Visual Motion Integration Controls Attractiveness of Objects in Walking Flies and a Mobile Robot

Walking fruit flies are attracted by near-by objects. They estimate the distance to these objects by the parallax motion of their images on the retina. Here we provide evidence from robot simulations that distance is assessed by motion integration over large parts of the visual field and time periods of 0.5 s to 2 s. The process in flies is not selective to image motion created by the self-motion of the fly but also sensitive to object motion and to the pattern contrast of objects. Added visual motion (e.g. oscillations) makes objects more attractive than their stationary counterparts. Front-to-back motion, the natural parallax motion on the eyes of a forward-translating fly, is preferred. A group of several more distant objects can be more attractive than one close object. Objects, that are most attractive in the fronto-lateral eye-field, act as deterrent in the rear visual field. Time to course changes doubles from front to rear. A cybernetical model based on weighted motion integration in just four compartments (frontal to +/-100 degrees lateral and +/-100 degrees to +/-160 degrees in the rear) can reproduce fly behavior. Implemented on a freely moving camera-equipped robot with panoramic vision it can reproduce various aspects of the orientation behavior of freely walking flies without the necessity to recognize objects. Tracks of walking fruit flies and traces of the robot model obtained in up-scaled environments have been rigorously compared in various arrangements of landmarks.