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A comparison of visual and haltere-mediated equilibrium reflexes in the fruit fly Drosophila melanogaster

Alana Sherman^1,* and Michael H. Dickinson²

¹ UCB/UCSF Joint Bioengineering Graduate Group, University of California at Berkeley, Berkeley, CA 94720, USA
² Department of Integrative Biology, University of California at Berkeley, Berkeley, CA 94720, USA

View larger version (33K): [in a new window]   Fig. 1. (A) The mechanosensory haltere is a small club shaped modified hind wing. (B) Oblique view and (C) side, top and end views of the apparatus for delivering visual and mechanosensory stimuli. A wrap-around light-emitting diode (LED) display is mounted within a 3-degree-of-freedom rotational gimbal. The fly is mounted in the center of the visual display, above a sensor that measures the left and right wingbeat amplitudes. (D) Visual patterns are used to simulate optic flow generated when the fly rotates around the roll, pitch and yaw axes.

View larger version (24K): [in a new window]   Fig. 2. Flies modulate wingbeat amplitude (WBA) in synchrony with oscillations in visual and mechanical roll. The sample responses of a single fly are shown. (A) Each trace represents the mean ± S.E.M. of 9 presentations of mechanical oscillations at the stated velocity. (B) Each trace represents the mean ± S.E.M. of 13 presentations of visual oscillations at the stated velocity. L, left; R, right. Scale bars represent 0.5 s and 0.5 V in relative WBA units.

View larger version (10K): [in a new window]   Fig. 3. Halteres encode faster rotations whereas the visual system is responsive to slower rotations along all three functional axes. The mean amplitude of the sinusoid fit to averaged wingbeat amplitude (WBA) data ± S.E.M. is plotted against the peak angular velocity for visual (open circles) and mechanical (filled circles) stimuli. The amplitude of WBA modulation is plotted in relative units and represents the difference between left and right WBA for roll and yaw, and the sum of the left and right WBA for pitch. For mechanical pitch, roll, and yaw, the number of flies (N) is 9, 10 and 10, respectively. For visual pitch, roll and yaw, N=11, N=10 and N=12, respectively, except for the leftmost two data points of roll, N=7, and the leftmost datum of pitch, N=6, which were measured in a separate experiment.

View larger version (22K): [in a new window]   Fig. 4. The responses to visual and mechanical rotations are offset by 180°. Response waveforms represent averages of five presentations of mechanical and visual oscillations for one fly. The lower trace shows the angular position trajectory of the stimulus. Scale bar, 1 s. WBA, wingbeat amplitude; L, left; R, right.

View larger version (8K): [in a new window]   Fig. 5. Response to visual yaw did not vary significantly across a fourfold change in the spatial wavelength of the striped panorama. Bars indicate mean amplitude of sine fit to wingbeat amplitude (WBA) data ± S.E.M. (N=7).

View larger version (31K): [in a new window]   Fig. 6. Wingbeat amplitude (WBA, blue) and wingbeat frequency (WBF, red) are modulated independently. (A) Mean ± S.E.M. of 13 presentations of mechanical pitch for one fly. (B) Mean ± S.E.M. of 9 presentations of visual pitch for one fly. L, left; R, right.

View larger version (18K): [in a new window]   Fig. 7. On average, wingbeat frequency (WBF) is modulated independently of the wingbeat amplitude (WBA) response when presented with both visual and mechanical pitch oscillations over a range of angular velocities. (A) Amplitude of sine fit to averaged WBA data versus peak angular velocity (mean ± S.E.M., visual N=11, mechanical N=9). (B) Amplitude of sine fit to averaged WBF data versus peak angular velocity (mean ± S.E.M., visual N=11, mechanical N=9).