Quantitative and qualitative aspects of writing to dictation were compared in 42 patients with Alzheimer's disease (AD) and 30 matched control subjects. Patients and controls wrote nonwords and regular words significantly better than non-regular words, without difference between nonwords and regular words. Patients made more errors than controls, and this effect was more pronounced for non-regular words. Spelling was also affected by word frequency but not by word class. Analysis of paragraphias showed that controls mainly produced phonologically plausible errors whereas patients wrote equivalent numbers of phonologically plausible and non plausible errors. These latter errors were affected by the length of the target words. This study suggests in AD a progressive impairment of lexical spelling followed by a less pronounced deficit of phonological spelling. Spelling errors were correlated with language difficulties, visuo-constructional disorders and increased severity of dementia, but was not affected by age, duration of illness, or memory difficulties.
