Brainwave interface goes 2D
By
Kimberly Patch,
Technology Research NewsIt would be useful to be able to move a cursor around a computer screen just by thinking about where you wanted it to go.
Researchers have been working on the task for more than a decade; some recent progress involved monkeys moving a cursor to specific spots on a computer screen. The price of being able to do this was fairly high, however -- electrodes implanted in the brain.
Researchers from the New York State Department Of Health have shown that it is possible to use brainwaves picked up by electrodes attached to the outside of the scalp to move a cursor around a computer screen. Previous efforts at monitoring brain waves through the scalp only allowed movement along one axis, like up and down.
The Noninvasive Brain-Computer Interface allows people to learn to move a cursor around a two-dimensional computer screen by controlling the electrical noise that the brain makes as it functions, said Jonathan Wolpaw, chief of the Laboratory of Nervous System Disorders at the Wadsworth Center of the New York State Department of Health. The keys to the system are recent improvements in signal processing and an algorithm that adjusts to the way an individual controls brainwave oscillations.
The method promises to enable people who are severely disabled to use a computer cursor. It could allow people who are completely locked in their bodies -- without control even of breath or eye movements -- to communicate, said Wolpaw. It may eventually be useful for people who are less severely disabled, and, long-term, may be appropriate in specific situations for anyone who needs to operate a computer hands-free, Wolpaw said.
In a four-person study of the interface, the researchers showed that it is possible for people to learn to move a cursor to one of 16 areas of a computer screen by changing the idling rhythms of the brain.
The method uses electrodes to record the rhythms, or oscillations of the electric field, that occur near the sensory motor parts of the brain -- the same electroencephalograph (EEG) signals that have been recorded for 70 years for various clinical purposes. The oscillations are not part of the brain's operations as far as we understand, said Wolpaw. "It's like the noise a car engine makes when a car is operating."
Different areas of the brain produce a variety of rhythms that reflect brain activity. "The question is how much control can people develop over them," said Wolpaw. "In our case we're giving the brain the opportunity to learn how to use the brainwaves we record for communication control," he said.
The program adapts in real-time to best leverage the way people are changing their brainwave rhythms, said Wolpaw. This is key to being able to use non-invasive sensors. "The big advance... is the on-line algorithm has a lot more built-in adaptations," he said. "It's continually adjusting to optimize the translation of whatever control the person has of cursor movement."
At the same time, the adjustments encourage the person to improve control. "This is really the interaction of two adaptive controllers," said Wolpaw. "That's what goes on over a series of training sessions -- the system and the user adapt to each other."
The researchers use brainwaves from the surface of the scalp above the left and right sensory motor cortices, which are located directly under the portion of the skull that rises above the ears. These are the areas of the cortex that are most directly involved in movement and sensation. The rhythms generated by the neurons in these areas "are basically... idling rhythms -- what those areas of the cortex tend to [generate] when they are awake and alert, but they're not doing anything," said Wolpaw. "What we have shown is that people can use various kinds of mental imagery to make [these] rhythms larger or smaller."
A person learning to use the control might start out thinking about walking or moving a hand, said Wolpaw. The right sensory motor cortex controls the left side of the body and vice versa. "If you think about moving your right hand, generally sensory motor rhythms will tend to get smaller over the left side of your brain." Relaxing increases the amplitude of the rhythm.
The rhythm amplitude gets converted into movement of the cursor on a screen, said Wolpaw. If the rhythm gets larger the cursor goes up the screen and if it gets smaller the cursor goes down the screen, and he said. "People start out with various kinds of motor imagery until they find what's best for moving the cursor in one direction verses the other."
A person acquires the skill of controlling brainwaves over a series of 24-minute training sessions. Once the person masters moving the cursor up verses down, he moves on to two-dimensional control.
Although the cursor is controlled using the signals from two electrodes, the researchers' subjects wear a cap of sixty-four electrodes during the training sessions. This is so the researchers can find ways to get the most out of the signals. "We look... to see where the control is on the head and what frequencies they're controlling and we can adjust the program off-line to focus on those rhythms," he said.
Although people picture moving a hand or leg when starting to use the system, as they gain more control it becomes more difficult for them to explain exactly what they are doing to move the cursor, said Wolpaw. "Generally after people get better, and particularly when they go on to two dimensions, they can't really tell you what they're doing," he said. "They really can't explain [in the same] way you really can't explain how you raise your arm -- it becomes more like a normal motor skill."
The researchers' subjects had from 10 to 30 hours of two-dimensional training. Two of the users are more skilled than the other two, but all four are able to control the cursor with about a third of the speed and accuracy of a joystick, he said. "They can hit as many as 16 different target locations... around a screen."
Initially, the skill requires considerable concentration. As people get better they can use the system to answer questions. "They can hear a question, they can think of the answer, and they can use [brainwaves] to move a cursor to the answer," said Wolpaw. "So it becomes more like a normal skill as you get better at it -- it requires less undivided attention."
In the short-term, the method could find practical use for people who are severely paralyzed, and medium-term for people who are perhaps not as disabled, said Wolpaw. "For the foreseeable future it is going to be for people with disabilities," he said.
Long-term, the method could find use under very specialized circumstances for people who are not disabled, "but I don't see that as an a major use... for quite awhile," said Wolpaw.
Although the brainwave control could be used as an additional communication channel, it remains to be seen whether it could be added without impinging on the function of the normal channels people used to communicate with and control computers, said Wolpaw.
The researchers' next step is to use the system for a project based in Germany that is designed to train people who are disabled to use the system. "We're developing [and] implementing clinical applications," said Wolpaw. "We're setting up to show that it can actually improve the quality of life." Applications include word processing and environmental control.
The researchers are also working on a selection, or grasp function. This will make it possible to move the cursor over an object without selecting it, and will also enable the method to be used with robotic arms, said Wolpaw. They are also working on three-dimensional cursor control.
Wolpaw's research colleague was Dennis J. McFarland. The work appeared in the December 6, 2004 issue of the Proceedings of the National Academy of Sciences. The research was funded by the National Institutes of Health (NIH) and the James S. McDonnell Foundation.
Timeline: Unknown
Funding: Government, Private
TRN Categories: Applied Technology; Biotechnology; Human-Computer Interaction
Story Type: News
Related Elements: Technical paper, "Control of a Two-dimensional Movement Signal by a Noninvasive Brain-Computer Interface in Humans," Proceedings of the National Academy Of Sciences, December 6, 2004
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February 9/16, 2005
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