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Semantic dementia with category specificity: A comparative case-series study
Lambon Ralph, M.A., PATTERSON, K., Garrard , P. & HODGES, J.R.
Cognitive Neuropsychology, 20(3-4-5-6), 307-326
Year of publication:
Patients with semantic dementia, the temporal variant of frontotemporal dementia, are relevant to both the neuroanatomical and neuropsychological debates in the category-specific literature. These patients present with a selective and progressive semantic deficit consequent on circumscribed atrophy of the inferolateral, polare temporal lobes bilaterally, including the inferotemporal gyrus. In this study, a patient KH with a significant advantage for artefacts over living things was compared to five other semantic dementia patients with commensurate levels of semantic impairment. KH demonstrated a consistent category-difference in favour of artefacts across all the expressive and receptive semantic tests. This difference was reliable even when familiarity, frequency and other potential confounding factors were controlled. While KH demonstrated an association between poor knowledge of sensory attributes and a consistently greater impairment on living things than artefacts, the other patients did not. As observed in a number of previous studies, all five of the patients, contrasted to KH, exhibited an advantage for functional/associative over sensory attributes but without demonstrating the category-specific deficit that the sensory-functional theory (and the locus of their atrophy) might predict. The results of this and other studies are discussed in relation to four accounts of category-specificity: the sensory-functions theory, domain-specific knowledge systems, intercorrelated features and individual differences.