Odor boosts visual object approach in flies

Multisensory integration is synergistic - input from one sensory modality might modulate the behavioral response to another. Work in flies has shown that a small visual object presented in the periphery elicits innate aversive steering responses in flight, likely representing an approaching threat. Object aversion is switched to approach when paired with a plume of food odor. The ‘open loop’ design of prior work facilitated the observation of changing valence. How does odor influence visual object responses when an animal has naturally active control over it’s visual experience? In this study, we use closed loop feedback conditions, in which a fly’s steering effort is coupled to the angular velocity of the visual stimulus, to confirm that flies steer toward or ‘fixate’ a long vertical stripe on visual midline. They tend to either steer away from or ‘anti-fixate’ a small object or to disengage active visual control, which manifests as uncontrolled object ‘spinning’ within this experimental paradigm. Adding a plume of apple cider vinegar decreases the probability of both antifixation and spinning, while increasing the probability of frontal fixation for objects of any size, including a normally aversive small object.