Scientists switch on predatory kill instinct in mice

January 12, 2017, Cell Press
A mouse demonstrating instinctual predatory behavior with a cricket. Credit: Ivan de Araujo

Researchers at Yale University have isolated the brain circuitry that coordinates predatory hunting, according to a study in the January 12 issue of Cell. One set of neurons in the amygdala, the brain's center of emotion and motivation, cues the animal to pursue prey. Another set signals the animal to use its jaw and neck muscles to bite and kill.

The researchers used optogenetics, a means of engineering specific neurons to fire upon light stimulation, to isolate and selectively activate each set of neurons. 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," says lead investigator Ivan de Araujo, Associate Professor of Psychiatry at the Yale University School of Medicine and an Associate Fellow at the John B. Pierce Laboratory.

The Walking Dead analogy is fair only to a certain extent, says de Araujo. In nature, predatory hunting takes the form of highly complex behaviors that are common to most jawed vertebrates, including humans. "It is a major evolutionarily player in shaping the brain," says de Araujo. "There must be some primordial subcortical pathway that connects sensory input to the movement of the jaw and the biting."

The animals did not, however, attack other mice in the cage. Hunger also affected predatory behavior. Hungry mice more aggressively pursued prey during light stimulation than mice that were not hungry. "The system is not just generalized aggression," says de Araujo. "It seems to be related to the animal's interest in obtaining food."

A mouse demonstrating instinctual predatory behavior with a cricket. Credit: Ivan de Araujo

The study grew out of de Araujo's efforts to understand the neural mechanisms underlying feeding behaviors in animals. His lab had been looking at mice living and eating in cages. "They have nothing else to do other than eat the pellets we throw in the cage," he says. "I began to wonder how natural and relevant this behavior is."

De Araujo's interest in more natural behaviors pointed him to a study that had mapped brain areas associated with hunting and feeding. Many areas were listed, but one responded almost exclusively to hunting and not to eating. That region, the central nucleus of the amygdala, also had projections that were linked to areas that control hunting muscles, such as the jaw and neck. "This area was perfectly compatible with an activation system that drives the motor behavior associated with hunting," he says.

By selectively manipulating the different types of neurons in this region, they found that one set of neurons controlled pursuit, and another controlled the kill. Experiments involved inanimate stand-ins for prey, such as sticks and bottle caps and animate bug-like toys, as well as live insects.

The researchers also specifically lesioned each type of neuron. They found that, if they lesioned the neurons associated with biting and killing, the animals would pursue the prey but could not kill. The biting force of the jaw was decreased by 50 percent. "They fail to deliver the killing bite," says 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," says de Araujo.

Explore further: Why binge drinking cause binge eating

More information: Cell, Han et al.: "Integrated Control of Predatory Hunting by the Central Nucleus of the Amygdala." www.cell.com/cell/fulltext/S0092-8674(16)31743-3 , DOI: 10.1016/j.cell.2016.12.027

Related Stories

Why binge drinking cause binge eating

January 11, 2017

(Medical Xpress)—A team of researchers affiliated with several institutions in the U.K. has found what they believe is the reason why consumption of alcohol leads to hunger pangs and excessive eating. In their paper published ...

Team deciphers sugar's siren song

January 25, 2016

Sugar's sweetness and calorie content combine to give it lethal power to destroy diets, many scientists have assumed. However, new study by Yale University researchers says the brain responds to taste and calorie counts in ...

When neurons are 'born' impacts olfactory behavior in mice

December 7, 2016

New research from North Carolina State University shows that neurons generated at different life stages in mice can impact aspects of their olfactory sense and behavior. The work could have implications for our understanding ...

Recommended for you

Houseplants could one day monitor home health

July 20, 2018

In a perspective published in the July 20 issue of Science, Neal Stewart and his University of Tennessee coauthors explore the future of houseplants as aesthetically pleasing and functional sirens of home health.

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

betterexists
5 / 5 (1) Jan 16, 2017
Just Make Goat To Attack Rat !
Nik_2213
not rated yet Jan 20, 2017
humour:
One of the tabby cats sprawled across my desk opened an eye, peered at predatory mouse piccy, flicked tail and went back to sleep.
#Google-translated, "Bring them on..."
/humour

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.