Conceptual apraxia and semantic memory deficit in Alzheimer's disease: two sides of the same coin?

J Int Neuropsychol Soc. 2000 Sep;6(6):693-703. doi: 10.1017/s1355617700666079.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Alzheimer Disease / complications*
  • Apraxia, Ideomotor / diagnosis*
  • Apraxia, Ideomotor / etiology
  • Educational Status
  • Female
  • Humans
  • Language Disorders / diagnosis
  • Language Disorders / etiology
  • Male
  • Memory Disorders / diagnosis*
  • Memory Disorders / etiology
  • Neuropsychological Tests
  • Semantics*
  • Severity of Illness Index