title: Surface errors without semantic impairment in acquired dyslexia: a voxel-based lesion-symptom mapping study.
abstract: 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.
authors.affiliation: Department of Neurology, Medical College of Wisconsin, Milwaukee, WI, USA jbinder@mcw.edu.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Binder
authors.affiliation: Department of Neurology, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Sara B
authors.initials: SB
authors.lastname: Pillay
authors.affiliation: Department of Neurology, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Humphries
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: William L
authors.initials: WL
authors.lastname: Gross
authors.affiliation: Department of Psychology, Rutgers University, Newark, NJ, USA.
authors.forename: William W
authors.initials: WW
authors.lastname: Graves
authors.affiliation: Department of Neurology, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Diane S
authors.initials: DS
authors.lastname: Book
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001931:Brain Mapping; D004411:Dyslexia, Acquired / Q000150:complications / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D009778:Occipital Lobe / Q000473:pathology; D010700:Phonetics; D012660:Semantics; D020521:Stroke / Q000150:complications / Q000473:pathology; D013702:Temporal Lobe / Q000473:pathology; D066127:White Matter / Q000473:pathology
keywords: alexia; brain mapping; phonology; reading; semantics