White matter microstructural differences linked to left perisylvian language network in children with dyslexia

Rimrodt, Sheryl L.; Peterson, Daniel J.; Denckla, Martha B.; Kaufmann, Walter E.; Cutting, Laurie E.

doi:10.1016/j.cortex.2009.07.008

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Volume 46, Issue 6 , Pages 739-749, June 2010

White matter microstructural differences linked to left perisylvian language network in children with dyslexia

Sheryl L. Rimrodt
- Kennedy Krieger Institute, Baltimore, MD, USA
- Department of Pediatrics, Johns Hopkins School of Medicine, Baltimore, MD, USA
Daniel J. Peterson
- Kennedy Krieger Institute, Baltimore, MD, USA
Martha B. Denckla
- Kennedy Krieger Institute, Baltimore, MD, USA
- Department of Pediatrics, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD, USA
Walter E. Kaufmann
- Kennedy Krieger Institute, Baltimore, MD, USA
- Department of Pediatrics, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Department of Radiology, Johns Hopkins School of Medicine, Baltimore, MD, USA
Laurie E. Cutting
- Kennedy Krieger Institute, Baltimore, MD, USA
- Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Department of Education, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Corresponding author. Kennedy Krieger Institute, Department of Developmental Cognitive Neurology, 707N Broadway, Suite 232, Baltimore, MD 21205, USA.

Received 16 October 2008; received in revised form 5 March 2009 and 5 June 2009; accepted 16 July 2009. published online 17 August 2009.

Action editor Marco Catani

Abstract

Studies of dyslexia using diffusion tensor imaging (DTI) have reported fractional anisotropy (FA) differences in left inferior frontal gyrus (LIFG) and left temporo-parietal white matter, suggesting that impaired reading is associated with atypical white matter microstructure in these regions. These anomalies might reflect abnormalities in the left perisylvian language network, long implicated in dyslexia. While DTI investigations frequently report analyses on multiple tensor-derived measures (e.g., FA, orientation, tractography), it is uncommon to integrate analyses to examine the relationships between atypical findings. For the present study, semi-automated techniques were applied to DTI data in an integrated fashion to examine white matter microstructure in 14 children with dyslexia and 17 typically developing readers (ages 7–16 years). Correlations of DTI metrics (FA and fiber orientation) to reading skill (accuracy and speed) and to probabilistic tractography maps of the left perisylvian language tracts were examined. Consistent with previous reports, our findings suggest FA decreases in dyslexia in LIFG and left temporo-parietal white matter. The LIFG FA finding overlaps an area showing differences in fiber orientation in an anterior left perisylvian language pathway. Additionally, a positive correlation of FA to reading speed was found in a posterior circuit previously associated with activation on functional imaging during reading tasks. Overall, integrating results from several complementary semi-automated analyses reveals evidence linking atypical white matter microstructure in dyslexia to atypical fiber orientation in circuits implicated in reading including the left perisylvian language network.

Keywords: Dyslexia, Perisylvian language network, Left inferior frontal gyrus, Diffusion tensor imaging, Fractional anisotropy