Task-Dependent Modulation of Upper-Extremity Muscle Synergies during Object Slippage

Abstract

Preventing object slippage requires the central nervous system to control and coordinate the muscle groups while adapting to the variations in the slip characteristics. Our study investigates how slip characteristics, such as slip direction, slip distance, and slip speed, affect the modulation of muscle synergies as a manifestation of object slippage. Our results reveal that there are shared synergies existing in the upward and downward slip emulation, and that these shared synergies are dependent on slip characteristics. However, there were no specific synergies found to exist in the upward and downward slip conditions. Our results also indicate the existence of combined synergies, as the motor modules in the upward slip direction were found to have shared synergies with multiple motor modules in the downward slip direction. We also observed that the number of shared synergies varied depending on the slip distance and slip speed. Together, these findings suggest that the CNS flexibly reconfigures a limited set of muscle synergies to accommodate varying slip dynamics, balancing control stability with adaptability.