Fig 1.
Flight simulator setup and the three flight control behaviors in the TPMP with a pattern contrast of 37%.
(A), Example of fly showing SPSccw. Yaw torque (light red, red is moving average) in the green area (solid green line at T = −4 × 1−10 Nm shows stabilization value) compensated ccw bias and led to almost stationary pattern orientation (dotted green line). (B), Same as in (A) but for cw bias. Pattern was stabilized with yaw torque in blue area (SPScw). (C), With yaw torque in yellow area around T = 0 Nm (solid black line), the fly stabilized the mean of the two bias values (MA behavior). (D), Virtual flight trajectories of a single 3 min flight in the TPMP in relation to the three references for straight flight, the two patterns (green, blue) and the MA (yellow), assuming a constant flight velocity (i.e., constant thrust). Underlying data can be found in S1 Data. arb, arbitrary; ccw, counterclockwise; cw, clockwise; MA, motion average; SPSccw, counterclockwise single pattern stabilization; SPScw, clockwise single pattern stabilization; TPMP, transparent panorama motion paradigm.
Fig 2.
Evaluation, patterns, and bias settings used in the TPMP.
(A), SPS led to bimodal distribution of MA of yaw torque. Mean histogram of MA of yaw torque over 2 s with random dots patterns at 37% pattern contrast. Colored areas indicate the ranges where cw (blue) and ccw (green) SPS as well as MA behavior (yellow) were detected; the dotted lines indicate the respective exact stabilization and MA values. (n = 20 flies). (B), Stabilization of a single random dots pattern with the second one stationary at the same contrast led to unimodal yaw torque distribution with the peak at the stabilization value. Mean histogram of moving average over 2 s (n = 20 flies). (C), With the feedback in the TPMP switched off (open loop), flies showed a broader, multi-modal yaw torque distribution (red; cw: 20° per s, ccw: 20° per s) than in open loop without any motion stimuli (black; cw: 0° per s, ccw: 0° per s), but with the patterns still present (n = 11 flies). (D), Overlays of the different patterns used in the TPMP. (E), Different panorama patterns gave similar results. Only between Reg. dots and bars were significant differences found (mean ± SEM; n = 20 flies per group, FSPS[F(2,57) = 3.341, p = 0.0425, R2 = 0.1049, ANOVA] with Tukey’s multiple comparisons test [p = 0.0384], FMA[F(2,57) = 3.988, p = 0.0239, R2 = 0.1227, ANOVA] with Tukey’s multiple comparisons test [p = 0.0238]). (F), Asymmetric bias settings caused preferential SPS with the less biased pattern. Flies performing in the TPMP with one bias set to 0° per s (SPS 1 hatched) and the other set to 40° per s (SPS 2 hatched) showed a significant preference for the pattern without a bias (t(19) = 4.340, p = 0.0004, paired t test). SPS 1 and SPS 2 values with a symmetric bias of 20° per s (solid) were not different (t(19) = 0.2384, p = 0.8142, paired t test). Also, for overall SPS (t(38) = 1.654, p = 0.1063, t test) and MA behavior (t(38) = 1.117, p = 0.2708, t test), values did not differ significantly between the two bias settings (n = 20 flies per group). Underlying data can be found in S1 Data and https://doi.org/10.6084/m9.figshare.5786922.v1. ccw, counterclockwise; cw, clockwise; MA, motion average; ns, not significant; Ran, random; Reg., regular; SPS, single pattern stabilization; TPMP, transparent panorama motion paradigm.
Fig 3.
Pattern contrast dependence of SPS and MA.
