IVAN DE ARAUJONeural circuits in the amygdala are responsible for predatory behavior in mice, according to a study published January 12 in Cell. Using optogenetics, a technique that uses light to turn neural circuits on and off, a group of researchers led by neuroscientist Ivan de Araujo of Yale University was able to turn docile mice into ruthless hunters.

Earlier research revealed that the amygdala, an almond-shaped brain structure most commonly linked to fear, was active when rats were hunting and feeding. To see whether this brain region was actually controlling predatory behavior, Araujo and colleagues decided to use optogenetics to selectively activate specific neurons in mice, with light.

When the researchers activated the amygdala, docile mice attacked everything from bottle caps to live insects. Even when there was no prey in sight, the mice displayed feeding behavior—moving their jaws and lifted their paws as if holding a...