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Hank explains the gift that your brain gives you every day: the gift of neural plasticity -- the ways in which your brain actually changes at the cellular level as you learn.


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You would not be here if you weren't interested in learning and neither would I, but here is something we haven't learned about together:  learning!  The ways in which we acquire and retain knowledge, which is the very definition of learning, is really a science in itself.  And, like any other discipline that involves the study of the human brain, it is practically still in its infancy.

Just 20 years ago most scientists believed that once we reached adulthood, our brains were pretty much fixed.  Not that we were incapable of learning anything new, exactly, but the assumption was that our brain's development phase was over and now it's pretty much there to remind our hearts to keep beating and occasionally let us remember where we left our phone.

But thanks to huge advances in things like functional brain imaging, we have a clearer picture than ever of how our brains work, and we're beginning to observe some wonderful things.  For one, we now know that the process of learning actually alters the structure of our brains at the cellular level and what's more, it turns out that our brains never stop changing to make room for new information.

People often compare the human brain to a computer, but imagine a computer than can actually grow new circuits as it acquires new facts and associations and you have a much more awesome comparison.  This is the gift known as neural plasticity.  You might think of plastic as being stiff and cheap, but in biology plasticity refers to the capacity of living things to mold themselves to new conditions, and our brains are great at it.

For one thing, your brain cells, or neurons, are always changing their connections to one another to meet changing demands.  Each of your neurons consists of a central body with spindly dendrites and a long axon stemming from it.  The neuron transmits electrochemical signals to other brain cells through its axon and receives signals through its dendrites via connections where the cells meet, called synapses.

When you're born, each neuron in your brain has about 2,500 synapses connecting it to other cells, but by the time you're three and you've become just a sponge of fascinating new information, like what sound a piggy makes an where your mom's face goes when she hides it behind her hands, you have six times as many, up to 15,000 synapses for each neuron in your brain.  And in this regard it's kinda true that your brain hits its peak when you're young because by the time you're an adult, your brain cells have about half as many synapses as when you were three.  But it turns out that's okay because we now know that synapses just shrink up when they're no longer needed.  Like, you know now that pigs go oink and that people still exist when you can't see their faces, so you don't need to keep those connections to remind you.

This process of winnowing down unused connections is known as synaptic pruning.  Meanwhile, your neurons experience all kinds of new growth as you continue to soak up new information, like how to drive, how to solve for x, and how to get through that one really hard level in your favorite castle-smashing game.

Here, the key to learning is memory because you need to retain that information in order to apply it to the future.  So your brain cells can change in different ways, depending on how long you remember what you've learned.  As you stockpile data in your short-term memory, for example, the structure of your existing synapses has been found to change.  With more and stronger dendrites growing to reinforce them.

So, for info that you retain for just a short time, like how to destroy digital castles using rocks and fire, you don't need to sprout whole new connections.  Just beefing up the existing ones you've used so far will help you master the game just fine.

But when it comes to important stuff, like the learning we do at school, or hopefully the stuff you learn here on SciShow, your neurons actually forge entirely new synapses over time as you re-learn, re-remember, and reuse the information.  This is how your brain builds the long-term memory you need to retain the learning you're doing right now at work and at school and to turn it into a lifetime of supplied knowledge.

So, I said it before and I'll say it again, take care of your brain and odds are it'll take care of you.

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