Assessing working memory and language comprehension in Alzheimer's disease

Studies of language impairments in patients with Alzheimer's disease have o ften assumed that impairments in linguistic working memory underlie compreh ension deficits. Assessment of this hypothesis has been hindered both by va gueness of key terms such as "working memory" and by limitations of availab le working memory tasks, in that many such tasks either seem to have little relationship to language comprehension or are too confusing or difficult f or Alzheimer's patients. Four experiments investigated the usefulness of di git ordering, a new task assessing linguistic working memory and/or languag e processing skill, in normal adults and patients with probable Alzheimer's disease. The digit ordering task was shown to be strongly correlated with the degree of dementia in Alzheimer's patients. The task correlated with me asures of language processing on which patients and normal controls perform ed differently. The results are interpreted as indicating that linguistic r epresentations, linguistic processing, and linguistic working memory are in tertwined, such that a deficit of one (e.g., working memory) cannot be said to ''cause'' a deficit in the other. The implications of this approach are explored in terms of task demands in comprehension and memory measures, an d interpretation of previous results in the literature. (C) 2001 Academic P ress.