The Brain That Changes Itself – Norman Doidge, MD Chapter 3 – Redesigning the Brain – Part 2

To continue our survey of the work of Michael Merzenich, PhD, Doidge tells of Merzenich’s next experiment. First, he mapped the hand map in the brain of a monkey. Then, he cut off the middle finger. Months later, he remapped the same area and found that the map for the middle finger was gone, but the mapping for the two adjacent fingers had taken over the area once used for the middle finger. He also learned that while there are similarities among the different species, there are no two identical mind maps. He also learned that the brain maps continued to change even without a major trauma like losing a finger. In writing up these findings, Merzenich used the word plasticity without qualification. He received hostile treatment from fellow scientists who refused to take his conclusions seriously.  P. 60-61

“The most frustrating thing,” says Merzenich, “was that I saw that neuroplasticity had all kinds of potential implications of human neuropathology and psychiatry. And nobody paid any attention.” P. 62

By mapping the monkey’s hand brain map periodically, he was able to demonstrate the change over time. Carl that Shatz, a neuroscientist, summarized “Neuron that fire together wire together.” P. 63

Beginning in the late 1980s, Merzenich began to demonstrate that two separate mind maps would merge as a result of sewing two fingers together. When researches touch any part of the two joined fingers, the whole area would light up in the brain. “The experiment showed that timing of the input to the neurons in the map was the key to forming it – neurons that fired together in time wired together to make one map.” P. 64

Others verified these findings on two humans who were born with webbed fingers. “In neuroscience this finding is now summarized as Neurons that fire apart wire apart – or Neurons out of sync fail to link.” P. 64

Next Merzenich found that when all five fingers stimulated simultaneously 500 times a day over a month, mapped as one “finger.” P. 64 Finally, a patch skin with nerve endings of one finger was surgically implanted on another finger, stimulation cased the new location to fire. P. 64

Eventually, Merzenich succeeded in convincing his colleagues of neuroplasticity in adults, but he had not yet explained how the maps organize themselves to become topogphical, or ordered as the body is ordered. “Topographical organization is efficient, because it manes that parts of the brain that often work together in the brain map, so signals don’t have to travel far in the brain itself.” P. 65

Bill Jenkins, a behavioral psychologist, joined Merzenich’s research team with an interest in how we learn. They taught a monkey to touch a spinning disk, mapping the sensory cortex before and after. The brain map increased in size when the monkey learned this new skill. “The experiment also showed that as brain maps get bigger, the individual neurons get more efficient in two stages. At first, as the monkey trained, the map for the fingertip grew to take up more space. But after a while individual neurons within the map became more efficient, and eventually few neurons were required to perform the task.” They also discovered that “individual neurons got more selective with training – overall the map became more precise.” Also, they learned that neurons began to process faster. All of this reflects on IQ scores so these experiments demonstrate the plasticity of ‘intelligence.’ Further, they learned that “paying close attention is essential to long-term plastic change.” P. 66- 69

These experiments form part of the foundation for the key words of neurodevelopmental approach: duration, frequency and intensity. For changes to occur, specific brain stimulation (activities on an individualized neurodevelopmental plan) must be done for short (duration – usually just minutes), throughout the day (frequency – number of times) with full focus (intensity). For more information visit:


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