Regional effect of visual clutter

Stabilizing responses to disturbances are a critical part of the flight control system in flies. While strongly mediated by mechanoreception, much of the final steering response results from the wide field motion detection system associated with vision. The accuracy of the optomotor responses is affected when the characteristics of the visual input exceed the dynamic range of the motion detecting system. This has been demonstrated for stimulus parameters such as contrast, brightness, velocity, and spatial and temporal frequencies in gratings, but less is known about the effect of variables in more complex moving stimuli. By presenting laterally-moving dotfields of different densities we found that, in Drosophila melanogaster, the amplitude of the optomotor response is significantly affected by the level of visual clutter in the stimulus. Flies countersteer strongly within a relatively low and narrow range of element densities. But this effect is exclusive to the ventral region of the ey...