Figure 2

Flies can robustly discriminate wide-field motion directions under noisy conditions. (a) Average of head yaw responses ±s.e.m. (upper panels) and distributions of head angle (lower panels) shown over the range of SNR at 1 and 4 Hz temporal frequencies. Stimulus patterns and SNR are depicted above each figure. Stripe denotes the stripe pattern without noise (red, CCW rotation; blue, CW rotation; n = 20 flies, 36 trials at 1 Hz temporal frequency; n = 9 flies, 17 trials at 4 Hz). (b) ROCs for the six pairs of CCW-CW response distributions illustrated in a. Increased separation between CCW and CW response distributions leads to an increased upward deflection of the ROC away from the diagonal. (c) Area under the ROC curve (AUC) illustrated in b. A ROC curve along the diagonal indicates that the fly cannot distinguish between CCW and CW rotations and the AUC is 0.5. As the ROC curve approaches the left axis and upper limit, it indicates that the fly reliably distinguishes between CCW and CW and the AUC is 1.0. (d) Mean ±s.e.m. of normalized OMR illustrated in a.