(A), Mean histograms of yaw torque (moving average over 2 s) in the TPMP with random dots patterns (see Fig 2A) under various contrast conditions. High pattern contrast led to unimodal distribution, whereas low contrast resulted in bimodal distribution. Blue and green dotted lines indicate the exact stabilization values for single patterns; the black dotted line for MA behavior; blue and green areas indicate the yaw torque ranges in which SPS is scored; the yellow area where MA is scored. (mean; n = 20 flies per contrast condition). (B), Low pattern contrast increased SPS (sum of SPS of cw and ccw bias; mean ± SEM; n = 20 flies per contrast condition), whereas high contrast led to MA behavior. (C), Stabilization of a single pattern gradually increased from 8% to 91% contrast. Pattern with a rotatory bias of 20° per s cw or ccw with the second pattern stationary. (mean ± SEM; n = 20 flies per contrast condition.) (D), Contrast dependence of the optomotor response (for experimental details see Materials and methods). It differed from that of SPS as well as that of MA behavior. (mean ± SEM, n = 36 flies per contrast condition). (E), OL motion increased SPS peak shift. Yaw torque distribution (2 s moving average) with one random dot pattern in CL and another one moving with 20° per s at three contrast values between 8% and 91% (mean, n = 20 per contrast condition). For all contrast conditions, the distributions are skewed into the direction of the OL motion. SPS was scored in the blue, MA behavior in the yellow area. (F), Asymmetric contrast settings caused preferential SPS with the higher contrasted pattern. Flies tested in the TPMP with one random dots pattern at 91% contrast and the other at 37% contrast showed a highly significant preference for the 91% contrast pattern. MA behavior was slightly below the level of MA behavior with two 37% contrast patterns (mean ± SEM; n = 28 flies; W = −390, p < 0.0001, Wilcoxon matched-pairs signed rank test). Underlying data can be found in S1 Data, https://doi.org/10.6084/m9.figshare.4668400.v1 and https://doi.org/10.6084/m9.figshare.5786931.v1. ccw, counterclockwise; CL, closed loop; cw, clockwise; MA, motion average; OL, open loop; SPS, single pattern stabilization; TPMP, transparent panorama motion paradigm.
Fig 4.
Object response may contribute to MA behavior.
(A), With a low number of bars, SPS decreased when their number increased, and with many bars SPS went up again with increasing numbers. MA behavior developed inversely (mean ± SEM; n = 20 flies per number of bars). (B), Increased contrast had no effect on ratio of SPS and MA behavior with low number of bars, but with 20 bars the effect was highly significant (mean ± SEM; n = 20 flies per number of bars and contrast condition; data of the 37% contrast condition are the same as in (A); SPS 1 Bar: t(38) = 0.0686, p = 0.946, t test; MA 1 Bar: U = 188.5, p = 0.764, Mann-Whitney test; SPS 2 Bars: t(38) = 0.4210, p = 0.676, t test; MA 2 Bars: t(38) = 0.521, p = 0.606, t-test; SPS 20 Bars: U = 26, p < 0.0001, Mann-Whitney test; MA 20 Bars: U = 15, p < 0.0001, Mann-Whitney test). (C), With one vertical bar per pattern (width = 6°; contrast: 37%), the flies preferentially stabilized the bars in the frontal visual field on the side where their bias drove them progressively. Position histograms of the one bar per pattern experiment of (A). Green: bias ccw; blue: bias cw. Horizontal dotted line indicates chance level. (D), With 20 evenly spaced bars per pattern, no 18° modulation of the position histograms is apparent. Horizontal dotted line: chance value as in (C). (E), Power spectra of position histograms of orientation in closed loop with a single pattern of 6, 8, 10, 12, or 20 vertical bars (n = 20 flies per number of bars). Fourier transform showed fixation of bars for the 6- and 8-bar patterns but not for those with 10, 12, and 20 bars. The color code indicates the number of bars in the respective experiment. (F), A selected 9 s flight episode with one bar per pattern, in which the fly switched from fixating the cw bar to fixating the ccw bar after the bars cross each other. Grey area indicates the time during which average yaw torque (light red) was in the MA range. (Compare to Fig 2). (G), A selected 9 s flight episode in which the fly stabilized the ccw bar shortly interrupted this behavior in favor of MA behavior (grey area) after the bars cross, then returned to stabilizing the ccw bar. (H) Flies in the 1–3 bar/pattern experiment in (A) showed significantly more MA behavior with diverging bars. Bar chart of the fraction of time of MA behavior when the two bars div and conv (1 bar: t(19) = 5.082, p < 0.0001, ratio paired t test; 2 bars: t(19) = 5.177, p < 0.0001, ratio paired t test; 3 bars: t(19) = 10.14, p < 0.0001, ratio paired t test; 4 bars: W = −68, p = 0.2162; Wilcoxon matched-pairs signed rank tests). Underlying data can be found in S1 Data, https://doi.org/10.6084/m9.figshare.4668559.v1 and https://doi.org/10.6084/m9.figshare.4668565.v1. ccw, counterclockwise; cw, clockwise; conv, converging; div, diverging; MA, motion average; SPS, single pattern stabilization.
