Linguistic and nonlinguistic impairments in writing: a comparison of patients with focal and multifocal CNS disorders.

The hypothesis that the language disorder in Alzheimer's disease (AD) depends on degenerative brain changes in classical left-hemisphere language zones was tested by comparing the written language performances of a group of AD patients with mild-moderate dementia and left-hemisphere stroke patients with equally severe naming and auditory comprehension deficits who were in varying stages of recovery from Wernicke's aphasia. The results indicated significant qualitative group differences in performances between tasks and in errors within tasks. The findings are consistent with hypothesized disruption of more diffusely organized neurolinguistic systems in AD. The hypothesis that the language disorder in AD represents an exaggeration of the pattern of language change in normal aging was also examined by comparing the performances of AD patients to the changes that occur with very advanced normal aging. The data indicate convergence between AD and very elderly healthy subjects in some aspects of written language production.