Cortical Reorganization
Scientists used to believe that certain clusters of neurons would process signals from your nose and other clusters of neurons would process signals from your fingers, and they’d do nothing else until the day you died. If you severed the nerve in your finger, the associated brain cluster should have "gone dark."
Michael Merzenich, PhD, and professor emeritus at the University of California at San Francisco, questioned these theories. In well-intended but controversial research, he severed the finger nerves of laboratory monkeys. Several months afterward, he found the part of the cortex that originally responded to the finger was now responding to signals from other parts of the hand![i]
Likewise, Edward Taub, PhD and behavioral neuroscientist at the University of Alabama at Birmingham, searched for solutions for stroke victims. He wondered if sensory feedback was necessary to move a limb. To find out, he surgically removed the sensory nerve from one or both arms of lab monkeys to stop all sensation from their limb(s). But before the experiment was finished, animal rights activists rescued the monkeys and removed them from the experiment.
However, twelve years later, scientists revisited the project. Several of the monkeys were to be euthanized to spare them further suffering. Aware of the original purpose of the experiment, the scientists persuaded authorities to allow a final examination of the monkeys’ brains to determine what happened to the “arm” region of the brain after having no sensation for years.
It wasn’t silent. It had changed jobs. It now processed signals from the face instead. And the region now responsible for receiving sensations from the face had grown 10 to 14 square millimeters, in what scientists described as “a massive cortical reorganization.”[ii]
The same phenomenon has been detected in humans. People blind from birth who become proficient in Braille provide evidence that the visual cortex can switch jobs to process tactile signals from the fingers.
[i] Sharon Begley, Train Your Mind and Change Your Brain, (New York: Balantine Books, 2008), 33.
[ii] Richard Davidson with Sharon Begley, The Emotional Life of Your Brain (New York: PLUME, 2013), 169.