This laser turns us *on*.

At least if we’re flies, it does. Nature has more on the laser beam that puts flies in the mood for love:

Optogenetics — triggering neurons with light — has been successful in mice but has not been pursued much in flies, says Barry Dickson, a neuroscientist at the Howard Hughes Medical Institute’s Janelia Farm Research Campus in Ashburn, Virginia. A fibre-optic cable embedded in a mouse’s brain can deliver light to cells genetically engineered to make light-activated proteins, but flies are too small for these fibre optics. Neither will these cells be activated when the flies are put into an illuminated box, because most wavelengths of visible light cannot penetrate a fly’s exoskeleton.

So Dickson’s lab has developed a system called the Fly Mind-Altering Device (FlyMAD), which uses a video camera to track the fly as it moves around in a box. The device then shines an infrared laser at the fly to deliver heat directly to the head.

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…. 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.