HOLD FOR RELEASE: October 29, 1997
Media Contact: Mario Aguilera, (619) 534-7572, [email protected]
ENIGMATIC BRAIN WAVE RELATED TO MOVEMENT COULD BECOME NEW TOOL IN MOTOR REHABILITATION
A little-known brain wave thought to be found in only a small percentage of people is instead sitting inside most of our heads and could one day become a key for understanding connections between movement and vision.
Till now, scientists thought that the human "mu" electroencephalograph (EEG) brain wave, named after the 12th letter of the Greek alphabet, was an "idling" rhythm of the brain's cortical cells because it is blocked during movement and turns on at rest.
But in a new study, scientists from the University of California, San Diego, have shown that the mu brain wave not only is blocked when a person moves, it also can be blocked when a person observes movement. What's more, the study suggests that most people possess a mu wave, whether outwardly evident or quietly hidden.
Combined, the results offer insights into how vision may help people rehabilitate motor functions.
"This evidence shows that the mu wave is really a useful tool," said Eric Altschuler, a student in the UCSD School of Medicine and UCSD's Department of Psychology Brain and Perception Laboratory, and the report's first author. "The fact that we've shown that everyone has a mu makes the EEG technique very useful, and a cheap, easy and safe window into studies of the brain."
Jaime Pineda, a professor in UCSD's Department of Cognitive Science and part of the study's research team, says the findings show that one day the mu wave could be useful in rehabilitating immobilization and paralysis related to stroke and brain damage.
"The mu has to do with an area that controls muscle movement, so if you can affect that area by simply looking, it may be that you can use it in motor rehabilitation as a utility to teach people who are immobilized," said Pineda, "Someone with a paralyzed arm, for example, may benefit by simply looking at people move their arms."
Pineda will present the study Oct. 29 at the Society for Neuroscience conference in New Orleans.
Altschuler, Pineda and a research team that included Vilayanur Ramachandran, a professor in UCSD's Department of Psychology, and Andrey Vankov, a visiting professor from the Bulgarian Institute of Physiology, began their study by asking whether humans have brain correlates of neurons found in monkeys that respond when monkeys perform action and when they see other monkeys act, otherwise known as "monkey-see-monkey-do" neurons.
The mu wave, which is recorded in the eight to 13 hertz range, has been tracked by scientists to the central region of the lower scalp overlying the brain's motor function cells.
Altschuler and his colleagues recorded the EEG waves of 17 subjects during four conditions: at rest; repeatedly snapping their thumbs against their middle two fingers in a "duck" movement; imagining the duck movement; and watching experimenters perform the duck movement. The researchers collected free-running EEG in each condition for two minutes.
The results displayed strong evidence that the mu wave was blocked not only by movement, or the mental imagination of movement, but also by the visual observation of the experimenter's actions. Furthermore, the mu wave was displayed in most of the 17 subjects, whether obvious in a large wave amplitude or more subtly hidden.
The researchers argue that the results thus put to bed the long-standing question in EEG research of why only a small percentage of people have a mu wave. Instead, they argue, all people have one.
"Most people had looked at the rhythm for only short periods of time and that's why the previous studies may have said that only a small percentage of people had the mu wave," says Pineda. "We wanted to look at it longer, for two full minutes, and we found the mu in all of our subjects."
Although the study made progress in the study of the mu, it poses several interesting questions about the mu's true function and capability. Because the report states that only eight of the subjects displayed a "large, readily visible amplitude" of mu, it still leaves open the question of why some people display a more prominent mu than others. The report also fails to explain why a large number of subjects blocked the mu not by moving, but by imagining movement.
The study does, however, argue that blocking the mu wave through visual input may be useful for understanding motor rehabilitation, how areas of the brain bind and for treating movement impediments related to neurological conditions. Knowing how the mu wave can be blocked, along with the relatively low cost of EEG monitors, could make the mu wave a useful tool for future neuroscience research.
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