Working memory and online syntactic processing in Alzheimer's disease: studies with auditory moving window presentation.

Twenty patients with dementia of the Alzheimer's type (DAT) and 20 controls were tested on six tests of working memory and a test of online auditory sentence comprehension in which listening times for each phrase in the sentence, as well as the time required for an end-of-sentence plausibility judgment, were measured. The sentences differed in syntactic complexity. Patients had lower working memory scores than controls and performed more poorly on the plausibility judgments. However, patients were not more affected than controls by the syntactic complexity of a sentence in these judgments, and both groups showed similar effects of syntactic structure in the listening-time data. The increase in listening times at syntactically capacity-demanding points in complex sentences, compared with comparable points in matched simpler sentences, did not correlate with measures of working memory. The results indicate that early-stage DAT patients are not impaired in their ability to assign syntactic structure and to use it to determine aspects of sentence meaning, despite their reduced working memories. This provides evidence for a specialization within working memory for syntactic processing.