A team of scientists from Yale University were able to increase aggressive and predatory behaviors in mice by stimulating their brains. The mice did not attack each other but chased and bit other moving objects, including crickets. The details are in a paper that was just published in the journal Cell.
A major evolutionary event right before the Cambrian period, half a billion years ago, led to the evolution of many predatory animal species. The evolution of predators is thought to be the event that gave jawed vertebrates an edge, allowing them to proliferate throughout the Cambrian period. The actual brain mechanisms that control predatory urges and behaviors are mostly unknown.
The researchers first pulled data from a previous study that had resulted in a mouse brain map. The map showed which regions controlled feeding and hunting behaviors. The research team focused on the hunting region, which was located in the central nucleus of the amygdala. The amygdala helps process memories while controlling both emotional responses and decision-making. The team stimulated this region in laboratory mice to see how it affected their behavior. They found two pathways—one caused mice to chase prey and the other set of neurons controlled killing behaviors. When these neurons were stimulated, docile mice began to actively hunt moving toys, lasers, sticks, bottle caps, and even live crickets. If only the pathway associated with prey pursuit was stimulated, the mice would chase the prey items but not kill them. It took the simulation of both sets of neurons to produce mice that would chase, catch, and kill prey.
The team’s findings show that there are specific parts of the brain that can trigger predatory behaviors in mice—neural pathways that are most likely shared with other animals. These pathways do not simply lead to aggression; the mice did not become aggressive towards their cagemates. The research team is continuing their study to learn the mechanisms behind the triggering of chasing and biting behaviors in mice.
Han et al. Integrated Control of Predatory Hunting by the Central Nucleus of the Amygdala. Cell (2017).