One does not have to be blind or deaf to tap into the brain’s mysterious and extraordinary power to learn, adapt and grow. I have seen hundreds of patients with various deficits  strokes, Parkinson’s and even dementia  learn to do things in new ways, whether consciously or unconsciously, to work around those deficits.

That the brain is capable of such radical adaptation raises deep questions. To what extent are we shaped by, and to what degree do we shape, our own brains? And can the brain’s ability to change be harnessed to give us greater cognitive powers? The experiences of many people suggest that it can.

One patient I knew became totally paralyzed overnight from a spinal cord infection. At first she fell into deep despair, because she couldn’t enjoy even little pleasures, like the daily crossword she had loved.

After a few weeks, though, she asked for the newspaper, so that at least she could look at the puzzle, get its configuration, run her eyes along the clues. When she did this, something extraordinary happened. As she looked at the clues, the answers seemed to write themselves in their spaces. Her visual memory strengthened over the next few weeks, until she found that she was able to hold the entire crossword and its clues in her mind after a single, intense inspection  and then solve it mentally. She had had no idea, she later told me, that such powers were available to her.

This growth can even happen within a matter of days. Researchers at Harvard found, for example, that blindfolding sighted adults for as few as five days could produce a shift in the way their brains functioned: their subjects became markedly better at complex tactile tasks like learning Braille.

Neuroplasticity  the brain’s capacity to create new pathways  is a crucial part of recovery for anyone who loses a sense or a cognitive or motor ability. But it can also be part of everyday life for all of us. While it is often true that learning is easier in childhood, neuroscientists now know that the brain does not stop growing, even in our later years. Every time we practice an old skill or learn a new one, existing neural connections are strengthened and, over time, neurons create more connections to other neurons. Even new nerve cells can be generated.