Harvard researchers found that the mice have a visual alarm system that is activated in the event of danger, and is aimed at the detection of predators.
The photoreceptors of the retina associated with ganglionic nerve cells. Ganglion cells collect information from the photoreceptors and transmit it to the brain. The smaller the associated photoreceptor, the worse the sensitivity, but the brain is formed by a sharper image. The density of cells in the retina is not uniform: in some areas is particularly high, and the picture to be treated, these portions have the greatest resolution.
In many animals, in particular humans, such accumulations ganglion neurons operate in conjunction with the entire retina and disabled during sleep. Some animals, such as mice, areas of high density of ganglion cells, by contrast, are usually found in an inactive state and are included in an emergency, when an individual is threatened.
For rodents, the main source of danger are birds of prey. When the mouse over the flying silhouette appears, in her retina immediately wake up clusters of ganglion neurons and begin to capture all traffic predator threatening the life of the individual. Thus, the high-resolution plots of mice retina play a role in the risk of air detector. The researchers note that these neurons are active only work when the bird of prey are at the center of the field of view. Rather, it tells the mouse that she was discovered and is now attacked. Through this visual indicator mice manage to find their way around and hide from predators.
In fact, rodents react not so much on the silhouette of some birds, as any moving background objects. Scientists have noticed an interesting feature: the closer a bird of prey, the nerve cells that are responsible for its detection are disabled. Apparently, at some point it becomes apparent that the mouse will not be able to graze, so that in the future the alarm about the dangers of simply makes no sense, that is, most likely, evolution has refused to further develop and improve this visual alarm system.