Does the right cerebral hemisphere contribute to limb praxis?, evidence from limb apraxia following unilateral stroke

Abstract

Five experiments are reported which examine limb praxis, and the frequency and severity of limb apraxia following left or right hemisphere stroke. Apraxia is a disorder of skilled, purposeful action (e.g., picking up a glass, waving goodbye) which cannot be attributed to basic sensory or motor impairments, inattention to commands or poor comprehension. Liepmann's (1908) writings at the turn of the century serve as doctrine for classical approaches to the study of apraxia, and subsequent adherence to the notion that apraxia follows lesions to the left cerebral hemisphere (e.g., Heilman, Rothi, & Velenstein, 1982). However, recent research employing quantitative measurement techniques has shown that apraxia can also be elicited following right hemisphere stroke (Haaland & Flaherty, 1984; Roy, Black, Blair, & Dimeck, 1998). The observation that right hemisphere lesions can also impair praxis served as the foundation for the present research. In two experiments (Experiments 1 and 3) the frequency and severity of apraxia during the pantomime and imitation of transitive (Experiment 1) and intransitive (Experiment 3) limb gestures was evaluated in a sample of patients with unilateral left (LHD) or right hemisphere lesions (RHD). A multi-dimensional error notation system was used to quantify gesture production errors. The results indicated that a significant number of LHD and RHD patients were classified as apraxic, with measures of apraxia severity failing to differentiate between stroke groups. Moreover, using the patterns of apraxia proposed by Roy (1996 [pantomime alone, imitation alone, pantomime and imitation]) it was revealed that LHD does not exclusively impair the selection/evocation stage of gesture production, as indicated by others (e.g., Barbieri & De Renzi, 1988). Rather, a significant proportion of LHD patients demonstrated impairments in the executive stage of gesture production.

The second experiment served as the basis for differentiating between transitive and intransitive limb gestures in Experiments 1 and 3. In this investigation, a case study involving an individual specifically impaired in the selection/evocation stage of intransitive limb gestures is discussed. Further, this case study provides emergent evidence for parallel and independent systems governing the production of separate gesture forms (transitive vs intransitive).

In the fourth experiment, a three-dimensional kinematic procedure was developed to examine limb praxis in healthy controls. The results from Experiment 4 provide important methodological detail for examining movement kinematics in unilateral stroke populations. Specifically, identifying a dominant (right) hand advantage for the production of transitive limb gestures.

In the fifth experiment, three-dimensional analyses were employed to examine spatial temporal errors in gesture production following left (N=4) and right (N=4) hemisphere stroke. Group results failed to reveal spatial parameterizations errors in either stroke group, however, individual patient analyses indicated that one LHD, and one RHD patient demonstrated joint synchronization and temporal coordination errors respectively. These data support previous observational analyses (Experiments 1 and 3) that apraxia can be elicited following right hemisphere stroke.

The results of this research project demonstrate that left or right hemisphere lesions can result in apraxia. Moreover, this research demonstrates that the quantitative assessment of apraxia, combined with careful manipulation of gesture forms (transitive vs. intransitive) and stimulus modality (pantomime vs imitation), provide detail critical in extending our knowledge of limb praxis.