Fighting Crime With Digital DNA (Science Journal)

DNA evidence is widely accepted in courtrooms. And now, so is our "Digital DNA" -- those trace zeroes and ones we leave behind on computer systems, in our smartphones, beneath the hoods of our cars and more.

"Digital evidence is the new DNA," Ira Victor, a forensic analyst with Data Clone Labs and a member of The High Tech Crime Investigator's Association (HTCIA), told FoxNews.com.

Last week the Supreme Court took a first stab at addressing how such evidence can be used, hearing arguments from the Justice Department defending the use of GPS devices planted on suspects' vehicles. But that's just one aspect of a growing body of data: From digital photographs to cellphones to emails and Word documents, we all create a trail that law enforcement agencies are increasingly using to put crooks at the scene of their crime.

Heck, even the Doobie Brothers are doing it.
Jeffrey "Skunk" Baxter a founding member of Steely Dan (he played guitar on "Rikki, Don't Lose That Number") and a current member of The Doobie Brothers, is also a contractor for a number of U.S. government agencies and an advisor on terrorism, cyber-warfare and forensic analysis.
"I want your help," Baxter told attendees at Paraben's Forensic Innovations Conference (PFIC), a leading conference on digital investigations in Utah that wrapped up Nov. 9. It called for the increased use of digital forensics in courtrooms and cases.

But with increasing prevalence comes an increasing risk of abuse. The Electronic Privacy Information Center (EPIC) told the Supreme Court last week that information from GPS devices could easily be abused.
"The proliferation of GPS tracking technology creates … detailed travel profiles of American citizens," the group wrote. "Law enforcement access to such information raises the specter of mass, pervasive surveillance."
Victor agrees. "Attorneys are very good at taking digital evidence out of context and then convincing a jury of the guilt of someone based on it," he said.

In 2002, "Jack" was sent to jail after police found pornographic images on his home computer. Security experts later told Wired News that the digital data had been mishandled: They suggested it could have been put on his computer remotely through what's called a "browser hijacker" -- a malicious bit of software that changes browser settings and can easily be built to store data on a PC.

As with DNA evidence, it can be hard to derive intent when examining a piece of digital evidence, explained Sgt. Kevin Stenger, computer crimes supervisor with the Orange County Sheriff's Office in Orlando, Fl.
"Exactly how did a criminal use a smartphone in the commission of a robbery, if at all?" Stenger told Foxews.com. "Was he using it to look up an address, to take pictures of the potential robbery site? Was he using it to text message other members of his crew? Did he use it when the robbery was in progress?"
But when properly used, GPS data, cell phone records and even "metadata" from digital photos are admissible in a court of law. And digital DNA is everywhere -- frequent shopper cards, EZPass toll technology, smartphones and more.
So can all that gear "testify" against you? It comes down to a question of reasonable use, said Andrew Hildebrand, associate dean of DeVry University's College of Business and Management and an expert in computer forensics.

"What is public? Where is the expectation of privacy coming in?" Hildebrand told FoxNews.com.
The digital devices we carry create an unprecedented array of information about us, he noted, and rules are only now being created.
"We're in a new era of technology," he said. "Where are the limits for that, within the bounds of the Constitution?"
A growing number of classes around the country aim to probe these issues, training a new generation of detective. The University of Central Florida, for example, created an interdisciplinary program in 2008 to offer a master of science in digital forensics.
The program has over 100 students, coordinator Sheau-Dong Lang said, and teaches technical detection, forensic sciences and criminal justice, as well as current issues in cyberlaw. Twenty-seven students graduated in 2008; the school could admit as many as 60 in 2012.

Even the tools these cybersleuths will use are still under development -- and they're neither simple nor cheap. At the PFIC conference, experts explored new software and wrestled with the increasing amount of digital evidence that prosecutors and law enforcement sift through today.
"Like DNA, the devil's in the details," Victor said. If information isn't properly recorded and a chain of custody preserved, it's all too easy for data to become corrupted or even falsified.
That at least may change.

