Investigating visual knowledge in dementia of the Alzheimer type (DAT): Evidence for a structured organization

Given that certain types of semantic dysfunction in DAT have been attribute d to difficulties in accessing visual knowledge, the issues of integrity of access to, and format of storage, within the "visual store" are particular ly important. In these experiments, we tested 10 DAT patients and matched c ontrols on the reality decision and part-whole matching tasks. Visual knowl edge was found to be significantly impaired in the DAT group. Moreover, DAT patients displayed disproportionate deficits in accessing visual knowledge of items from nonliving categories. Results are interpreted within a frame work of differential hierarchical access to visual representations of perce ptually similar and perceptually distinct categories of items. (C) 2000 Aca demic Press.