Meeting Abstract
Gaze stabilization relies upon the detection of self-motion cues, which are subsequently suppressed for active gaze shifts. Yet, it is poorly understood how animals lacking standard vestibular systems, such as flying insects, discriminate self-motion from external body rotations. Flies are unique among this group of organisms as they possess organs that operate in part as vestibular sensors known as halteres. Evolutionarily derived from the hindwings, the halteres provide mechansensory feedback to structure the wingstroke. However, the potential for the haltere to serve as more than a passive sensor to initiate or control maneuvers remains unclear. The haltere possesses tiny steering muscles that are serially homologous to those of the forewings that receive visual input. Thus, haltere reflex circuits may be co-opted during voluntary maneuvers. We tested the capacity for the visual system to modulate mechanosensory input by expressing the genetically-encoded calcium indicator GCaMP6f in the haltere afferents and steering muscles of the fruit fly, Drosophila melanogaster. Adapting preparations to image calcium activity from the muscles or brain of Drosophila with epifluorescent or 2-photon microscopy, we simultaneously recorded flies’ behavioral responses to visual motion stimuli in tethered flight. We show that mechanosensory feedback from the halteres is modulated by visual feedback for both gaze stabilization and redirection maneuvers. This modulation is the result of changes to the haltere’s kinematics, through the visual system’s connection to the haltere’s steering muscles. Our results point to a mechanism by which flies can modify hard-wired flight reflexes to produce voluntary behaviors.
