Agraphia in Alzheimer's disease: an independent lexical impairment.

This study was conducted to delineate the pattern of the writing impairments in 12 patients with Alzheimer type dementia. The patients performed writing tasks involving regular and irregular words and nonwords given by dictation as well as a decision test composed of printed words and pictures requiring phonologic, lexical, and semantic processing. Writing from dictation demonstrated a predominant, but nonisolated, lexical deficit. In order to better evaluate this lexical disorder, the correlation between the dictation writing scores and the decision task scores was analyzed. No significant correlation was found among scores for irregular words, phonologically plausible errors, and scores of the lexical or semantic decision tasks, but there was a significant correlation among scores for the nonwords, nonphonological spelling errors, and scores of the phonologic decision task using printed words. These results would suggest that the "lexical" deficit in agraphia, i.e., difficulty in retrieval or loss of the spelling representations of words, is independent of the lexical or semantic capacities involved in other modalities.