40.1 Saturday, Jan. 5 The intrinsic dynamical properties of muscle are self-stabilizing for rhythmic movements TYTELL, E.D.; Tufts Univ. email@example.com
Animal locomotion is a rhythmic behavior that requires the effective coupling of multiple feedback loops, including mechanical coupling between the animal's body and the environment, coupling between muscular force production and body movement, and sensory feedback. Computational models were used to analyze how the intrinsic dynamical properties of neural and mechanical systems interact to produce stable, but adaptable locomotion. Floquet theory, a branch of nonlinear dynamics, includes ways to analyze how such rhythmic systems respond to perturbations. We analyzed the dynamics of a mathematical model of lamprey muscle and developed several robust ways of estimating the Floquet modes of a rhythmic system, which are canonical patterns of activity after a perturbation. We found that when a block of muscle is forced to change length sinusoidally and is cyclically activated, as in the standard work-loop protocol, it is strongly self-stabilizing, even with no sensory feedback. When two muscles act antagonistically, as they do around most vertebrate joints, then the system is less stable naturally. However, if the animal has sensory input regarding the joint position, it can be stabilized very easily.