Visual orientation in motion-blind flies is an operant behaviour

Abstract

Insect visual orientation is mostly considered as a stimulus-response phenomenon^1,2. This view may be challenged in Drosophila melanogaster by genetic dissection, as we show here. When suspended in a fixed position in a flight simulator³, which transforms torque into angular velocity of the panorama, Drosophila establishes a state of zero net rotation of the panorama (optomotor balance⁴). The genetic variant rol sol, with greatly reduced optic lobes, is entirely motion-blind but can respond with turning manoeuvres to the position of landmarks. Mutant flies maintain optomotor balance but do so irrespective of the sign of the visual feedback in the simulator, that is, whether angular velocity is inversely or directly proportional to torque. Using the amount, but not the direction, of pattern motion the flies stabilize the panorama by trying out which value of torque has the desired effect. We conclude that operant behaviour is a basic constituent of visual orientation in flies.