Impaired spelling in Alzheimer's disease: a linguistic deficit?

Different kinds of real words and pronounceable pseudowords (PWs) were pres ented for writing to dictation to patients with the diagnosis of probable A lzheimer's disease (AD) and to age- and education-matched healthy controls. Though spelling less accurately on all tasks, AD patients responded in a m anner generally qualitatively similar to controls. Except for a slightly en hanced effect of spelling regularity in real word writing accuracy, AD pati ents showed the same sensitivity to various lexical, orthographic and phono logical variables as controls. Both groups showed no difference in spelling accuracy for words and PWs with regular vs ambiguous spelling patterns, an d groups also showed similar orthographic preferences when spelling PWs hav ing several different acceptable pronunciations. Finally, AD patients and c ontrols produced similar types of errors when spelling real words. Dementia severity was related to the overall accuracy, but not to the pattern, of s pelling responses. It is suggested that the decline in response accuracy in cognitively demanding writing tasks in patients with more advanced dementi a is most likely due to semantic impairment and impairments of nonlinguisti c functions of attention, executive control and praxis, rather than to a di sturbance within language specific processes. (C) 1999 Elsevier Science Ltd . All rights reserved.