London, May 22 : Bionic eye implants that will enable blind people to see without an optic nerve is on the horizon, for US scientists have developed software that will perceive moving images just like a cat's brain.
Researchers at the Smith-Kettlewell Eye Research Institute, San Francisco, conducted their study based on the models of the way the brain responds to visual input used simple images like dots, bars and grids.
While they were unable to perceive the complex scenes a human would usually see, they tried and developed a more sophisticated model and made a record of the responses of 49 individual neurons located in the cat's brain, particularly in a part called the lateral geniculate nucleus (LGN).
The LGN mainly works by receiving and processing visual information from the retina, through the optic nerve, and then sends it on to the cerebral cortex.
In order to determine the basics of the LGN's response to visual features, the researchers used a mixture of simple stimuli, like dots and bars and then progressed towards more complex moving artificial scenes.
With the data in hand, it was possible for them to build a software model of the LGN that can roughly tell how the neurons would respond to real scenes. This model was tested on scenes recorded by a "catcam," camera attached to a cat's head.
"We chose the catcam because it was the most natural stimulus we could think of, the closest to what a cat would see when walking around," New Scientist quoted Matteo Carandini, as saying.
The researchers even used a scene from Disney's animated film Tarzan, as the footage provided by the catcam did not have elements moving independently from the rest of the scene. The model gave predictions which were 80 percent accurate when artificial scenes were shown. However, it fell down to 60 percent with the natural scenes or the Tarzan movie.
"This is still impressive, but shows a way to go. [The researchers] recognise that the perceptual world is not a single frame at a time but a constant stream of data," said Stephen Hicks, a neuroscientist at Imperial College London, UK.
The research was mainly aimed at developing an implant in the distant future that utilises visual data for directly stimulating the LGN of blind people whose optic nerve or retina has degenerated from lack of use.
"For these people, a prosthesis in the eye doesn't help," explained Carandini.
However, such implants, that stimulate the retina or optic nerve, currently being tested in humans, can only help people who have recently become blind.