Enhanced spatial discrimination in paretic hands

Objective Proper interaction between the sensory and motor system is essential for adequate control of voluntary movement. The influence of sensory alteration on motor activity is well known, while the effect of motor disturbance on sensory activity has yet to be clarified. We performed this study to investigate the influence of motor deactivation on sensory discrimination. Methods Using Johnson–Van Boven–Phillips domes, we evaluated tactile spatial discrimination (grating orientation threshold; GOT) in 62 patients with acute pure motor stroke and 75 age-matched healthy controls. Results In controls, the GOT was significantly lower in the dominant than in the non-dominant hands. The GOT was significantly reduced in patients’ paretic hand, as compared to their unaffected hand and the hands of healthy controls in both the dominant and non-dominant side. The GOT of patients’ paretic hand was significantly and inversely correlated to severity of their initial motor deficit in the non-dominant side (r = 0.40, p < 0.05), but not in the dominant side. Conclusions These results suggest that motor deprivation enhances ascending sensory inputs. Significance This study provides additional information about the relationship between the motor and sensory system in humans.