Manual asymmetry of time-delay effect on visual feedback in arm movements

A number of studies have demonstrated the advantages of the nondominant arm in some types of motor tasks, suggesting that manual asymmetry in motor control does not mean that the nondominant arm is inferior. It has been reported that visual feedback control differs in each arm, although it is not clear what control system mainly affects asymmetry. The purposes of this study were to focus on the time delay of visual feedback control and to investigate the asymmetry of time-delay processing. In experiment 1, circular movements were measured in normal conditions and in delay conditions, during which a subject´s hand position was displayed with a 250-ms time delay. In experiment 2, reaching movements were measured in normal, delay, and lead conditions. To display a subject´s hand position with a 50-ms time lead, it was assumed that reaching movements could be approximated with a polynomial equation. The results revealed that the time-delay/lead and arm interactions were significant in the accuracy of movements. The motor control system of the nondominant arm was more susceptible to delayed visual feedback and less susceptible to lead visual feedback. We suggest predictive control of the dominant arm in the motor control system and nonpredictive control of the nondominant arm in the motor control system.