MORENO, C.A.*; TU, M.S.; DANIEL, T.L.: Visual-motor feedback in the tracking behavior of hovering Manduca sexta.

Insight into the complex interplay of sensory information, musculoskeletal mechanics, and aerodynamic forces is critical for understanding the fundamental determinants and limits of insect flight performance. While feeding at flowers in the wind, hovering hawkmoths must track a moving target in a spatially complex environment. Although the visual system can discriminate motion in different directions, characteristcs of the musculoskeletal system could constrain the precision of directional control (eg., by introducing ‘crosstalk’ into control pathways). Moreover, frequency tuning in the visual system may be insufficient to account for the frequency response of tracking behavior at the organismal level. To understand the constraints that emerge from sensorimotor integration, we used 30Hz video to record hovering moths as they fed at artificial flowers. We oscillated the flowers sinusoidaly at 1,2, and 3 hz, and three amplitudes (~ 1, 2, 3 cm) for motion in the x- (looming), y- (vertical), and z-(lateral) directions. For each feeding bout, we calculated the gain of the moths’ tracking behavior as the amplitude of moth motion relative to flower motion at the driving frequency. For all three directions, the gain was lowest at 3hz. Tracking behavior, however, had the greatest match of animal motion to flower motion at 2 hz for both looming and lateral motions. Moreover, there is strong coupling between these components at all frequencies. The peak in tracking ability is consistent with predictions from models of motion detection. Our data, therefore, show a close alignment of whole organism dynamics with retinal and neuronal processing. (NSF IBN9511881, ONR to C. Diorio).