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Sherlock Holmes, the legendary detective
had a theory that the brain is like an attic
where a person can only store a limited amount of memories.
Dr. Watson once told him that the Earth travels around the sun,
duh, to which Holmes replied,
“Now that I do know it, I shall do my best to forget it.”
clutter your attic with random facts and trivia,
and you won’t have room for the things that matter,
like identifying the tiny differences between lethal poisons.
Was Holmes right?
Is our memory limited, like the storage capacity of a computer?
Or is our memory unlimited?
And if we did have perfect memory,
what would life be like if you never forgot anything?
The animated film Inside Out depicted memories
as glowing spheres stacked in the brain,
like books in a library.
But the reality is a little more complicated.
There is no one place in the brain
that serves as our memory bank.
Instead, individual memories are scattered all over the brain.
Many brain cells, in several different regions,
work together to make one memory.
For example, a memory of eating grandma’s apple pie might involve
some brain cells to help you remember what the pie looked like,
others to remember the smell of the cinnamon,
and even cells to remember the delicious taste
just name a few.
In reality, though, a memory isn’t a physical thing
然而 事实上 记忆并不是
that we can find in any given brain cell.
It’s an action, not an object.
Think of baseball fans doing “the wave”:
no single fan IS the wave,
the magic only happens when all the fans are together,
doing their thing in a specific order.
In the same way, a memory only happens
when many connected neurons fire in a specific pattern.
Because the same cells can fire in many unique patterns,
one group of neurons can encode multiple memories.
This increases the memory storage capacity of the brain.
Buried deep in the middle of the brain
we find a group of cells shaped like a seahorse,
which is why 18th century scientists named this bit the ‘hippocampus.’
Without your seahorse, you might never remember.
We owe a lot of our understanding of memories to one famous patient,
known for years only by his initials, H.M..
多年来 我们只知道他名字的缩写是 H.M.
In 1953, H.M. underwent a surgery for epilepsy,
which demolished most of his hippocampus.
For the rest of his life,
he exhibited a severe type of amnesia
where he was unable to form new memories of facts or events.
But, he was still able to remember things
he had learned before the surgery.
They showed us the hippocampus is a key to making memories,
but it isn’t where memories are stored.
So how do experiences become memories?
If we look inside the brain of a mouse in a maze,
we could draw a kind of map,
showing which brain cells are active
as the mouse experiences something.
Later, we would see the mouse’s brain cells
firing in the same patterns,
replaying the experience in fast forward,
快速 一次次 来来回回地
over and over, backwards and forwards
to make the connections between cells stronger.
This is called consolidation and it’s how animals, including humans,
这被称为巩固 是动物 包括人类
commit new memories to long-term storage.
Days or weeks later,
a smell might trigger the same pattern of cells firing in the mouse’s brain,
a recall of the maze memories,
just like smelling cinnamon might trigger memories of grandma for you.
But the brain’s way of creating memories isn’t foolproof.
Sometimes, our mental replay of something we only imagined
can feel as vivid as a real experience.
If you picture all the sights, smells, and sounds of a crime scene
from someone’s description,
you activate similar brain networks
as if you had really been there.
The more you replay the scene in your mind,
the more it feels like a real memory.
That’s why a detective who asks leading questions
can inadvertently plant a false memory in a witness.
We’re able to remember a lot, but we forget even more.
Some forgetting just happens,
but our brains also forget on purpose.
We have at least three different ways of forgetting.
The first is what happens when a memory fades over time,
so-called “passive oblivescence”
(a term you will probably forget).
This may happen because
the connections between brain cells gradually weaken over time;
or perhaps the memory is still there,
but you might lose the triggers–sights, sounds, smells–you need to retrieve it.
但你失去了能激发它的场景 声音 气味
Another idea says memories could theoretically last forever,
when the same neurons get used in other memories,
this “interference” disrupts the original memory.
This slow fade type of forgetting happens to all of us, eventually.
A second type of forgetting- targeted forgetting –
happens at night while we sleep.
