Metalinguistic judgments in normal aging and Alzheimer's disease.

This study compared sentence acceptability judgments from young and healthy older adults and older adults with dementia due to probable Alzheimer's disease. Two types of sentences were contrasted: one type involved contrasts among verb alternations in which semantic distinctions between verbs regulate the acceptability of phrase structure variations; the second type involved contrasts among directional transformations in which constraints on the movement of noun phrases determine the linear order of main and embedded clauses. The primary findings were that metalinguistic judgments by healthy older adults as well as those with probable Alzheimer's reflected processing demands on working memory. In addition, metalinguistic judgments by adults with probable Alzheimer's reflected the breakdown of semantic information about verbs.