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Category specific semantic loss in dementia of Alzheimer’s type: Functional-anatomical correlations from cross-sectional analyses.
Garrard, P., PATTERSON, K., WATSON, P.C. & HODGES, J.R.
Brain, 121, 633-646.
Year of publication:
In the context of focal brain injury, selective loss of semantic knowledge in the domain of either natural kinds or artefacts is usually considered to reflect the differential importance of temporal and fronto-parietal regions to the representations of perceptual and functional attributes, respectively. It is harder to account for as a feature of a more diffuse process, and previous cross-sectional analyses of DAT patients have differed over whether category effects occur. In our series of 58 patients with probable DAT we demonstrated a significant group advantage for artefacts, and explored possible reasons for the inconsistency of this finding in other studies. A multiple single-case strategy revealed individuals with consistent advantages for both domains of knowledge. By ranking the individuals according 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 but not the latter variable. The findings are discussed in the context of two competing theories of semantic breakdown in DAT. One differentiates between domains of knowledge in terms of the structure of semantic representations within a single distributed network; the other emphasises the importance of different brain regions in the category distinction. We conclude that our findings are in keeping with the predictions of the latter hypothesis.