Fig. 8. Schematic model for the spatial organization of visuomotor reflexes in Drosophila. Image motion within individual quarter-fields is temporally filtered and spatially summed (see text for details). Motion across the frontal visual hemisphere results in a syndirectional turn, whereas motion in the rear results in a counterdirectional turn. By summation, full-field rotation results in a weak syndirectional turn. However, a pattern of expansion centered laterally produces a stronger turn away from the focus of expansion. Note that the polarity of turning responses to motion within the rear quarter-fields is independent of the direction of image motion.