Lexical agraphia in Alzheimer's disease.

We studied spelling in 11 patients with senile dementia of the Alzheimer type (SDAT), and their performance was contrasted with that of normal controls. A consistent and specific pattern of linguistic agraphia was identified in the group with SDAT. Although patients with SDAT spelled regular words and nonwords as well as controls, they performed significantly worse when they spelled irregular words. These findings indicated an impairment of the lexical spelling system, consistent with the diagnosis of lexical agraphia. Our observations suggested a loss of word representations from the orthographic lexicon in SDAT and/or an inability to access these representations. However, phonological spelling (phoneme-grapheme conversion) was largely spared.