The two-component hypothesis of memory deficit in Alzheimer's disease.

Becker (1988) has argued that Alzheimer's disease is particularly characterised by a combination of amnesic and dysexecutive deficits. He has supported this hypothesis by identifying patients who represent a relatively pure example of each of these. We describe a search for similarly pure patients in a sample of 55 carefully selected Alzheimer cases. We succeed in identifying one case each of relatively pure amnesia and relatively pure dysexecutive syndrome. We also, however, find cases of predominant STM deficit, as well as cases with defective visual but not verbal memory, and cases of the converse pattern. These cases do not seem to reflect simple random variation in the data, since less theoretically coherent patterns of symptoms are not found in this pure form. We conclude that AD can give rise to relatively specific cognitive deficits during its early stages, but that these do not necessarily argue for Becker's two-component interpretation of the cognitive deficit in Alzheimer's disease.