Predatory mice

Physiologists have turned mice into zombie predators

Anna Manshina, N+1

Scientists forced mice to chase and attack prey, obeying photostimulation of the amygdala. The experiment showed the key role of the amygdala in coordinating the movements of predators. An article about the work was published in the journal Cell (Han et al., Integrated Control of Predatory Hunting by the Central Nucleus of the Amygdala).

Predators face a lot of difficult tasks – to find prey, catch up with it, keep it and eat it. The coordination of motor and sensory activity required to perform these tasks requires a complex brain structure.  

The transition to predation has thus become one of the most important stages in the development of the vertebrate nervous system. By understanding which part of the brain of modern animals is responsible for the hunting instinct, scientists will be able to better understand the evolution of the sensory-motor system.

To date, it is known that during the pursuit of prey in animals, neurons of the central nucleus of the amygdala, an area of the brain located in the temporal lobe, are activated. Also, the central nucleus of the amygdala is involved in the control of the maxillofacial system.

Based on this knowledge, the authors of the new work suggested that the central nucleus of the amygdala is involved in predatory hunting. They tested their guess on mice, omnivorous animals that prefer plant foods.

To do this, the optogenetics technique was used: a structure containing a photosensitive site was introduced into two separate sections of the central amygdala of mice. Then the amygdala neurons were stimulated with blue light through a thin optical fiber implanted in the brains of mice.

Stimulation of one site initiated the pursuit of prey.

Irradiation of the other activated the maxillofacial muscles and forced the mouse to pounce and hold the prey.

This behavior of the mouse did not depend on how full it was. Also, the "turned on" mouse hunted not only live prey, but also inedible baits – its key task was not food, but hunting. As soon as the stimulation of neurons stopped, the mouse immediately returned to normal behavior.

Stimulation of the amygdala did not affect either the appetite or aggression of the mice. They did not eat more of the plant food offered to them and did not try to attack their relatives. Their actions were limited to chasing and attacking insects and similar objects.

As a result of the experiment, scientists confirmed the hypothesis about the key role of the central nucleus of the amygdala in predation and found two separate modules that control hunting behavior in mice.

Stimulation of the PAG site of the central amygdala includes a prey pursuit module (top), stimulation of the PCRt site includes a prey capture module, activating the cervical and jaw muscles (bottom). A drawing from an article in the Cell Journal.

The authors suggest that the complication of the functions of the amygdala was closely related to the formation of a pronounced shoulder girdle, neck and maxillofacial system, which required a separate neural circuit for coordination.

Also, one of the authors of the work admitted that a similar stimulation of the amygdala can trigger a hunting instinct that is not consciously controlled, including in humans.

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16.01.2017