By surgically "rewiring" the brains of newborn hamsters, researchers at the University of Maryland School of Medicine and the University of Montreal have shown that they can create new brain circuits that take over the functions of damaged ones. The researchers found that the hamsters could still see visual patterns even after key areas of the brain devoted to sight had been removed. In some cases, the researchers demonstrated that the animals were using the hearing regions of the brain to see.
Although it is not yet possible to create new neural pathways in humans, the research raises the possibility that a similar technique might one day be used to treat brain damage in people. The study is published in the September 19th issue of the Proceedings of the National Academy of Sciences (PNAS).
"This is the first time that a surgically created brain circuit has been used to take over the functions of a damaged one," says Douglas O. Frost, Ph.D., lead investigator and professor of Pharmacology and Experimental Therapeutics at the University of Maryland School of Medicine. "Other studies have shown that when the eye is connected to the hearing system, "rewired" animals perceive visual stimuli as sight rather than sound, but we have shown for the first time that surgically created connections are useful in seeing."
In nine hamsters, the researchers surgically created connections between the retina of the eye and parts of the brain that normally contribute to hearing. They then eliminated the brain pathway responsible for seeing visual patterns. The "rewired" animals were then placed in a special maze that required them to distinguish different visual patterns in order to reach a food reward. All nine hamsters made it through the maze, performing as well as a normal control group.
The researchers determined that in some cases, the hamsters were processing the visual pattern information through a pathway they had created from the eye to hearing regions of the brain. In these animals, the hearing pathway had taken over the job of the damaged vision pathway, enabling the hamsters to distinguish the visual stimuli.
"Even after we surgically removed the "primary visual cortex" of the rewired hamsters, they could still distinguish horizontal from vertical stripes, and other pairs of patterns," says Dr. Frost. "Non-rewired hamsters and people lose their ability to perform these tests when the visual cortex is surgically damaged.
The study suggests that surgically created neural pathways might someday be used to bypass damaged areas of the brain and restore lost functions, such as vision or hearing. But Dr. Frost says right now, that is not possible in humans. The research was done on newborn hamsters because their brains are at a stage of development that still allows the formation of new neural connections. By the time a human baby is born, the brain is too mature to establish new pathways.
Dr. Frost says additional research in animals with more complex visual systems is necessary to determine to what extent vision in "rewired" animals is normal.
Ellen Beth Levitt (firstname.lastname@example.org) (410)-328-8919