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First published online November 24, 2003
Journal of Experimental Biology 207, 133-142 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00731

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Summation of visual and mechanosensory feedback in Drosophila flight control

Alana Sherman¹ and Michael H. Dickinson^2,*

¹ UCB/UCSF Joint Bioengineering Graduate Group, University of California, Berkeley, CA 94720, USA
² Bioengineering, California Institute of Technology, Pasadena, CA 91125, USA

View larger version (14K): [in a new window]   Fig. 1. (A) Cartoon of fly showing the compound eyes and mechanosensory halteres. (B) The flight simulator, which delivers visual and mechanosensory stimuli, is composed of a wrap-around light-emitting diode (LED) display mounted within a 3 degrees-of-freedom rotational gimbal. The fly is mounted in the center of the display, above a sensor that measures the left and right wingbeat amplitudes. (C) Moving striped patterns simulate the optic flow generated when the fly rotates along the roll and pitch axes.

View larger version (34K): [in a new window]   Fig. 2. Flies respond to mechanical, visual and concurrent oscillations with sinusoidal modulations of wingbeat amplitude. Rotational stimuli were applied around the roll axis. Each trace represents the time-averaged response to six trials for a single fly. (A) Concurrent visual and mechanical oscillations phase shifted by 180° elicit strong responses (Rm+v) that are approximately equal to the sum of the responses to each stimuli presented separately (Rm+Rv). (B) When visual and mechanical stimuli are presented with a 0° phase offset, flies display almost no response. (C) At a 270° phase offset, responses are intermediate in amplitude. L, left; R, right; , phase offset; , position. Wingbeat amplitude (WBA) is plotted in normalized units.

View larger version (16K): [in a new window]   Fig. 3. The magnitude of the wingbeat responses to concurrent oscillations about the pitch (A) and roll (B) axes is a function of the phase offset between mechanical and visual stimuli. (A) Pitch axis responses (mean ± S.E.M., N=10 flies). (B) Roll axis responses (mean ± S.E.M., N=14 flies). The amplitude of the sine fits to wingbeat data (Rm+v; green circles) are plotted against phase offset (). In addition, two possible fits for the data are plotted: linear summation (Rm+Rv; black curve) and scaled summation (Rm+ßRv; red curve). The two fitted functions are 4th order polynomials.

View larger version (14K): [in a new window]   Fig. 4. The attenuation of visually elicited motor responses is not a linear function of the magnitude of haltere stimulation. With set to 1, the scaling factor ß was calculated for multiple flies during concurrent oscillations in which the amplitude of the visual stimulus was fixed at 30° and the amplitude of the mechanical stimulus (u) was varied. (A) ß (mean ± S.E.M.) versus u for three phase relationships (): 180°, 270° and 90° (N=8, 9 and 9 flies, respectively). (B) Amplitude of sine fit to time-averaged wingbeat responses versus u for =180°, 270° and 90° (N=8, 9 and 9, respectively). Data fit by weighted sum (spline approximation of the fit), Rm+ßRv, with =1.17 and ß=0.65.

View larger version (16K): [in a new window]   Fig. 5. Responses to mechanical and visual oscillations about orthogonal axes have both a pitch and roll component. (A) The wingbeat response to mechanical pitch (Rm), visual roll (Rv) and the two stimuli concurrently (Rm+v) of a single fly. Each trace represents the time-averaged response to 21 trials of each stimulus. (B) Magnitude of roll and pitch components in response to simultaneous visual roll and mechanical pitch (mean ± S.E.M., N=10 flies). (C) Responses to visual pitch and mechanical roll (mean ± S.E.M., N=13 flies). The y-axis represents normalized wingbeat amplitude (WBA) units.

View larger version (16K): [in a new window]   Fig. 6. Input from the halteres and visual system are combined in a weighted sum by the flight control system. The weighting of the visual feedback is dependent on the presence of haltere input but appears to be constant over a wide range of haltere stimulation. The processing of each sensory input is represented by a transfer function based on our previous frequency response analysis. G, gain; , angular velocity.

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