Model-Based Investigation of the Roles of Efferent and Afferent Noise in Balance Control in the Postural Control System

The objectives of this study were to evaluate the performance of two 2D balance control model structures and to make model-based inferences regarding balance control mechanisms, specifically the degree to which afferent vs. efferent noise is involved in generating sway. The balance control model structures were based on an optimal control strategy, and differed in the sources of noise in postural control (efferent vs. afferent). Results showed that all 95% confidence intervals of traditional measures resulting from both model structures included unity, indicating that there were no significant differences between the simulated and experimental measures. The model structure with efferent noise input generated a smaller cost function and smaller scalar errors compared with that with afferent noise input. Smaller cost function and smaller scalar errors are associated with better performance in terms of simulating postural sway. Thus, it might be concluded that efferent noise in the postural control system plays a relatively important role in driving postural sway. These findings may be useful for the development of intervention strategies for the improvement of balance and reduction of fall risks.