Lucasfilm Ltd.
Luke Skywalker's prosthetic hand could become a reality — if scientists can get artificial limbs to communicate sensory information to the brain.
updated 10/5/2011 5:27:32 PM ET 2011-10-05T21:27:32

A new method of feeling without touching may allow people with paralyzed or lost limbs to interact with the world using sophisticated prosthetic devices that send sensations directly to the brain.

The method, tested only in monkeys so far, is "a major milestone" for neural prosthetics, according to study researcher Miguel Nicolelis, a physician and neurobiologist at Duke University Medical Center. Neural prosthetics are robotic limbs or exoskeleton-like devices controlled only by nerve signals. Nicolelis and other researchers plan to test these devices in humans within the next one to three years.

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"I like to say that we actually liberated the brain from the physical limits of the monkey's body," Nicolelis told LiveScience. "He can move and feel using the brain only."

Movement and sensation
Researchers worldwide are hard at work developing devices that would work a bit like Luke Skywalker's prosthetic hand in the 1980 film "The Empire Strikes Back." After losing his hand in a light-saber duel, the fictional Jedi gets a new limb with all the functionality of his original hand.

"He gets his arm chopped off, and an hour later, they put a prosthetic limb on him and start poking the arm, and he experiences those pokes as if it were a real limb," said Sliman Bensmaia, a sensory researcher at the University of Chicago who was not involved in Nicolelis' study.

The closest thing to Skywalker's hand today is the Defense Advance Research Project Agency's (DARPA) brain-controlled robotic arm, which is scheduled for human testing in about a year. The arm can bend and twist much like a natural limb and is controlled by electrodes implanted into the brain. The electrodes translate electrical activity from brain cells into commands for the arm, transmitted via wireless signal.

But the trick to getting devices like the DARPA arm to work, Bensmaia said, is getting the false limb to talk back to the brain. An arm, for example, can move in so many directions and take so many forms that it's simply not possible to control such movements efficiently based on sight alone. You need to be able to feel what the arm is doing. But while scientists have made great strides in hooking brain signals up to robotics to create motor movement, the sensory side has lagged behind. 

"For every one of us working on it, there are 10 people working on the motor side," Bensmaia said.

A big challenge, Nicolelis said, is that these devices use electrodes in the brain to stimulate neurons. Electricity is a rather blunt way to get the brain moving compared with the intricacy of our sensory receptors, and sending electrical sensory signals to the brain while trying to extract electrical motor signals can scramble both signals, leaving a big mess.

Nicolelis and his colleagues get around this problem by interweaving the sensory and motor signals. In a red-light, green-light pattern, the new brain-machine interface reads brain commands, and then switches over to sending tactile signals back to the brain for milliseconds at a time.

The technique "allows us to deliver these signals during a window of time in which we don't lose much or almost anything in terms of recording the motor signals the brain is generating," Nicolelis said. He and his colleagues reported their method online Wednesday in the journal Nature.

Katie Zhuang
A team of Duke University researchers headed by Miguel Nicolelis have added an artificial tactile sensations to their brain-machine interface that enacted reaching movements of a virtual-reality upper limb (monkey avatar, depicted in the image).

Monkeying around
To test the method, Nicolelis and his colleagues implanted two rhesus monkeys with brain electrodes. One batch of electrodes went in the motor cortex of each monkey, the part of the brain that controls movement. Another batch went into the sensory areas of the monkeys' brains.

The researchers then trained the monkeys to look at a computer screen at three identical objects. The only difference between the three was that one object had a "virtual texture." The motor electrodes allowed the monkeys to move a virtual arm over the objects using only brain signals. If the monkey "touched" the textured object with the virtual arm, it would receive a signal to the sensory part of its brain.

The animals had to choose the correct textured object with the virtual arm; if they succeeded, they were rewarded with a squirt of fruit juice.

The monkeys were aces at the test, Nicolelis said, providing what he called "proof of principle" that electrodes can indeed send information to the sensory brain regions in near-real time. One monkey learned how to find the textured object within four trials, while the other took nine. As the trials went on, the monkeys got better and better, eventually getting almost as good at the brain-only task as they would have if they'd been using their real hands and arms.

"It was pretty quick," Nicolelis said. "Since we cannot talk to the monkeys, I assume with human patients, it's going to be much easier."

