Selective impairment for reading numbers and number words: a single case study.

The article reports the case of a patient who showed a selective inability in reading multi-digit numbers following recovery from aphasic disorders. Although his ability to read words, non-words, syntagms and sentences was almost preserved, he made errors with Arabic numerals and number words. Different types of errors with alphabetic material were also observed: he made only rare phonological substitutions with linguistic stimuli, whereas errors were almost always lexical in reading number words. A series of experiments showed that his ability to access number semantics was intact. In contrast, he selectively failed in all production tasks (including calculation), but only when the required response was in the oral output modality. This pattern was interpreted in terms of a selective deficit to the spoken number name production system. Furthermore, the different types of errors made with alphabetic materials belonging to the two classes of stimuli (numerical versus non-numerical) further support the hypothesis of a categorical organisation in the lexical-semantic system.