Brain cells that may turn normal mice into The Walking Dead-style zombie killers have been found and successfully activated in lab experiments, according to a new study published this week.
One set of the cells, found in the brain's center of emotion and motivation called amygdala, is responsible for prey pursuit, while another set is responsible for controlling the kill, said the study, which appeared in the U.S. journal Cell.
Researchers from the U.S., China and Brazil used optogenetics, a means of stimulating specific brain cells with laser light, to isolate and selectively activate each set of these cells.
When the laser is off, the animals behave normally. But turn the laser on, and the mice take on qualities of "walkers" from The Walking Dead, pursuing and biting almost anything in their path, including bottle caps and wood sticks.
"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 at the Yale University.
The Walking Dead analogy is fair only to a certain extent since the animals did not attack other mice in the cage, said de Araujo.
Hunger also affected predatory behavior as hungry mice more aggressively pursued prey during light stimulation than mice that were not hungry.
"The system is not just generalized aggression," said de Araujo. "It seems to be related to the animal's interest in obtaining food."
The researchers also specifically lesioned brain cells associated with biting and killing and found this would lead the animals to pursue the prey but could not kill.
Furthermore, the biting force of the jaw was decreased by 50 percent. "They fail to deliver the killing bite," said de Araujo.
The team is now exploring the sensory input into the amygdala to determine what triggers predatory behaviors and investigating how the two modules -- one controlling pursuit and the other controlling the kill -- are coordinated.
"We now have a grip on their anatomical identities, so we hope we can manipulate them even more precisely in the future," said de Araujo.
