Geneticists produce laser-activated killer mice

Sunday, January 15, 2017

In research released on Thursday in Cell, scientists from Yale University report they managed to trigger instinctive hunting behavior in mice using optogenetics, a manner of priming cells within an organism's brain to switch on when exposed to a laser.

These experiments were performed on laboratory mice.
Image: Ciotu Cosmin.

The research team used an engineered virus to target and alter specific sets of neurons. Then they fitted the mice with intracranial optical fibers so they could expose their brains to blue light at will. The system excited two different sets of neurons, both located in the amygdala, which is the part of the brain associated with emotion and aggression. One set stimulated prey pursuit behavior, such as stalking, and the other stimulated the animal to use its jaw and neck muscles. When exposed to the laser, the primed mice would first stalk and then pounce on and bite any object in their enclosure, even objects without any food scent or prey value, like sticks and bottle caps.

"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," says lead investigator and Yale Associated Professor of Psychiatry Ivan de Araujo. The mice behaved normally at all other times.

The work was inspired by Araujo's desire to study natural feeding behavior, as opposed to animals passively munching on food pellets. The study covered many parts of the brain already known to be associated with feeding, and the results suggested some areas are associated with both hunting and feeding and others only with just one behavior. Stimulation of the periaqueductal gray (PAG) portion of the brain controlled stalking and stimulation of the reticular formation controlled biting. The researchers say this shows the amygdala is likely to control hunting and biting behavior across many or all jawed vertebrates. The experiments were funded by national research organizations in the United States and China and the government of Brazil.

The findings inspired comparisons by the research team and the press to zombies from The Walking Dead, especially since the behavior was more pronounced when the animals were hungry. Researchers noted the subjects did not attack any of the other mice. The scientists say this shows they were stimulating predatory behavior specifically and not making the animals generally more angry or aggressive.

However, the study did not state whether the laser resembled the light of a full moon.