title: Conceptual apraxia and semantic memory deficit in Alzheimer's disease: two sides of the same coin?
abstract: This study was designed to examine the patterns of apraxic disturbances and the relationships between action knowledge and other measures of semantic knowledge about objects in 10 well-characterized Alzheimer's disease (AD) patients. Five tasks were used to assess components of action knowledge (action-tool relationships, pantomime recognition, and sequential organization of action) and praxis execution (actual use, pantomiming) according to the cognitive model of praxis. Three tasks (verbal comprehension, naming, and a visual semantic matching task) were used to assess verbal-visual semantics. Considering patterns of apraxia first, conceptual apraxia was found in 9 out of the 10 AD patients, suggesting that it is a common feature even in the early stages of AD. Second, we found partly parallel deficits in tests of action-semantic and verbal-visual semantic knowledge in 9 AD patients. Impaired action knowledge was found only in patients with a semantic language deficit. These findings provide no evidence that "action semantics" may be separated from other semantic information. Our results support the view of a unitary semantic system, given that the representations of action-semantic and other semantic knowledge of objects are often simultaneously disrupted in AD.
authors.affiliation: Centre de recherche de l'Institut Universitaire de Gériatrie de Montréal, Quebec, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Dumont
authors.forename: B
authors.initials: B
authors.lastname: Ska
authors.forename: Y
authors.initials: Y
authors.lastname: Joanette
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000150:complications*; D020240:Apraxia, Ideomotor / Q000175:diagnosis* / Q000209:etiology; D004522:Educational Status; D005260:Female; D006801:Humans; D007806:Language Disorders / Q000175:diagnosis / Q000209:etiology; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis* / Q000209:etiology; D009483:Neuropsychological Tests; D012660:Semantics; D012720:Severity of Illness Index