The deterioration of semantic networks in patients with Alzheimer's disease: a cross-sectional study.

Previous studies showed that the semantic networks of Alzheimer's disease (AD) patients are disrupted in the early stages of the disease. The present study examined the semantic networks of 33 AD patients in different stages of disease severity to compare the quantitative and qualitative changes in their networks as the disease progresses. The properties of the semantic networks (e.g. the dimensionality and strength of the connections) were examined with multidimensional scaling and Pathfinder analyses. The results showed that, as AD patients became more demented, they focused less on abstract attributes in categorizing concepts, and have an alteration in the relative strength of associations between concepts. These findings indicate that the structure of semantic knowledge deteriorates in a systematic manner throughout the course of AD.