The Brain That Changes Itself

For more than a hundred years, medical schools taught that the adult brain was like a finished machine: the circuits formed in childhood and after that, only maintenance remained. If an area died in a stroke, that function was lost forever. This idea, called the localizationist brain, became dogma, repeated in textbook after textbook, and any doctor who disagreed was seen as a quack.

Norman Doidge, a Canadian psychiatrist and psychoanalyst affiliated with the University of Toronto and Columbia University, spent years visiting scientists and patients who defied that dogma in practice. The book grows out of those visits: it's the account of someone who saw up close people regaining function that medicine had written off as lost.

The name in the book's title is neuroplasticity, the brain's ability to change its own physical structure, creating new connections, strengthening the paths in use and weakening the abandoned ones, at any age. It's not abstract willpower: it's the actual tissue of the brain reshaping itself, something imaging scans can now record.

Cheryl had her vestibular system, the inner ear's balance system, destroyed by a medication she took. She felt as if she were always falling, had to lean on walls just to get from one room to another, and no conventional treatment worked.

Paul Bach-y-Rita, a physician and researcher, built a device with a strip of electrodes that sat on her tongue, connected to a motion sensor fixed to her head. Every time her body lost its upright position, she felt a tingling on her tongue showing the right direction to correct herself.

With repeated use, Cheryl's brain learned to interpret that tingling as the balance information itself, something so automatic that even after she took the device off, the stability effect lasted minutes, then hours. Doidge opens the book with this case because it literally shows one sense being replaced by another, proof that the brain reads information, not the specific organ that sends it.

Michael Merzenich, a neuroscientist, spent decades precisely mapping how the brain represents each part of the body in a kind of physical map in the cortex. He found that these maps are not fixed and change size depending on use.

In animal experiments, the area that represented an amputated finger was taken over by the neighboring fingers within a few weeks. In musicians who practiced many hours a day, the brain area devoted to the fingers of the hand used on the instrument visibly grew compared to people who had never played anything.

This finding became the phrase that sums up much of the book: use it or lose it. A circuit exercised often gains more cortical space and becomes more efficient. An abandoned circuit shrinks and gives way to its neighbors, which helps explain both why a good habit takes hold and why an addiction clings so deep.