Neural coding of naturalistic motion stimuli

We study a wide-field motion-sensitive neuron in the visual system of the b lowfly Calliphora vicina. By rotating the fly on a stepper motor outside in a wooded area, and along an angular motion trajectory representative of na tural flight, we stimulate the fly's visual system with input that approach es the natural situation. The neural response is analysed in the framework of information theory, using methods that are free from assumptions. We dem onstrate that information about the motion trajectory increases as the ligh t level increases over a natural range. This indicates that the fly's brain utilizes the increase in photon flux to extract more information from the photoreceptor array, suggesting that imprecision in neural signals is domin ated by photon shot noise in the physical input, rather than by noise gener ated within the nervous system itself.