Journal of Autism and Developmental Disorders

, Volume 40, Issue 1, pp 21–29 | Cite as

Increased White Matter Gyral Depth in Dyslexia: Implications for Corticocortical Connectivity

  • Manuel F. Casanova
  • Ayman S. El-Baz
  • Jay Giedd
  • Judith M. Rumsey
  • Andrew E. Switala
Original Paper


Recent studies provide credence to the minicolumnar origin of several developmental conditions, including dyslexia. Characteristics of minicolumnopathies include abnormalities in how the cortex expands and folds. This study examines the depth of the gyral white matter measured in an MRI series of 15 dyslexic adult men and eleven age-matched comparison subjects. Measurements were based upon the 3D Euclidean distance map inside the segmented cerebral white matter surface. Mean gyral white matter depth was 3.05 mm (SD ± 0.30 mm) in dyslexic subjects and 1.63 mm (SD ± 0.15 mm) in the controls. The results add credence to the growing literature suggesting that the attained reading circuit in dyslexia is abnormal because it is inefficient. Otherwise the anatomical substratum (i.e., corticocortical connectivity) underlying this inefficient circuit is normal. A deficit in very short-range connectivity (e.g., angular gyrus, striate cortex), consistent with results of a larger gyral window, could help explain reading difficulties in patients with dyslexia. The structural findings hereby reported are diametrically opposed to those reported for autism.


Autistic disorder Cerebrum Corpus callosum Dyslexia Gyral window 

List of Symbols


Surface area




Cerebral cortex (gray matter)


Cerebral white matter

\( \left\langle g \right\rangle \)

Mean gyral depth (gyral window)



This work was supported by grant funding from the National Alliance for Autism Research (NAAR) (MFC), and NIH grant numbers MH62654 and MH69991 (MFC). The series of patients and controls were collected under the guidance and support of Dr. Judith Rapoport, Chief of the Child Psychiatry Branch at the National Institute of Mental Heath.


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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • Manuel F. Casanova
    • 1
    • 2
  • Ayman S. El-Baz
    • 3
  • Jay Giedd
    • 4
  • Judith M. Rumsey
    • 5
  • Andrew E. Switala
    • 1
  1. 1.Department of Psychiatry and Behavioral SciencesUniversity of LouisvilleLouisvilleUSA
  2. 2.LouisvilleUSA
  3. 3.Department of Biomedical EngineeringUniversity of LouisvilleLouisvilleUSA
  4. 4.Child Psychiatry BranchNational Institute of Mental HealthBethesdaUSA
  5. 5.Neurodevelopmental Disorders Research BranchNational Institute of Mental HealthBethesdaUSA

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