[Selective disturbance in lexical knowledge in the elderly with or without dementia]

In elderly with and without dementia a facilitating effect of word imagery on word association was found, as was in younger subjects with whom Dutch word association norms were assembled. Words with high imagery values evoke more common responses and less blanks than words with low imagery values. In the younger group also an interaction of imagery and age of acquisition was found, i.e. the effect of imagery on commonality in this group was only present in late acquired words. The absence of this interaction in both elderly with and without dementia indicates a disturbance of lexical knowledge dependent on the age of acquisition of words. Early acquired words have a strong sensorimotor basis, whereas words acquired later are predominantly based on verbal definition (conceptual versus propositional knowledge). Both subject groups have difficulties in retrieving words that specify a property relationship to a late acquired stimulus word, as in 'desert-sand', while words that specify an 'is a' relationship with the stimulus word, as in 'dagger-knife', are easily retrieved. The main difference between elderly with and without dementia was the large number of multiword responses in dementia, a result that indicates a loss of lexical strategies in word finding. Whether the incidentally reported increase in multiword responses in some normal elderly forecasts an approaching dementia needs further research.