Removal of the visuospatial component from tracking performance and its application to Parkinson's disease

Subjects with Parkinson's disease perform poorly on complex sensory-motor tasks but the extent to which this is due to visuospatial deficits is unclear. We measured the performance of 16 patients with Parkinson's disease and 16 control subjects on preview and non-preview random tracking tasks and a test of dynamic perception. The parkinsonian group was impaired impaired on all tasks. A technique was developed which, by the concept of a visuoperceptual buffer-zone, allowed the visuospatial component of tracking performance to be removed. It was then possible to show that the parkinsonian subjects remained impaired on both tracking tasks and that limitations in visuospatial function play only a minor role in the errors seen on tracking in both parkinsonian and control subjects.