This is when we clear out random, useless tidbits of information we’ve learned during the day
and erase outdated memories.
For example, if yesterday, you thought the Earth was, say,
a flat disk supported by three elephants,
and today you learned that the Earth is round,
your brain needs to purge one of these contradictory ideas
hopefully the one about the elephants.
In certain stages of sleep,
we trim and prune connections between cells
and erase unneeded memory circuits.
The third type of forgetting is motivated forgetting,
something we all wish we could do
for one thing or another.
This is when a person intentionally suppresses unpleasant memories.
Forgetting on purpose is a way to regulate our emotions
and to focus on what needs to be done in the present,
instead of getting lost in negative memories of the past.
We may need motivated forgetting to maintain our self-image,
to maintain confidence, to stay optimistic about the future,
or to be able to maintain relationships with people who have hurt us.
We don’t know exactly how motivated forgetting happens,
but part of our brain seems to step in
and block the troubling memory from being retrieved.
So that even though it’s still somewhere in our brain,
eventually we can’t find it.
Our brains have so many ways to forget
because forgetting is one of the most important things we do.
Forgetting allows us to move past traumatic life events.
In fact, PTSD may be a problem
where someone simply remembers too much.
Forgetting also allows us to clear out junk.
Imagine every sight, sound, smell, and piece of information
your brain processes every day!
每个场景 声音 气味和信息
If our brains didn’t sweep out the garbage every night,
we would soon overflow our neural networks with random useless trivia,
just like Sherlock Holmes predicted.
We also wouldn’t be able to replace things
that are no longer true with better information,
update our mental models of the world.
Deep in the scientific literature
we find stories of a handful of people who never forget anything.
They are so rare that their unforgetfulness has a medical name: hyperthymesia.
The most famous case is Jill Price,
an American woman now in her fifties.
Starting from age 14,
Jill’s memory of her life is nearly perfect.
For any date in the past,
she remembers what she wore and had for lunch that day,
key historical events that she paid attention to,
and detailed incidents from her life.
She describes memories playing in her mind in vivid detail
like a video reel that has been enhanced with smells and emotions,
whether the events occurred yesterday or decades ago.
This might sound like a blessing, especially if you’re in school,
but Jill has described being haunted by upsetting memories and by regrets,
because unlike the rest of us,
she can clearly remember every choice she made and how it turned out.
There’s probably something you truly ‘want’ to forget,
like that extremely embarrassing moment in high school
that always seems to pop up at the worst times.
Can we erase those unwanted memories somehow?
In an episode of House, MD,
Dr. House treated a patient suffering from painful memories
by performing something called electroconvulsive therapy:
controlled electric shocks to the brain.
People who undergo ECT do lose some memories –
only not necessarily the ones they hope.
When it comes to erasing memories in humans,
our best tool still works like a hammer, not a scalpel.
It’s no accident that our ability to forget,
like our ability to remember,
is a complex and finely-tuned mechanism.
If humans couldn’t remember and learn from important events,
our species probably wouldn’t have survived.
But it seems that being able to forget is just as critical,
an elementary part of solving this great mystery we call life.
So you probably can’t teach yourself to have perfect memory,
and never forget anything.
Not without a massive brain injury or something.
But is memorization really the best way to learn something?
Memorizing can definitely help you get started with a new concept.
However, truly understanding it requires much more –
seeing how concepts are related to each other,
looking for different interpretations, dealing with new information.
These are the skills that will help you learn anything,
and if you’d like to sharpen your brain and develop these tools,
then Brilliant could be the place to go for that.
Check out this Brilliant course on logic and deduction. [screen recording]
It’s got fun and challenging riddles and mind-benders broken up into bite size pieces,
and they’ll guide you through the problems until you’re a Sherlock Holmes-level logical thinker…
To support It’s Okay To Be Smart and learn more about Brilliant,
go to brilliant dot org slash BESMART and sign up for free.
Also, the first 200 people that go to that link will get 20% off the annual Premium subscription.
Oh, pop quiz.
What’s the term for when the memory fades over time?
Told you’ll forget.
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