Fig 5.
Temporal dynamics and behavioral stability over time in the TPMP.
(A), SPS did not change over time. Mean SPS values per minute measured with random dots patterns at 8% contrast (mean ± SEM; n = 18 flies; F(3.84, 65.21) = 0.94, p = 0.446, R2 = 0.052, rm-ANOVA). (B), Number of SPS phases did not change over time. Mean number of SPS phases per minute (Q(5) = 7.45, p = 0.189, Friedman test). (C), Mean number of ISPs per minute. One ISP was detected as onset of SPS 1 when the last SPS was SPS 2 and vice versa (Q(5) = 5.502, p = 0.357, Friedman test). (D), Mean duration of SPS phases differed among flies. Duration of one SPS phase was calculated as t(SPS1_offset)-t(SPS1_onset) or t(SPS2_offset)-t(SPS2_onset), respectively. Tukey-Boxplot. (E), Mean duration of ISPs differed strongly among flies. Duration of one ISP was calculated as t(SPS2_onset)-t(SPS1_onset) or t(SPS1_onset)-t(SPS2_onset). Tukey-Boxplot. (F), Probability distribution of normalized SPS phase duration fit gamma distribution (R2 = 0.84). Individual SPS durations were normalized to the mean SPS phase duration of the respective fly. A replicates test for lack of fit showed no lack of fit (F = 0.24, p = 0.999). (G), Probability distribution of normalized ISP duration fit gamma distribution (R2 = 0.55). Single ISP durations were normalized to the mean ISP phase duration of the respective fly. A replicates test for lack of fit showed no lack of fit (F = 0.13, p = 1). Underlying data can be found in S1 Data and https://doi.org/10.6084/m9.figshare.4668376.v1. ISP, inter-switch-phase; SPS, single pattern stabilization; TPMP, transparent panorama motion paradigm.
Fig 6.
Monocular TPMP reduces SPS for regressively moving bias and MA behavior.
(A), Monocular stimulation with regular dots patterns. (B), One pattern in closed loop (progressive or regressive bias, 20° per s), the other stationary (mean ± SEM, n = 20 flies per group, F(F(2, 57) = 0.4453, p = 0.0272, R2 = 0.1188, ANOVA)). Pro bias was more extensively stabilized than Reg bias (p = 0.0203, Tukey’s multiple comparisons test). Neither performance value was significantly different from PS with binocular stimulation (grey) (preg = 0.3822, ppro = 0.3289, Tukey’s multiple comparisons test). (C), In the TPMP, flies with monocular input stabilized the pro moving pattern significantly more than the reg moving one (mean ± SEM; n = 21 flies for binocular stimulus, n = 42 flies for monocular stimulus; H(3, 123) = 31.3, p < 0.0001, Kruskal-Wallis test; ppro-reg = < 0.0001, pbino1-bino2 > 0.9999; ppro-bino1 = 0.2677, preg-bino2 = 0.3702, Dunn’s multiple comparisons test). With monocular stimulation (pro+reg), MA behavior was reduced compared to binocular stimulation (binocular)(U = 401.5, p = 0.57, Mann-Whitney test), while overall SPS was not different (U = 205, p = 0.0004, Mann-Whitney test). Underlying data can be found in S1 Data and https://doi.org/10.6084/m9.figshare.4668571.v1. MA, motion average; Pro, progressive; PS, pattern stabilization; Reg, regressive; SPS, single pattern stabilization; TPMP, transparent panorama motion paradigm.