Welcome to the home page of the LGN Visual Prosthesis Project.

¤ The fundamental idea we are pursuing is to provide restoration of sight to the blind. We hope to accomplish this by implanting multi-wire electrodes in the lateral geniculate nucleus (LGN), the part of the thalamus that relays signals from the retina in the eye to the primary visual cortex at the rear of the head. In leading causes of blindness, the eye ceases working as a light-sensitive organ, but the remainder of the visual system is largely intact. By sending signals from an external man-made sensor such as a digital camera into the brain through carefully implanted electrodes in the LGN, we hope to provide a crude approximation to normal vision and restoration of sight to the blind.

It is important to understand that we do not anticipate restoring vision that is in any way close to normal. Our best guess is that a visual prosthesis will provide the patient with an improvement in their quality of life, being able to navigate more easily through familiar and perhaps unfamiliar surroundings. We hope that it will allow the patient to distinguish and identify simple objects, perhaps even help recognize people. But, it is important to understand that these hopes are some time to come. There is a tremendous amount of work to be done before we have even the crudest initial experimental device temporarily implanted in a human.

¤ We have published a scientific paper describing our first high-profile results:

J. S. Pezaris and R. C. Reid, "Demonstration of artificial visual percepts generated through thalamic microstimulation," Proceedings of the National Academy of Science, 104(18):7670-7675, May 1, 2007 [PDF]

¤ Here are a few selected examples of the press coverage on the paper:

The Economist
BBC
Neurophilosophy
The New Scientist
Associated Press (NYT)
Technoglogy Review

¤ The following illustration depicts a schematized version of an initial device and shows the basic elements of the design.

This diagram shows how a visual prosthesis might work someday. The patient would wear a special set of glasses with a small digital camera mounted in the lens. The camera would have a wire that communicates to an external signal processor, worn in a pocket or on a belt. The signal processor would translate the image from the camera into the neural impulses and transmit them wirelessly to an implanted stimulator. The stimulator would drive the electrode, surgically placed in the brain, delivering images to the visual system.

Credit: J. S. Pezaris, adapted with permission from D. H. Hubel.

¤ The first of two small movies accompanying the article and press coverage helps understand what the animals are doing in this experiment.

This animation combines the animal's eye position, what it sees on the screen normally, and a simulation of the artificial percept. As part of the experiment, the animal's eye position is measured, and we show where it was looking on the computer screen by a blue dot. Targets that appear on the screen are white dots, and the animal has been trained to look at them, from a first one that appears in the center, to a normal second one that appears further away. In some instances the second point is not on the screen, but is created artificially through electrical stimulation. Although there is a yellow star depicting the electrical stimulation in this movie, in the experiment, nothing appeared on the screen in front of the animal. When the second point is artificial, the animal looks down and to the right, just as if it saw one of the normal points. By changing the placement of the electrode, we can change where the percept appears.

Credit: J. S. Pezaris.

¤ The second of the two movies helps us understand what prosthetic vision might appear like to the patient. This could be called an artist's rendition of the experience. There are numerous assumptions that underly the simulation, many of which are likely incorrect; this movie should serve only as a guide.

On the left is a movie made with a small digital camera. On the right is the same movie, as it would appear to a patient with bilateral implants having 350 pixels per hemisphere. As the simulated patient moves their gaze around, as indicated by the red point, you see the pattern of pixels shifting across the image.

There are two things to notice in this movie. The first is that before the movie begins, the image on the right is not identifiable, but as soon as the animation starts to run, the brain does a marvelous job of integrating different facets of the image and the woman's face becomes clear. The second is that the right image contains about 700 pixels, while the left image contains 70,000; while not all of the fine details are resolvable, a remarkable amount of information can be conveyed in a relatively small number of pixels.

Credit: J. S. Pezaris.