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What is the Brain-Machine Interface
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Victor D. Chase, 02/13/2007
A family of new medical devices designed to return sight to the blind, movement to the paralyzed, and hearing to the deaf are poised to enter the physician’s arsenal of weapons. Known collectively as neural prostheses, these implantable devices interact directly with the nervous system and allow for the amelioration of conditions that heretofore have been beyond the pale of medical ministrations.
Neural prostheses include retinal implants, auditory brainstem implants, functional electrical stimulation systems to activate paralyzed muscles, and brain-computer interface systems to enable locked-in patients to manipulate a computer via their thoughts. Cochlear implants, which have already returned hearing to thousands of deaf individuals, also fall into this category. Eventually, electrodes implanted in the brain ? currently used for a brain-computer interface ? could conceivably be used to enhance the memory, learning ability, concentration, and visual and auditory capabilities of able-bodied individuals as well.
Along with the potential to do great good, neural prostheses also present a minefield of ethical questions that must be dealt with as the technology approaches clinical utilization. Having learned from the missteps of some earlier medical researchers, it is now difficult, if not impossible, to find a neural prosthetic investigator who has not, to one extent or another, considered the ethical ramifications of his or her work. This fact became evident to me as I researched my recently released book about neural prostheses, Shattered Nerves: How Science Is Solving Modern Medicine’s Most Perplexing Problem.
Because many neural prosthetic devices are at or near the human testing stage, the ethical questions of most immediate concern revolve around determining when an implant is ready for human testing and how researchers can ensure that volunteers fully appreciate what they are getting into. As for when to test these implants in humans, physicians ? who by nature and training are oriented toward taking quick action ? are generally prone to come down on the side of implanting sooner rather than later, whereas engineers tend to be a more cautious lot who favor waiting until every conceivable facet of animal testing is exhausted.
Indicative of the lack of census on this issue are the stances taken by Philip Troyk, a professor of bioengineering at the Illinois Institute of Technology in Chicago, who heads a visual cortex project, and Terry Hambrecht, a physician who is also an electrical engineer and the former head of the National Institutes of Health’s Neural Prosthesis Program. Hambrecht had experimentally implanted penetrating microelectrodes in the visual cortices of several humans following years of safety testing in monkeys. The work demonstrated that an individual who was totally blind could experience spots of light at precise locations in the visual field. Troyk, however, is not convinced that the brain will be able to create coherent images out of spots of light, and feels that before further human testing is conducted, his team needs to understand more about how the brain breaks the signals received from the million nerve fibers in the optic nerve into their constituent parts and then processes them to create vision.
“We feel we are obligated to try, to the best we scientifically can, to understand that we can manipulate the visual system at the fundamental level. Then we will have something to offer the human volunteer. . . . It’s a much more sophisticated argument than just saying, ‘Put it in, try it, and see what you get,’” said Troyk. Hambrecht takes exception. He feels that Troyk’s further experimentation in monkeys could “seriously delay the development of a visual prosthesis for blind humans. I feel that our NIH group’s human experimentation answered essentially all the significant questions that might have been asked in monkeys and raised pattern recognition, stimulation interaction, and cognitive adaptation questions that can only be answered with more sophisticated implants in blind humans,” he said.
When it comes to the related question of informed consent, however, there is universal acceptance of the need to ensure that potential test subjects are made fully aware of the risks involved and are not swayed by desperation. The numerous interviews I conducted with recipients of various neural prostheses indicate that investigators are doing a good job of informing volunteers of the pros and cons of their participation. All of the patients said they had been made fully aware of the fact that the devices they were receiving were experimental in nature and held little if any promise of benefiting them directly. While they obviously hoped to realize at least some improvement in their conditions, the patients had realistic views of the potential outcomes. In fact, I did not speak to one person who voiced regret over having volunteered to receive an implant, even though in some cases the benefit was small and in others there were setbacks. And surprisingly, none of them was greatly concerned about having an unproven foreign object implanted in their bodies.
While the physical risks of receiving experimental neural prosthetic implants are given careful scrutiny, academic discussions of informed consent tend to overlook the psychological impact of participation in test programs, which in the vast majority of cases is positive and substantial. Some test subjects draw considerable satisfaction from feeling that they are full-fledged members of the research teams developing their implants, a feeling that is reciprocated by the researchers themselves. The volunteers also derive satisfaction from knowing that they may be helping future generations of people with similar maladies. It seems to give their deprivations purpose. As Harold Churchey, an experimental retinal implant recipient blinded by retinitis pigmentosa, put it, “Even though I might be over the hill, if I can help some young person, I’m for it, so long as the good Lord gives me strength.”
As for the physical improvements realized by the volunteers, however small, it was uncanny that even though each of the patients I spoke with was interviewed individually, they virtually all used essentially the same language to describe their response, namely that “something is better than nothing.”
As Connie Schoeman who can now see small spots of light generated by the 16-electrode array that sits on her right retina told me, “With something like retinitis pigmentosa, where there has never been anything that could be done to help people, this is going to offer an opportunity, maybe not to get complete vision back, but something. And something, I tell you, sure beats nothing.” Ditto for Marilyn Davidson, who was the first person to be implanted with an auditory brainstem implant. The original device had to be removed due to complications, and though the hearing it afforded her was quite limited, she clamored for another system saying, “I had the ABI long enough to know it helped me, and anything is better than nothing.”
Then there is Jim Jatich, a quadriplegic who wears two hand manipulation implants, who asked, “How do you repay someone for giving you the use of your hands back?” And Jennifer French, paralyzed in a snowboarding accident yet able to walk down the aisle at her wedding with an experimental standing implant, who said, “There is nothing better than looking back at an empty wheelchair.”
The potential for neural prostheses to do good must be tempered with the understanding that the road to realization is pitted with potholes that remain to be negotiated. Yet the promise is stimulating indeed.
- Victor D. Chase is a science and technology writer based in Yorktown Heights, NY.
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