Intuitive feeling
Adding sensory feedback to motor action is a "key innovation," Bensmaia said. But more needs to be done to make sure the sensory signals actually make sense. In the monkey study, the signals stimulated one monkey's hand and the other monkey's leg, but there is no way to know how the animals experienced the sensation. To move a complex limb, Bensmaia said, the signals have to be as close as possible to what the original limb would have produced.

"There's this barrage of signals coming from the arm that can actually serve to confuse rather than assist in the control of the arm unless these signals are intuitive in some way," Bensmaia said. "That's the next major challenge."

Another challenge, Nicolelis said, is to record more neuron activity at once. The more neuron signals, the more control, he said. He and his colleagues are part of the international Walk Again Project, which aims to develop a full "exoskeleton" for paralyzed patients. The idea is that the exoskeleton, controlled by the brain, would replace a person's lost muscle control, allowing them to sit, stand and walk.

The goal, Nicolelis said, is to have the exoskeleton ready in three years — in time for the 2014 World Cup in his home nation of Brazil.

"We think we can do this in the next three years or so," Nicolelis said. "We are hoping that a teenager who was quadriplegic until then will be able to walk into the opening game and kick the opening ball of the World Cup."

You can follow LiveScience senior writer Stephanie Pappas on Twitter @sipappas. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

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Explainer: The 2011 Weird Science Awards

  • Image: Stone Age sex toy; Beer and civilization; Slime-mold transit; Cricket testicles
    SNHB / U. Penn / AAAS / U. Derby

    Sex, booze and strange animal tricks: You had to know the 2011 Weird Science Awards would hit on those themes. After all, past award winners have included scientists' successful quest to reattach rabbit penises, a 2,700-year-old marijuana stash and glow-in-the-dark kitties. This year, users were asked to select the weirdest stories from a list of 30 nominees. Click ahead to count down the top 10 selections, plus some bonus picks.

    — Alan Boyle, science editor

  • 10. Oops! Maya doomsday date corrected

    El Castillo
    MSNBC file
    The El Castillo pyramid at Chichen Itza in Mexico is one of the monuments left behind by the Maya.

    Are we having doomsday yet? Some folks say the ancient Maya calendar's "Long Count" runs out on Dec. 21, 2012, and that a world-changing crisis will occur at that time. Other folks, including the modern-day Maya, say that's just a load of llama crap ... and that 12/22/2012 will merely mark the start of a new calendar cycle.

    And then there's Gerardo Aldana, a professor at the University of California at Santa Barbara, who says they're all probably wrong.

    Aldana contends that the calculations we've used to match up the Maya calendar to our modern reckoning could be off by as much as 50 to 100 years, and that the Long Count may have already ended. If Aldana is right, the timetable for the apocalypse may already be up. Which might explain why "Apocalypto" director Mel Gibson's been acting so weird lately.

  • 9. Why it's OK for birds to be gay

    Image: Gay geese
    Nearly one-fifth of all long-term greylag geese couples are gay, composed of two males.

    Scientists have found more than 130 bird species that engage in some sort of same-sex hanky-panky — and the males in some of those species, such as penguins and greylag geese, occasionally form long-term sexual relationships with each other.

    That's presented a puzzle for some evolutionary biologists, because same-sex relationships would seem to reduce the birds' chances of reproductive success. Believe it or not, gay birds are quite a research topic ... not that there's anything wrong with that.

    Geoff MacFarlane, a biologist at the University of Newcastle in Australia, and colleagues reviewed studies of 93 bird species and suggested that there was a relationship between the rearing of young and same-sex mating. Male homosexual behavior would be likelier if the females of the species took care of the chicks. "Homosexual behavior is more likely to be maintained and not be selected against than if you are a sex that cares a lot for offspring and only has one or few reproductive partners," MacFarlane said.

    Are you still curious? Find out why some scientists think mercury pollution may spark bird homosexuality, and learn more about the bizarre study of a homosexual necrophiliac duck.

  • 8. The race to create A.I. as smart as a cat

    Are cats worried about the Pentagon's efforts to match their intelligence with an artificial brain? What do you think?

    Puss-Bob is not amused: He's heard the reports claiming that Pentagon-funded scientists are trying to create an artificial brain as intelligent as a cat, of course, but he realizes this is a grossly oversimplified description of the SyNAPSE project.

    He knows the real point of the research is to build electronic networks that mimic biological brains, using new types of devices known as memristors. Such networks could "learn" by taking in additional information from the environment and adapting accordingly.

