I recently read a fascinating book, The Brain That Changes Itself by Norman Doidge. He describes case histories and research indicating that the brain is far more malleable than we once thought. We used to think each function was localized to a small area of the brain and if you lost that area of brain tissue the function was gone forever. We once thought you couldn’t teach an old dog new tricks. Now we know better.
Learning a new skill actually changes the structure and function of the brain, even into old age. If you exercise one finger, the area of the brain devoted to that finger enlarges. The old concept of dedicated brain areas for specific functions no longer holds. Areas of the cortex that normally process vision can learn to process totally different inputs such as hearing. This is what happens with blind people: their hearing skills are enhanced when new neural connections for hearing invade the disused visual cortex. They may not actually have better hearing acuity, but they have learned to pay more attention to auditory input and to use it to build up a representation of the world around them.
One of the more intriguing experiments he describes was in monkeys. When sensory input nerves to one arm were severed, the monkey stopped using the arm, even though the motor nerves were intact. When the good arm was put in a sling, the monkey started using the impaired arm again. When both arms were deprived of sensory input, the monkey used both arms. (more…)