Software firm Katana Forensics announced at PFIC that it would soon release a free, "light" version of its Lantern software package, a $600 forensic tool that digs data out of iPhones and is sold only to law enforcement and government agencies. It should make digital forensics analysis more accessible.
As digital DNA becomes a more common tool in court, potential abuses may grow as well, at least until case law is firmly set in place.
"Yes, we should be worried, but not to the point of paralysis," Hildebrand told FoxNews.com.
"But this is a national dialog that needs to take place."

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Mega-rover ready to hunt for life signs on Mars

Plutonium powered and as big as an SUV, NASA's Curiosity rover is crammed with souped-up sensors and a new sky-crane landing system

THE flying-saucer-shaped probe hurtles through space, firing thrusters and flinging off weights to point its heat shield forwards for the scorching trip through Mars's atmosphere. Once it has slowed, the heat shield drops away and, 10 kilometres above the surface, a parachute billows out. More weights are jettisoned, pointing the craft's radar-tipped belly towards the fast-approaching ground.

The probe cuts loose its parachute and upper shell, then fires thrusters towards the ground, slowing its speed further to 3 kilometres per hour. Hovering 20 metres above the Martian surface, the probe starts to unspool an SUV-sized rover from its belly. Dangling on cables like a giant spider, the payload is gently lowered by a "sky crane" to the surface. Curiosity has landed.

So begins a slick animation of NASA's newest rover, which is due to blast off on 25 November. The manoeuvres are so precise in their choreography and timing that their successful implementation seems improbable - especially given that Mars is the Bermuda Triangle of the solar system, dooming to failure two-thirds of the missions that attempt to visit it. "Everything has to behave according to plan," admits mission leader John Grotzinger of the California Institute of Technology in Pasadena.

The stakes could barely be higher. The $2.5 billion rover will be the most ambitious and expensive mission ever sent to Mars, carrying state-of-the-art tools that will reveal whether its landing site was ever habitable and search for signs of life preserved in its rocks. The first rover to be powered by the radioactive decay of plutonium rather than sunlight, Curiosity will be able to work around-the-clock and through the Martian winter.
"It's going to be a huge step forward," says Steve Squyres at Cornell University in Ithaca, New York, lead scientist for the Mars Exploration Rovers Spirit and Opportunity, which landed on different sides of the planet in 2004.

But first Curiosity has to touch down safely. "Anytime you land on Mars, it's a slightly scary thing," says Squyres. Both Spirit and Opportunity were swaddled in airbags and bounced to a landing, but Curiosity weighs five times as much and would simply punch through airbags as if they weren't there. "We pushed the airbag technology about as far as you could push it," says Squyres. "The sky crane system is a good engineering solution to the problem."

Balletic precision

Developing the gargantuan mission, which is also known as Mars Science Laboratory, has not always been smooth. Engineering troubles - including problems with motor-driven gears called actuators - forced a two-year launch delay and added millions of dollars to its already outsized budget. "This has been a trial," admits Jack Mustard of Brown University in Providence, Rhode Island. "But if NASA can pull this off, you've got a demonstrated landing system for large masses, which will be important for the next phase of landing on Mars - bringing samples back."

The ballet of moves that precedes the sky crane's deployment is also an advance. Tilting the probe by jettisoning weights gives it much greater aerodynamic control, enabling the target landing site to be an ellipse just 20 kilometres long - one-seventh of that needed for Spirit and Opportunity. "When you have a larger ellipse, you rule out all the most interesting places," says Grotzinger. That's because larger footprints are more likely to include steep slopes or fields of boulders - terrain too dangerous to risk landing on. "This is the first time in the history of the exploration of Mars where we have been unencumbered by engineering constraints to really debate landing site options," he says.

After years of consideration, the winning siteMovie Camera finally emerged in July: the 150-kilometre-wide Gale crater near the Martian equator, whose floor plunges 5 kilometres below the surrounding surface. "It's a pretty deep hole in the ground," says Ralph Milliken at the University of Notre Dame in Indiana. Bizarrely, a mound of rocks within it rises up about as high as the crater walls.
How did such a giant structure form? Geologists are divided, although they are certain water was involved in some way. That's because rocks at the bottom of the mountain are made of layers of clays and sulphate salts, both of which need water to form. Orbiting spacecraft have dated the formation of these rocks to about 3.5 billion years ago.
"If any place had a lake on Mars, Gale would," says David Blake of NASA's Ames Research Center in Moffett Field, California. Rain, snow or rising groundwater might have pooled in the crater, and the clays and sulphates might have been left behind when the water evaporated.

