Journal Article

Surface errors without semantic impairment in acquired dyslexia: a voxel-based lesion–symptom mapping study

Jeffrey R. Binder, Sara B. Pillay, Colin J. Humphries, William L. Gross, William W. Graves and Diane S. Book

in Brain

Published on behalf of The Guarantors of Brain

Volume 139, issue 5, pages 1517-1526
Published in print May 2016 | ISSN: 0006-8950
Published online March 2016 | e-ISSN: 1460-2156 | DOI: https://dx.doi.org/10.1093/brain/aww029
Surface errors without semantic impairment in acquired dyslexia: a voxel-based lesion–symptom mapping study

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  • Neuropathology
  • Disorders of the Nervous System

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Patients with surface dyslexia have disproportionate difficulty pronouncing irregularly spelled words (e.g. pint), suggesting impaired use of lexical-semantic information to mediate phonological retrieval. Patients with this deficit also make characteristic ‘regularization’ errors, in which an irregularly spelled word is mispronounced by incorrect application of regular spelling-sound correspondences (e.g. reading plaid as ‘played’), indicating over-reliance on sublexical grapheme–phoneme correspondences. We examined the neuroanatomical correlates of this specific error type in 45 patients with left hemisphere chronic stroke. Voxel-based lesion–symptom mapping showed a strong positive relationship between the rate of regularization errors and damage to the posterior half of the left middle temporal gyrus. Semantic deficits on tests of single-word comprehension were generally mild, and these deficits were not correlated with the rate of regularization errors. Furthermore, the deep occipital-temporal white matter locus associated with these mild semantic deficits was distinct from the lesion site associated with regularization errors. Thus, in contrast to patients with surface dyslexia and semantic impairment from anterior temporal lobe degeneration, surface errors in our patients were not related to a semantic deficit. We propose that these patients have an inability to link intact semantic representations with phonological representations. The data provide novel evidence for a post-semantic mechanism mediating the production of surface errors, and suggest that the posterior middle temporal gyrus may compute an intermediate representation linking semantics with phonology.

Keywords: reading; alexia; semantics; phonology; brain mapping

Journal Article.  6370 words.  Illustrated.

Subjects: Neuropathology ; Disorders of the Nervous System

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