Scientists from Washington University in St. Louis have figured out how the human brain is deformed during movement. The results will be useful for computer models of brain biomechanics and the development of protective equipment for the head. The study is published in the Journal of Biomechanical Engineering .
With any movement of the head, from nodding to an injury in a car accident, the brain moves inside the skull, which leads to tissue deformation. These changes are key to understanding traumatic brain injury, but they are difficult to study because the brain is hidden inside the skull. Therefore, earlier scientists used animals or human corpses.
In the new study, the researchers measured the brain’s impulse response when moving the head from side to side and its harmonic response to vibration at a specific frequency. This effect can be compared to shaking when driving on a bad road.
In the first case, six volunteers in an MRI machine were asked to gently rotate their heads from side to side. In the second experiment, light sound pressure generated by a loudspeaker was applied to the volunteers’ heads to provoke a harmonic response. At the same time, brain movement was measured using MR elastography, a non-invasive technique that combines MRI scans with low-frequency vibrations to create a visual map that displays information about body tissues.
The scientists found that shaking the head from side to side produced a complex pattern of response waves at several frequencies, while vibrating the response was simpler and more stable.
There were also individual differences in the response to vibration associated with age, features of the skull, and the size of individual areas of the brain.