Quantitative evaluation of position sense in patients with parietal lesion

A position reproduction task was performed, in a controlled experimental environment, by seven patients with a parietal lobe lesion. We obtained mainly three findings: (a) even for patients who failed a thumb localization test, the accuracy of position reproduction was adequate and did not deviate from the range of error observed in healthy young participants, (b) the patients showed a centralizing tendency in localization, and (c) they initially moved in the wrong direction when reproducing the remembered positions. The study also indicated that patients whose lesion sites included the postcentral gyrus exhibited stronger exploratory movements than those who had no such lesions and lacked smoothness of movement. In patients without the lesion of the postcentral gyrus, a higher-order dysfunction, rather than the pure position sense problem, was suggested to contributed to their task performance. The present study provided fundamental data for sensorimotor skills of patients with parietal lesion, and these quantitative findings would also contribute to reconsideration of current assessments and rehabilitations for sensory deficits.