Space deficits in Parkinson's disease patients: quantitative or qualitative differences from normal controls?

Twenty-seven patients with idiopathic Parkinson's disease (PD) and the same number of normal controls (NCs) were studied on a test battery including five conceptual categories of spatial ability. The two groups of subjects were matched for age, sex, years of education, socioeconomic status and non-verbal (Raven Standard Progressive Matrices) intelligence. A multivariate analysis of variance (MANOVA) showed that the PD patients performed less efficiently on almost all the tasks. A logistic regression analysis (LRA) classified 81.48% of the subjects into the PD group and 92.59% into NC group, indicating that left-right and back-front Euclidean orientation, three dimensional mental rotation and visuospatial immediate recognition memory of mirror image patterns discriminate well between the two groups. Application of a structural model (confirmatory factor analysis) demonstrated that both PD patients and the NC group stemmed from a homogeneous population, suggesting that the differences found between the two groups are of a quantitative rather than of a qualitative nature.