With Curiosity, NASA is going beyond its previous aim to "follow the water". Barely a week seems to go by without instruments on the Mars Reconnaissance Orbiter and Mars Express probe beaming back evidence for past or even present water. No one doubts any more that liquid water once featured on the Red Planet.
"We've kind of beaten that horse to death," says Milliken. "We know there was plenty of water during certain parts of Mars's history," he adds, referring to large water-carved channels and valleys thought to have formed in the planet's early history. "Now it's a matter of trying to understand which of those environments had water for the longest time, and was it the right pH? We're asking much more difficult - and also much more informed - questions."

Planet organic?

Curiosity will be able to provide better answers than any previous mission. Spirit and Opportunity could only detect specific elements in rocks, such as iron, by measuring the spectrum of light they reflect. Curiosity will do this sort of elemental chemistry too, but in a more Jedi-like fashion: zapping rocks with a laser from up to 7 metres away and studying the spectrum of light emitted by the ionised rock vapour. If it spots elements of interest, it will approach and use a drill on its robotic arm to collect rock samples from as deep as 5 centimetres.

Next it will perform a feat that has so far only been done on Earth - identifying the specific minerals, such as iron sulphate or magnesium sulphate, in rock samples. The pulverised rock will be placed into an instrument called CheMin, which will shoot X-rays at it and study the resulting diffraction patterns. Just like a fingerprint, each of the 7000 or so minerals on Earth has a unique X-ray diffraction signature. "CheMin will tell you all the minerals that are present and how much of each mineral there is," says Blake, lead scientist for the instrument. That provides big clues about the temperature, pressure, acidity and other conditions in which the minerals formed, he says.

So CheMin could reveal whether Gale crater was just right for life. But did it actually host it? Detecting unambiguous signs of life is fraught with difficulty (see "Why isn't NASA hunting for life?"). So Curiosity will do its best to answer the question by looking for organic molecules. These complex carbon-containing molecules do not necessarily signal life - they float in the harsh environment of interstellar space, for example - but they do form the building blocks of life as we know it. Instruments on-board the rover will be able to detect organic molecules at concentrations of just 40 parts per billion. "It's not a direct sign of life," says Grotzinger, "but if it had been there, we might see organic compounds preserved."

Finding them won't be easy, as other missions have shown. Organic molecules should be raining down on Mars regularly on meteorites, yet none were found by NASA's twin Viking landers in 1976 or by its Phoenix probe in 2008. That may be because it's very easy to destroy them. Ancient organic matter trapped in rock might have been destroyed by water flowing through the rock, which would have split apart the organic molecules and produced carbon dioxide gas. If the rocks were below the surface, the heat of the planet may also have destroyed anything organic, and if they were on the surface, cosmic rays or oxidising chemicals like hydrogen peroxide could have severed the molecular ties. "Detecting organic compounds is more than a needle in a haystack," says Grotzinger.

Curiosity has a better chance of success, in part because of its landing site. On Earth, organic molecules tend to be trapped and preserved in fine particles. That makes landing next to clays at the base of Gale crater's enormous mountain so promising.
Shortly after it has landed, the rover will begin to climb the mound. As it ascends, it will also encounter other water-related features where life may have found a toehold, including channels that might once have held water. The diversity of these features was a draw to landing at Gale, says Grotzinger: "We get to study not just one but several potentially habitable environments."

Finding any type of organic molecule would count as a huge success. Yet the rover's instruments could give us more telling hints of life, including a toolkit called SAM, which stands for sample analysis at Mars. Of most interest to researchers studying the possibility of carbon-based life on Mars is that SAM can measure the relative abundance of the isotopes carbon-12 and carbon-13. Life on Earth prefers to use the lighter isotope, so "if you measure more light carbon, it's at least consistent with the hypothesis that biology could have been involved", says Grotzinger. However, he cautions that the natural isotopic abundances might be different on Mars than on Earth, which would complicate the analysis.

