Stress assignment errors in surface dyslexia: evidence from two Italian patients with a selective deficit of the orthographic input lexicon

Surface dyslexia designates a selective impairment in reading irregular words, with spared ability to read regular and novel words, following a cerebral damage usually located in the left dominant hemisphere. In Italian language, which is regular at the segmental level, surface dyslexia is characterized by stress assignment errors. Here we report on two cases of Italian surface dyslexic patients who produced stress assignment errors, mainly in reading irregular words. In reading nonwords they usually applied the regular stress pattern. Both patients were also impaired in lexical decision and in semantic discrimination tasks when the processing of homophones was required. Our patients’ performance relied almost exclusively on the phonological coding of the stimulus, revealing a deficit in accessing the orthographical input lexicon. In addition, one patient showed a cerebral lesion limited to the right thalamus, providing evidence of a possible role of the right hemisphere in the reading process.