When he was two years old, Ben stopped seeing out of his left eye, and soon his vision was gone forever. But by the time he was seven years old, he had devised a technique for decoding the world around him: he clicked with his mouth and listened for the returning echoes.【G1】_____________________________

Echolocation may sound like an incredible feat for a human, but thousands of blind people have perfected this skill, just like Ben did. Then how could blindness give rise to the stunning ability to understand the surroundings with one’s ears? The answer lies in a gift bestowed on the brain by evolution: tremendous adaptability.

【G2】_____________________________Neurons, the cells responsible for rapidly processing information in the brain, are interconnected by the thousands—but like friendships in a community, the connections between them constantly change: strengthening, weakening, and finding new partners. The field of neuroscience calls this phenomenon “brain plasticity,” referring to the ability of the brain, like plastic, to assume new shapes and hold them. More recent discoveries in neuroscience suggest that the brain’s brand of flexibility is far more sophisticated than holding onto a shape, though. To capture this, we refer to the brain’s plasticity as “livewiring” to spotlight how this vast system of 86 billion neurons and 0.2 quadrillion connections rewires itself every moment of your life.

【G3】___________________________But more recent discoveries have failed to cohere with the old theory. One part of the brain may initially be assigned a specific task; for instance, the back of our brain is called the “visual cortex” because it usually handles sight.【G4】__________________________But in the sightless, these same neurons can rewire themselves to process other types of information.

Mother Nature endowed our brains with flexibility to adapt to circumstances. Just as sharp teeth and fast legs are useful for survival, so is the brain’s ability to reconfigure. The brain’s livewiring allows for learning, memory, and the ability to develop new skills.

【G5】_____________________________In one study, sighted participants intensively learned how to read Braille. Half the participants were blindfolded throughout the experience. At the end of the five days, the participants who wore blindfolds could distinguish subtle differences between Braille characters much better than the participants who didn’t wear blindfolds. Even more remarkably, the blindfolded participants showed activation in visual brain regions in response to touch and sound. After the blindfold was removed, the visual cortex returned to normal within a day, no longer responding to touch and sound.

But such changes don’t have to take five days; that just happened to be when the measurement took place. When blindfolded participants are continuously measured, touch-related activity shows up in the visual cortex in about an hour.

[A] Neuroscience used to think that different parts of the brain were predetermined to perform specific functions.

[B] As a result, Ben had more neurons available to deal with auditory information, and this increased processing power allowed Ben to interpret soundwaves in shocking detail.

[C] Recent decades have yielded several revelations about livewiring, but perhaps the biggest surprise is its rapidity. Brain circuits reorganize not only in the newly blind, but also in the sighted who have temporary blindness.

[D] Whenever we learn something new, pick up a new skill, or modify our habits, the physical structure of our brain changes.

[E] We suggest that the brain preserves the territory of the visual cortex by keeping it active at night. In our “defensive activation theory,” dream sleep exists to keep neurons in the visual cortex active, thereby combating a takeover by the neighboring senses.

[F] This method enabled Ben to determine the locations of open doorways, people, parked cars, garbage cans, and so on. He was echolocating: bouncing his sound waves off objects in the environment and catching the reflections to build a mental model of his surroundings.

[G] But that territory can be reassigned to a different task. There is nothing special about neurons in the visual cortex: they are simply neurons that happen to be involved in processing shapes or colors in people who have functioning eyes.

【G4】