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First published online August 31, 2007
Journal of Experimental Biology 210, 3218-3227 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.007807

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The spatial, temporal and contrast properties of expansion and rotation flight optomotor responses in Drosophila

Brian J. Duistermars, Dawnis M. Chow, Michael Condro and Mark A. Frye^*

Department of Physiological Science, University of California, Los Angeles, CA 90095-1606, USA

View larger version (22K): [in this window] [in a new window]   Fig. 1. Experimental apparatus. (A) A digital flight simulator comprises a wrap-around cylinder of light emitting diodes (LED). An infrared (IR) beam casts a shadow of the tethered fly's two wings on an optoelectronic sensor that measures instantaneous changes in right and left wing beat amplitude and frequency in response to image motion. (B) Panoramic patterns of vertical stripes move horizontally to elicit compensatory optomotor steering responses. Visual expansion (bottom) differs from visual rotation (top) only in the direction of motion across the rear field of view.

View larger version (47K): [in this window] [in a new window]   Fig. 2. Optomotor steering responses to panoramic image motion. (A) Example response to a test expansion (Exp) and rotation (Rot) stimulus. In response to expansion from the left, the amplitude of the right wing beat decreases while the amplitude of the left increases. As such left minus right amplitude (WBA) increases in response to both stimuli, but with varying amplitude. Between test periods, the fly has active control of a single vertical stripe. (B,C) Mean responses to systematic variation in the spatial period (B) and velocity of pattern motion (C). Solid line, mean time-averaged responses; gray envelope, s.e.m.; N=36 flies. Red segments, 3-s open-loop expansion test periods; blue segments, rotation tests; black segments, intervening 5-s closed-loop control periods. Each row shows mean responses to striped grating spatial period as indicated. WBA, (L–R, V) refers to left minus right wing beat amplitude encoded in V. The time-varying voltage signal is directly proportional to yaw torque.

View larger version (19K): [in this window] [in a new window]   Fig. 3. Temporal frequency tuning curves for expansion and rotation optomotor responses. Responses to different spatial wavelengths are pooled. Values are means ± s.e.m. for N=36 flies. A Gaussian waveform (to facilitate visual comparison only) is plotted in both panels and is shifted downward 20% for the rotation plot. Maximum WBA (R/Rmax) refers to the peak left minus right wingbeat amplitude response (R), divided by the maximum response in the trial (Rmax).

View larger version (19K): [in this window] [in a new window]   Fig. 4. Tuning curves for spatial wavelength over velocity for expansion and rotation optomotor responses. Data are fitted with shape-preserving interpolant functions (piecewise cubic polynomial) to facilitate visual comparison.

View larger version (40K): [in this window] [in a new window]   Fig. 5. Optomotor responses vary with the vertical extent of pattern motion. (A) Diagram of visual stimuli. Top row: stimuli used to find the vertical location of the strongest sensitivity to horizontally moving stripe patterns. Bottom row: representations of stimuli that vary in vertical stimulus extent. (B) Response magnitude for a single pixel row of expansion stimuli plotted against the vertical location of the row in the arena, indicating maximum sensitivity in the middle of the arena, where the fly is positioned. (C) Mean response waveforms to visual expansion (top) and visual rotation (bottom) that vary for the vertical extent of image motion (color coded). Insets indicate responses to motion restricted to only the front or rear 180° of the cylindrical arena. (D) Steady-state response amplitude of the waveforms indicated in C for N=50 flies.

View larger version (21K): [in this window] [in a new window]   Fig. 6. Mean time course of responses to 1 pixel image displacements (3.75°) at 2 steps s–1. Each waveform represents the mean response for N=36 flies at the color-coded spatial wavelength.

View larger version (19K): [in this window] [in a new window]   Fig. 7. Optomotor responses vary with image contrast. (A) Mean responses for N=30 flies indicated for an unadapted treatment; flies had no prior exposure to the test stimulus. (B) Mean responses for N=40 flies indicated for a `same-contrast adapted' treatment; flies were presented with the test pattern contrast for 7 s prior to the open-loop test (see Materials and methods). Data are fit with the sigmoid function indicated. The three function variables were identified with a non-linear least-squares optimization algorithm (see Materials and methods). Within-subject design obviates the need for error bars. Variance across animals was similar to that of Fig. 2.

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