Spatial updating in Parkinson's disease

We compared the ability of 48 patients with Parkinson's disease (PD) (24 mild, 24 moderate) and 35 controls to remain oriented to the starting position after being transported passively in a wheelchair in two conditions: visual and vestibular. The moderate PD group demonstrated the poorest performance in both sensory conditions. The visual condition discriminated between the mild PD group and the controls, but both groups had similar performance in the vestibular condition. Poor performance of the PD group in the visual condition and controls in the vestibular condition correlated significantly with poor performance on selected balance tests. Poor performance in the visual condition correlated significantly with poor performance on judgment of line orientation in the mild PD group. Spatial updating, or maintaining a sense of orientation while being moved in the environment, may be impaired in PD and should be investigated as a possible contributing factor to problems with spatial orientation noted clinically in some patients.