In search for the core of apraxia

Abstract

First paragraph: One of Georg Goldenberg's great contributions to apraxia research is his elegant experimental work demonstrating the body schema specificity of imitation deficits in apraxia. Rather than arising from a generic imitation deficit, the evidence suggests that imitative errors in apraxia are highly specific to body schema coding in the interpolation between perception and reproduction of imitative gestures. This underlying deficit of body schema implementation in motor output would naturally lead to explaining tool-use errors and impaired pantomime in terms of defect manipulation knowledge of the hand acting on an object. However, Goldenberg accounts for the different core manifestations of apraxia (imitation, pantomime, tool-use) each in their own right. When explaining tool-use errors in apraxia Goldenberg does not attribute these to an impairment of manipulation knowledge but coins a largely independent theory of mechanical problem solving based on his tool-use research. In the below we will argue that it is unfortunate that he seeks to explain part of apraxia in functional mechanical terms rather than bodily manipulation terms, as body movement implementation appears central in apraxia. We will further comment on connectivity accounts and the potential of linking apraxia to motor imagery.