Using young male mice, they applied relatively mild jolts, designed to result in a sudden, strong jerking of their heads, much as occurs during head-to-head tackles and other impacts. Afterward, some animals showed symptoms of a rodent version of a concussion, stumbling and performing poorly on memory tests.
The scientists then injected some animals with a dye that cannot cross a healthy blood-brain barrier and scanned the living animals’ brains. In about half of the mice, they saw signs of the dye in their brains, indicated that their blood-brain barriers had become permeable. Many of the mice also showed signs of leaky blood vessels and other damage, including inflammation and disruptions in the electrical activity within their brains.