In addition, SAM will investigate the chirality, or handedness, of organic molecules to look for hints that they came from life. Many molecules come in left and right-handed versions, and non-biological processes tend to create these in equal numbers. "In the case of life, you don't have the same ratio," says Michel Cabane, a SAM instrument leader at the Pierre and Marie Curie University in Paris, France. "If there is not the same quantity of left and right molecules, we can begin to postulate a biological source."

For any microbes living in Gale crater, August 2012 will be unlike any other month. Their tranquil lives will be shattered by the appearance of a flying saucer from another planet and a curious six-wheeled plutonium-powered beast trundling across the landscape. It will truly be an alien sight.

Why isn't NASA hunting for life?

Even the most ardent fans of the Red Planet must occasionally wish for more than just hints of water popping up in ever-new places. So why not send a robot to hunt directly for little green men?
One word: Viking. NASA's Viking landers did just that in 1976, laying out a tasty solution of nutrients to attract any microbes that might be living in a soil sample, like cookies left on a plate for Santa. The nutrients were laced with radioactive carbon, so if the solution was digested, a radiation monitor above the sample would detect the resulting gas.

Intriguingly, radioactive carbon was detected, but then another experiment found no evidence of organic compounds in the soil - there were no alien bodies. "They were hoping to find signs of life but the results came back basically negative - there is no life as we know it," says Ralph Milliken at the University of Notre Dame in Indiana. The US did not send another mission to Mars for 20 years.
The $2.5 billion Curiosity rover will hunt for organic molecules and isotopic hints of life, but NASA is still shying away from the L word. "NASA cannot say to taxpayers that they put $2.5 to $3 billion to search for life, and then say, 'We have found no life - thank you, bye bye'," says Michel Cabane, leader of one of Curiosity's organics-sniffing instruments, who is based at the Pierre and Marie Curie University in Paris, France.

"If you project the message that you are hunting for life, even though it is very important to many of us, and you return with a null or ambiguous answer, people would be disappointed," says Jack Mustard of Brown University in Providence, Rhode Island, who is a former chair of NASA's advisory panel on Mars.
In any case, he and others say the problem may simply be too hard to solve. "If I posed the question 'prove that life existed in Earth's past' to you, it would be tough," Mustard says. "Geologists would say, we'll go find a fossil. But bodies are not always preserved on Earth."

He points out that Curiosity and other missions that touch down on the planet are only exploring a limited region for a limited time. Bethany Ehlmann at the California Institute of Technology in Pasadena agrees. "Think locally, not globally - that's a slight perversion of what the environmental movement thinks we should do here on Earth," she says.
Curiosity's landing site may once have been a lake, but other intriguing sites suggest life might have found a refuge in hydrothermal springs below the surface. "Environments during the first billion years of Mars history varied substantially," she says. "Now that we know there's this diversity out there, it becomes harder to say that the evidence says 'Mars did not have life'."
Images Credit: NASA/ Credit: CBC NEWS & AP

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So That’s What Dreams Are Made Of

Scientists measure dream content for the first time and find that dreams activate the brain in a similar way to real actions.

