FIG. 1. Saccades are sharp, right angles turn elicited by visual expansion. (A) Flight trajectory of fruit fly seen from above. (B) Definition of saccade angle and approach angle. (C) Relationship between approach angle and saccade angle. Histogram of saccade amplitude shows that flies turn either left or right. (D) Experiments in tethered flight arena confirm the role of visual expansion in saccade initiation. See text for details. Modified from Tammero and Dickinson (2002a
, b)
FIG. 2. Organization and function of flight muscles. (A) Powerful indirect flight muscles (IFMs) are arranged in two antagonistic groups. Tiny steering muscles insert directly at the base of the wing hinge. (B) The IFMs drive the gross pattern of wing motion. (C) Changes in recruitment and firing phase of steering muscles produce subtle changes in the wingstroke. Modified from (Dickinson and Tu, 1997b)
FIG. 3. Haltere-mediated flight reflexes. (A) Simplified diagram of flight control circuits. Descending visual input is thought to converge with mechanosensory input from wing and haltere on motor neurons of steering muscles such as b1. (B) In Calliphora, input from wing mechanoreceptors can repetitively drive spiking in the b1 motor neuron. When active, haltere input can over-ride the wing input, advancing the phase of the motor neuron. Modified from (Fayyazuddin and Dickinson, 1999). (C) Mechanical rotation, encoded in part by the halteres, elicits compensatory changes in stroke amplitude. Modified from (Dickinson, 1997)
FIG. 4. Kinematics and dynamics of saccade. (A) Changes in body motion during saccade. (B) Wing motion and resultant forces during hovering. Mean flight force during hovering indicated on fly at right. (C) Torque, velocity, and acceleration about the yaw axis during saccade. (D) Wing patterns generating low and high yaw torque. Data modified from (Fry et al., 2003)
FIG. 5. Schematic model of saccade. See text for details.
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