Freeze or flight: it’s all in the eyes

Having two eyes is crucial to escaping danger, according to a new study conducted by an international team of researchers.

The research, published in Current Biology, shows how mice process visual information from both eyes when under threat.

According to first author of the paper, Assistant Professor Robin Broersen from Erasmus MC and The Australian National University (ANU), mice, like all animals, have a “freeze or fight” response when faced with a predator.

“In our experiment, we simulated a bird of prey attack and studied how the mice responded,” Assistant Professor Broersen said.

“We observed that mice with two eyes opted for the flight response more often, while mice with only one eye were more likely to freeze.

“Additionally, mice with two eyes escaped more quickly and effectively. This suggests that binocular vision is crucial for assessing threats and triggering the most effective survival response.”

The researchers were then able to work out how visual information from both eyes comes together in the brain.

“A region called the superior colliculus plays a key role in this process. We examined what happens in the neurons of this part of the brain when we stimulate a mouse’s eyes with flashes of light or visual patterns,” Assistant Professor Broersen said.

“We discovered that visual information from the eye travels to the superior colliculus via multiple ‘highways.’ So, the superior colliculus acts as a crossroad, where different visual pathways converge. We now also have a better understanding of how the superior colliculus integrates information from different sources.”

Humans also have a superior colliculus, but relative to the entire brain, it is much smaller than in mice.

“Despite differences between species, the superior colliculus still plays a significant role in humans,” Assistant Professor Broersen said.

“People with damage to the visual cortex—who are therefore blind—can still perceive moving objects, a phenomenon known as blindsight.”

Study co-author Felix Thomas from ANU added: “Our findings provide important insights into how the brain combines visual information to make rapid decisions.”

“This study brings science one step closer to unravelling the complex workings of the brain and how sensory information is translated into behavior. As a result, it lays the foundation for the development of new applications and therapies.”