Current perspectives on disruptions to limb praxis.

This article briefly presents the disruptions to limb praxis, the clinical features of the disorders, the types of errors observed for each disorder, and the mechanisms proposed to explain these disorders. The paper then focuses on a proposed model of the action system that provides a basis for examining performance of the apraxic patient. The model proposes that the action system requires the operation of two subsystems: a conceptual system and a production system. The former provides a perceptual and linguistic knowledge base for action; the latter provides the mechanisms for performing actions. Within this framework, the conceptual and production bases for disruptions to gesturing and action sequencing observed in patients with apraxia are discussed. Finally, implications for assessment and future research are presented.