Integrity of semantic fields in Alzheimer's disease.

It has been suggested that Alzheimer patients retain general semantic knowledge about concrete objects (e.g., category membership) but lose information about objects' distinctive features and functions. To test this hypothesis, normal young and old subjects and Alzheimer patients were given a concrete concept. They were then shown a series of words and for each had to say whether it was related to the concept. Of the words that were related to a given concept, one was a physical feature, another a function, another the object's superordinate category, and another a generally associated concept. In comparison to the normals, Alzheimer patients were not disproportionately worse at making decisions about features and actions than they were about categories and general associates. Also, while Alzheimer patients were less accurate in generating features, actions and associates to a given concept than were normals, they were not differentially more impaired on any one type.