Word form access dyslexia: understanding the basis of visual reading errors.
We report the case of a patient V.E.M. who exhibits the infrequently described syndrome of visual dyslexia. V.E.M. read many single words accurately and rapidly; however, when words were read inaccurately, the majority of responses were alternate real words bearing a strong visual relationship to the target items. A series of observational and experimental investigations of her reading skills revealed that response accuracy was strongly affected by word frequency and mildly affected by concreteness but not influenced by word length, orthographic neighbourhood size, or semantic priming. It is argued that V.E.M.'s visual dyslexia results from a deficit of the visual word form system. More specifically, we propose that this deficit has an "access" quality, with visual word form representations remaining relatively intact despite an impairment in the processes by which these representations are activated. Taking the results of this study together with previous reports of dyslexic patients who make a high proportion of visual paralexic errors, we also suggest that visual dyslexia represents a multicomponent dyslexic syndrome for which phonological impairment and not semantic impairment may be a necessary condition.
Crutch
Sebastian J
SJ
Dementia Research Centre, Department of Neurodegeneration, Institute of Neurology, University College London, London, UK. s.crutch@dementia.ion.ucl.ac.uk
Warrington
Elizabeth K
EK
D001921:Brain / Q000473:pathology; D032882:Comprehension / Q000502:physiology*; D004410:Dyslexia / Q000503:physiopathology* / Q000523:psychology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010700:Phonetics; D011932:Reading; D012660:Semantics