A season of head hits left its mark on the brains of college football players. Those hits didn’t even need to cause concussions, a new study finds. Just routine head bumps throughout the football season were enough to show up as a “signature” of abnormal changes in the players’ brain stems.
Adnan Hirad at the University of Rochester in New York led the new study. It looked for signs of brain changes due to head impacts. Hirad's team recruited college players to participate in the study during the 2011, 2012 and 2013 football seasons. Each player wore an accelerometer in his helmet. That device captured the intensity and direction of hits at all practices and games during a single season. The players also underwent pre- and post-season brain scans.
A key job of healthy brain tissue is to relay signals from one neuron (nerve cell) to the next. To measure this how well that signaling was, the researchers focused on something called fractional anisotropy (An-eye-so-TROH-pee). It allowed researchers to estimate how well parts of the brain’s white matter carried those neural messages.
Thirty-eight players took part in the study. Together they sustained 19,128 hits to the head. By the end of one season of play, the players’ fractional anisotropy scores had dropped, on average, in their right midbrains. This is a part of the brain stem.
How big the drop was tended to be linked more tightly to the number of hits that rotated a player’s head rather than to the number of direct head-on hits. Those rotational forces might be especially damaging to brain tissue.
Hirad’s team shared its findings August 7 in Science Advances.
It’s unclear if the brain-stem changes affect mental performance. Similarly, it’s unknown if the changes will be permanent. But the study suggests that even smaller knocks to the head can cause trouble.
accelerometer An instrument for measuring vibrations or a change in the rate of movement. These sensors typically can measure movement changes in all three dimensions (front-to-back, side-to-side and up-and-down).
average (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.
brain scan A technique to view structures inside the brain, typically with X-rays or a magnetic resonance imaging (or MRI) machine. With MRI technology — especially the type known as functional MRI (or fMRI) — the activity of different brain regions can be viewed during an event, such as viewing pictures, computing sums or listening to music.
brain stem A region at the base of the brain that includes many control centers for functions essential to life. These include (but are not limited to) breathing, swallowing and blood pressure. Doctors refer to a patient in whom the brain stem no longer functions as being “brain dead.”
concussion Temporary unconsciousness, or headache, dizziness or forgetfulness due to a severe blow to the head.
force Some outside influence that can change the motion of a body, hold bodies close to one another, or produce motion or stress in a stationary body.
fractional anisotropy A gauge of the connectivity of white-matter fibers in the brain based on imaging of this tissue in certain types of brain scans.
neural (adj.) Having to do with nerves.
tissue Made of cells, it is any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.
white matter One of the two main tissue types found in the brain and spinal cord. It consists mainly of bundles of nerve fibers.