A laser beam can alter a fly’s behavior and make it mate with just about anything — even a ball of wax, according to scientists at the Howard Hughes Medical Institute. The researchers have developed an experiment which involves shining an infrared laser directly at the head of a fly whose brain has been altered using heat-activated proteins. This alteration allows the laser, dubbed the "Fly Mind-Altering Device" (FlyMAD), to activate specific neurons involved in mating.

In the experiment, turning on FlyMAD caused a fly to suddenly "court" the closest object in its vicinity — in this case, a ball of wax — by circling it and vibrating its wings. The resulting behavioral modification was so strong that it persisted for about 15 minutes after the laser was turned off. This technique resembles previous attempts to control mouse neurons, and therefore mice themselves, using light. But the light method, called optogenetics, isn’t suitable for flies because light can’t penetrate exoskeletons, and a fly’s head is too small to accommodate the type of fibre-optic cables that scientists implant in mouse brains.

It persisted for about 15 minutes after the laser was turned off

The researchers would eventually like to see if they can determine what happens when two neurons with opposing effects are activated simultaneously. This could mean activating a neuron that makes a fly walk backward as well as a neuron that makes it move forward, the scientists say. Such an experiment could eventually help us understand, and perhaps even map, the neuronal hierarchy that governs our own brains and decision-making processes — in addition to making these flies feel just a little bit crazy.