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Monday, November 12, 2007

Thinking Makes It So: Science Extends Reach Of Prosthetic Arms.

Thinking Makes It So: Science Extends Reach Of Prosthetic Arms.

Diagram of the new prosthetic arm, still under development, which will respond directly to the brain's signals.

Motorized prosthetic arms can help amputees regain some function, but these devices take time to learn to use and are limited in the number of movements they provide.

Todd A. Kuiken, M.D., Ph.D., a physiatrist at the Rehabilitation Institute of Chicago and professor at Northwestern University, has pioneered a technique known as targeted muscle reinnervation (TMR), which allows a prosthetic arm to respond directly to the brain's signals, making it much easier to use than traditional motorized prosthetics. This technique, still under development, allows wearers to open and close their artificial hands and bend and straighten their artificial elbows nearly as naturally as their own arms.

"The idea is that when you lose your arm, you lose the motors, the muscles and the structural elements of the bones," Kuiken explained. "But the control information should still be there in the residual nerves." He decided to take the residual nerves, which once carried the commands from the brain to produce arm, wrist and hand movements, and connect them to the chest muscles so that the signals can be used to move the artificial limb.

Nearly a dozen patients who have undergone TMR so far have motorized prosthetic arms that produce two arm movements: open and close hand and bend and straighten elbow. But in a new study from the Journal of Neurophysiology, published by The American Physiological Society, Kuiken and his colleagues demonstrate that TMR has the potential to provide an even greater number of arm and hand movements, beyond the four they've already achieved. The researchers have begun work with two U.S. Army medical centers to help soldiers who have lost limbs.

Redirects nerves

Kuiken first got the idea for TMR when he was a graduate student during the 1980s. In his first patient, Kuiken took four nerves that had gone to the amputated arm and redirected them to the patient's chest muscles. As a result, when the patient wants to close his hand - a hand that is no longer there - the impulse travels down the nerve, into his chest and causes the chest muscle to contract.

The next step was to use the muscle contraction in the chest to move the prosthetic arm. This was accomplished with the help of an electromyogram (EMG), which picks up the electrical signal that the muscle emits when it contracts.

The signal is directed to a microprocessor in the artificial arm which decodes the signal and tells the arm what to do. In their work thus far, Kuiken and his colleagues have programmed the processor in the prosthetic arm to recognize four signals to produce two arm movements: open and close hand and bend and straighten elbow.

The result? When the patient thinks 'close hand' the hand closes. Contrast this with current motorized prosthetic arm technology: The patient has to learn to use new muscle groups to move the prosthetic arm; can perform only one movement at a time; and must contract two muscles at once to achieve a new movement.

"It's not very common to flex your chest muscle to close your hand or bend your wrist," said Kuiken. "Quite frankly, most people with a unilateral shoulder disarticulation amputation don't wear a prosthesis at all: It's just too cumbersome."

More moves

While TMR is more intuitive and natural, Kuiken and his team wanted to see if they could extract more of the wealth of information from the electrical signals produced by the nerves and chest muscles and harness it to provide a greater number of hand and arm movements.

In the study published in the Journal of Neurophysiology*, they placed between 79-128 electrodes from the EMG onto the chest muscles of five patients to see if they could identify the unique EMG patterns emitted with 16 different elbow, wrist, hand, thumb and finger movements they asked the patients to perform. The EMG signals from each of the 16 movements were analyzed using advanced signal processing techniques. The study found that the researchers could recognize the signals associated with the different arm movements with 95% accuracy.

The next step is to use this information to program these new moves into the microprocessor of the artificial arm, so that instead of just opening and closing a hand and bending and straightening an elbow, now the signals can produce various hand grasp patterns, such as the one needed to hold a baseball, pick up a pen or grasp a tool.

May benefit soldiers

Kuiken and his colleagues have begun to work with the military at Brooke Army Medical Center at Fort Sam Houston in Texas and the Walter Reed Army Hospital in Washington, D.C. to apply this technology to soldiers who have lost limbs.

"We're excited to move forward in doing this surgery with our soldiers some day," he said. "We've been able to demonstrate remarkable control of artificial limbs and it's an exciting neural machine interface that provides a lot of hope."

There are a couple of additional things to note in the work of Kuiken and his colleagues: They performed nerve transfer surgery 9-15 months after the injury that led to amputation, showing that these neural pathways remain intact, even when they have not been used for awhile.

Also, when the researchers touch these patients on their chests, the patients say it feels like they are being touched somewhere on their arm or hand -- the arm or hand that is no longer there. That's not really surprising, because the brain receives an impulse from a nerve that used to go to the arm. The brain doesn't know the nerve is now embedded in a different muscle, and interprets this touch as it always has.


In medicine, a prosthesis is an artificial extension that replaces a missing body part. It is part of the field of biomechatronics, the science of fusing mechanical devices with human muscle, skeleton, and nervous systems to assist or enhance motor control lost by trauma, disease, or defect. Prostheses are typically used to replace parts lost by injury (traumatic) or missing from birth (congenital) or to supplement defective body parts. In addition to the standard artificial limb for every-day use, many amputees have special limbs and devices to aid in the participation of sports and recreational activities.

Mechanical and Electronic Components.

In order for a robotic prosthetic limb to work, it must have several components to integrate it into the body's function:

Biosensors detect signals from the users nervous or muscular systems. It then relays this information to a controller located inside the device, and processes feedback from the limb and actuator (e.g., position, force) and sends it to the controller. Examples include wires that detect electrical activity on the skin, needle electrodes implanted in muscle, or solid-state electrode arrays with nerves growing through them.

