PRODUCTION OF COMPLEX SYNTAX IN NORMAL AGING AND ALZHEIMERS-DISEASE

Word-finding difficulties are among the earliest symptoms of Alzheimer 's disease (AD), but most AD patients retain the ability to produce we ll-formed sentences until the late stages of their disease. This disso ciation has been used to argue for a modular distinction between gramm ar and the lexicon. In this paper, we offer an alternative view. First , we show that grammatical production is impaired in AD patients when grammar is assessed under highly constrained conditions in a film desc ription task. Furthermore, these grammatical deficits are comparable i n some respects to the patterns of lexical impairment observed in this and other studies of AD; specifically, patients do not produce frank lexical or grammatical errors, but they do find it difficult to access the ''best fit'' between meaning and form. We propose that difference s in the onset time for lexical and grammatical symptoms in AD are due not to a disconnection between modules, but to fundamental difference s in the automaticity and/or accessibility of content words and gramma tical structures within a unified lexicon that breaks down gradually a cross the course of this disease.