title: Bilateral flight muscle activity predicts wing kinematics and 3-dimensional body orientation of locusts responding to looming objects.
abstract: We placed locusts in a wind tunnel using a loose tether design that allowed for motion in all three rotational degrees of freedom during presentation of a computer-generated looming disc. High-speed video allowed us to extract wing kinematics, abdomen position and 3-dimensional body orientation. Concurrent electromyographic (EMG) recordings monitored bilateral activity from the first basalar depressor muscles (m97) of the forewings, which are implicated in flight steering. Behavioural responses to a looming disc included cessation of flight (wings folded over the body), glides and active steering during sustained flight in addition to a decrease and increase in wingbeat frequency prior to and during, respectively, an evasive turn. Active steering involved shifts in bilateral m97 timing, wing asymmetries and whole-body rotations in the yaw (ψ), pitch (χ) and roll (η) planes. Changes in abdomen position and hindwing asymmetries occurred after turns were initiated. Forewing asymmetry and changes in η were most highly correlated with m97 spike latency. Correlations also increased as the disc approached, peaking prior to collision. On the inside of a turn, m97 spikes occurred earlier relative to forewing stroke reversal and bilateral timing corresponded to forewing asymmetry as well as changes in whole-body rotation. Double spikes in each m97 occurred most frequently at or immediately prior to the time the locusts turned, suggesting a behavioural significance. These data provide information on mechanisms underlying 3-dimensional flight manoeuvres and will be used to drive a closed loop flight simulator to study responses of motion-sensitive visual neurons during production of realistic behaviours.
authors.affiliation: Department of Biology, University of Saskatchewan, Saskatoon, SK, Canada.
authors.forename: Glyn A
authors.initials: GA
authors.lastname: McMillan
authors.forename: Vicky
authors.initials: V
authors.lastname: Loessin
authors.forename: John R
authors.initials: JR
authors.lastname: Gray
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004576:Electromyography; D005426:Flight, Animal; D006110:Grasshoppers / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D009949:Orientation; D010775:Photic Stimulation; D014921:Wings, Animal / Q000502:physiology
keywords: Locusta migratoria; collision avoidance; insect flight; loom; motor control