly limited. Further, while spelling has been reported to activate a large network of brain areas, the connectivity among the brain regions in this distributed network remains unclear. This study looked into the functional connectivity patterns as they relate to spelling behaviour in adults with and without dyslexia. An understanding of the dynamic nature of the distributed neural systems associated with skilled and impaired spelling is critical for the development and advancement of theoretical models of written communication. Methods. 19 skilled individuals and 15 individuals with dyslexia completed the spelling-based fMRI task called letter probe task (LPT) in MRI. During LPT, the participant first hears the word, then sees a letter on the screen and then is asked to indicate if the letter they just saw was in the spelling of the word that they just heard. Participants completed three conditions of LPT: 1) retrieval of the whole word spelling representations is required (exception words e.g. ‘c’ in yacht), 2) retrieval of the whole word spelling representation is optional (regular words e.g. ‘r’ in charm), and 3) retrieval of the whole word spelling representation is impossible thus they must generate the spelling (nonwords e.g. ‘b’ in bint). Analyses. Overall functional connectivity between left hemispheric brain regions involved in orthographic processing (fusiform gyrus, inferior temporal gyrus), speech input (inferior frontal gyrus), articulatory processing (supplementary motor area, putamen, cerebellum, precentral gyrus) and phonological processing (superior marginal gyrus, caudate and superior temporal gyrus) was calculated and correlated with the in-scanner accuracy and reaction time performances. Results. Overall, individuals with dyslexia had under-connective functional networks for regular and nonword spelling conditions and over connective networks for exception word condition. Assessing the connectivity-behaviour relationships revealed similarities and differences for both groups. Across the three spelling conditions, supplementary motor area connectivity emerged as being positively related to spelling accuracy for both skilled and impaired groups. Additionally, the functional network of inferior frontal gyrus consistently came up as being positively related to accuracy performance in skilled individuals while precentral gyrus connectivity emerged as being positively linked to accuracy in impaired readers. Conclusion. We provide evidence for aberrant connectivity patterns responsible for impaired spelling performance in dyslexia, and illustrate the importance of inferior frontal gyrus for skilled spelling behaviour. These results contribute to the advancement of neuroanatomical models for spelling, in addition to increasing the current state of knowledge regarding the underlying neurobiology of spelling performance.

Topic Area: Writing and Spelling