Patient in a functional magnetic resonance imaging machine. © MPI of Psychiatry

The ability to dream is a fascinating aspect of the human mind. However, how the images and emotions that we experience so intensively when we dream form in our heads remains a mystery. Up to now it has not been possible to measure dream content. Max Planck scientists working with colleagues from the Charité hospital in Berlin have now succeeded, for the first time, in analyzing the activity of the brain during dreaming. They were able to do this with the help of lucid dreamers, i.e. people who become aware of their dreaming state and are able to alter the content of their dreams. The scientists measured that the brain activity during the dreamed motion matched the one observed during a real executed movement in a state of wakefulness.
Methods like functional magnetic resonance imaging have enabled scientists to visualize and identify the precise spatial location of brain activity during sleep. However, up to now, researchers have not been able to analyze specific brain activity associated with dream content, as measured brain activity can only be traced back to a specific dream if the precise temporal coincidence of the dream content and measurement is known. Whether a person is dreaming is something that could only be reported by the individual himself.
Scientists from the Max Planck Institute of Psychiatry in Munich, the Charité hospital in Berlin and the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig availed of the ability of lucid dreamers to dream consciously for their research. Lucid dreamers were asked to become aware of their dream while sleeping in a magnetic resonance scanner and to report this “lucid” state to the researchers by means of eye movements. They were then asked to voluntarily “dream” that they were repeatedly clenching first their right fist and then their left one for ten seconds.
This enabled the scientists to measure the entry into REM sleep – a phase in which dreams are perceived particularly intensively – with the help of the subject’s electroencephalogram (EEG) and to detect the beginning of a lucid phase. The brain activity measured from this time onwards corresponded with the arranged “dream” involving the fist clenching. A region in the sensorimotor cortex of the brain, which is responsible for the execution of movements, was actually activated during the dream. This is directly comparable with the brain activity that arises when the hand is moved while the person is awake. Even if the lucid dreamer just imagines the hand movement while awake, the sensorimotor cortex reacts in a similar way.
The coincidence of the brain activity measured during dreaming and the conscious action shows that dream content can be measured. “With this combination of sleep EEGs, imaging methods and lucid dreamers, we can measure not only simple movements during sleep but also the activity patterns in the brain during visual dream perceptions,” says Martin Dresler, a researcher at the Max Planck Institute for Psychiatry.
The researchers were able to confirm the data obtained using MR imaging in another subject using a different technology. With the help of near-infrared spectroscopy, they also observed increased activity in a region of the brain that plays an important role in the planning of movements. “Our dreams are therefore not a ‘sleep cinema’ in which we merely observe an event passively, but involve activity in the regions of the brain that are relevant to the dream content,” explains Michael Czisch, research group leader at the Max Planck Institute for Psychiatry

Source: Max-Planck-Gesellschaft   

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Journal/How the miracle fruit changes sour into sweet

Pop a “miracle berry” into your mouth, and you might wonder if it was named by an overreaching marketing department. The small red fruit tastes of very little – it has a “mildly sweet tang… [like] a less flavorful cranberry”. But it’s not the taste of the fruit itself that matters. To understand why the berry gets its name, you need to eat something acidic. The berries have the ability to make sour foods taste deliciously sweet. Munch one, and you can swig vinegar like it was a milkshake, or bite lemons as if they were candy.

The secret to the fruit’s taste-transforming powers is a protein called miraculin. Now, Ayako Koizumi from the University of Tokyo has discovered just how the protein acts upon our tongues.
Two groups of scientists independently isolated miraculin from miracle berries in 1968, but people have been experiencing its effects for far longer. West Africans have chewed miracle berries (Richadella dulcifica) before their meals for centuries, to get those unusual sweet hits from otherwise sour food. Europeans became aware of the fruit in 1725, when French explorer Chevalier des Marchais described its use.

In the 1970s, an American company called Miralin tried to develop miraculin as a simple way of getting a sugar rush without having to gorge on cakes and sweets. Their attempt was nixed by the US Food and Drug Administration, who decided to classify miraculin as an additive, dooming it to years of further testing. Miralin folded, amid suspicions of foul play from the sugar industry. The miracle berries never quite hit the big time, but they do make occasional appearances at high-class events known as “flavour-tripping parties”.

While party-goers thrilled at the miracle fruit’s tongue-teasing trick, scientists were equally intrigued. Various groups have pored over miraculin’s properties in great detail. Thanks to their efforts, we know a lot about the protein’s structure, and how acidity, temperature and dose affect its taste-altering powers. By comparison, we still know very little about how it actually works.

The general idea is that miraculin changes the shape of proteins on our tongues called sweet receptors. These proteins are normally set off by sugars, but when miraculin disfigures them, they respond to acids too. Suddenly, sour mouthfuls are registered as sweet ones.
According to Koizumi’s experiments, this explanation is not quite right. She showed that miraculin does stick directly to sweet receptors, and it latches on more strongly than do other conventional sweeteners like aspartame or saccharin. In neutral conditions, neither acidic nor alkaline, miraculin stops these other sweeteners from getting a hold on the sweet receptors. It actually represses the receptors, stopping them from doing their job. Under acidic conditions, the opposite happens – miraculin supercharges the sweet receptors. It distorts them into an active shape, while also making them extra-sensitive to sweeteners like aspartame.

