Rats move their eyes in opposite directions in both the horizontal and the vertical plane when running around. Each eye moves in a different direction, depending on the change in the animal’s head position,  according to a behavioral tracking study that used miniaturized high-speed cameras.


An analysis of both eyes’ field of view found that the eye movements exclude the possibility that rats fuse the visual information into a single image like humans do. Instead, the eyes move in such a way that enables the space above them to be permanently in view – presumably an adaptation to help them deal with the major threat from predatory birds that rodents face in their natural environment.


Rats process visual information from their eyes similar to other mammals but, unlike human eyes, the eyes of rats can move in opposite directions. Credit: MPI for Biological Cybernetics/ Kerr

A research team from the Max Planck Institute for Biological Cybernetics have observed and characterized the eye movements of freely moving rats. They fitted minuscule cameras weighing only about one gram to the animals’ heads, which could record the lightning-fast eye movements with great precision. The scientists also used another new method to measure the position and direction of the head, enabling them to reconstruct the rats’ exact line of view at any given time.

Although rats process visual information from their eyes through very similar brain pathways to other mammals, their eyes evidently move in a totally different way. “Humans move their eyes in a very stereotypical way for both counteracting head movements and searching around. Both our eyes move together and always follow the same object. In rats, on the other hand, the eyes generally move in opposite directions,” explains Jason Kerr from the Max Planck Institute.

In a series of behavioral experiments, the neurobiologists also discovered that the eye movements largely depend on the position of the animal’s head. “When the head points downward, the eyes move back, away from the tip of the nose. When the rat lifts its head, the eyes look forward: cross-eyed, so to speak. If the animal puts its head on one side, the eye on the lower side moves up and the other eye moves down.” says Kerr.


Citation: Rats maintain an overhead binocular field at the expense of constant fusion
Damian J.Wallace, David S. Greenberg, Juergen Sawinski, Stefanie Rulla, Giuseppe Notaro,&Jason N. D. Kerr ,, Nature, online May 26, 2013: doi:10.1038/nature12153