New study shows that playing a single football season in high school can lead to changes in the brain of teenage girls

The researchers used a new type of magnetic resonance imaging (MRI) to perform brain exams of 16 high school players aged 15 to 17, before and after a football season. They discovered significant changes in the structure of gray matter in the front and back of the brain, where the impacts are most likely to occur, as well as changes in structures located in the brain. 39, inside the brain. All participants wore helmets and none received head shocks severe enough to constitute a concussion.

This study, which is on the cover of the November issue of Neurobiology of Disease, is one of the first to examine the impact of sport on the brain of children of this critical age.

"It is becoming increasingly clear that repetitive impacts on the head, even over a short period, can cause brain changes," According to the main author of the study, Chunlei Liu, professor of electrical engineering and computer science and member of the Helen Wills Neuroscience Institute of UC Berkeley. "This is the time when the brain is still developing when it has not yet reached maturity. So, there are many critical biological processes going on, and we do not know how these changes we observe can affect the maturation and development of the brain. "

Regarding trends

A bonk in the head can be nothing to sweat. There is growing evidence that repeated blows to the skull, such as when playing sports such as hockey or football, or injuries caused by explosions in military combat, can lead to cognitive decline in long-term and increased risk of neurological disorders, even when the blows do not cause concussion.

Over the past decade, researchers have discovered that an alarming number of retired soldiers and academic and professional football players were showing signs of a newly identified neurodegenerative disease, called Chronic Traumatic Encephalopathy (CTE). ), characterized by an accumulation of pathogenic tau protein in the brain. . Although still poorly understood, it is thought that ETC causes mood disorders, cognitive decline and possibly motor impairment as the patient ages. The definitive diagnosis of CTE can only be established by examining the brain to detect tau protein during an autopsy.

These findings have raised concerns about the possibility that repeated blows to the head may cause brain damage in youth or high school students, and it is possible to detect these changes at a young age.

"There is a lot of emerging evidence that simply doing sports that impact the brain actually changes the brain, and you can see these changes at the molecular level in the accumulation of different pathogenic proteins associated with neurodegenerative diseases. such as Parkinson's disease and dementia ", Liu said. "We wanted to know when this really happens – what time does it happen?"

A question of gray and white

The brain is made up of white matter, long neuronal threads that send messages between different regions of the brain, and gray matter, a tight network of neurons that gives the brain its characteristic wrinkles. Recent studies in MRI have shown that playing a season or two of high school football can weaken the white matter, which is found mostly nested inside the brain. Liu and his team wanted to know if repetitive blows to the head could also affect the gray matter of the brain.

"The gray matter in the cortex area is located outside the brain, so we expected this area to be more directly related to the impact itself," Liu said.

The researchers used a new type of MRI, Kurtosis diffusion imaging, to examine complex neuronal tangles constituting gray matter. They found that the organization of gray matter in players' brains changed after a football season and that these changes were correlated with the number and position of head impacts measured by the accelerometers mounted inside the helmets. players.

The changes were concentrated at the front and back of the cerebral cortex, responsible for higher order functions such as memory, attention and cognition, and in the thalamus and the putamen located in the center, which transmit sensory information and coordinate movements.

"Although our study did not examine the consequences of the observed changes, new evidence suggests that such changes would be detrimental in the long run," Liu said.

The tests revealed that the cognitive function of the students had not changed during the season, and it is not yet clear whether these changes in the brain are permanent, say the researchers.

"The cerebral microstructure of young players continues to develop rapidly, which could compensate for the alterations caused by the repeated impacts of the head", said the first author, Nan-Ji Gong, a postdoctoral researcher in the Department of Electrical and Computer Engineering at UC Berkeley.

However, researchers still urge caution – and frequent cognitive and cerebral surveillance – among high school and high school students involved in impact sports.

"I think it would be reasonable to debate how old it would be crucial for the brain to suffer such consequences, especially given the popularity of youth football and other sports that have an impact on the brain", Liu said.

The co-authors are Samuel Kuzminski of the University of Oklahoma; Michael Clark, Melissa Fraser and Kevin Guskiewicz of the University of North Carolina at Chapel Hill; Mark Sundman of the University of Arizona; and Jeffrey R. Petrella of the Duke University School of Medicine.

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