Introduction: Following a traumatic noxious event, pathologic pain sometimes occurs. Pathologic pain sometimes impairs motor function of the affected limb, but the underlying mechanisms of the motor dysfunction are still unclear. In this study, we focused on the relationship between pathologic pain and higher brain function-associated motor function. Methods: Under the light or dark conditions, six patients with pathologic pain in their upper limb were asked to perform two-way pointing between three visual targets and their nose by their index finger of the affected and unaffected limb. We evaluated the response time during the respective pointing movements and inaccuracy of the pointing trajectories. To analyze these data statistically, we used 3-way ANOVA for three factors [laterality (affected or unaffected) ×condition (light or dark) × two-way task (go-task from their nose to targets or back-task from targets to their nose].
　Results: Regarding the response time, there was no significance among three factors. There was a significant interaction of the inaccuracy of pointing trajectories between two factors (laterality and condition)(p<0.01). Other factors revealed no significance. Discussion: In the dark condition, the patients performed the pointing task on the basis of proprio-motor reference frame. On the other hand, in the light condition, the patients performed the task on the basis of not only proprio-motor reference but also visuo-motor reference. Considering that the patients showed almost accurate pointing trajectories in the dark, the peripheral motor system (e.g., muscle, joint, and bone) would not be impaired. Further, the visuo-motor reference of the affected limb would interfere with the intact proprio-motor reference and thereby the eye-hand coordinative linkage of the affected limb is impaired.
　Conclusions Our finding suggest that pathologic pain concerns with motor dysfunction of the affected limb, which is dependent on the higher brain function.

DESCENTE SPORTS SCIENCE Vol.29/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE