The role of functional and perceptual attributes: evidence from picture naming in dementia

We examined the performance of a group of people with moderately severe Alzheimer's type dementia on a naming task. We found that functional information plays an important role in determining naming performance on both living and non-living things. Perceptual information may play some role in naming living things. We also found some evidence that the semantic category to which an item belongs may also have some effect on naming performance. We argue that both the sensory-functional and domain-specific knowledge hypotheses may be correct: the brain is to some organized on taxonomic grounds, while the semantic representations of living and non-living things depend differentially on perceptual and functional information. These representations can be differentially disrupted by damage to modality-specific stores. At a moderate level of severity, dementia causes global damage that has the effect of disrupting both the localized taxonomic and the modality-specific stores. We discuss the nature of functional information.