Fig. 3. (A) Yaw velocity of head (blue), body (red) and headified (yaw-tuned) body (green). This flight segment corresponds to the segment for which yaw angles are shown enlarged in Fig. 1A inset. (B) Same as A, vertically zoomed. Yaw velocities in A and B were obtained from the differential rotation matrix of the body or head (van Hateren and Schilstra, 1999) and were low-pass filtered with a Gaussian (standard deviation 3 ms) to reduce measurement noise. (C) Average response of an horizontal system south neuron (HSS) cell to optic flow corresponding to yaw velocities shown in A. Broken line at 0 mV corresponds to the resting potential; responses are shifted backwards by 22.5 ms to account for response latencies and low-pass filtered with a Gaussian, standard deviation 3 ms.