Encoding of motion in real time by the fly visual system

Direction-selective cells in the fly visual system that have large receptiv e fields play a decisive role in encoding the time-dependent optic flow the animal encounters during locomotion. Recent experiments on the computation s performed by these cells have highlighted the significance of dendritic i ntegration and have addressed the role of spikes versus graded membrane pot ential changes in encoding optic flow information. It is becoming increasin gly clear that the way optic flow is encoded in real time is constrained bo th by the computational needs of the animal in visually guided behaviour as well as by the specific properties of the underlying neuronal hardware.