The effect of action goal hierarchy on the coding of object orientation in imitation tasks: evidence from patients with parietal lobe damage.

In order to explore parietal patients' difficulties in the processing of orientation information, we asked parietal patients (N = 8) and healthy and brain-damaged controls to imitate multicomponent actions where object orientation was one component. In Experiment 1 orientation was not the most relevant aspect of the action to be imitated, and the parietal group showed significant difficulties in processing object orientation. However, in Experiment 2, where orientation was placed at the top end of the goal hierarchy, the parietal group were able to process stimulus orientation sufficiently to place it within the goal hierarchy of the action and to reproduce it accurately. We conclude that patients with parietal lesions might be able to include object orientation in a goal hierarchy, but if their processing of orientation information is impaired they might be disproportionately prone to errors when object orientation is lower in the goal hierarchy and so not prioritized for processing resources.