Distinct patterns of spontaneous speech deterioration: an early predictor of Alzheimer's disease.

Although distinctive patterns of language impairment have been identified in Alzheimer's Disease (AD) patients, few studies have been conducted to identify the errors that consistently differentiate minimal and mild AD patients from healthy elderly individuals. Twenty-two AD patients (11 minimal and 11 mild) and 22 age- and education-matched healthy controls, were assessed on a simple and complex picture description task. The task assessed several aspects of spontaneous speech, including melodic line, articulation, grammatical form, phrase length, paraphasias, word-finding difficulties, error monitoring, information conveyed, and information content. Although both pictures could differentiate between the AD patients and the healthy controls, results suggested that the complex task was most sensitive. Performance on the latter task indicated that minimal AD patients and healthy controls could be differentiated on several measures of semantic processing. Errors point to a breakdown in lexical semantic processing, which occurs earlier in the disease process than previously reported.