MIAMI/BRUSSELS - US scientists have ramped up predatory behavior in mice by stimulating a region of the brain known for its role in emotions like fear and pleasure, according to a study published Thursday.

The experiment turned the lab mice into super-eating machines, vigorously attacking food, bottle caps, and sticks as prey, said the findings in the journal Cell.

However, scientists cautioned that their goal was not to create an army of killer mice.

Rather, it was to better understand how the brain works and perhaps one day improve the treatment of degenerative brain diseases that affect motion and coordination.

“A major issue for neuroscientists is how the brain figures out how to respond appropriately to objects in the world,” lead author Ivan de Araujo, associate professor of psychiatry at the Yale University School of Medicine, told AFP.

“Predatory behavior is the perfect model. It is a great window into how the brain solves the problem of how we respond to external stimuli by moving our bodies in an appropriate way.”

Mice are omnivores, and will eat fruit, vegetables, insects and meat. They are natural hunters, even though they are more often thought of as prey for larger creatures like snakes, hawks and cats. Researchers decided to see how mice’s behavior would change if certain neurons were stimulated using a process called optogenetics, which is also being experimented with to restore muscle movement in people who have been paralyzed, and to treat those with epilepsy or Parkinson’s disease.

Using an implantable brain device and a laser to activate certain neurons in the part of the brain known as the amygdala, researchers found two different pathways to changing a lab mouse’s behavior - one that triggered the animal’s pursuit of prey, and another that signaled it to bite and kill. “We could make them more efficient hunters in the sense that they would spend less time to be able to capture live prey and subdue it and kill it,” said Araujo. “Perhaps more strikingly, when we used a bug made of plastic that was moving around the cage, we could make the animals pursue an object that they would normally avoid,” he added. “We triggered the behavior toward objects that were not live prey.”

Meanwhile, the unstoppable rise of robots in our everyday lives requires urgent EU rules such as “kill switches”, European Parliament members warned Thursday as they passed a resolution urging Brussels into action on automaton ethics. Mady Delvaux, a Socialist MEP from Luxembourg, led the campaign and warned that Europe is passively standing by as robots take an increasingly powerful role that will grow even stronger with the emergence of driverless cars.


The amygdala is an almond-sized region of the temporal lobe known for its role in emotions like fear and pleasure, as well as motivation and survival instincts.

However, researchers also noted that when other mice were included in the experiments, they did not attack each other.

“I wouldn’t like people to think that this could be used for generating aggression,” Araujo said.

“In fact, I don’t think this is actually possible. I think the behavior is very specific to looking for food. They showed no interest in attacking things that are as large as they, or other mice.”

The brain stimulation only worked under the control of lab technicians, and if any of the mice were to escape, they would likely soon become another animal’s meal, he said.

“We are uncovering brain areas that weren’t known before to have a direct relationship to muscle activity,” explained Araujo.

“Over the long term, I expect this would help us understand why motor disease and degeneration affect mastication (chewing) and swallowing, which are very traumatic effects of motor diseases in people.”

Asked for comment on the study, psychiatrist Monica Michell of Lenox Hill Hospital in New York said what is new about the research is how it delineates the exact pathways for predatory behavior, and that its location is in the amygdala was “not all that surprising.”

“Anybody who has a dog knows that no matter how well-fed they are, if they see a squirrel they will run,” she said.

“In terms of humans, it sort of confirms what we have been believing for a while - that the amygdala is involved in emotions and that aggressive behavior is hard-wired and part of our makeup.”


To encourage EU action, Delvaux tabled a resolution at the European Parliament that also includes the need for an EU agency specialised in dealing with artificial intelligence.

Once passed, Delvaux’s resolution could force the European Commission, the EU’s executive arm, to begin work on laws that deal with these issues head-on.

“A growing number of areas of our daily lives are increasingly affected by robotics,” Delvaux said after a committee vote on her measure.

“In order... to ensure that robots are and will remain in the service of humans, we urgently need to create a robust European legal framework,” she said.

Delvaux’s resolution was easily passed by the European Parliament’s legal affairs committee on Wednesday and now faces a plenary vote, probably in February.

Her report is a broad overview on how robots are creeping into the lives of humans and what the EU can do to stay in control.

Its recommendations are wide-ranging, including the kill switch allowing humans to shut down a robot at the smallest sign of danger.

- ‘Apocalyptic scenario’ -

Without such rules, “humanity could face the apocalyptic scenario where robots turn on their human masters,” Delvaux warned in an interview with EU affairs website EurActiv.

Delavaux also warned that robots cannot be your friend, no matter how emotionally involving they may become.

“We always have to remind people that robots are not human and will never be. Although they might appear to show empathy, they cannot feel it,” she added.

The report recommends an EU agency for robotics to oversee all European regulation involving robots, like the bloc already has for food safety or aviation.

Most urgently, the report demands that the EU draw up a legal framework for driverless cars.

Auto builders want to see robotic cars on the roads by 2020, but difficult questions remain on who would be legally liable in the case of a car crash.

“If all decisions of a machine are no longer directly attributable to the actions of a person, it must be clarified who is liable if something goes wrong,” said Greens MEP Julia Reda, who backed the report.

To fill this void, the MEPs called for an obligatory insurance scheme and a fund to ensure victims are fully compensated in cases of accidents.

The report also called for the EU to find ways to help the millions of workers who will inevitably lose their jobs as industries become increasingly automated.