Cognitive mechanisms for processing nonwords: evidence from Alzheimer's disease.

Repetition and reading of various types of pronounceable nonwords (pseudowords) was examined in patients with probable Alzheimer's disease (AD) and healthy elderly controls. Overall accuracy of performance was lower in AD patients compared to controls, but the two groups showed qualitatively similar response patterns when reading different kinds of pseudowords aloud and when repeating pseudowords composed of familiar phonological forms, analogous to those in real English words. AD patients diverged in performance from controls, however, when repeating pseudowords composed of phonologically unusual forms. These results support two conclusions: (1) Aspects of phonological processing may become disrupted in AD patients in association with increasing dementia severity, while orthographic processing remains comparatively less impaired. (2) The results are consistent with the view that the processing of pseudowords is achieved through the same system as real words, and further show that the influence of prior language experience on the processing of novel linguistic forms occurs primarily at the level of phonological, rather than orthographic processing.