RESUMO
In this study a simple model of the postural control system is implemented and its parameters are adjusted to explain the differences between Parkinson's disease patient's measures and healthy young adult's measures by performing simulations of spontaneous sway with center-of-pressure traces. An optimization procedure was performed varying four parameters of the model. The best adjustment obtained was when the proportional and derivative factors where the same as for healthy young adults and noise level gain and force feedback gain varied independently. Differences in the latter parameter can be explained because of insufficient and slowed force production necessary to counteract perturbations in Parkinson's disease patients while the former may be due to noise in the sensory system that estimates the vertical deviation angle and/or perturbations in the execution of the movement.