How complex is the human brain, and how much can brain surgeons do to repair brain damage?

First, the human brain is really, really complex. Some scientists describe the brain as the most complicated object in the universe.

This is because our brains have over 100 billion neurons, or nerve cells. Our brains are so complex that even the most highly skilled brain surgeons have a difficult time repairing injured brains. When someone has an injury that disconnects parts of the person's brain, there's really very little doctors can do to get nerve cells to grow back across gaps in brain tissue.

However, brain surgeons may soon have a better way of reconnecting parts of the brain. MIT's Rutledge Ellis-Behnke has developed a material that assembles inside the brain into a sort of lattice of interwoven fibers. The fibers can be made to stretch across parts of the brain that have been severed and allow brain cells on one side to grow back and reconnect with cells on the other side.

So far Ellis-Behnke's team has tested the material on hamsters with severed optical nerves, causing them to lose vision. When it was injected into the hamsters' brains, Ellis-Behnke's material formed a bridge that allowed the optical nerve to grow back and restore the hamsters' sight.

With more testing, the material could one day be used to help people regain sight, hearing, and other bodily functions that are lost when brains are damaged.