Refractory dyslexia: evidence of multiple task-specific phonological output stores.

We investigated the case of a patient whose reading was characterized by multiple phonemic paraphasic errors. An error analysis of a large corpus of reading responses (758 words, 86 non-words) highlighted the preponderance of phonological errors which did not occur in his naming, repetition or spontaneous speech. His comprehension of the written word was relatively preserved, even for words he was unable to read aloud. We suggest that his impairment lies at the level of the phonological output store. We also demonstrate that his reading performance was facilitated by increasing the response-stimulus delay. The strong influence of temporal factors is shown to be task-specific. Two main points are drawn from our results. First, we argue that our patient can be characterized as having a refractory access type of deficit; to our knowledge, no previous case of a refractory deficit affecting word reading has been reported. Secondly, the task specificity of both the phonological error pattern and the sensitivity to temporal factors is difficult to reconcile with the idea of a unitary phonological output store. Contrary to orthodox neuropsychological models, we propose that there are independent stores specific for reading and spoken output.