Contribution of Proprioceptive Feedback to Ankle Extensor Activity in Freely Walking Cats

SUMMARY Our objective is to gain insight into the relative importance of feed forward (FF) control and different proprioceptive feedback (FB) pathways to ongoing ankle extensor activity during walking in the conscious cat. We assume that the FF signal can be characterized by a simple trapezoidal function, and that muscle modulation during level walking is due to feedback. Apart from testing this assumption, we want to verify the following main hypothesis: the same central command (FF signal) and the same proprioceptive gains used during level walking can automatically compensate for changes in the walking slope. Therefore, we formulate and solve two least-squares parameter estimation problems based on a simple muscle activity model to determine the relative contribution of the feedback signals and the feed forward signal. The results of the optimization problems allow us to verify our hypothesis.