The relationship between measures of working memory and sentence comprehension in patients with Alzheimer's disease.

Patients with dementia of the Alzheimer's type (DAT) and age- and education-matched older volunteers were tested on a battery of working memory tests, as well as on two tests of sentence comprehension. Patients had reduced spans and impaired central executive processes in working memory but showed normal effects of phonological and articulatory variables on span. On the sentence comprehension tasks, DAT patients showed effects of the number of propositions in a sentence but not of syntactic complexity. Impairment in the central executive processes of working memory in DAT patients was correlated with the effect of the number of propositions in a sentence on the sentence comprehension tasks. The results suggest that patients with DAT have working memory impairments that are related to their ability to map the meanings of sentences onto depictions of events in the world.