Impairments of Mental Rotation in Parkinson's Disease

It is controversial whether parkinsonian patients are impaired on visuospatial tasks. In the present study, patients and normal control subjects judged whether pairs of wire-frame figures in different orientations were the same or different. The orientation difference between the figures was either in the picture plane (around the z-axis, or two-dimensional) or in depth (around the y-axis, or three-dimensional). Reaction times and error rates were measured. For the two-dimensional task, there were no significant differences in errors between the two groups, though Parkinsonian subjects were significantly slower to respond than the control group. In the three-dimensional task, patients had a different pattern of reaction times from the controls and made significantly more errors, which were systematic at large angular differences. The results suggest a visuospatial deficit in Parkinson's disease, which reflects problems in some aspect of the perception of extra-personal space.