The house mouse is a relatively benign animal, feeding almost entirely on plant matter. Its scientific counterpart, the laboratory mouse, is even more so, dieting on nutritive food pellets. But tickle a specific part of its brain, and this humble rodent instantly transforms into a predatory killer.

When Ivan Eid Tavares de Araujo, an Associate Professor of Psychiatry and of Cellular and Molecular Physiology at Yale University, uncovered this fascinating neurological quirk, he wasn't aiming to create a murderous army of super mice. Rather, he was merely curious about the neural mechanisms underlying feeding behaviors in animals. A study published in 2005 pointed to a specific location in the brain that's highly active when hunting prey: the central nucleus of the amygdala. de Araujo hypothesized that manipulating this brain region in mice could produce some fascinating behaviors.

His educated hunch proved to be correct.

de Araujo and his team used optogenetics, a technique that employs laser light to activate specific neurons, to stimulate the central nucleus of the amygdala in lab mice. Upon stimulation, mice attacked and attempted to eat anything in their cages, including wood sticks, bottle caps, tape rolls, tiny robots, and live crickets. They did leave other mice alone, however. When the experimenters switched off the laser light, mice abruptly ceased their attacks.

A subsequent experiment utilizing chemical stimulation narrowed down the mice' behavior to two specific sets of neurons in the central nucleus of the amygdala (see figure above). The periaqueductal gray area (PAG) controlled the decision to pursue prey, while the reticular formation (PCRt) regulated the muscles involved in grabbing and biting prey.

There are actually two amygdalae in the brains of complex vertebrates, and they are commonly linked to emotional reactions and fear response. The present research hints that the amygdalae also oversee more precise behaviors.

"Our findings imply the central amygdala as a modular command system for predatory hunting," de Araujo and his team write.

The research was published January 12th to the journal Cell.

Source: Han et al., "Integrated Control of Predatory Hunting by the Central Nucleus of the Amygdala", Cell (2017), http://dx.doi.org/10.1016/j.cell.2016.12.027