As these circuits grow larger and more complex, Dr. Kaas said, they become less malleable and, probably with the help of changes in neurochemistry, become stabilized. This is why a mature brain is less able to recover from injury than a very young brain. Young brains are astonishingly plastic, Dr. Kaas said. For example, he said, children who suffer from a severe form of epilepsy that is treatable only by removing one-half of their brains can learn to walk, talk, throw balls and otherwise develop normally with only half a brain, if operated on early in life, he said. But in recent years, scientists are also discovering that adult brains, as well, can undergo surprising changes in response to experience.
Touch seems to be residing in visual areas.
Similar experiments on deaf people show that they use the auditory cortex to read sign language, whereas people who can hear use the visual areas of the brain for this purpose. Dr. Sur said his laboratory was now searching for molecules that help produce these kinds of changes in mature and developing brains. If the chemistry of regrowth and reorganization can be understood, he said, it would offer new avenues for helping people recover from damage caused by strokes, accidents and various brain diseases.