Deterioration of word meaning: implications for reading.

We investigated six patients with progressive focal dementia or progressive aphasia, who showed impairments in knowledge of word meaning ranging from moderate to very severe. In all cases, a test of oral word reading demonstrated preserved reading of words with regular spelling-to-sound correspondences (e.g. MINT), but impaired reading of words with atypical correspondences (e.g. PINT). The level of success on these "exception" words was significantly related to word frequency, and the most common error was the assignment of a more typical spelling-sound correspondence. Various explanations are considered for this common association between loss of word meaning and a surface alexic pattern of reading performance.