Mechanical sensors process aspects affecting the device (e.g., limb position, applied force, load) and relay this information to the biosensor or controller. Examples: force meters and accelerometers.

The controller is connected to the user's nerve and muscular systems and the device itself. It sends intention commands from the user to the actuators of the device, and interprets feedback from the mechanical and biosensors to the user. The controller is also responsible for the monitoring and control of the movements of the device.

An actuator mimics the actions of a muscle in producing force and movement. Examples include a motor that aids or replaces original muscle tissue.

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Intel to Unveil Chips for Improving Video Quality on the Web

Intel to Unveil Chips for Improving Video Quality on the Web

Intel plans to announce a family of microprocessor chips on Monday that it says will speed the availability of high-definition video via the Internet.

Sean Maloney, Intel's chief sales and marketing officer, said last week that the chips' increased computing power would begin the transformation of today's stuttering and blurry videos, the staple of YouTube and other video streaming sites, into high-resolution, full-screen quality that will begin to compete with the living room HDTV.

"It's biggest impact is high-definition video," he said. "It will be highly addictive."

As consumers clamor for more Internet video, a huge computing burden is placed on companies like Google, Microsoft and providers of digital video, who must compress the video files so they can be streamed to desktop and portable computers.

Intel's new family, made up of 16 processors, would first be used in servers and high-end desktops that compress the video. They are the first chips based on a new manufacturing process that Intel says will give it a significant competitive advantage by increasing computing performance while reducing power consumption.

The chips, which were developed under the code name Penryn, use a re-engineered transistor that is about half the size of its predecessor. It switches more quickly, requires less switching power and leaks less current than that previous transistor.

The chip industry measures its progress by the width of one of the smallest features of a transistor. Much of the industry is now building chips in what is known as 90-nanometer technology (a nanometer is one-billionth of a meter). At that scale, about 1,000 transistors would fit in the width of a human hair. Intel began making chips at 65 nanometers in 2005, about nine months before its closest competitors.

The Penryn chips are at the next stage of refinement, just 45 nanometers. The company said it would be able to squeeze up to 820 million transistors onto a single silicon die. The company is making the chips at two factories, in Oregon and Arizona. Next year, it will add two plants, in Israel and New Mexico.

The first products based on the new manufacturing technology will be Intel Core 2 and Xeon microprocessors. Chips for notebook PCs, marketed as the Intel Core 2 Extreme and Intel Core 2 Duo, will be available in the first quarter of next year.

To get better video compression, Intel has added a set of 46 instructions it calls SSE4 to the new microprocessors.

The leading designer of the new processor, Steve Fischer, said the new instructions would make possible a new generation of servers that enhance the compression of digital video.

"Video is becoming ubiquitous on the Web," he said.

"This is a step in the right direction," said Richard Doherty, president of Envisioneering, "and it's probably the best use for this 45-nanometer technology over the next couple of years."

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Intel Launching New Chip Lineup

Intel Launching New Chip Lineup

Intel Corp. plans to roll out its newest generation of processors Monday, flexing its manufacturing muscle with a sophisticated new process that crams up to 40 percent more transistors onto the company's chips.
The world's largest semiconductor company expects to start shipping 16 new microprocessors - which also boast inventive new materials to stanch electricity loss - for use in servers and high-end gaming PCs .
The most complex chips being launched Monday have 820 million transistors, compared with the 582 million transistors on the same chips built using the current standard technology. Intel's first chips, introduced in the early 1970s, had just 2,300 transistors.

Advances in chip technology occur as smaller and smaller lines are etched onto the chips. Intel's new chips shrink the width of those lines to an average of 45 nanometers, or 45 billionths of a meter, compared to 65 nanometers on the previous generation of chips .

The smaller circuitry allows Intel to squeeze more transistors - the building blocks of computer chips - onto the same slice of silicon. That accelerates performance and drives down manufacturing costs.

The transistors on the new chips are so small that more than 30 million of them can fit onto the head of a pin. Performance zooms ahead with smaller transistors because more of them are available, they twitch faster to process data and less energy is required to power them.

Perhaps more importantly, the transistors on the Santa Clara-based company's new chips are built with new materials that help solve the critical problem of electricity loss as the circuitry gets smaller and smaller.

As electricity escapes from the chip, more power is needed to fuel its operations, leading to shorter battery life in laptop computers or higher electricity costs to run the machines.

"This is more than just a new process shrink," Tom Kilroy, general manager of Intel's Digital Enterprise Group, said. "Forty-five nanometers is wonderful and we get an uplift, but it really is the reinvention of the transistor."

Intel, which plans to spend up to $8 billion on upgrading or building factories for the 45-nanometer chips, is at least six months ahead of smaller rival Advanced Micro Devices Inc. in moving to the new technology.

Intel plans to launch new chips designed for mainstream desktop and laptop computers in the first quarter of 2008. Sunnyvale-based AMD, which partners with IBM Corp. on chip-making technology, is targeting mid-2008 to start selling its 45-nanometer chips.

AMD has long maintained that its chips have certain design advantages that keep them competitive with Intel's best offerings. One of those features is an integrated memory controller, which AMD has long championed.

Intel only said recently it would begin incorporating the controllers into future generations of chips.

"When you get myopic on the focus on the nanometers in the CPU, you can lose focus on the entire solution," said AMD spokesman John Taylor.

Intel's launch Monday includes server chips with frequencies of 2 gigahertz to 3.20 gigahertz for the quad-core models, which have four processing engines. The clock speed for dual-core models, which have two processing engines, goes up to 3.40 gigahertz. The measurements refer to the chips' processing cycles, or how fast they can process information.

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