A head injury serious enough to affect brain function, such as that caused by a car accident or sudden fall, leads to changes in the brain beyond the site of impact, Tufts University School of Medicine scientists recently reported in the journal Cerebral Cortex. In an animal model of traumatic brain injury, the researchers found that both hemispheres work together to forge new neural pathways in an attempt to replicate those that were lost. “Even areas far away from the injury behaved differently immediately afterward,” says first author Samantha Bottom-Tanzer, an MD/PhD student in neuroscience at the School of Medicine. “Traumatic brain injury research tends to focus on the region of injury, but this study makes a good case that the entire brain can be affected, and imaging in distal regions can provide valuable information.” Bottom-Tanzer and colleagues are the first to use an imaging technique combining fluorescent sensors of neuronal activity and electrodes to record how many parts of the brain talk to each other after a brain injury. The team tracked neural activity in mice for up to 3 weeks post-injury during periods of exercise and rest.
While overall neuron-to-neuron connectivity decreased after brain injury, all the mice could use an exercise wheel as normal. However, the activity of injured brains throughout both periods of running and rest was remarkably different from healthy brains. Surprisingly, they did not display distinct brain wave patterns when they were moving versus when they were still, which is what the researchers would have expected.
“Whether paying attention or walking, brains switch states depending on the task you’re doing,” says senior author Chris Dulla, professor and interim chair of neuroscience at the School of Medicine. “After traumatic brain injury, this ability is not as robust, indicating such events are impairing how the brain switches states in a way that we don’t yet understand.” “What we can see from the data is that the brain has new solutions for how to do all these complex tasks,” he adds.
