Abstract
The aim of this study was to verify the hypothesis advanced by Hécaen and Assal (1970) and Warrington et al. (1966) that constructive disorders of left brain-damaged patients may be due to a planning disorder, while those of right brain-damaged patients may be due to visualspatial disturbances.
Twenty-one severe apraxic patients (8 with left-sided posterior lesions and 13 with right-sided posterior lesions) were given two tests involving copying of drawings. In the first task, the patients were asked to copy a drawing of a cube directly. In the second task, they were asked to draw on the cube's perimeter gradually, in accordance with a demonstration by an examiner.
The performances of all the apraxics due to left lesions were improved markedly in the latter test, where no organization plan for performing the task was required, although they did not score at a normal level. By contrast, in the group with right-sided lesions we found that 7 patients out of 13 also improved but not to the same remarkable extent ; in 2 cases no amelioration was observed and in the other 4 cases performances were inferior to the results obtained in the first task.
These results suggest that visual-spatial disturbances may underlie the constructive disabilities of patients with right-sided lesions, whereas both planning and visual-spatial disorders could be responsible for constructive disturbances shown by patients with left-sided lesions.
