Effects of grating location on the optomotor responses of WTB flies.

(A) Schematic of the experimental setup for testing the optomotor response of Drosophila. Θ, elevation angle between the center of the grating and the tethered fly. (B) Periodic yaw torque responses to gratings at different vertical locations. Yaw torques were normalized. The black curve is the mean of the yaw torques (n = 19); the gray shadow is the standard deviation of the yaw torques. From top to bottom, the vertical location Θ of the gratings changed from +40° to −40°; the red curve in the middle panel was the sine curve used as the ideal response model. (C&D) The acute zone for optomotor response is near the equator of the visual field. (C) Box plots of the amplitudes of the yaw torques at all 9 vertical locations. There was no significant location dependence (p = 0.3887). (D) Box plots of the amplitudes of the 0.25 Hz component of the yaw torques, which were calculated by fast-Fourier transform. There was no significant location dependence (p = 0.3418). The p values were calculated by the Kruskal-Wallis test; the red crosses represent outliers; the y-axes of certain charts are truncated for compactness.