Difference between mean heading direction during stim. A and stim. B trials for each fly (black dots). Mean s.e.m. across flies is indicated. Dashed red line indicates the expected difference in heading direction based on the mean difference in the stimulation location for each group (see Extended Data Fig. 4e). V-test for CsChrimson flies: = -173.4° (left dashed line), P = 1.49 x 10 -3. V-test for no CsChrimon flies: = -164.9° (right dashed line), P = 0.93.
