The eyes have their own version of night vision


In order to have the ability to see at night the photosensitive cells of the retina change completely. Retinal circuits that were considered unchanged and programmed for specific tasks adapt to different light conditions, says Duke University researchers.

"To see the night had to adapt to the limit of an elementary particle, a photon," said Greg Field, professor of neurobiology at Duke University, UK. "It's remarkable how few photons are at night," he added.

According to MedicalXpress, the discovery shows how the movement of sensitive retinal cells changes. Even under good light conditions, identifying the presence and direction of movement of an object is the key to survival for much of the animal. But motion detection when there is only one reference point does not work very well. Thus, the retina of vertebrates has four types of cells sensitive to movement, each specific to a upward, downward, left and right movement.

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When an object moves precisely at one of these points, if the motion occurs in the middle, both types of cells are activated but do not have the same capacity. "For complex tasks, the brain uses large clusters of neurons, because one can not do the job," Field said.

In humans, these neurons represent 4% of the cells that transmit signals from the retina to the brain. In mice, the percentage is 20-30%, because motion detection is vital. In the study, the researchers analyzed rodent retinas at a microscope in a darkened room. Thus, Xiaoyang Yao student at Field's lab has discovered that retinal cells sensitive to upward movement change when light is dimmed. Neurons for this direction are activated under such conditions even if the movement is not ascending.

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