title: Children with dyslexia lack multiple specializations along the visual word-form (VWF) system.
abstract: Developmental dyslexia has been associated with a dysfunction of a brain region in the left inferior occipitotemporal cortex, called the "visual word-form area" (VWFA). In adult normal readers, the VWFA is specialized for print processing and sensitive to the orthographic familiarity of letter strings. However, it is still unclear whether these two levels of occipitotemporal specialization are affected in developmental dyslexia. Specifically, we investigated whether (a) these two levels of specialization are impaired in dyslexic children with only a few years of reading experience and (b) whether this impairment is confined to the left inferior occipitotemporal VWFA, or extends to adjacent regions of the "VWF-system" with its posterior-anterior gradient of print specialization. Using fMRI, we measured brain activity in 18 dyslexic and 24 age-matched control children (age 9.7-12.5 years) while they indicated if visual stimuli (real words, pseudohomophones, pseudowords and false-fonts) sounded like a real word. Five adjacent regions of interest (ROIs) in the bilateral occipitotemporal cortex covered the full anterior-posterior extent of the VWF-system. We found that control and dyslexic children activated the same main areas within the reading network. However, a gradient of print specificity (higher anterior activity to letter strings but higher posterior activity to false-fonts) as well as a constant sensitivity to orthographic familiarity (higher activity for unfamiliar than familiar word-forms) along the VWF-system could only be detected in controls. In conclusion, analyzing responses and specialization profiles along the left VWF-system reveals that children with dyslexia show impaired specialization for both print and orthography.
authors.affiliation: MR-Center, University Children's Hospital, University of Zurich, Zurich, Switzerland.
authors.forename: Sanne
authors.initials: S
authors.lastname: van der Mark
authors.forename: Kerstin
authors.initials: K
authors.lastname: Bucher
authors.forename: Urs
authors.initials: U
authors.lastname: Maurer
authors.forename: Enrico
authors.initials: E
authors.lastname: Schulz
authors.forename: Silvia
authors.initials: S
authors.lastname: Brem
authors.forename: Jsabelle
authors.initials: J
authors.lastname: Buckelmüller
authors.forename: Martin
authors.initials: M
authors.lastname: Kronbichler
authors.forename: Thomas
authors.initials: T
authors.lastname: Loenneker
authors.forename: Peter
authors.initials: P
authors.lastname: Klaver
authors.forename: Ernst
authors.initials: E
authors.lastname: Martin
authors.forename: Daniel
authors.initials: D
authors.lastname: Brandeis
mesh_terms: D000293:Adolescent; D002540:Cerebral Cortex / Q000503:physiopathology*; D002648:Child; D004410:Dyslexia / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011932:Reading; D013647:Task Performance and Analysis