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The Human Body Shop
By Jim Stallard
Once the stuff of science fiction, bionic devices are quickly becoming integrated into medical practice and transforming human lives. As bioengineering becomes more sophisticated, researchers are developing novel devices that allow individuals with certain physical impairments to regain independence and better interact with the world.
Although bionics may be associated in the popular imagination with THE SIX MILLION DOLLAR MAN, efforts in this field are focused more on restoring a person's capacities, not improving them. Rather than becoming "better, stronger, faster," most potential users of these technologies simply want to achieve the capacities of the average person -- in many cases, like the patients themselves used to be.
Linking with the Brain
Synthetic devices in the body are nothing new; it has become routine to implant artificial hips, pacemakers, and insulin pumps. But over the next two decades technologies that interact with the nervous system, or more specifically the brain, may become more commonplace. These advances may restore a blind woman's ability to see or a paralyzed man's power to move -- capacities that otherwise would have been lost forever.
Of all the body's cell types, nerve cells (neurons) in the central nervous system (the brain and spinal cord) are thought to be unique in lacking the ability to regenerate. Elsewhere in the body, a cut in the skin will heal, broken bones will mend, and blood will be replenished, but a damaged or diseased cell in the brain or spinal cord will not be replaced. Until now, a person who suffers loss of vision or hearing or is paralyzed by a stroke has mostly been resigned to that fate forever. This severe consequence is what makes advances in neurally interactive technology so profound.
Decades of basic research have clarified how individual neurons pass signals to one another and along pathways to the brain or muscles. Scientists know how electrical events trigger an impulse within a neuron, and how chemical processes transmit the signal from one neuron to another or to a muscle cell. Scientists also are able to monitor or stimulate a single neuron. The passage of information is a matter of electrical input and output on a minute scale, and technological advances have allowed researchers to measure these transmissions and impart their own. On a very basic level, the language spoken by humans and machines is the same.
This understanding has led to the development of neuroprosthetics, artificial devices that link the body's nervous system (mainly the brain) with the external environment. Neuroprosthetics allow passage of electrical signals in either direction. They can transmit sensory information from the external world to the brain, to restore--to some extent--the ability to see or hear. They also can receive commands from the brain to create motion through artificial limbs or communicate thoughts or wishes.
One neuroprosthetic, the cochlear implant, is already helping people who are hearing-impaired. These devices operate through small electrodes placed in the cochlea, a snail-shaped organ of the inner ear. The implant bypasses faulty nerve endings, transmitting sounds through the auditory nerve to the brain. So far, more than 59,000 people worldwide have received these devices.
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