Shortly after receiving his doctorate in biomedical engineering, Illinois Institute of Technology scientist Philip Troyk attended his first meeting on neuroprosthesis research at the headquarters of the National Institutes of Health (NIH) in Bethesda, Maryland.
He immediately became enthralled with pioneering research in NIH’s Neural Prosthesis Program. Most intriguing was a project to develop a device for the blind that would restore vision by channeling electronic stimuli into the brain’s visual cortex—where, normally, neural impulses from the eyes are converted into the moving images called “sight.” Such a device could benefit as many as two million persons who are blind or suffer severe visual impairment.
“All of the neuroprosthesis projects that were being done at the NIH were interesting, but it was clear that a visual prosthesis that could be implanted in the brain to restore vision was the big trophy—the Holy Grail of neural-prosthesis research,” Troyk says.
The year was 1983, and Troyk pledged to attend future meetings on neural-prosthesis research, immerse himself in the literature, and get acquainted with leaders in the field.
“I always had a fascination with marrying electronic technology and the human body. The possibilities stirred the imagination,” says Troyk, now associate professor of biomedical engineering in IIT’s Pritzker Institute of Biomedical Engineering.
Troyk’s imagination was put to a big test in 1996, when events moved IIT rapidly—and unexpectedly—from the sidelines into the vanguard of visual-prosthesis research. Early in the year, IIT was awarded a $1 million NIH contract to design and fabricate an implantable visual prosthetic device for the blind, based on electronic stimulation of the visual cortex. However, several months into the project, NIH officials announced plans to abandon the human research, citing as one of the reasons its inability to guarantee human volunteers lifelong maintenance of visual-prosthesis implants.
Initially, the decision was a devastating blow for those whose careers had been devoted to advancing the research and who now felt the once unimaginable was within reach. In addition, IIT researchers had already made major progress under its NIH contract. Although NIH would honor the IIT contract, there were no plans to use the implantable device. “It appeared that we now had a solution in search of a problem,” Troyk thought.
Soon, some NIH researchers began pitching the visual prosthesis project elsewhere, hoping that the NIH might continue funding under the auspices of a different organization. Troyk was dedicated to reviving the work, and quickly assembled a 20-member team of distinguished biological, behavioral and visual scientists from the University of Chicago, an international leader in psychophysical research and neurosurgery; Huntington Medical Research Institute, Pasadena, California, which pioneered the development and safety testing of electrode arrays used in intra-cortical visual prosthesis research; and EIC Laboratories, a Newton, Massachusetts-based leader in advanced electrode technology. In addition, Troyk enlisted two retired NIH scientists, including the neurosurgeon who performed the landmark brain implant of a visual prosthesis at NIH, as well as an NIH expert in electrode design.
Assuming the Lead, Advancing the Research
Under Troyk’s leadership, the newly formed team began putting together an NIH proposal for restarting the project. Meanwhile, IIT tapped into private funding to support its development and testing of a visual prosthesis.
In the near future, IIT researchers will test a prototype intra-cortical visual prosthesis. The system uses four 256-channel electric stimulators that would act as “command central”—sitting on a patient’s skull under the skin to produce the tiny currents needed to drive 1,024 miniature electrodes implanted in the visual cortex. Small in size (one-inch by one-inch by one-quarter-inch), the ceramic-encased stimulator module contains 40 separate microchips that control the 256 electrodes. The implant is powered and communicated with remotely, by a magnetic coil placed on the surface of the skin. No wires will cross the skin. The system’s multi-channel capabilities offer unprecedented coverage of the visual cortex. (Implants of this size for other applications typically provided only eight to fifty channels, while heart pacemakers use only two to four channels.)
The ultimate goal is to link the electric stimulator to a video camera mounted on a pair of glasses to act as the “eye.” Signals passing through the lens to the device would selectively stimulate different electrodes in the visual cortex to produce spots of light, called phosphenes. Researches expect that the resulting image “seen” in the mind will actually correspond to an object in the environment. But they’re really not sure what patients will perceive. “At first, they might only sense pinpoints of light, or crude ‘Light-Bright’ facsimiles of images in which there are only outlines of images,” explains Troyk. “But given the brain’s ability to modify neural pathways and form new connections, patients might—after months of training—be able to integrate these points of light into nebulous forms, or even sharper images. In the worst case, they might only see the outline of a door. In the best case, they might see the Mona Lisa.”
Whether the mind will “see” doorframes or Renaissance portraits may well be determined in a privately-funded program that got under way last summer under Troyk’s leadership. The new multi-institutional team faces an ambitious agenda that is expected, one day, to culminate in brain implants of the IIT-developed visual prosthesis in human volunteers.
The effort will build on an extensive history—a point that Troyk repeatedly insists on making. “It just so happens that a series of circumstances have brought this work to the point where I inherited it,” says Troyk. “In one form or another, this project has been going on for more than 30 years. There’s a traceable path back to many people who dedicated their careers to advancing pieces of this technology, including several who are now part of this team.”
Research in Context
Scientists knew as early as 1918 that touching electrodes to the visual cortex of conscious patients produced spots of light. By the 1940s, researchers had established the concept of artificial electrical stimulation of the visual cortex, and in the late 1960s, British scientist Giles Brindley produced breakthrough findings with a system for placing electrodes on the brain’s surface. When specific areas of the brain were stimulated in blind volunteers, all reported “seeing” phosphenes that corresponded to where they would have appeared in space. However, experiments were discontinued because of the uncomfortably high currents required for stimulation on the surface of the brain.
