Syntactic preservation in Alzheimer's disease.

Language ability of 20 patients with probable Alzheimer's disease (AD) was evaluated. Analysis of spontaneous speech revealed a normal range and frequency of syntactic constructions but poor lexical use. A writing task showed a similar divergence, with the ability to use syntactic cues significantly more intact than the ability to use semantic cues. The results are taken to indicate that syntactic ability is selectively preserved in AD. These findings are consistent with a modular theory of grammar and of mental functions more generally. A tentative explanation of these phenomena is proposed in which the overlearned and automatic nature of syntactic ability helps account for its resilience to cognitive dissolution and cortical degeneration.