Scientists from the University of California, Irvine have discovered that an injury to one part of the brain changes the connections between nerve cells across the entire brain. The new research was published this week in Nature Communications.
Every year in the United States, nearly two million Americans sustain a traumatic brain injury (TBI). Survivors can live with lifelong physical, cognitive and emotional disabilities. Currently, there are no treatments.
One of the biggest challenges for neuroscientists has been to fully understand how a TBI alters the cross-talk between different cells and brain regions.
In the new study, researchers improved upon a process called iDISCO, which uses solvents to make biological samples transparent. The process leaves behind a fully intact brain that can be illuminated with lasers and imaged in 3D with specialized microscopes.
With the enhanced brain clearing processes, the UCI team mapped neural connections throughout the entire brain. The researchers focused on connections to inhibitory neurons, because these neurons are extremely vulnerable to dying after a brain injury. The team first looked at the hippocampus, a brain region responsible for learning and memory. Then, they investigated the prefrontal cortex, a brain region that works together with hippocampus. In both cases, the imaging showed that inhibitory neurons gain many more connections from neighboring nerve cells after TBI, but they become disconnected from the rest of the brain.
“We’ve known for a long time that the communication between different brain cells can change very dramatically after an injury,” said Robert Hunt, PhD, associate professor of anatomy and neurobiology and director of the Epilepsy Research Center at UCI School of Medicine whose lab conducted the study, “But, we haven’t been able to see what happens in the whole brain until now.”
To get a closer look at the damaged brain connections, Hunt and his team devised a technique for reversing the clearing procedure and probing the brain with traditional anatomical approaches.
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