The Contribution of White and Gray Matter Differences to Developmental Dyslexia: Insights from DTI and VBM at 3.0 T

• Published in: Neuropsychologia Vol. 46; no. 13; pp. 3170 - 3178
• Main Authors: Steinbrink, C, Vogt, K, Kastrup, A, Muller, H. P, Juengling, F. D, Kassubek, J, Riecker, A
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier 01-11-2008; Elsevier Science
• Subjects: Adolescent; Adult; Adult and adolescent clinical studies; Adults; Analysis of Variance; Anisotropy; Biological and medical sciences; Brain; Brain - pathology; Brain - physiopathology; Brain Hemisphere Functions; Brain Mapping; Child Development; Correlation; Developmental Disabilities; Diffusion Magnetic Resonance Imaging - methods; Dyslexia; Dyslexia - pathology; Female; Foreign Countries; Germany; Graphemes; Humans; Image Interpretation, Computer-Assisted - methods; Male; Medical sciences; Organic mental disorders. Neuropsychology; Phonemes; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Reading; Reading Processes; Reading Rate; Germany; Human; Communication disorder; Reading disorder; Anisotropy; mean diffusivity); Dyslexia; Grey matter; Adult; Dyslexia; Developmental disorder; White matter; Language disorder; VBM (gray matter); DTI (fractional anisotropy
• ISSN: 0028-3932; 1873-3514
• DOI: 10.1016/j.neuropsychologia.2008.07.015

Developmental dyslexia is one of the most common neuropsychological disorders in children and adults. Only few data are available on the pathomechanisms of this specific dysfunction, assuming--among others--that dyslexia might be a disconnection syndrome of anterior and posterior brain regions involved in phonological and orthographic aspects of the reading process, as well as in the integration of phonemes and graphemes. Therefore, diffusion tensor imaging (DTI) and voxel-based morphometry (VBM) were used to verify the hypothesis of altered white and gray matter structure in German dyslexic adults. DTI revealed decreased fractional anisotropy (FA) in bilateral fronto-temporal and left temporo-parietal white matter regions (inferior and superior longitudinal fasciculus). Significant correlations between white matter anisotropy and speed of pseudoword reading were found. In dyslexics, gray matter volumes (as measured by VBM) were reduced in the superior temporal gyrus of both hemispheres. So far, our results, based on a combined analysis of white and gray matter abnormalities, provide exceedingly strong evidence for a disconnection syndrome or dysfunction of cortical areas relevant for reading and spelling. Thus, we suggest that this imbalance of neuronal communication between the respective brain areas might be the crucial point for the development of dyslexia. (Contains 2 tables and 2 figures.)