Basic mechanisms of constructional apraxia in unilateral brain-damaged patients: role of visuo-perceptual and executive disorders.

The basic mechanisms of constructional apraxia (CA) are still a matter of debate. In this study we assessed the possible relationships between CA and performance on tasks assessing visual perception, low-level motor skill, manipulo-spatial ability, and general intellective efficiency in samples of healthy subjects, right-brain-damaged (RBD) and left-brain-damaged (LBD) patients. Multiple regression analyses, performed separately for the three groups, demonstrated that efficiency in perceiving the model as a whole is the factor mainly related to drawing performance of normal subjects. In the RBD group, instead, a disorder of the manipulo-spatial ability seems to play the most important role in producing CA. As for the LBD group, the most relevant finding is that patients drawing with the left hand are significantly more impaired than patients using the right hand and than control subjects. These results are discussed in relation to various hypotheses so far advanced to account for basic mechanisms of CA in unilateral brain-damaged patients.