In eyes found an unknown mechanism

Scientists have discovered how the eye distinguishes fine details in the image. It turned out that this process is based on a previously unknown mechanism of positive feedback in the retina, the researchers report in the journal PLoS ONE.
One of the key processes that determine the ability to sight - is the distinction of light and dark objects, or contrasting vision. It is supported by the negative feedback mechanism that operates between adjacent cells of the retina.
Cells located just beneath the surface of the retina receive the signal from the photoreceptors (rods and cones), and, when the eye sees a dark spot, photoreceptors release glutamate, which leads to depolarization of the membranes of these cells, and they stimulate the termination glutamate neighboring photoreceptors. As a result, the eye does not see a blurred spot and stain with clear boundaries.
A side effect of this process would have to be the loss of the ability of the eye to distinguish fine detail - but it does not.
The authors of the new work found that dark objects stimulate additional release of glutamate by the photoreceptors and their nearest neighbors. Such a local positive feedback allows the eye to distinguish fine details while not blurring the boundaries of the dark spot.
Researchers believe that so far they have not been able to detect this mechanism in a very well-studied object - the retina, for the reason that it is very easily destroyed, even with minimal preparation of the drug for the study.