The relationship between visuospatial ability and perceptual motor function in Parkinson's disease.

To assess the contribution of visuoperceptual function to complex visuomotor responding in Parkinson's disease, 14 patients with idiopathic PD and 12 normal controls matched for age, education and general intellectual function were administered a visual tracing task. No difference was found between the groups on two visuoperceptual tests, the Benton Line Orientation test and a test of trajectory judgement. However, patients were significantly impaired in tracing a sawtooth design when two consecutive angles of the sawtooth were occluded. This impairment occurred in reproducing the basic form of the stimulus and not with accuracy of fine detail. These results suggest higher-order perceptual motor dysfunction independent of any breakdown in basic visuoperceptual processing or loss of fine motor control. It is concluded that Parkinsonian patients are unable to use sensory information accurately to plan and execute complex or new movements.