    The technology could produce smarter robotic scout vehicles for the U.S. military, IEEE Spectrum reports. But Puss-Bob highly doubts that memristor-based neural networks will ever match the intelligence of cats. Dogs, maybe ... but not cats.

  • 7: 'Da Vinci code' in Mona Lisa's eyes?

    V.A Sole  /  CNRS via AP
    Leonardo da Vinci's "Mona Lisa" is examined with X-ray fluorescence spectroscopy.

    The Mona Lisa is one of the great masterpieces of the art world, but it's also a great generator of weird science. In past years, researchers have said that they've tracked down the inspiration for Leonardo da Vinci's portrait, found a nude version of the painting and figured out what Mona Lisa's voice sounded like.

    In 2010, Italy's national committee for cultural heritage claimed that Leonardo painted tiny, almost invisible letters in Mona Lisa's eyes. The committee's president, Silvano Vinceti, said the lines in one eye appear to form the initials "LV," perhaps standing for the artist's name. The other eye seems to contain the letters "CE" or perhaps "B." And still more letters and numbers were spotted in other areas of the painting.

    But are they really there? Several experts have said the committee is probably reading too much into the painting's patterns of tiny cracks. Among art historians, at least, this "Da Vinci Code" is no best-seller.

  • 6. Which came first, chicken or egg?

    Image: Chicken and egg
    Which came first, the chicken or the egg? The scientific answer is problematic.

    Which came first? The chicken or the egg? The question is really more of a philosophical conundrum, like the old "immovable object vs. irresistible force" conflict. But in 2010, British research into the process of eggshell formation was heralded as providing a scientific answer to the riddle.

    Biologists from Sheffield and Warwick universities reported that ovocleidin-17, a protein found in a chicken's ovaries, played an essential role in building eggshells from calcium carbonate crystals. That led some chicken-or-egg philosophers to claim that the first chicken egg could exist only if it was created inside a chicken.

    Actually, it all depends on your definitions: We know that dinosaurs laid eggs, for example, so eggs clearly predate chickens. And if a prehistoric not-quite-chicken laid an egg that contained the first honest-to-goodness chicken, based on its genetic coding, do you count that as a chicken, or a chicken egg? Try using that one if you're ever captured by "Star Trek" androids.

  • 5. Giant storks may have fed on hobbits

    Inge van Noortwijk
    The extinct giant stork Leptoptilos robustus would have dwarfed the "hobbit" Homo floresiensis living on the Indonesian island of Flores.

    "The storks! The storks! They're eating Frodo!" J.R.R. Tolkien's "Lord of the Rings" saga might have had a horror-movie ending if it reflected the fossil evidence found on the Indonesian island of Flores.

    Flores is known as the site where scientists discovered the remains of a species of hominids known as Homo floresiensis. The creatures, which apparently went extinct about 12,000 years ago, have been nicknamed "hobbits" because of their short stature.

    Now paleontologists say they've unearthed wing and leg bones from carnivorous storks in the same cave where the Homo floresiensis bones were discovered. The storks, which apparently stood nearly 6 feet tall, could have fed on other birds as well as fishes and lizards — "and possibly in principle even small, juvenile hobbits, although we have no evidence for that," the Smithsonian Institution's Hanneke Meijer told LiveScience.

    What sound do giant storks make when they're swallowing? Gollum! Gollum!

  • 4. Cricket's testicles set world record

    University of Derby
    The male Tuberous bushcricket has testicles (shown here) that amount to 14 percent of its body weight.

    Now here's a bug with balls: The tuberous bushcricket's testicles account for 14 percent of its body weight, according to researchers at the University of Derby in England. That means the cricket's cojones are the largest in the animal world, based on proportion to total body mass.

    To put the cricket's statistics in perspective, the testicles of a man weighing 200 pounds (91 kilograms) with that ball-to-body ratio would weigh 28 pounds (12.7 kilograms). Or basically the weight of two bowling balls.

    Why would a cricket need testes that big? The researchers suggest that the large size lets male crickets capitalize quickly on breeding opportunities with multiple mates. But size is always relative, and often deceiving. Turns out that the runner-up in the ball-to-body competition is the humble fruit fly, with testes that make up more than 10 percent of body weight.

  • 3. Better transit design through ... slime mold?

