Semantic memory deterioration in Alzheimer's subjects: evidence from word association, definition, and associate...

The nature of semantic memory impairment in 23 persons with dementia of the Alzheimer type (DAT) was studied using three semantic tasks: word association, definition, and associate rank ordering. Using hierarchical log-linear analysis of the responses to the word association task, DAT subjects were more likely than normal control subjects to give multiword, repetitious, or unrelated responses. Additionally, the ratio of paradigmatic to syntagmatic responses was significantly decreased in DAT subjects. Surprisingly, DAT subjects were able to provide definitions for many stimulus words for which they were unable to provide meaningful associates. This finding suggests the need for caution in interpreting a decrease in the number of paradigmatic responses as indicative of a loss of conceptual knowledge. Results of other analyses demonstrated that DAT subjects had significant impairment in identifying highly related and unrelated semantic associates of words. Taken together, results of this study indicate that one feature of DAT is deterioration in the associative relations between concepts.