Here, then, is what happens when you chomp on a miracle berry. Miraculin sits on your sweet receptors for an hour or so. For most of that time, it silences the receptors, which is why the fruit itself tastes of very little. Whenever you take a bite or swig of something acidic, miraculin gains a few extra protons and changes shape. In doing so, it also changes the shape of the sweet receptors it has stuck to, sending them into a signalling frenzy.
Koizumi also looked at a second taste-changing protein called neoculin. This one comes from the Malaysia lumbah plant; it also converts sourness to sweetness, and it also sticks to sweet receptors. But the similarities stop there.
Amazingly, miraculin and neoculin are completely unrelated. They have different shapes and sizes, they are made from different chains of amino acids, and they stick to different parts of the sweet receptor. Unlike miraculin, neoculin tastes sweet in its own right, and it transforms sour tastes into an even stronger sweet buzz. The miraculous aspect of these two proteins is not that they turn sour into sweet, but that they have evolved to do the same thing through two completely different means.

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Journal/"I See," Said the Blind Man With an Artificial Retina

For 100 million people around the globe who suffer from macular degeneration and other diseases of the retina, life is a steady march from light into darkness. The intricate layers of neurons at the backs of their eyes gradually degrade and lose the ability to snatch photons and translate them into electric signals that are sent to the brain. Vision steadily blurs or narrows, and for some, the world fades to black. Until recently some types of retinal degeneration seemed as inevitable as the wrinkling of skin or the graying of hair—only far more terrifying and debilitating. But recent studies offer hope that eventually the darkness may be lifted. Some scientists are trying to inject signaling molecules into the eye to stimulate light-collecting photoreceptor cells to regrow. Others want to deliver working copies of broken genes into retinal cells, restoring their function. And a number of researchers are taking a fundamentally different, technology-driven approach to fighting blindness. They seek not to fix biology but to replace it, by plugging cameras into people’s eyes.

Scientists have been trying to build visual prostheses since the 1970s. This past spring the effort reached a crucial milestone, when European regulators approved the first commercially available bionic eye. The Argus II, a device made by Second Sight, a company in California, includes a video camera housed in a special pair of glasses. It wirelessly transmits signals from the camera to a 6 pixel by 10 pixel grid of electrodes attached to the back of a subject’s eye. The electrodes stimulate the neurons in the retina, which send secondary signals down the optic nerve to the brain.

A 60-pixel picture is a far cry from HDTV, but any measure of restored vision can make a huge difference. In clinical human trials, patients wearing the Argus II implant were able to make out doorways, distinguish eight different colors, or read short sentences written in large letters. And if the recent history of technology is any guide, the current $100,000 price tag for the device should fall quickly even as its resolution rises. Already researchers are testing artificial retinas that do not require an external camera; instead, the photons will strike light-sensitive arrays inside the eye itself. The Illinois-based company Optobionics has built experimental designs containing 5,000 light sensors.

Commercial digital cameras hint at how much more improvement might lie just ahead. Our retinas contain 127 million photoreceptors spread over 1,100 square millimeters. State-of-the-art consumer camera detectors, by comparison, carry 16.6 million light sensors spread over 1,600 square millimeters, and their numbers have improved rapidly in recent years. But simply piling on the pixels will not be enough to match the rich visual experience of human eyes. To create a true artificial retina, says University of Oregon physicist and vision researcher Richard Taylor, engineers and neuroscientists will have to come up with something much more sophisticated than an implanted camera.

it is easy to think of eyes as biological cameras—and in some ways, they are. When the light from an image passes through our pupil, it ends up producing a flipped image on our retina. The light that enters a camera does the same thing. Eyes and cameras both have lenses that adjust the path of the incoming light to bring an image into sharper focus. The digital revolution has made cameras even more eye-like. Instead of catching light on film, digital cameras use an array of light-sensitive photodiodes that function much like the photoreceptors in an eye.

