Category-specific impairment in patients with Alzheimer's disease as a function of disease severity: a cross-sectional investigation

Several questions about category specificity associated with lexical-semantic deficits in Alzheimer's disease (AD) patients are still being debated. In this study, we enrolled 53 AD patients and 30 normal control subjects to investigate the following issues: Is category specificity consistently associated with AD? Do AD patients show both possible patterns of category specific impairment, i.e. selective impairment for either living things or artifacts? Is the direction of the category specific effect predictable as a function of disease severity? Is a selective impairment for living things secondary to a disproportionate loss of perceptual knowledge? We found an overall advantage for artifacts even when controlling for several confounding factors. We did not find any relation between direction of category specificity and severity of the disease or between category specificity and loss of knowledge about perceptual or functional attributes.