Experimental devices that read brain signals have helped paralyzed people use computers and may let amputees control bionic limbs. But existing devices use tiny electrodes that poke into the brain. Now, a University of Utah study shows that brain signals controlling arm movements can be detected accurately using new microelectrodes that sit on the brain but don't penetrate it.
"The unique thing about this technology is that it provides lots of information out of the brain without having to put the electrodes into the brain," says Bradley Greger, an assistant professor of bioengineering and coauthor of the study. "That lets neurosurgeons put this device under the skull but over brain areas where it would be risky to place penetrating electrodes: areas that control speech, memory and other cognitive functions."
For example, the new array of microelectrodes someday might be placed over the brain's speech center in patients who cannot communicate because they are paralyzed by spinal injury, stroke, Lou Gehrig's disease or other disorders, he adds. The electrodes would send speech signals to a computer that would covert the thoughts to audible words.
For people who have lost a limb or are paralyzed, "this device should allow a high level of control over a prosthetic limb or computer interface," Greger says. "It will enable amputees or people with severe paralysis to interact with their environment using a prosthetic arm or a computer interface that decodes signals from the brain."
The study is scheduled for online publication July 1 in the journal Neurosurgical Focus.
The findings represent "a modest step" toward use of the new microelectrodes in systems that convert the thoughts of amputees and paralyzed people into signals that control lifelike prosthetic limbs, computers or other devices to assist people with disabilities, says University of Utah neurosurgeon Paul A. House, the study's lead author.
"The most optimistic case would be a few years before you would have a dedicated system," he says, noting more work is needed to refine computer software that interprets brain signals so they can be converted into actions, like moving an arm.
An Advance over the Penetrating Utah Electrode Array
Such technology already has been developed in experimental form using small arrays of penetrating electrodes that stick into the brain. The University of Utah pioneered development of the 100-electrode Utah Electrode Array used to read signals from the brain cells of paralyzed people. In experiments in Massachusetts, researchers used the small, brain-penetrating electrode array to help paralyzed people move a computer cursor, operate a robotic arm and communicate.
Meanwhile, researchers at the University of Utah and elsewhere are working on a $55 million Pentagon project to develop a lifelike bionic arm that war veterans and other amputees would control with their thoughts, just like a real arm. Scientists are debating whether the prosthetic devices should be controlled from nerve signals collected by electrodes in or on the brain, or by electrodes planted in the residual limb.
The new study was funded partly by the Defense Advanced Research Projects Agency's bionic arm project, and by the National Science Foundation and Blackrock Microsystems, which provided the system to record brain waves.
House and Greger conducted the research with Spencer Kellis, a doctoral student in electrical and computer engineering; Kyle Thomson, a doctoral student in bioengineering; and Richard Brown, professor of electrical and computer engineering and dean of the university's College of Engineering.
Microelectrodes on the Brain May Last Longer than Those Poking Inside
Not only are the existing, penetrating electrode arrays undesirable for use over critical brain areas that control speech and memory, but the electrodes likely wear out faster if they are penetrating brain tissue rather than sitting atop it, Greger and House say. Nonpenetrating electrodes may allow a longer life for devices that will help disabled people use their own thoughts to control computers, robotic limbs or other machines.
"If you're going to have your skull opened up, would you like something put in that is going to last three years or 10 years?" Greger asks.