U. WASHINGTON (US)—A rare peek at a human brain hooked up to a computer shows that the two can adapt to each other quickly—and possibly to the brain’s benefit.
Researchers looked at signals on the brain’s surface while using imagined movements to control a cursor and found that watching a cursor respond to one’s thoughts prompts brain signals to become stronger than those generated in day-to-day life.
The finding holds promise for rehabilitating patients after stroke or other neurological damage. It also suggests that a human brain could quickly become adept at manipulating an external device such as a computer interface or a prosthetic limb. Details are reported in the Proceedings of the National Academy of Sciences.
“Bodybuilders get muscles that are larger than normal by lifting weights,” says lead author Kai Miller, a doctoral student in physics, neuroscience, and medicine at the University of Washington.
“We get brain activity that’s larger than normal by interacting with brain-computer interfaces. By using these interfaces, patients create super-active populations of brain cells.”
During the week leading up to epilepsy surgery at two Seattle hospitals, eight patients had electrodes attached to the surface of their brains and agreed to participate in research that would look at connecting brains to a computer.
Asking people to imagine doing a movement—such as moving an arm—is commonly done to produce a brain signal that can be used to control a device. But how that process works is poorly understood.
The researchers first recorded brain patterns when human subjects clenched and unclenched a fist, stuck out a tongue, shrugged their shoulders, or said the word “move.”
Next, the scientists recorded brain patterns when subjects imagined performing the same actions. These patterns were similar to the patterns for actual action but much weaker, as expected from previous studies.
Finally, the researchers looked at signals when subjects imagined performing the action and those brain signals were used to move a cursor toward a target on a computer screen.
After less than 10 minutes of practice, brain signals from imagined movement became significantly stronger than when actually performing the physical motion.
“People have been looking at imagined movements as a way to control computers for a long time. This study provides a glimpse of the underlying neural machinery,” explains coauthor Rajesh Rao, associate professor of computer science and engineering who is Miller’s neuroscience dissertation advisor.
After less than 10 minutes of training, two of the subjects also reported they no longer had to imagine moving the body part and could just think about moving the cursor.
The new findings also provide clues about which brain signals to tap. Researchers compared the patterns in low-frequency signals, usually used to control external devices, and high-frequency signals, typically dismissed as noise.
They discovered that the high-frequency signals are more specific to each type of movement.
Because each one occupies a smaller portion of the brain, several high-frequency signals could be tapped simultaneously to control more sophisticated devices.
Rao has used electrodes on the surface of the scalp to record low-frequency brain signals for brain-computer communication and will now try using such non-invasive methods to harness high-frequency signals.
The research was funded by the National Science Foundation, the National Institutes of Health, NASA’s graduate student research program, and the National Institute of General Medical Sciences’ medical scientist training program.
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