Meeting Abstract

58.4  Sunday, Jan. 5 14:15  Characterization of nonlinear mechanisms in the optomotor system of the tobacco hawkmoth MüLLER, T.*; WINDSOR, S.P.; TAYLOR, G.K.; University of Oxford, UK; University of Bristol, UK; University of Oxford, UK tonya.muller@zoo.ox.ac.uk

Flying insects are known to use optic flow information to stabilize their flight; however the functional properties of the optomotor system and its relation with an insect’s flight dynamics are not well understood. The focus of this work was to explore how tobacco hawkmoths (Manduca sexta) use wide-field vision to stabilize their motion. In order to characterize the relationship between optic flow and flight response, we used a virtual reality flight simulator where a moth was exposed to oscillating wide-field, sinusoidal gratings. During these open-loop experiments, moths were tethered to a 6 degree of freedom force sensor, allowing us to measure their corresponding flight responses. The optomotor system was characterized in the frequency domain, where we explored the properties of homogeneity and additivity. The roll, pitch and yaw magnitude responses demonstrated different sensitivities to changes in the amplitude and frequency of the stimulus motion. We explored this phenomenon further by applying a model selection process, and found that the responses were best predicted by nonlinear combinations of stimulus parameters. These models suggest that roll, pitch and yaw stabilization are elicited by different combinations of stimulus amplitude, frequency and angular velocity as control inputs. We conclude that although quasi-linear models account for a large proportion of the response, nonlinear models are needed to capture many of the salient features of the response behaviour. The variation in sensitivity to roll, pitch and yaw motions is discussed both in terms of saturation effects in the visual system and in the context of the insect’s flight dynamics.