Conceptual apraxia from lateralized lesions

Abstract

Models of praxis have posited two major components, production and conceptual. Conceptual praxis disorders may occur in two domains: associative knowledge (tool-action associations such as hammer pound; tool-object associations such as hammer nail) and mechanical knowledge such as knowing the advantage that tools afford. Patients with Alzheimer's disease not only have conceptual apraxia (CA) but can dissociate CA from language deficits and from praxis production deficits (ideomotor apraxia). These findings suggests that knowledge about tools (action semantics) is independent of verbal semantics as well as movement representations. To learn if conceptual praxis knowledge is stored in one hemisphere (right or left) and if associative and mechanical conceptual praxis knowledge can be dissociated, we studied 29 right-handed subjects with unilateral strokes. Ten had left-hemisphere damage with no ideomotor apraxia. Eleven had left-hemisphere damage with ideomotor apraxia. There were eight right-hemisphere-damaged controls and 10 normal controls. These subjects were given tests for conceptual apraxia. There was a significant difference between groups, the left-hemisphere group with ideomotor apraxia being most impaired on both the associative and mechanical CA tests. There was a trend for associative and mechanical knowledge to be dissociated. Although conceptual praxis representations are stored in the left hemisphere, analysis of lesion sites did not reveal where in the left hemisphere they may be stored.

Apraxia of Single Tool Use

“…Generally speaking, apraxia of tool use has been related to lesions in the left hemisphere, especially in the left temporal and inferior parietal lobes for right-handed persons [18, 19]. Our patient also had a lesion involving the wide area of the left superior and middle temporal gyri extending into most part of the supramarginal and angular gyri.…”

“What” and “how”: Evidence for the dissociation of object knowledge and mechanical problem-solving skills in the human brain

“…According to this viewpoint, the apparently normal usage of objects observed in patients with a profound loss of general semantic knowledge would reflect the fractionation of a ''multimodal semantic system'' of the type first advocated by McCarthy and Warrington (1). A very similar position was adopted by Heilman and colleagues (2)(3)(4) to explain the apparently specific loss of knowledge of tool action and usage (ideational or conceptional apraxia) in patients with vascular lesions or Alzheimer's disease. In a more recent formulation of a multimodal framework, Lauro-Grotto et al (5) proposed that object-specific action procedures constitute part of the visual semantic system preferentially accessed by objects and pictures.…”

Repetition suppression for performed hand gestures revealed by fMRI

“…This is concordant with an extensive patient literature. [Haaland et al, 2000;Heilman et al, 1997;Leiguarda, 2001;Ochipa and Gonzalez Rothi, 2000]. Ideomotor apraxia is most commonly associated with left inferior parietal or middle frontal lesions.…”