SEMANTIC MEMORY IN ALZHEIMERS-DISEASE - REPRESENTATIVENESS, ONTOLOGICCATEGORY, AND MATERIAL

Alzheimer's disease (AD) patients with semantic memory difficulty and AD patients with relatively preserved semantic memory named pictures a nd judged the category membership of words and pictures of natural kin ds and manufactured artifacts that varied in their representativeness. Only semantically impaired patients were insensitive to representativ eness in their category judgments. AD subgroup judgments did not diffe r for natural kinds compared to manufactured artifacts nor for words c ompared to pictures. AD subgroup differences could not be explained by dementia severity, memory, reading, and visuoperception. The similari ty process for relating coordinate members of a taxonomic category con tributes to the normal appreciation of word and picture meaning, and t his process is compromised in AD patients with semantic difficulty.