Smarter eEyes Focus on Cure for Blind

R. Colin Johnson | Date: 05-24-11 | Comments: 1
Smarter eEyes Focus on Cure for Blind - Technology For Change

# By designing electronic-eye (eEye) implants using fractal interconnects, researchers aim to overcome the mismatch between using conventional image chips in bionic eyes.
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Today, several efforts are under way worldwide to create silicon retinas that can be implanted in the eyes of the blind, thereby enabling them to see again, albeit at vastly reduced resolution. Now researchers are aiming to remedy that by replicating the fractal-like interconnection topology of real eyes.

Real biological eyes contain the equivalent of 127 million pixels, whereas conventional eEyes are currently using sensors with less than 64 pixels, and even next-generation designs are only aiming for about 1,024. What is even worse, these researchers say, is that the interconnection topology of an image chip is a square array, whereas the interconnection matrix for the "pixels" in a real biological eye is a branching structure called a fractal.

Real biological eyes—diagrammed at top—use arrays of retinal cells that are lined up in rows, but their interconnections (middle) use a fractal pattern common in nature, according to University of Oregon professor Richard Taylor. (Source: University of Oregon)

Fractals are common among all living things as a result of growing techniques that repeat a basic set of instructions—a fractal algorithm. For instance, the trunk of a tree divides into branches using the same fractal algorithm that is used for the veins in a leaf. In nature, trees, clouds, rivers, galaxies, lungs and neurons use the same fractal pattern of interconnections.

Now researchers are aiming to replicate this technique for interconnecting imaging elements in eEyes. Today's eEyes just sink metallic electrodes—one for each pixel—into the ganglia behind the eye, which then depends on the plasticity of the visual cortex in the brain to decipher the output from these new pixels—even though they do not match the normal topology of the biological retina. However, new research efforts are developing a technique that starts with a metallic seed that then grows all the repeated branching structures that in turn mate to the optic nerve behind the eye, thereby delivering to the brain the same kind of signals as retinal neurons.

The specific algorithm harnessed by the technique is called "diffusion limited aggregation," which researchers are using to grow image sensor interconnections that mimic a natural neural topology before being surgically implanted and interfaced to the optic nerve.

This summer Professor Richard Taylor and doctoral candidate Rick Montgomery will begin a yearlong quest with Professor Simon Brown at the University of Canterbury in New Zealand to grow these metallic fractal interconnection topologies for the backside of silicon image chips.

Instead of just providing a single output for each pixel, as with conventional eEyes, image sensors with the fractal interconnects will connect to the optic nerve with the same overlapping topology used by real biological retinal neurons. As a result, the researchers hope that the brain's visual cortex can perform the same sort of functions for eEyes that it does for real eyes, enabling the blind to recover not just some vision, but a visual experience that rivals that of normal people.

One challenge cited by the researchers is finding metals that can be coaxed with diffusion limited aggregation to form the Brownian trees typical of retinal cells and yet can be safely implanted into humans without side effects. Funding is being provided by the Office of Naval Research (ONR), the U.S. Air Force and the National Science Foundation.

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Study looks at how blind people can see with tongue, ears

By Amy Minsky, Postmedia News May 25, 2011 10:02 PM

Study looks at how blind people can see with tongue, ears

There's a small number of people who use their tongue and ears to see. The process, known as echolocating, is also used by dolphins and bats.

Those mammals — and some blind people — are able to determine the size, location and other qualities of surrounding objects by emitting short bursts of sound — a click of the tongue, in the case of humans — and listening to the echoes bounce back.

And now, researchers from the University of Western Ontario have discovered that when blind people use this skill, the part of the brain responsible for decoding the echoes is the same part that sighted people use to see.

"We had a feeling the visual part of the brain would be recruited," said Mel Goodale, the senior researcher on the study and Canada Research Chair in Visual Neuroscience.

When a part of the brain is deprived of input because of injury — the loss of an eye, for example — that territory of the brain is up for grabs, able to be cannibalized by any other sensory system, Goodale explained.

"Blind people who read braille also use the visual cortex," he said.

For the study, Goodale and his colleagues recorded the tongue clicks of two blind echolocating experts, then created two tapes — one with the clicks and echoes, the other with only the clicks.

What was so surprising to the researchers was that the visual cortex was activated by the echoes, enabling the subjects to "see" the objects even while sitting in the lab.

Also surprising, Goodale said, was that the auditory cortex maintained the same level of activity regardless of whether the echo was present.

"Clearly the auditory cortex must be processing information, but when it comes to interpreting the echoes, it's the visual cortex that plays the main role," said Goodale, director of the university's Centre for Brain and Mind in London, Ont.

Daniel Kish, a leading expert on echolocation who heads World Access for the Blind in California, was one of two subjects whose brains were scanned for this study, which is the first of its kind.

Goodale described Kish's clicks as loud and powerful noises made by placing his tongue on the roof of his mouth and pulling back.

Kish, 45, had both his eyes removed when he was 13 months old and suffering from eye cancer.

His parents have said they remember him making the clicking noises when he was as young as 18 months old. Kish has said he doesn't remember ever not using echoes to find his way around.

"I've seen him do some remarkable things," Goodale said, describing the man's ability to detect a slight change in the angle of a metal rod held metres away. "He can tell a curved surface from a flat surface, and when we go outside, he can tell a car from a tree from a flagpole."

Kish is so adept at echolocation, he uses it to safely navigate unfamiliar territories while mountain biking.

The study is being published this month in the scientific journal the Public Library of Science ONE.

aminsky(at)postmedia.com

Twitter.com/amyminsky
© Copyright (c) Postmedia News

Read more: Study looks at how blind people can see with tongue, ears

__________________
"Patriotism means being loyal to your country all the time and to its government when it deserves it."-- Mark Twain

"Inter arma silent Musae"--when the weapons speak, the muses fall silent.

An't nanum hearm deth, doth hwaet ye willath.

It is forbidden to kill; therefore all murderers are punished
unless they kill in large numbers and to the sound of trumpets. -Voltaire

Economic Left/Right: -3.88
Authoritarian/Libertarian: -4.36