Effects of background illuminance and panorama contrast on the optomotor responses of WTB flies.

(A) Box plots of the amplitudes of the 0.25 Hz component of the yaw torques recorded from the optomotor response following a single black stripe on a white background (n = 20). The preferred location was in the lower visual field. There was no significant location dependence (p = 0.6653). (B) Box plots of the amplitudes of the 0.25 Hz component of the yaw torques recorded from the optomotor response following single white stripe on a black background (n = 20). The preferred location was in the upper visual field. There was no significant location dependence (p = 0.2625). (C) Data in (A&B) are shown as the mean±SEM. There was significant difference at θ = 20° (p = 0.0066). Blue line, black stripe on a white background; purple line, white stripe on a black background. (D) Box plots of the amplitudes of the 0.25 Hz component of the yaw torques recorded from the optomotor response following single black stripe on a gray background (n = 20). The preferred location was in the lower visual field. There was a significant location dependence (p = 0.0177). (E) Box plots of the amplitudes of the 0.25 Hz component of the yaw torques recorded from the optomotor response following single white stripe on a gray background (n = 20). The preferred location was also in the lower visual field. There was no significant location dependence (p = 0.0798). (F) Data in (D&E) are shown as the mean±SEM. Their distributions were similar for all 9 locations. Blue line, black stripe on a gray background; purple line, white stripe on a gray background. The p values for location dependence were calculated by the Kruskal-Wallis test; significant difference between two groups was judged by the rank-sum test; the red crosses represent outliers; the-y axes of certain charts are truncated for compactness; ** (p<0.01).