title: Atypical balance between occipital and fronto-parietal activation for visual shape extraction in dyslexia.
abstract: Reading requires the extraction of letter shapes from a complex background of text, and an impairment in visual shape extraction would cause difficulty in reading. To investigate the neural mechanisms of visual shape extraction in dyslexia, we used functional magnetic resonance imaging (fMRI) to examine brain activation while adults with or without dyslexia responded to the change of an arrow's direction in a complex, relative to a simple, visual background. In comparison to adults with typical reading ability, adults with dyslexia exhibited opposite patterns of atypical activation: decreased activation in occipital visual areas associated with visual perception, and increased activation in frontal and parietal regions associated with visual attention. These findings indicate that dyslexia involves atypical brain organization for fundamental processes of visual shape extraction even when reading is not involved. Overengagement in higher-order association cortices, required to compensate for underengagment in lower-order visual cortices, may result in competition for top-down attentional resources helpful for fluent reading.
authors.affiliation: Department of Brain and Cognitive Sciences, McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America. yzhang00@mit.edu
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Susan
authors.initials: S
authors.lastname: Whitfield-Gabrieli
authors.forename: Joanna A
authors.initials: JA
authors.lastname: Christodoulou
authors.forename: John D E
authors.initials: JD
authors.lastname: Gabrieli
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology; D001519:Behavior / Q000502:physiology; D004410:Dyslexia / Q000503:physiopathology*; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology*; D006801:Humans; D008297:Male; D009778:Occipital Lobe / Q000503:physiopathology*; D010296:Parietal Lobe / Q000503:physiopathology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult