Published April 13, 2010
Adapted from the book The Scientific American Brave New Brain.
The six-million dollar man was pure fantasy in the 70s -- but largely realistic technology today. And the future of this tech is even wilder: Implantable brain electrodes may be just around the corner.
Futurists and science-fiction writers have long speculated about merging human and machine, especially human brains and computers. These dreams are slowly becoming reality: The deaf are hearing with bionic "ears," the blind see with the aid of electrodes, an amputee is moving a prosthetic arm by thought, a man paralyzed with locked-in syndrome is "speaking" through a brain electrode connected to a computerized synthesizer.
One such bionic advance -- thought-driven neural implants -- could change the lives of millions of people, including the many thousands conscious but now entombed within their own bodies in what's called locked-in syndrome, and the thousands of wounded warriors returning from battle with missing limbs and devastating brain injuries. And it could open tremendous opportunities for people in the future who would like to take their minds where no man's body has gone before -- into deepest space or the deepest of ocean depths, for example, through the "senses" of a thought-driven robot.
Neural implants listen to the brain's instructions for movement, even when actual movement is no longer possible, and decode the signals for use in operating a computer or moving a robot or an artificial limb. The technology for the basic requirements -- powerful microprocessors, improved filters, and longer-lasting and smaller batteries -- has advanced rapidly, boosted by funds from many sources, including the U.S. Department of Defense, which sponsors research in prosthetics for wounded war veterans. Years of animal research have revealed neuron activity and the brain's amazing plasticity: the ability to revise itself.
But the research application has been slow. Scientists first had to determine what parts of the brain were controlling movement so they could figure out where to apply the brain wave sensors or electrodes. It's quite complex. Several approaches have been taken, involving tapping into various places in the brain involved with the interface between muscle movement and thought.
One of the ongoing experiments with implanted electrodes could possibly lead to the level of targeting needed. Philip R. Kennedy of Neural Signals, Inc., and his colleagues designed a device that records the output of neurons. The hookup lets a stroke victim send a signal, through thought alone, to a computer that interprets it as, say, a vowel, which can then be vocalized by a speech synthesizer, a step toward forming whole words.
"Thought is gazillions of neurons firing in ensembles," says Kennedy. "We're trying to pick the right ones, and there's an enormous amount of trial and error." He compares thought to a wind blowing over a vast field of wheat and his work as looking for the specific stalks of wheat that move. He has had to find a way to separate speech signals from neural noise without animal research to guide him, because no other animal except humans has speech.
Brown University neuroscientist John Donoghue, the second scientist after Kennedy to develop a neural prosthesis for human implantation, is teaming up with biomedical engineer Hunter Peckham of Case Western Reserve University, who has developed an electrical device that stimulates nerves or muscles to enable some movement after a partial or lower-level spinal cord injury. Peckham has a system that allows simple, preprogrammed motions, such as boosting a person from a wheelchair to a walker. By linking a neural prosthesis to the device, Donoghue and Peckham hope to create an enormously more effective system.
Tapping into individual neurons is next: using nanoscale fibers, measuring 100 nanometers or less in diameter (a nano is one billionth of a meter) that could easily tap into single neurons because of their dimensions and their electrical and mechanical properties. Jun Li of Kansas State University and his colleagues have crafted a brush-like structure in which nanofiber bristles serve as electrodes for stimulating or receiving neural signals. Li foresees it as a way to stimulate neurons to allay Parkinson's disease or depression or to flex astronauts' muscles during long space flights to prevent the inevitable muscle wasting that occurs in zero gravity.
We're not there yet. But consider the potential, from the prosaic to the grand. A neurochip and computer backpack might allow a person to move limbs that have been stilled by spinal injury. The rest of us would just like to be able to download traveler's Japanese for that trip to Tokyo.
Adapted with permission of the publisher, John Wiley & Sons, Inc., from The Scientific American Brave New Brain by Judith Horstman. Copyright © 2010 by John Wiley & Sons, Inc. and Scientific American.