Well-organized conceptual domains in Alzheimer's disease.

We used a novel apparatus called the flags board to elicit similarity judgments from 32 Alzheimer's disease (AD) patients and 32 elderly normal (EN) controls for two 12-member conceptual domains, ANIMALS and (musical) INSTRUMENTS. Based on Pathfinder and multidimensional scaling (MDS) analyses, performance by AD patients was nearly identical to that of EN controls for ANIMALS. Performance differed for INSTRUMENTS, but the AD group's Pathfinder network was found to agree with the intuitions of a panel of 18 raters as well as the EN group's. MDS analysis showed no deficit on abstract dimensions for the AD group, for either domain. The results are discussed in the context of degradation versus preservation of semantic memory in AD.