Preserved Implicit Memory for Lexical Information in Alzheimer's Disease

Abstract

Recent studies have suggested that there is a specific impairment of implicit memory for lexical priming in Alzheimer's Disease. However, there are problems in accepting data from the word-stem completion paradigm as evidence of pure implicit-memory performance. To assess whether Alzheimer's Disease patients are relatively impaired on implicit memory for lexical information an anagram-solution task was adopted. A group of 16 early stage Alzheimer's Disease patients and a group of 16 normal elderly subjects were presented a list of 40 target words. Subsequent free recall was significantly poorer in the former group, but while both groups were significantly better at solving anagrams for words they had previously seen, there was no difference between the two groups in the amount of priming. The data are consistent with the view that previous reports of an implicit deficit in Alzheimer's Disease may not generalise to implicit tasks independent of explicit-memory performance.