Physiologists at Stanford University were able to partially restore vision in mice with severed optic nerves. For this, a combined approach was applied, including both visual stimulation and the use of chemicals. An article describing the experiment was published in Nature Neuroscience.
The eyes of most animals contain the retina, a thin layer of light-sensitive cells. It contains photoreceptors that respond to different wavelengths of light, as well as ganglionic neurons. In total, there are several dozen types of ganglion cells, each of which is responsible for processing specific visual information (movement of objects or color). They also have processes - axons that collect in the optic nerve and go to the brain.
If axons are torn apart, then visual information ceases to flow to the brain. At the same time, ganglionic neurons lack the ability for automatic regeneration. However, scientists have found a way to trigger repair mechanisms by stimulating a signaling pathway from a chain of molecules, including the TOR protein, a cell growth regulator.
The researchers exposed experimental mice with damaged optic nerves to substances that increase TOR activity. In addition, the animals were shown videos with moving black and white lines. After three weeks, the scientists evaluated the rodents' ability to respond to certain visual stimuli, and the degree of axonal regeneration was also tested.
The results showed that most of the axons grew again, reaching the corresponding areas in the brain. However, the restoration of vision was incomplete, since, as scientists believe, not all types of ganglion cells were able to "reach" the cerebral hemispheres. Future research by physiologists will focus on solving this problem.