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

Full Abstract

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.

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Author information

Author/s: Cao, Fan (F); Bitan, Tali (T); Chou, Tai-Li (TL); Burman, Douglas D (DD); Booth, James R (JR);

Affiliation: Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL 60208, USA.

Grants: DC06149 (Agency:NIDCD NIH HHS) ; HD042049 (Agency:NICHD NIH HHS)

Journal and publication information

Publication Type: Journal Article; Research Support, N.I.H., Extramural

Journal: Journal of child psychology and psychiatry, and allied disciplines (J Child Psychol Psychiatry), published in England. (Language: eng)

Reference: 2006-Oct; vol 47 (issue 10) : pp 1041-50

Dates: Created 2006/10/31; Completed 2007/02/06; Revised 2007/12/03;

PMID: 17073983, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adolescent
Brain - blood supply; physiopathology
Cerebrovascular Circulation - physiology
Child
Dyslexia - metabolism; physiopathology
Female
Frontal Lobe - blood supply; physiopathology
Functional Laterality
Humans

Judgment
Magnetic Resonance Imaging
Male
Nerve Net - blood supply
Phonetics
Reaction Time
Temporal Lobe - blood supply; physiopathology
Verbal Behavior
Visual Perception - physiology

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