Researchers call it the Fly Mind-Altering Device (aka "FlyMAD"), and to demonstrate the system's effectiveness, they've shown that firing a laser at the head of a fly can compel it to flirt, and attempt to copulate, with a ball of wax. (Come on. You know you want to watch this.)
Photo Credit: Alex Wild | A female D. melanogaster, and one bearing a white- rather than TRPA1-mutation, but a beautiful photograph
FlyMAD works by tracking a fly's movement and firing an infrared laser directly at its head. The heat from the laser triggers neural circuits in the fly's brain that have been genetically engineered to activate when heated. Conceptually, the technique is similar to optogenetics (which triggers neurons with light), but while optogenetics has been successfully demonstrated in mice, it's proven difficult to implement in flies, whose heads are too small to accommodate the fibre-optic cables necessary to deliver light to the brain.
Heat activation can be engineered into neural circuits by outfitting them with a heat-sensitive protein called TRPA1. Previous studies have studied how fly behavior can be altered by adding TRPA1 to neural circuits involved in mating. When TRPA1 flies are placed in a hot box, the neurons are activated, and the flies get randy.
But triggering neurons with a hot box can be slow-going, and that's why researchers led by HHMI Janelia Farms neuroscientist Barry Dickson – in collaboration researchers Dan Bath, John Stowers, Dorothea Hörmann and Andrew Straw – developed FlyMAD. FlyMAD's laser channels heat quickly and directly to the flies' heads, allowing them to trigger behavioral changes almost immediately. Nature News' Sara Reardon explains the video demonstrating the technique featured above:
As proof that the FlyMAD works, the group made flies with TRPA1 in a neural circuit involved in courtship. When the researchers activated the TRPA1 neurons with the laser, the fly began trying to mate with a ball of wax, circling it and 'singing' by vibrating its wings (see 'Laser love'). The fly continued courting for about fifteen minutes after the laser was shut off, suggesting that the heat had triggered a lasting, complex behavioural state. The researchers also made flies with TRPA1 in neurons involved in muscular coordination. Switching the laser on instantly made the flies walk backwards. They immediately stopped when it was switched off.
Dickson's group is in the process of submitting its work to peer-reviewed journals, so we'll have more details on FlyMAD when the publication lands. Until then, you can read more over at Nature News.