A visually-evoked roll response in the housefly

Abstract

1. A flying, tethered housefly exhibits a turning response about its long axis when presented with a visual stimulus consisting of a rotating radial grating. This roll response is isometrically measured as a torque (Fig. 2). 2. Comparison of the dynamic characteristics of the roll response with those of the classical optomotor response reveals that similar neuronal mechanisms mediate visual stabilization of roll and yaw motions. 3. The changes of wingbeat amplitude that are elicited by a rotating radial grating are photographically measured and compared to those elicited by a vertically-moving, linear grating (Fig. 4). This data reveals that the flight mechanism generates a roll torque by creating an asymmetry in the lift-forces produced by the two wings. 4. The manner in which a fly detects and responds to roll is consistent with a scheme in which the lift produced by a given wing is controlled by the vertical component of motion seen by the ipsilateral eye (Table 1). 5. Under closed-loop conditions the flying, tethered fly exhibits a strong tendency to orient visual patterns consisting of a stripe or a linear grating along a direction perpendicular to the equatorial plane of the eyes (Figs. 5, 6).