Deficient orthographic and phonological representations in children with dyslexia revealed by brain activation patterns

• Published in: Journal of child psychology and psychiatry Vol. 47; no. 10; pp. 1041 - 1050
• Main Authors: Cao, Fan, Bitan, Tali, Chou, Tai-Li, Burman, Douglas D., Booth, James R.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.11.2006; Wiley-Blackwell
• Subjects: Adolescent; Brain - blood supply; Brain - physiopathology; Brain Hemisphere Functions; Brain imaging; Brain research; Cerebrovascular Circulation - physiology; Child; Child psychology; Children; Comparative Analysis; Control Groups; Diagnostic Tests; Dyslexia; Dyslexia - metabolism; Dyslexia - physiopathology; Female; Frontal Lobe - blood supply; Frontal Lobe - physiopathology; Functional Laterality; Functional magnetic resonance imaging; Humans; Judgment; learning difficulties; Magnetic Resonance Imaging; Male; Medical imaging; Nerve Net - blood supply; Neuroimaging; NMR; Nuclear magnetic resonance; Orthographic processing; Phonetics; Phonological processing; Phonology; Reaction Time; reading disorder; Rhyme; Spelling; Task Analysis; Temporal Lobe - blood supply; Temporal Lobe - physiopathology; Verbal Behavior; Visual Perception - physiology
• ISSN: 0021-9630; 1469-7610
• DOI: 10.1111/j.1469-7610.2006.01684.x

Background:  The current study examined the neuro‐cognitive network of visual word rhyming judgment in 14 children with dyslexia and 14 age‐matched control children (8‐ to 14‐year‐olds) using functional magnetic resonance imaging (fMRI). Methods:  In order to manipulate the difficulty of mapping orthography to phonology, we used conflicting and non‐conflicting trials. The words in conflicting trials either had similar orthography but different phonology (e.g., pint‐mint) or similar phonology but different orthography (e.g., jazz‐has). The words in non‐conflicting trials had similar orthography and phonology (e.g., gate‐hate) or different orthography and phonology (e.g., press‐list). Results:  There were no differences in brain activation between the controls and children with dyslexia in the easier non‐conflicting trials. However, the children with dyslexia showed less activation than the controls in left inferior frontal gyrus (BA 45/44/47/9), left inferior parietal lobule (BA 40), left inferior temporal gyrus/fusiform gyrus (BA 20/37) and left middle temporal gyrus (BA 21) for the more difficult conflicting trials. For the direct comparison of conflicting minus non‐conflicting trials, controls showed greater activation than children with dyslexia in left inferior frontal gyrus (BA 9/45/46) and medial frontal gyrus (BA 8). Children with dyslexia did not show greater activation than controls for any comparison. Conclusions:  Reduced activation in these regions suggests that children with dyslexia have deficient orthographic representations in ventral temporal cortex as well as deficits in mapping between orthographic and phonological representations in inferior parietal cortex. The greater activation for the controls in inferior frontal gyrus could reflect more effective top‐down modulation of posterior representations.