Untertitel: WDR mediagroup digital GmbH im Auftrag des WDR
While he sleeps, Christian's brain
sorts out what he's experienced during the day.
This reinforces his memories.
A lot happened yesterday.
Christian was bombarded with countless sensory stimuli.
Some things he will still remember today.
But he forgot the cup of water in front of his bed.
Oh no, my politics essay.
I have to hand this in today. Damn.
The essay is beyond repair.
But Christian can still remember what was in it.
Actually, he can rewrite the essay directly.
When we remember things, lots of nerve cells work together.
Several at the same time.
These nerve cells were already active together in the past.
Remembering is like reviving a pattern.
The nerve cells are linked together.
They transfer nerve impulses to each other.
In this way, they pass on information.
This is how memories, among other things, are created.
A memory pattern like this one
was created when Christian wrote his politics essay the first time.
His brain stored this information.
Our memory is not a shoebox
that we can put things into and take things out of.
Our memory is our brain and a bit like modelling clay.
The more we work with it, the more it changes.
And the more this change remains in place afterwards.
I'll give an example.
If we've been talking to someone, just a bit of superficial chit chat,
perhaps listening to our MP3 player at the same time.
And there was a lot going on in the background,
then the memory will store very little.
But if we've written something down, and writing isn't so easy,
we have to consider:
How do I start, how do I continue, how do I finish?
Then that alone will make sure that the whole thing
will stay in our memories much more effectively.
The more we repeat something, the more intensive the memory will be.
Christian types his PIN into his mobile phone every morning.
This is why he remembers it well.
"Hey Chris, can I copy your politics essay?"
If Christian would remember everything about his way to school,
he'd go crazy.
Our brains disregard all the unimportant things straight away,
after about half a second.
Important information lands in the short-term memory.
This means: a certain pattern of nerve cells remains active,
for 20 to 40 seconds, no more than a few minutes.
At the same time, the connections between the nerve cells
are strengthened for the short term.
This improves the transfer of information between them.
A sub form of the short-term memory is the working memory.
It ensures that we have all the information to hand
that we need here and now.
Whatever directs me here and now,
that's important for me to function in a given moment.
Information handled by the working memory does not stick automatically.
The working memory does other things.
For example, it makes me realize:
I'm talking now and answering the question
"what is our short-term memory",
which is called working memory today and keeps me going.
There are the nerve cells up here which are transmitting
"Manfred say the answer now, Manfred say the answer now".
They are there to keep objectives in place,
plans, whatever is important right now, and to put these into action.
As soon as something else interesting happens,
some of the unimportant information is disregarded.
Christian can't remember the details of his way to school so easily now.
The rules and moves in basketball
have moved into Christian's long-term memory.
This means that they will remain available for hours, days, months
or years, probably his whole life long.
The first time Christian held a basketball in his hands of course,
this knowledge had to go into his head first.
It first of all went into his short-term memory.
But everything that we want to remember for longer
has to pass through a key portal in the brain: the hippocampus.
This is the central switch point for the transition
from a short-term to long-term memory.
Here all incoming information is filed chronologically and analysed.
Everything important is stored for the long term.
The brain puts everything else at the back.
When a memory is stored in the long-term memory,
the connections between the nerve cells become stronger.
New connections are formed.
This makes the memories particularly sturdy.
Depending on what we remember, there are different types of memory.
Some memories are stored unconsciously.
For example, when Christian has practiced the basketball moves well
that they come without him having to think about it.
We've been talking about the political systems in Germany
as well as in the US.
Christian remembers other things consciously.
For example,
when he draws on his existing knowledge in a politics class.
How long is the legislators' term in the US?
That's five years.
And then there are personal memories.
These are what make it possible for us to know who we are.
However our brains often distort our personal memories especially.
In Christian's memory the pillow fight looked like this.
But it wasn't just the two of them, there were three people there.
And it was in the living room.
Because our brains aren't a shoebox, the memories we've stored
aren't as fixed as we would like them to be.
Memories are especially changeable if we think about them.
Because if we remember them, then we take them in our hands, so to speak.
They are like soft modelling clay.
When we have it in our hands it changes,
there's no way of preventing it.
And memories are just like this.
The more we remember a memory, the more we change it.
Because Christian has a crush on Felicity,
his memory is manipulated by his desires and feelings.
This means that the pattern of nerve cells that is reactivated
when he remembers is no longer identical to the original pattern.
Sometimes Christian simply can't retrieve a piece of information.
Stupid password.
It's on the tip of my tongue.
Maybe Christian just hasn't used his password for a long time.
It could also be that Christian is stressed.
Because he's about to have an unpleasant appointment.
When we want to retrieve information under stress, it often doesn't work.
The stress hormones adrenalin and noradrenalin
put our bodies in alert mode.
If the stress lasts longer,
the stress hormone cortisol is released as well.
Stress hormones influence the processes in the brain.
They can trigger disruptions in the parts of the brain
in which our memories are processed.
When the stress is over, the memory works again.
We know a lot, we've stored a lot, so if I want to access something,
in other words find the particular book or page in the book,
how do I do that?
If I have a very small searchlight
and have to illuminate one book after the other,
I'll take forever to find something.
But if I can switch on the light and everything becomes bright,
oh yes, there it is.
We can imagine our brains a bit like this,
depending on what mood I'm in.
If I'm in a good mood, that's like "the light is on, I can remember".
And if I'm in a bad mood, the light is off,
but there's a very bright searchlight.
Normally Christian can remember his passwords without any trouble.
He's 17 and his memory is still very efficient.
But that will change over time.
From the age of just 20 onwards,
more nerve cell connections break down than new ones are built.
This means that our memory gets worse and worse, the older we get.
However, it depends on what type of memory we want to retrieve.
In some memory tasks, old people do better than young people.
Older people score well, for instance,
when they have to recall experiences from their long lives.
But young people are quicker.
For instance, when processing new information.
Sleep is an important requirement for remembering.
For example, the deep sleep phase immediately after falling asleep.
Brain researchers believe that personal memories
and factual knowledge are reinforced during deep sleep.
And that unconscious motor memories are reinforced in the dream phases
afterwards, such as the moves in basketball.
When we sleep, we process what we've learned during the day again.
This means that our brains don't sleep.
They are completely active.
Just as active as when we are awake, and pass through various stages.
For instance during deep sleep things are downloaded,
information is transferred from a kind of buffer memory
to the long-term memory.
And then those in the long-term memory are analysed again
during the dream phases.
This is why there is so much going on in our heads.
We're thinking about what happened during the day again,
making new associations, connecting these to other feelings
and trying to figure out what it was all about.
Then we perform another download.
During deep sleep new information is uploaded,
from the buffer memory to the cerebral cortex
and then it is analysed again.
And we perform this download and the analysis
and the download again five or six times a night.
Our brains work hard to process what we're learned during the day.
One night is not always enough.
Sometimes it takes months for certain memories
to become fixed in Christian's brain.
But without sleep, we wouldn't be able to form memories at all.
Copyright WDR 2012