Meeting Abstract
As a fish swims, both the flow around it and the sensory information received by the nervous system are influenced by the mechanical properties of its body. Body stiffness depends on the material properties of the body and its cross-sectional shape. Fish bodies are also probably viscoelastic, which means that the effective stiffness would change as bending frequency changes. Finally, muscle activation patterns, including co-activation of the left-right axial musculature, are also likely to be key determinants of body stiffness and damping properties. We study a widely used model for swimming neuromechanics, the lamprey Ichthyomyzon unicuspis, to investigate the mechanical properties of an in situ whole body preparation. In this preparation, a servomotor bends the lamprey body laterally, and the forces and torques are measured by an in-line force transducer. Axial muscle at the point of bending is stimulated electrically. We ask how bending frequency, body location, and muscle activation patterns affect body stiffness and damping. Preliminary results show anterior body regions are stiffer than tail regions and the effect is most pronounced at high bending frequencies. We also find that muscle activation does not change body stiffness much compared to passive bending when the muscles are activated in phase with bending, i.e. during muscle shortening. However, coactivation of left and right side muscle substantially increases body stiffness. We will further discuss these trends as well as the effect of body location, bending frequency, and muscle activation on the body’s damping properties.
