How much battering can a brain take?

Professor Songbai Ji hopes to be able to give real-time information on blows to the brain as they occur to athletes.
David L. Ryan/Globe Staff
Professor Songbai Ji hopes to be able to give real-time information on blows to the brain as they occur to athletes.

WORCESTER — As researchers in Boston release one high-profile study after another about the effects of head injuries, a biomechanical engineer 50 miles to the west is pursuing a project that might someday help prevent such harm in the first place.

Worcester Polytechnic Institute professor Songbai Ji is developing animated brain maps that show how brain tissue deforms and stretches after impact. The maps are an educated guess about what occurs within the skull, when, for example, two heads collide on the football field.

If enough data from the dead and the living can be streamed into his computer models, Ji hopes someday to show players and coaches what each hit has probably done to the brain — the minute it happens. That information could alert them to the need to stop playing or the risk of a future injury.


Such real-time diagnosis is a long way off. More data from active players must be collected. Big challenges remain, including accounting for individual differences and assuring the accuracy of head-impact sensors. And doctors still don’t know how long a concussion lasts.

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But as Ji and colleagues reach toward their goal, they are amassing a trove of invaluable data and converting it into brain maps. Their work may prove especially useful as researchers try to understand why repeated hits that don’t initially cause symptoms seem to raise the risk of chronic traumatic encephalopathy, or CTE, the degenerative brain disease now famous for being diagnosed after death in nearly 200 football players, including Aaron Hernandez, whose family blames CTE for his suicide.

The Worcester research, which began a few years ago when Ji and his collaborators were at Dartmouth College, contributes to a nationwide push to better understand brain injury and how to prevent it, as concern grows about the hazards of contact sports for both youths and professionals.

And it exemplifies the extraordinary complexity of what happens when the human head takes hits it was not designed to withstand.

The brain is a fragile organ, said Dr. Thomas W. McAllister, chairman of the Indiana University School of Medicine Department of Psychiatry, and one of Ji’s principal collaborators on the National Institutes of Health grant that supports the brain-mapping research.


But, McAllister said, humans evolved brain protections: a hard skull and cushion of spinal fluid within. This works well when people fall down or get bonked by broken tree limbs. But evolution did not prepare the brain for crashes in vehicles going 60 miles per hour or the rapid, angled jolts of contact sports.

In trying to predict injury, McAllister said, “We thought that this was going to be a fairly simple question: How hard do you have to get hit in order to sustain a concussion? That was a very simplistic view, as it turns out.”

Research soon showed that some people get hit very hard without developing a concussion, while others get concussions after mild impacts. Some of the discrepancy might be explained by differences among people, but clearly more factors are involved, McAllister said. “It may be,” he said, “that the way the brain moves in response to the direction of the hit sets up a very different topography of forces within the brain.”

It is that topography that Ji is exploring.

Much research has focused on direct hits to the head. But concussions and mild brain injury are more often caused by twisting motions, such as when a boxer takes a punch on the chin. These rotating impacts have diffuse effects throughout the brain, Ji said.


“For mild traumatic brain injury, the deep white matter is most vulnerable to brain injury,” Ji said. The white matter is the brain’s communication network, the neurons that transmit signals between brain structures.

‘It may be that the way the brain moves in response to the direction of the hit sets up a very different topography of forces within the brain.’

Thomas W. McAllister, Indiana University School of Medicine 

Researchers using MRI machines have measured how the brain moves when living people turn their heads in harmless ways. At the other extreme, cadaver heads have been studied to see how the brain is displaced by more severe smacks.

Meanwhile, data continues to be gathered from football and hockey players who agreed to wear sensors on their helmets or in their mouthguards. Some of that information is being correlated with injuries the players experience and their symptoms.

Ji crunches all those statistics and feeds them into a grid-like computer model of a human head. When he enters information about the angle, velocity, and force of a given hit, the computer predicts the tissue stretch, depicting its severity with colors from milder blue to worsening red spreading along the hairlike fibers of white matter.

Ji has collected a large database of these simulations, so that once an impact is recorded from a sensor on a player’s head, the appropriate map can be instantly retrieved. As more is learned about the effects of tissue stretches, accurate guesses can be made about the injury risk of each particular hit.

Although concussions can be diagnosed based on symptoms, it takes time to go through the checklist, and athletes eager to get back on the field may underplay what they’re experiencing. Sometimes the symptoms don’t emerge until the next day. Ji hopes his model and database will eventually give players and coaches instant, reliable information on the warning signs of injury.

Arthur Toga, director of the Mark and Mary Stevens Neuroimaging and Informatics Institute at the University of Southern California, said Ji’s work is making a valuable contribution to the busy field of brain mapping and concussion research. But he will have big hurdles to surmount in translating his work into a real-life decision tool, Toga said.

One challenge is the variability in the accuracy of sensors used to measure impacts. Another is the differences among people, from their genetic makeup to the thickness of their skull to what they ate that day. “There’s so many variables at play,” Toga said.

Dr. Frank Conidi, director of the Florida Center for Headache and Sports Neurology, raised similar caveats about Ji’s work. But in an e-mail he called it an “interesting concept” that may prove useful in measuring the cumulative effects of concussion and, by following individuals over time, developing “brain maps to see which areas are most vulnerable and which individuals are most vulnerable.”

Going forward, Ji said he is working to pump up his algorithms with “real injury data from real people, a lot of them.” Working with other researchers, he needs to correlate the impacts recorded on head sensors with the experiences of players. That will enable him to figure out exactly the angle and severity of hits, or the intensity and location of tissue stretch, that lead to injury.

Which types of hits are most dangerous? How much stretching can nerve fibers take before damage occurs? “What’s the threshold? That is the ultimate question,” Ji said.

Ji and his colleagues are amassing a trove of invaluable data on concussions and converting it into brain maps.
David L. Ryan/Globe Staff
Ji and his colleagues are amassing a trove of invaluable data on concussions and converting it into brain maps.

Felice J. Freyer can be reached at [email protected]. Follow her on Twitter @felicejfreyer.