title: Role of the superior parietal lobules in letter-identity processing within strings: FMRI evidence from skilled and dyslexic readers.
abstract: Traditionally, the ventral occipito-temporal (vOT) area, but not the superior parietal lobules (SPLs), is thought as belonging to the neural system of visual word recognition. However, some dyslexic children who exhibit a visual attention span disorder - i.e. poor multi-element parallel processing - further show reduced SPLs activation when engaged in visual multi-element categorization tasks. We investigated whether these parietal regions further contribute to letter-identity processing within strings. Adult skilled readers and dyslexic participants with a visual attention span disorder were administered a letter-string comparison task under fMRI. Dyslexic adults were less accurate than skilled readers to detect letter identity substitutions within strings. In skilled readers, letter identity differs related to enhanced activation of the left vOT. However, specific neural responses were further found in the superior and inferior parietal regions, including the SPLs bilaterally. Two brain regions that are specifically related to substituted letter detection, the left SPL and the left vOT, were less activated in dyslexic participants. These findings suggest that the left SPL, like the left vOT, may contribute to letter string processing.
authors.affiliation: INSERM, Imagerie Cérébrale et Handicaps neurologique, UMRS 825, F-31059 Toulouse, France. caroline.reilhac@gmail.com
authors.forename: Caroline
authors.initials: C
authors.lastname: Reilhac
authors.forename: Carole
authors.initials: C
authors.lastname: Peyrin
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Démonet
authors.forename: Sylviane
authors.initials: S
authors.lastname: Valdois
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology; D002531:Cerebellum / Q000502:physiology; D003627:Data Interpretation, Statistical; D004410:Dyslexia / Q000503:physiopathology* / Q000523:psychology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010296:Parietal Lobe / Q000502:physiology* / Q000503:physiopathology*; D010775:Photic Stimulation; D017397:Prefrontal Cortex / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D011932:Reading; D021641:Recognition, Psychology / Q000502:physiology; D013702:Temporal Lobe / Q000502:physiology; D055815:Young Adult