Elements of Feed-Forward and Feedback Control in Drosophila Body Saccades

Author: Bender, John Andrew

Year: 2007

Degree: Dissertation (Ph.D.)

Advisor: Dickinson, Michael H.

Committee Members: Laurent, Gilles J.; Dickinson, Michael H.; Murray, Richard M.; Siapas, Athanassios G.

Option: Biology

Abstract

I have developed a new experimental preparation of the fruit fly, Drosophila melanogaster. A fly is glued to a steel pin, which is held in the field between two magnets such that the fly is free to rotate about only one axis. Such "magnetically tethered" flies perform rapid yaw turns, similar to the behaviors termed "body saccades" in free flight. Saccades can be evoked by visual stimulation, in a manner suggesting that the underlying neural circuitry may be performing an angular threshold calculation. Once a saccade is initiated, however, visual feedback has very little effect on its dynamics, but rotational feedback from the haltere system plays an important role in structuring the time course of saccades. Vision is important, though, in maintaining a stable orientation in both intact flies and flies with asymmetrical wing alterations. The halteres are known to mediate responses to Coriolis forces correlated with the fly's rotations in flight, but flies with modified halteres also exhibit distorted saccade dynamics when they are not free to rotate. This suggests that the halteres may be involved in saccade initiation, although the precise mechanisms are not clear. There is preliminary evidence suggesting that the haltere strokes may be actively modulated during flight.

Files

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