17 May 2011—Want to insult someone’s intelligence? Tell him he doesn’t have the mental capacity to walk and chew gum at the same time. But it turns out that the inability to handle two seemingly simple tasks simultaneously may be the key to determining whether a person has suffered a serious brain injury.
Researchers at the Georgia Tech Research Institute, in Smyrna, have developed a radar system that shows there is a demonstrable difference between the way a healthy person and a person suffering from a concussion walk if they are given a cognitive task to perform while doing so. When asked to stroll a few meters, turn around, and come back while engaged in a mental task, a concussed person will exhibit movement that is slower and jerkier than that of a healthy subject.
These differences are not perceptible to the naked eye, however, so the Georgia Tech team built a concussion radar system that employs the type of radar used by police to catch speeders. The team, which presented the details of its work at the SPIE Defense, Security, and Sensing conference, held in Orlando, Fla., last month, says getting such a device into the hands of youth sports coaches is important. It is estimated by the U.S. Centers for Disease Control (CDC) that roughly 300 000 sports-related concussions occur annually in the United States, with high school athletes making up the bulk of those affected. (The figure is probably much higher, because the CDC counts only incidents where a player loses consciousness.) Many such brain injuries go undiagnosed. In other cases, players may be cleared to resume the sport when headaches, nausea, and disorientation abate. But very often the brain has not fully recovered. University of Oregon researchers recently found that even in cases of so-called mild brain injury, this motor skill anomaly can be detected for as long as four weeks after the impact that caused a concussion.
The 10.5-gigahertz, continuous-wave radar system the Georgia Tech team used captures the entire body in its field of view and reports the velocity of the head, torso, arms, legs, and feet. Software then compares the speed and height at which an impaired subject’s foot kicks—and the speed and regularity of his or her head and torso movements—with those of a healthy person. The gait analysis software, says research engineer Kristin Bing, does not have to handle the tasks of identifying, aligning, and comparing the various parts of the body in successive images, as is usually the case when scientists analyze biomechanics. This, says Bing, saves time and requires less processing power.
To test the system—which comprises a couple of shoebox-size containers for the transmitter and receiver and a somewhat larger unit containing the signal conditioner—the researchers asked 10 subjects to take four 30-second walks along a line taped on a flat, level concrete surface. The subjects did the first walk without anything to tax them. On the second trip, they were asked to recite the months of the year in reverse order. The third and fourth passes mirrored the first and second, respectively, the only difference being that the subjects wore Fatal Vision goggles. These goggles, used to educate people about the effects of drunk driving, have lenses that affect the wearer’s visual perception, causing a loss of equilibrium and the ability to judge relative distance. These impairments make otherwise simple tasks exceedingly difficult. (The Georgia Tech team had drawn on an earlier study by neuropsychologists at the Mental Health Research Institute of Victoria, just outside Melbourne, Australia, who showed that the effect of a concussion on motor coordination was analogous to having a blood alcohol level of 0.05 percent. So the team used goggles designed to mimic that level of inebriation.)
The team confirmed that without the added challenge of the cognitive task, there was no perceptible difference in the gait patterns of the subjects, whether they were wearing the goggles or not. ”It’s easy for a person to concentrate on one task,” says Bing. ”But when that person has to multitask, we can begin to discriminate between someone who is impaired and someone who is not.”
Jeffrey J. Chu, director of engineering at Simbex, in Lebanon, N.H., which makes a helmet-mounted system that measures the force of head impacts endured by American football players, says he generally likes Georgia Tech’s design concept because the continuous-wave radar permits the collection of a large number of parameters. From there, he says, ”you simply have to judge which factors give you the best data.” But Chu, whose company has collected data on more than 1.6 million head impacts, wonders whether the Georgia Tech team went to enough lengths to discriminate the effects of a concussion from other impairments. He notes that a person who is fatigued or dehydrated might exhibit motor coordination difficulties, too. Just as important, Chu says, is the fact that different questions elicit different cognitive responses and create different cognitive loads. Those differences should be familiar to anyone who has no problem handling math problems with numerals and symbols but is stumped when the same concepts are presented as word problems.
Georgia Tech’s Bing says her team intends to try different types of questions. This, she says, will limit false positives and keep neurological problems that are not the result of a concussion from being misdiagnosed.