Controlling Fruit Fly Movements With A Mind-Altering Device

Alan McStravick for – Your Universe Online

A joint collaboration between the Vienna University of Technology and US researchers, has resulted in the development of a unique and novel technique to control Drosophila melangogaster, perhaps better known as the fruit fly, via thermogenetic means. The control the researchers exert is ultimately able to be analyzed at the neural level within the brains of the insects.

Much of the work was conducted at the Information Management and Preservation Lab within the Department of Software Technology and Interactive Systems at VUT by Andrew Straw and his team. In the course of their study, they developed the FlyMAD (Fly Mind Altering Device) which targets either light or heat to a specific body region of a fly that is in motion, triggering a response. FlyMAD has allowed Straw to zero in on two specific neuronal cell types that deal with courtship behavior of the fruit fly. This is due to the fact that FlyMAD, unlike previous techniques used in this field, provides researchers with a much more highly improved temporal resolution of their subject animals.

Until FlyMAD, it was impossible to control the activity of specific neurons in moving flies. That fact had been unfortunate as the fruit fly presents a most ideal experimental system for the analysis of circuit functions within brain cells. For FlyMAD to work, the team had to utilize a subject base of genetically modified, temperature-sensitive flies.

The entire system basically consists of an enclosed box in which the flies are housed. A video camera, able to simultaneously track several flies at once, captures the motion of the flies. The flies are then subjected to targeted irradiation that effectively allows the researchers to alter neural pathways in the brain of the fly.

The infrared light used by FlyMAD causes the temperature of the targeted body region of the fly to increase to 30 degrees Celsius (approximately 86 degrees Fahrenheit) which induces a change of behavior in the animal that is not observed in the animals kept in the control temperature group. Said behavior (and the neuronal processes behind it), though occurring in mere fractions of a second, are able to be observed and recorded by the FlyMAD device. This approach, known as optogenetics, is one of the aspects that makes FlyMAD unique. Previously, optogenetics had been restricted solely to research involving mice.

As noted above, Straw and colleagues were primarily interested in studying the courtship behaviors of the fruit fly. Once the efficacy of FlyMAD was established – they were able to control flies and make them “moonwalk” – the team aimed their focus at certain specific neurons that had previously been linked to courtship behaviors in the animals, specifically their courtship song.

The experiment undertaken by the team explored how one type of neuron was almost singly tied to the act of courtship while the other was important for the action of singing. To determine this fact, the team focused a laser beam at a specific region on the male fruit fly. This action resulted in a mating attempt with a ball of wax while simultaneously vibrating their wings in such a way to create their mating song.

While this experimentation relied on either light or heat, Straw claims future studies will combine the two factors. This, he says, would allow the activation or repression of different genetic elements in one fly.

“FlyMAD offers the fantastic opportunity to address many of our questions,”stated Straw. “We could, for example, analyze how single neurons function in a cascade within the neuronal circuit.”

The results of this study, which could potentially yield new and further insight into the mammalian brain, was published online on May 25 in the journal Nature Methods.

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