The term neuroplasticity refers to the fact that your brain changes the way it’s wired throughout your life. At birth, a given neuron (brain cell) has about 2500 synapses (connections to other neurons); by the age of three, each neuron has expanded to 15,000 synapses. By adulthood, synaptic pruning shrinks this number to about 7,500, because the connections you use a lot get reinforced, while the ones you don’t use get eliminated. Your body is efficient like that. This process can be summed up in the aphorism, “neurons that fire together, wire together” — in other words, repeated practice of a particular neural pathway creates a habit. (By the way, this is the reason why it takes between 21-30 days of repeated activity to build a habit—that’s how long it takes to create a dominant neural connection.)

What we didn’t know until relatively recently was that, while for the most part we no longer produce new brain cells after adulthood, our brains can actually change the amount of gray matter (the neurons themselves) dedicated to a particular task, based on our use of that task.

In some cases, this amounts to recovery of abilities lost due to injury. In others, it means we can develop abilities outside the realm of normal human experience. 

Functional Plasticity: Adaptation After Injury

Tests on those who have lost limbs reveal that the parts of the brain formerly dedicated to the missing body parts get taken over by sections of the brain that register sensations from other body parts. The brain isn’t wasteful, in other words—it uses the space for something else.

This brings up an interesting question—can victims of a stroke or a traumatic brain injury (TBI) learn to adapt and regain function using principles of neuroplasticity? A technique called Constraint-Induced Movement Therapy suggests that repeated use of body parts affected by the brain injury causes the brain to redeploy uninjured gray matter to facilitate movement in the affected areas. Compared to placebo patients, CIMT patients showed “large to very large” improvements in functional use of previously affected body parts. This paper suggests similar techniques may be used for other neurological impairments, such as Parkinson’s Disease.

Learning Extrarordinary Skills

Dennis Charney, MD (below) states that POWs who were in solitary confinement developed outstanding cognitive abilities because they spent so much time with nothing to do but think. 

One learned to multiply twelve figure numbers by twelve figure numbers, accurately; another discovered that he could recover lost memories, remembering his classmates from kindergarten. Another envisioned every detail of a house he wanted to build, down to the last nail. When he got out, he built the very house he had imagined.

What were these POWs doing during that time? They were exercising their brains.

Changing Your Brain’s Hardwiring Based on Demand

The usual autonomic response of the human pupil is to constrict in response to bright light, and dilate in response to darkness, in an attempt to let in as much light as possible. The problem is, a dilated pupil can’t perceive fine detail very well. You trade illumination for clarity. 

But in this particular village in Thailand (below), that isn’t true. These Moken children spend years diving under the ocean for food. As a result, their pupils constrict rather than dilate in the low undersea lighting—enabling them to see up to 22% more clearly under water than a human without this adaptation.

These kids aren’t born with this ability, though—as it turns out, anybody can override the normal pupillary reflex in this way. It all depends upon the demand.

Reallocating Limited Resources

The longer a person has been employed as a taxi driver in London (or presumably in any equally complex city), the larger his posterior hippocampus becomes relative to the anterior hippocampus. 

Why? The hippocampus generally is responsible for the formation of memories; however, the posterior hippocampus is responsible for memory of spatial relationships in particular, while the anterior hippocampus is responsible for other memory tasks. 

Presumably this is because a taxi driver constantly exercises his spatial memory, requiring the brain to redistribute the gray matter of his hippocampus to accommodate the demand.

The Power of Your Mind

It turns out our brains have a great deal more potential than most of us ever realize. Dr. Vernon Mountcastle, neuroscientist at Johns Hopkins University, said in 1992, “Most brains never reach their full potential. Perhaps we don’t train them correctly.”

The take-home message: what you exercise will get stronger, while what you ignore will atrophy. Just make sure you are exercising the right things!

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