TEASING APART THE CONTRIBUTION OF MEMORY AND LANGUAGE IMPAIRMENTS IN ALZHEIMERS-DISEASE - AN ONLINE STUDY OF SENTENCE COMPREHENSION

Sentence comprehension is a complex activity that depends on many diff erent component skills, including the ability to understand individual words, integrate the meanings of adjacent words, and interpret gramma tical structures. Tests of sentence comprehension, such as sentence-pi cture matching, require patients to use all of these linguistic abilit ies and to remember the meaning of a sentence while performing the tas k. Therefore, it is often difficult to determine, in cases of comprehe nsion impairment, precisely why a sentence is misunderstood. This is p articularly true for patients with Alzheimer's disease, who have both severe semantic and working memory disorders. This paper presents data from an online (cross-modal naming) sentence comprehension test desig ned to minimize the memory requirements of test performance while stil l assessing the ability of patients to integrate the meanings of two n ouns and a verb in a sentence. This task has the advantages of measuri ng comprehension as the sentence is processed and not requiring the su bjects to reflect on, or make judgments about, the sentence meaning af terward. The results suggest that patients with Alzheimer's disease ca n successfully process sentences with relatively complex meanings as t hey hear them. Therefore, these patients' sentence comprehension defic its are likely due to an inability to maintain active information in m emory and not due to a purely semantic impairment.