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The Influence of Personal Familiarity and Context on Object Use in Semantic Dementia
BOZEAT, S., Lambon Ralph, M.A., PATTERSON, K.P. & HODGES, J.R.
Neurocase, 8, 127-134
Year of publication:
Several previous studies of semantic dementia, involving formal assessment of the ability to demonstrate the use of individual objects, have revealed a significant deficit that corresponded directly to the patientsí remaining semantic knowledge for the same items. Until late in the course of disease, however, patients with semantic dementia are reported to demonstrate completely normal use of some objects that are relevant to their everyday living or hobbies. The aim of this study was to explore the apparent difference between formal assessment of object use in the clinic and informal observations of patients in their own homes using their own objects. Specifically, we examined the influence of two factors: personal familiarity with object exemplars and the contexts in which they are typically used. Two patients with severe semantic impairment were asked to demonstrate the use of a set of their own objects that they were still using at home on a regular basis. Performance on these items was compared with two additional sets: perceptually-similar and perceptually-different exemplars of the same objects. All three sets were tested both in the patientsí own homes and in a neutral environment. Both patients demonstrated better use of their own objects than of the perceptually different exemplars. An advantage for ëowní relative to perceptually similar exemplars characterised only one of the two patients. Neither patient showed a significant benefit of familiar home context on object use. This study confirms a discrepancy between impaired performance on objects selected for clinical assessment and relative preservation for a limited set of objects that are used for daily living. The results suggest that repeated experience with personally familiar objects helps to maintain appropriate responses to them in the face of severe degradation of conceptual knowledge.