Imagine the scene. An elite team of superheroes is closing in on the evil scientist to put an end to his ne'er-do-well ways. Just as they're about to deliver the final clobber, said scientist activates his laser ray and, as it passes over crates of mice they suddenly go berserk and attack our heroes, letting Dr. Dastardly get away. While this scenario might be a bit farfetched, scientists at Yale University have indeed created mice that can have their hunt and kill behaviors triggered with a simple blast from a laser beam.
To be fair, the research wasn't carried out to create an army of menacing superhero-fighting mice. It was to study the predatory instinct in animals through the science of optogenetics – triggering neuronal activity in the brain by hitting cells with light. Thus far the technique has been experimented with to deliver drugs deep inside the brain; reverse blindness and control pain.
In this particular study, the researchers stimulated neurons in the amygdala section of the brain using a laser, and found that one set of the nerves produced a predatory instinct while another triggered the jaw muscles, causing a biting gesture.
"We'd turn the laser on and they'd jump on an object, hold it with their paws and intensively bite it as if they were trying to capture and kill it," said lead investigator Ivan de Araujo, associate professor of psychiatry at the Yale University School of Medicine.
The researchers said the neuronal stimulation led the mice to chew nearly everything in their path – including bottle caps, sticks, bug-like toys and live insects – although they did not attack the other mice in the cages. When the mice were hungrier, they were more aggressive.
"The system is not just generalized aggression," says de Araujo. "It seems to be related to the animal's interest in obtaining food."
To further test out their findings, the researchers applied lesions to the neurons associated with biting and saw that the force of the animal's jaws were decreased by 50 percent, making it impossible for them to kill their prey.
These prey-related sections of the amygdala are found in nearly all vertebrates, but are absent in other species like the jawless lamprey fish, making the study of this brain area interesting from an evolutionary standpoint.
De Araujo and his team are now further researching how the pursuit and kill section of the amygdala coordinate with one another. "We now have a grip on their anatomical identities, so we hope we can manipulate them even more precisely in the future," he said.
So who knows, maybe laser-controlled killer mice aren't really all that far off.
The work of the Yale team has been published in the journal Cell.