Effects of semantic impairment on language use in Alzheimer's disease.

Many studies present apparently conflicting results and conclusions about the effects of Alzheimer's disease (AD) on language use. This review attempts to reconcile these apparently conflicting results regarding the language impairments in AD by discussing how the slow deterioration of the semantic system at the feature level interacts with the task demands of tests used to evaluate performance. In particular, performance is impaired on tasks that require relatively complete, elaborate semantic representations but is preserved when the task requires only partial semantic representations consisting largely of shared features. The variety of language impairments reported in complex, multiword tasks are likely attributable to a combination of the deterioration of semantic representations and reduced working memory resources. The few available treatment studies for language impairments in AD suggest that treatments designed for adults with other language impairments, such as aphasia, may also be effective in AD.