Meeting Abstract
62.1 Thursday, Jan. 6 The control potential of power muscles in a flying insect SPONBERG, S*; FECHKO, AS; DANIEL, TL; Univ. of Washington; Univ. of Washington; Univ. of Washington bergs@uw.edu
Control of flight is often attributed to neural feedback to specific steering muscles modulating the steady-state wingstrokes generated by large, power muscles whose commands are assumed invariant. Our recent results challenged this dichotomy of control, showing that the bilateral pairs of power muscles in the hawkmoth, Manduca sexta, can also undergo significant phase modulation. Our challenge now is to quantify how control is distributed among the many contributing muscles. Since the changes in power muscle activation are subtle, with time shifts of only a few milliseconds, their contribution to flight control remains unclear. To capture the translation of precise timing changes into body dynamics, we developed a high-resolution optical torque sensor integrated into a dorsally-mounted tether. In response to visual stimulus, moths shifted both the mean yawing torque of each wing stroke as well as the peak-to-peak variation of torque within a stroke, supporting greater asymmetry in aerodynamic force production. To directly test the control potential of power muscles in these maneuvers, we elicited steady-state flight and then imposed a change in timing between the left and right dorsal-longitudinal muscles (DLMs) using real-time detection and stimulation of individual muscle action potentials. By injecting motor activity into the system, we experimentally isolate a specific control signal. Within individuals there was significant modulation of both the mean torque and the torque impulse when activation of one muscle was advanced with respect to the other by even a few milliseconds. Power muscles have significant control potential on yaw torque production, but are not sufficient to fully explain yaw maneuvers, indicating that concomitant feedback to steering muscles or modulation over multiple wingstrokes is also necessary.
