LEXICAL PRIMING BY PICTURES AND WORDS IN NORMAL AGING AND IN DEMENTIAOF THE ALZHEIMERS TYPE

Alzheimer's disease causes a progressive loss of semantic memory, one manifestation of which is a progressive language deficit. In order to delineate the relationship between cognitive processing deficits and l anguage disturbance, word-word and picture-word lexical-decision primi ng tasks were administered to patients with mild dementia of the Alzhe imer's type (DAT) (n = 6), very mild DATs (n = 7), and older normals ( n = 23). The mild DATs differed from the other two groups in both task s. When pictures were used as primes, significant identity priming was seen in the normals and very mild DATs, but not in the mild DATs. The mild DATs showed an aberrant pattern-responses significantly slower w ith picture primes than with nonsense primes in all three picture-word conditions. This may reflect residual inhibitory activity within a da maged associational network. In the word-word paradigm, the mild DAT s ubjects demonstrated significant priming both when the prime and targe t were identical (identity priming, e.g., dog-dog) and when they were semantically related (semantic priming, e.g., cat-dog). The other two groups showed no significant priming. These data reinforce other studi es which have found that DAT subjects show a supranormal amount of wor d-word lexical-decision priming. This ''hyperpriming'' may occur due t o partially degraded internal representations which benefit from primi ng more than intact representations (a cognitive crutch). Both paradig ms thus exposed information-processing deficits which distinguished mi ld DATs from the other two groups. DAT-induced changes in selective at tention are probably contributing to these results. (C) 1996 Academic Press, Inc.