Encouraged by Brindley’s findings, the NIH began working toward an intra-cortical visual prosthesis in the early 1970s. First, they abandoned the idea of brain-surface stimulation, theorizing that microelectrodes could be implanted in the visual cortex and safely stimulated using much less current. The NIH work led to the development of new electrodes—finer than the could be safely implanted in animals to electrically stimulate, and passively record, electrical activity in the brain. The efforts produced significant advances in neurophysiology, with publication of hundreds of papers in which researchers attempted to develop an electronic interface to the brain.
By 1995, NIH researchers decided they were ready to proceed to human testing of an intra-cortical visual prosthesis. Thirty-eight electrodes, connected to fine wires penetrating the scalp, were implanted in the brain of a 42-year-old woman. Although blinded by glaucoma 22 years earlier, using the electrical stimulation she was still able to sense phosphenes, and eventually became adept at perceiving those dots under a variety of stimulation patterns.
As the work of the new IIT-led efforts gets under way, team members are confident that “there’s a solid foundation for what we’re attempting to do, and a reasonable expectation from an engineering standpoint that it’s technologically feasible,” Troyk said.
Topping the research agenda are testing and perfecting the IIT-developed hardware to ensure its safety and reliability for human testing. In tandem, the researchers will develop an animal model to perform crucial psychophysical and electrical-stimulation studies. Such a model would provide quantitative results on using a 1,000-plus array of electrodes to talk to the visual cortex. Once dismissed by many as pointless, advances in psychophysical research now allow scientists to track the eye movement of animals, helping researchers to understand what they see.
“Today, you can set up training tasks where you can pretty well determine what these animals are looking at,” says Troyk. “If we’re going to learn how to talk the language of the brain, we need to be able to do hundreds of thousands of trials in a systematic, quantitative manner, something you can’t get with human volunteers because of the inevitable time lapse between experiments and the unreliability of self-reporting.”
Although Troyk predicts that human implants are at least five to ten years away, the animal trials could alter that schedule. “If the first animal experiments of the intra-cortical prosthesis prove spectacularly successful—which I wouldn’t rule out—we would prepare the hardware for human trial as quickly as possible. “Troyk defines spectacular results as ”the ability of the animals to recognize lines in a variety of orientations, dots in different locations in the visual field, and motion in one direction vs. motion in another direction. If we were to get those three types of features, we would have access to the primary features normally used to construct images in our brains. In other words, we would have the building blocks of vision.”
In addition to the project’s technology focus, researchers will address key psychological and ethical issues associated with implants of an intra-cortical visual prosthesis in human subjects.
IIT’s Institute of Psychology will lead focus groups of blind individuals to ensure that the technology being developed meets their expectations about useful vision. Actively soliciting and studying the opinions of the blind in this coordinated manner would be a first, and could help researchers understand the threshold of utility for a future implantable device, as well as help identify the best implant candidates.
Dr. Vivian Weil, director of IIT’s Center for Study of Ethics in the Professions, has also been designated to oversee an ongoing ethical review process. As Troyk notes, “We’re entering pioneering territory of man-machine interfaces. When you’re implanting hardware in the brain, the risks can be significant, and must be properly weighed against the benefits. For instance, we might not be able to justify potentially risky brain surgery if all we can provide blind individuals is ‘Lite-Brite’ or scoreboard images. Ongoing input from ethicists will also help ensure that as researchers, we balance the expectations of blind individuals with their understanding of the technology’s capabilities, so that in our zeal, we don’t exploit the vulnerability of patient volunteers during experiments.”
Avoiding the Spotlight
While the IIT-led team has devised a project that ensures free and multiple exchanges of information, Troyk is adamant about avoiding publicity in the popular press. He’s declined every media request for an interview since IIT began working on the project in 1996. “There’s an aspect of reporting in this field that’s destructive to the research,” says Troyk, “particularly if other researchers perceive that what’s being reported is not only inaccurate, but self-promoting. The fact is that nobody has anything that is ready to cure blindness in anybody.”
Ironically, Troyk has witnessed the upside of unwelcome publicity. In January 2000, a Business Week writer called Troyk for comment on a reported surface-electrode brain implant in a blind volunteer. He declined. However, when the article “Now, Electronic ‘Eyes’ for the Blind” appeared, it contained one sentence about IIT’s brain implant research. The reference caught the attention of a philanthropist, who sent a consultant with whom he regularly works to check out the project. After a few meetings to investigate the team’s research, the philanthropist issued a check that would aid the team in their pursuit. Troyk isn’t at liberty to divulge the amount of the donation (sizable) or the donor’s identity (an internationally recognized figure). Nevertheless, that donation, coupled with other private contributions, ensured that IIT’s visual-prosthesis research would be able to continue, in anticipation of new NIH funding.
Though making progress in this groundbreaking research is a thrilling enough motivation in itself, Troyk is driven by is the human benefit that the work would have in helping blind individuals overcome their social isolation. “We’re not merely interested in showing an individual with blindness the outline of a doorway—you can use a seeing-eye dog to do that,” Troyk says. “What could be more rewarding is that one day, using our technology, they could see their granddaughter’s face, or gaze upon Renaissance paintings. These are things that most of us take for granted.”