CATEGORY-SPECIFIC SEMANTIC LOSS IN DEMENTIA OF ALZHEIMERS TYPE - FUNCTIONAL-ANATOMICAL CORRELATIONS FROM CROSS-SECTIONAL ANALYSES

In the context of focal brain injury, selective loss of semantic knowl edge in the domain of either natural kinds or artefacts is usually con sidered to reflect the differential importance of temporal and frontop arietal regions to the representations of perceptual and functional at tributes, respectively. It is harder to account for as a feature of a more diffuse process, and previous cross-sectional analyses of patient s with dementia of Alzheimer's type (DAT) have differed over whether c ategory effects occur. In our series of 58 patients with probable DAT, we demonstrated a significant group advantage for artefacts, and expl ored possible reasons for the inconsistency of this finding in other s tudies. A multiple single-case strategy revealed not only individuals with consistent advantages for artefacts but also individuals with con sistent advantages for natural kinds. By ranking the individuals accor ding to measures of naming performance and global intellectual ability we showed that the strength of the group advantage for artefacts was dependent on the former brit not the latter variable. The findings are discussed in the context of two competing theories of semantic breakd own in DAT. One differentiates between domains of knowledge in terms o f the structure of semantic representations within a single distribute d network; the other emphasizes the importance of different brain regi ons in the category distinction. We conclude that our findings are in keeping with the predictions of the latter hypothesis.