Flies in the flight simulator

Written by Thomas Hesselberg

Friday, 10 August 2007

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Flies in the flight simulator
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A schematic drawing of the flight simulator with a fly tethered in the centre and the infra-red light coming from above. Below the fly is the infra-red sensitive mask, which from the wing shadow determines wing beat amplitude and frequency.

The LED screen is controlled by a computer, which can be programmed to show different patterns in the flies’ field of view. If, for instance, a random pattern of white and black dots which rotate clockwise are shown to the flies, they will continuously attempt to turn counter-clockwise despite being prevented from physically rotating. If on the other hand a single black stripe is shown they will for the majority of time attempt to maintain the stripe right in front of them. This behaviour is a bit more difficult to explain as a natural behaviour although it is also found in free flying flies. The flies are perhaps attracted to the stripe, because they in nature ensure they fly in the same direction by orientating towards distant and conspicuous objects in their surroundings such as trees.

Virtual reality for fruit flies
It is possible to study the behaviour of the flies in the flight simulator in two different situations. The stripe or the pattern can be pre-programmed to move in a certain independent of the fly’s behaviour (a so-called open-loop situation) or the movement of the pattern can be determined by the behaviour of the fly (a so-called closed-loop situation). The latter is what we expect from a true flight simulator, which places the fly in a kind of virtual reality. The fly can control the pattern in the flight simulator in the same way in which it turns during free flight i.e. by asymmetric differences between the right and the left wing beat amplitude. The difference in wing beat amplitude is fed into a computer which uses the magnitude to determine the rotation of the pattern in the arena. Despite the unnatural conditions in the flight simulator, the majority of flies can control the pattern within a few seconds after being introduced to the flight simulator.

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