DIMENSIONALITY AND CLUSTERING IN THE SEMANTIC NETWORK OF PATIENTS WITH ALZHEIMERS-DISEASE

The organization of semantic memory in patients with Alzheimer's disea se (AD) was investigated with a triadic comparison task. A multidimens ional scaling statistic was used to analyze proximity data and to gene rate 3-dimensional cognitive maps that were then compared by a discrim inant function analysis. The results suggest that the structure of sem antic memory in AD patients differs from that of elderly normal contro ls (NC) in 2 ways. First, AD patients are less consistent in using the attributes (predation, domesticity, and size) of concepts. Second, AD patients focus primarily on concrete perceptual information (size), w hereas NC Ss stress abstract conceptual knowledge (domesticity). These results are consistent with the notion that AD is characterized by a breakdown in the structure of semantic knowledge.