But once you get up close, the similarities break down. Cameras are boringly euclidean. Typically engineers build photodiodes as tiny square elements and spread them out in regularly spaced grids. Most existing artificial retinas have the same design, with impulses conveyed from the photodiodes to neurons through a rectangular grid of electrodes. The network of neurons in the retina, on the other hand, looks less like a grid than a set of psychedelic snowflakes, with branches upon branches filling the retina in swirling patterns. This mismatch means that when surgeons position the grid on the retina, many of the wires fail to contact a neuron. As a result, their signals never make it to the brain.

Some engineers have suggested making bigger electrodes that are more tightly spaced, creating a larger area for contact, but that approach faces a fundamental obstacle. In the human eye, neurons sit in front of the photoreceptors, but due to the snowflake-like geometry, there is still lots of space for light to slip through. An artificial retina with big electrodes, by contrast, would block out the very light it was trying to detect.

Natural photoreceptors are quirky in another way, too: They are bunched up. Much of what we see comes through a pinhead-size patch in the center of the retina known as the fovea. The fovea is densely packed with photoreceptors. The sharp view of the world that we simply think of as “vision” comes from light landing there; light that falls beyond the fovea produces blurry peripheral images. A camera, by contrast, has light-trapping photodiodes spread evenly across its entire image field.

The reason we don’t feel as if we are looking at the world through a periscope is that our eyes are in constant motion; our focus jumps around so that our foveas can capture different parts of our field of view. The distances of the jumps our eyes make have a hidden mathematical order: The frequency of a jump goes up as distance gets shorter. In other words, we make big jumps from time to time, but we make more smaller jumps, and far more even smaller jumps. This rough, fragmented pattern, known as a fractal, creates an effective means of sampling a large space. It bears a striking resemblance to the path of an insect flying around in search of food. Our eyes, in effect, forage for visual information.

Once our eyes capture light, the neurons in the retina do not relay information directly to the brain. Instead, they process visual information before it leaves the eye, inhibiting or enhancing neighboring neurons to adjust the way we see. They sharpen the contrast between regions of light and dark, a bit like photoshopping an image in real time. This image processing most likely evolved because it allowed animals to perceive objects more quickly, especially against murky backgrounds. A monkey in a forest squinting at a leopard at twilight, struggling to figure out exactly what it is, will probably never see another leopard. Unlike a camera that passively takes in a picture, our eyes are honed to actively extract the most important information we need to make fast decisions.

Right now scientists can only speculate what it might be like to wear an artificial retina with millions of photoreceptors in a regular grid, but such a device would not restore the experience of vision—no matter how many electrodes it contains. Without the retina’s sophisticated image processing, it might just supply a rapid, confusing stream of information to the brain.

Taylor, the Oregon vision researcher, argues that simplistic artificial eyes could also cause stress. He reached this conclusion after asking subjects to look at various patterns, some simple and some fractal, then describe how the images made them feel. He also measured physiological signs of stress, like electrical activity in the skin. Unlike simple images, fractal images lowered stress levels by up to 60 percent. Taylor suspects the calming effect has to do with the fact that our eye movements are fractal too. It is interesting to note that natural images—such as forests and clouds—are often fractal as well. Trees have large limbs off which sprout branches, off which grow leaves. Our vision is matched to the natural world.

An artificial retina that simply mirrors the detector in a digital camera would presumably allow people to see every part of their field of view with equal clarity. There would be no need to move their eyes around in fractal patterns to pick up information, Taylor notes, so there would be no antistress effect.

The solution, Taylor thinks, involves artificial retinas that are more like real eyes. Light sensors could be programmed with built-in feedbacks to sharpen the edges on objects or clumped together to provide more detail at the center. It may be possible to overcome the mismatch between regular electrodes and irregular neurons. Taylor is developing new kinds of circuits that he hopes to incorporate into next-generation artificial eyes. His team builds these circuits so that they spontaneously branch, creating structures that Taylor dubs nanoflowers. Although nanoflowers do not exactly match the eye’s neurons, their geometry would similarly admit light and allow circuits to contact far more neurons than can a simple grid.

Taylor’s work is an important reminder of how much progress scientists are making toward restoring lost vision, but also of how far they still have to go. The secret to success will be remembering not to take the camera metaphor too seriously: There is a lot more to the eye than meets the eye.

SOURCE : DISCOVER MAGAZINE

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