    Image: Slime mold
    Science / AAAS
    The left image shows slime mold growing out to connect food sources laid out like a map of rail stations. After 26 hours, the mold resolved itself into an efficient network of tubes connecting the sources

    It's hard to imagine a scientific specialty that's weirder than slime mold, but researchers from Hokkaido University in Japan has been able to make the weird life form do some wonderful things.

    First, the scientists used slime mold's food-finding prowess to solve labyrinth puzzles. This year, they published research showing how the mold's growth patterns could reflect the optimal routes for mass transit links ... on a map where bits of food stood in for train stations. Those dubious achievements earned them not just one, but two Ig Nobel Prizes for silly science.

    The Hokkaido team isn't the only one working with the humble organism: British scientists say they've constructed a rudimentary slime-mold computer nicknamed the Plasmobot. So where does America stand in the race to harness slime mold? And what are we going to do about the slime gap?

  • 2. How beer sparked civilization

    Image: ancient vessel
    University of Pennsylvania
    Fragments of a jar unearthed in Iran contain the chemical residues of beer from more than 5,000 years ago.

    Some people might say the invention of fire sparked the rise of civilization. But Brian Hayden, an archaeologist at Simon Fraser University, suggests that another innovation may have played a crucial role: beer.

    The age of agriculture dawned about 11,500 years ago when Neolithic peoples began domesticating wild grains such as barley and rice. Hayden is among a number of archaeologists who say the motivation for domesticating those cereals might have been to brew alcoholic drinks for ceremonial use. "It's not that drinking and brewing by itself helped start cultivation, it's this context of feasts that links beer and the emergence of complex societies," Hayden says.

    The earliest chemical evidence for beer comes from residues inside a jar excavated in Iran that is dated to between 3400 and 3100 B.C. Other evidence suggests that beer gave ancient Africans a healthy dose of antibiotics, and that women took on the primary role for brewing beer in ancient Peru. For still more, check out our interactive gallery of ancient drinks.

  • 1. Stone Age carving may be ancient sex toy

    Image: Bone carving
    Peter Zetterlund  /  Swedish National Heritage Board

    The top vote-getter in the 2010 Weird Science Award competition may not be totally suitable for work ... but hey, this is archaeology, right? Researchers suspect that a carved piece of antler bone, found at a Stone Age site in Sweden that goes back as far as 6000 B.C., might have been an ancient sex toy.

    The object is about 4 inches long and an inch wide, with a knobby end as well as a pointy end. The pointy end suggests that despite its phallic appearance, the bone could have been used for chipping flakes of flint. Sigmund Freud is said to have observed that "sometimes a cigar is just a cigar," and sometimes a Stone Age tool is just a Stone Age tool.

    Even if the antler bone is judged to be a sex toy, it's not the oldest of its type: A polished stone phallus found in Germany is thought to be about 28,000 years old, while a 35,000-year-old female figure with exaggerated breasts could be considered the world's oldest-known porn.

  • Weirdly honorable mentions

    Image: Mouse
    Stephanie Pappas / LiveScience
    This mouse is among many that was born with genetic contributions from two male mice.

    Even though we offered up a long list of nominees for the Weird Science Awards, there are always some additional discoveries that deserve recognition. Here are four honorable mentions for 2010:

    • Mice with two dads: Researchers reprogrammed mouse cells and then used unconventional breeding tricks to produce some cute babies with genetic contributions from two male mice (but carried to term by mommy mice, of course). The experiment suggested a method by which same-sex human couples could eventually have genetic progeny.
    • Chimps with stick dolls: Female chimpanzees have been observed in the wild cuddling and playing with sticks and small logs, much like human children do. In contrast, such behavior has not yet been seen among male chimps, leading researchers to wonder whether gender differences in styles of play extend beyond humans to other species.
    • Mice that sing like birds: In the course of developing new breeds of genetically engineered mice, Japanese researchers happened upon a mouse that made tweeting noises like a bird. The tweeting trait could be passed along to the generations that followed, and the lab says it now has more than 100 "singing mice." Listen to the chirping mice on YouTube.
    • 8-year-olds publish scientific paper: One of the more unusual papers published in Biology Letters was illustrated with diagrams that looked as if they were scrawled by elementary-school students. That's because they were. The peer-reviewed report, written by 8- to 10-year-olds from Blackawton Primary School in Devon, England, represented a "genuine advance" in the study of bumblebee vision, the Royal Society said.

    For still more scientific strangeness, review the 2010 Weird Science Awards.


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