Neurofeedback Can Enhance The Brain's Signal-to-noise Ratio
September 23, 2013

Brain-computer Interface Allows For Eavesdropping On Previously Undetectable Mental Activity

April Flowers for - Your Universe Online

As a needle sweeps across the grooves of a worn vinyl record, it carries the distinct sounds of hisses, scratches and even the echo of skips. For many years, however, if someone yearned to hear Frank Sinatra sing "Fly Me to the Moon," they were able to listen to his crooning baritone with technical clarity, courtesy of the increased signal-to-noise ratio of digital re-masterings.

Recent advances in neurofeedback techniques have made it possible to remaster the signal-to-noise ratio of the brain activity underlying our thoughts, according to a new study led by Stephen LaConte, an assistant professor at the Virginia Tech Carilion Research Institute.

The research team specializes in real-time functional magnetic resonance imaging (fMRI), which is a relatively new technology that can convert thought into action. It does so by transferring noninvasive measurements of human brain activity into control signals that drive physical devices and computer displays in real time. Most importantly, this rudimentary form of mind reading enables neurofeedback, which is helpful in the fight to treat disorders of the brain.

"Our brains control overt actions that allow us to interact directly with our environments, whether by swinging an arm or singing an aria," LaConte said. "Covert mental activities, on the other hand — such as visual imagery, inner language, or recollections of the past — can't be observed by others and don't necessarily translate into action in the outside world."

Previously undetectable mental activities are now open to eavesdropping because of these computer interfaces, adds LeConte.

In the current study, published in the Proceedings of the National Academy of Sciences, the research team used whole-brain, classifier-based real-time fMRI to understand the neural underpinnings of brain–computer interface control. Two dozen test subjects were asked to control a visual interface by silently counting numbers at fast and slow rates. The subjects were asked to use their thoughts to control the movement of the needle on the device they were observing for half the tasks. For the other half, the participants were asked to simply watch the needle.

A feedback effect found by the researchers is one that LeConte had long suspected the existence of, but proving it had been challenging. They found that a better whole-brain signal-to-noise ratio was achieved by the participants who were in control of the needle than those who simply watched the needle move.

"When the subjects were performing the counting task without feedback, they did a pretty good job," LaConte said. "But when they were doing it with feedback, we saw increases in the signal-to-noise ratio of the entire brain. This improved clarity could mean that the signal was sharpening, the noise was dropping, or both. I suspect the brain was becoming less noisy, allowing the subject to concentrate on the task at hand."

The act of controlling the computer-brain interface also led to increased classification accuracy, the team found. This increased accuracy corresponded with improvements in the whole-brain signal-to-noise ratio.

LeConte added that this enhanced signal-to-noise ratio holds implications for brain rehabilitation.

"When people undergoing real-time brain scans get feedback on their own brain activity patterns, they can devise ways to exert greater control of their mental processes," LaConte said. "This, in turn, gives them the opportunity to aid in their own healing. Ultimately, we want to use this effect to find better ways to treat brain injuries and psychiatric and neurological disorders."

"Dr. LaConte's discovery represents a milestone in the development of noninvasive brain imaging approaches with potential for neurorehabilitation," said Michael Friedlander, executive director of the Virginia Tech Carilion Research Institute and a neuroscientist who specializes in brain plasticity. "This research carries implications for people whose brains have been damaged, such as through traumatic injury or stroke, in ways that affect the motor system—how they walk, move an arm, or speak, for example. Dr. LaConte's innovations with real-time functional brain imaging are helping to set the stage for the future, for capturing covert brain activity and creating better computer interfaces that can help people retrain their own brains."