Artificial limbs to gain touch sense
June 13th 2011 21:44
In an underground laboratory at the University of Chicago, neuroscientist Sliman Bensmaia peered at a blue computer monitor attached by wires to a rhesus monkey's brain.
A lab technician grazed the animal's finger using a metal probe, and the computer screen erupted in red.
"That's pretty cool," said Bensmaia, grinning. "You can see the brain becoming active just by tapping the hand."
Next, instead of tapping the animal's hand, the technician planned to run a small current of electricity through electrodes in the animal's brain to simulate the probe. If the animal looked in a certain direction, the scientists would know the virtual touch worked.
The research is part of a groundbreaking quest to accomplish what was once the stuff of science fiction -- build a machine that helps humans to feel.
Funded by the Defense Advanced Research Projects Agency (DARPA) and spurred by the return of injured Iraq and Afghanistan war veterans, these researchers aim to design prostheses that will not only be able to move, but also provide amputees and quadriplegics with a sense of touch.
Scientists have known for more than a century that applying electricity to neurons can elicit certain reactions -- a muscle twitch, a sudden feeling of euphoria, a long-forgotten memory recalled. But stimulating those cells to help people overcome certain disabilities has only been done more recently, spearheaded in the 1960s by the development of the Cochlear implant for hearing.
Unlike hearing or vision, however, touch research languished for decades, hobbled by the expensive machinery needed to perform experiments and a certain "not as sexy quality," Bensmaia said.
But then hundreds of wounded veterans began returning to the U.S. without arms or legs or the use of their limbs because of spinal cord injuries, and interest in developing better prostheses spiked.
Through the DARPA project, scientists at Johns Hopkins University Applied Physics Laboratory last year completed a new prosthetic arm, which can rotate, twist and bend in 26 different ways. Scientists also recently outfitted patients with brain electrodes that allowed them to move simpler robotic arms with their thoughts.
Without any tactile feedback, however, the usefulness of the prostheses is limited. Lacking the sense of touch, patients could not, for example, differentiate between corduroy and silk, a pen and a pencil or a poke and a punch.
More important, "they have to constantly be visually monitoring what they are doing, or they wouldn't know whether they were holding or crushing something," Bensmaia said.
So last year, Johns Hopkins gave Bensmaia's lab about $1.5 million of its federal money to develop even more advanced prostheses that will eventually give the users a simulated sense of touch through the machine's metal and motors.
But how do you replicate the feeling of a coffee cup in your hand or the difference between a 5- and 50-pound weight? The Chicago scientists set out to identify and replicate the qualities of touch, including texture, shape and force, through complex mathematical equations known as algorithms.
Scientists implanted platinum alloy electrode arrays, each the size of a pencil eraser, into the rhesus monkeys' brains. The scientists then created neural impulses by emitting small, but focused, electrical currents, and recorded the animal's behavior in response.
After simulating thousands of different touch sensations, Bensmaia and his team hope to build algorithms, essentially mapping out the way the brain reads those touches. They will then use those sensory algorithms to build software for the robotic arm's computerized sensors that will transmit impulses to electrodes in the human brain, mimicking touch.
Josh Berg, Bensmaia's study director, took a step back from the testing room and grasped at an apt summary.
"Up here, we are not vision, touch or smell," said Berg, grabbing his head between his hands. "We are all electricity. What we are trying to do is translate information into a language the brain can understand."
Since 2006, the DARPA, which is part of the Department of Defense, has poured $129 million into its Revolutionizing Prosthetics program. Johns Hopkins and its collaborators expect to implant electrodes in the first human patient this summer.
A second patient would get implants in 2012 that would include a feedback loop, providing a sense of touch based on algorithms developed in Bensmaia's lab. And a third patient would get implants in 2013 that may allow the patient to operate two prosthetic arms using a wireless transmission system.
University of Chicago neuroscientist Nicho Hatsopoulos recently applied to work on the development of that wireless system. Hatsopoulos, who specializes in the neuroscience of movement, co-founded Cyberkinetics Neurotechnology Systems, which was one of the first companies to implant electrodes in humans in order to control machines with their thoughts.
"Where we are right now is basically the beginning stages of the $6-million man," said Hatsopoulos, standing in his laboratory while a rhesus monkey moved a cursor around a computer using only his thoughts.
But some worry that the same technology might also be used for more ethically complicated purposes. They imagine soldiers using their thoughts to fly airplanes and maneuver combat robots in war zones.
| 39 |
| Vote |
Add To: 
subscribe to this blog
Comment by katyzzz
Photography Tips
MS Paint Art