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A battery of neuropsychological tests designed to assess semantic knowledge about
the same items both within and across different modalities was administered to a group
of 22 patients with dementia of the Alzheimer type (DAT) and 26 matched controls.
The DAT patients were impaired on tests of category fluency, picture naming, spoken
word-picture matching, picture sorting and generation of verbal definitions. A relative
preservation of superordinate knowledge on the sorting and definition tests, as well
as a disproportionate reduction in the generation of exemplars from lower order categories
was noted. Analysis of the errors made by each patient across the different tests,
revealed a significant correspondence between the individual items. These findings
offer compelling evidence that the semantic breakdown in DAT is caused by storage