Deep dyslexia in the two languages of an Arabic/French bilingual patient

We present a single case study of an Arabic/French bilingual patient, ZT, w ho, at the age of 32, suffered a cerebral vascular accident that resulted i n a massive infarct in the left perisylvian region. ZT's reading displays t he characteristics of the deep dyslexia syndrome in both languages, that is , production of semantic, visual, and morphological errors, and concretenes s effect in reading aloud and impossibility of reading nonwords. In the fir st part of this paper, using a three-route model of reading, we account for the patient's performance by positing functional lesions, which affect the non-lexical, the semantic lexical and the non-semantic lexical routes of r eading. Phonological priming observed in a cross-language visual lexical de cision task indicates that implicit assembled phonological recoding is poss ible. The above lesions and implicit nonword reading characterize the outpu t form of deep dyslexia. However, error distribution reveals dissociations across languages (e.g. the semantic error rate is higher in French whereas translations are more frequent in the Arabic testing) that cannot be accoun ted for within a three-route model. In the second part, extensions to Plant and Shallice's connectionist model (Cognitive Neuropsychology, 10 (5) (199 3) 377) are proposed to account for the translinguistic errors observed. ZT 's error distribution is compared to that obtained by Plant and Shallice af ter lesions had been applied at different locations through the 40-60 netwo rk. The overall syndrome of deep dyslexia found in both languages is explai ned as resulting from lesions along the direct (O --> I) and output (S --> Ip, Ip --> P) pathways of reading. Lesions along the output pathway mostly affecting S --> Ip connections in French and Ip --> P connections in Arabic account for discrepancies in ZT's error pattern across tasks and languages . This case study demonstrates the superiority of a connectionist approach for predicting the error pattern in deep dyslexia. (C) 2001 Elsevier Scienc e B.V. All rights reserved.