Spatial features of angular drawing movements in Parkinson's disease patients.

The present study shows that drawings from Parkinson's disease (PD) patients display specific spatial features when compared to those produced by age-matched controls. Their drawings are globally smaller, or more precisely, the larger the requested size, the greater the size reduction. PD subjects have also more difficulties in producing obtuse than acute angles: angles of obtuse patterns are shrinking and their segment lengths are shortened. This could be due to the fact that an obtuse angle brings the effector joints close to the limits of their functional ranges of motion, which may be reduced in PD patients. Results related to segment direction show that PD patients are globally more imprecise than controls in the production of movement directions, but perform nevertheless relatively well for horizontals and verticals drawn in preferred directions. These results are referred to two contradictory models relating movement direction to the type of movement coordination involved.