- Our memories for what happened are not reality.
(intense music playing)
Your memory is not a video camera,
recording a constant stream of every sight
and sound you're exposed to.
Memory is part of our biology.
So our brain is not separate from our body.
It's part of the whole system.
Human memory is amazing,
and it's fallible.
My name is Lisa Genova.
I am an author and neuroscientist.
The name of my book is "Remember: The science of memory
and the art of forgetting."
(intense music continues)
Memory is the pattern of neural activity
that represents the sights sound, smells, feelings,
information, language that you experienced
when you learn something in the first place,
reactivated as a neural circuit in your brain.
There's a physical location where we process vision
or language,
or movement.
But memory is different.
Memory is located throughout your brain
in all of the disparate places
that are involved in what that memory consists of.
So if I'm thinking of the sight and sound of Mickey Mouse,
I'll have neurons in the back of my head,
that's my occipital cortex,
my visual cortex will be activated.
Those represent what Mickey Mouse looks like.
But the sound of Mickey Mouse is located somewhere else.
(whistling)
That's in my auditory cortex, sort of near my ears.
And so the circuit,
the memory will involve the activation
of neurons in those very different places.
Your hippocampus is your memory weaver.
This is the part of your brain that links together,
the sights, the sounds, the smells,
the feelings, the language, the information,
so that they become connected into a neural circuit.
Our human brains are pretty phenomenal
at remembering what is meaningful,
emotional, surprising or new,
and what's repeated.
They're pretty bad at remembering what's same old, same old,
been there, done that, not emotional, not repeated.
Our brains are also great at remembering things
that are visual and where those things are in space.
Evolutionarily, it was really important for our survival
for us to remember where the food is, where safety is,
where the predators live.
So how accurate are our memories?
It depends on which kind of memory we're talking about.
There are three kinds of long-term memory.
There's semantic memory.
Semantic memories are the facts and data,
the information you learned in school, six times six,
who was the first president, that kind of information.
Also your biographical information,
where you were born, your street address, your phone number.
So if we're talking about semantic memory,
that's pretty stable and accurate.
For example, if you learned that six times six
is 36, when you were in the third grade,
you're not gonna suddenly misremember
that decades later as six times six is 75.
That's not going to happen.
There's also muscle memory.
Muscle memory is similarly stable over time.
It's a little bit of a misnomer.
Muscle memory doesn't live in your muscles.
This actually lives in a part
of your brain called the motor cortex.
That part of your brain tells all
of the voluntary muscles in your body what to do.
Muscle memory is the memorized choreography,
the procedure for how to do things,
how to brush your teeth
how to swing a golf club,
how to eat an ice cream cone.
This is where the expression "just like riding
a bike comes in", right?
You can not ride a bike for decades
and then get back on the bike
and your brain will remember the choreography.
You'll get on the bike and ride.
Episodic memory is a little different.
This is your memory for the stuff that happened.
This is the story of your life.
This is, "oh, remember when."
That that's a little strange.
It turns out that every time we recall
a memory for something that happened,
we have the opportunity to change it.
Often not consciously.
We might add a detail.
We might leave a detail out.
If somebody else experienced the same event,
they might add some information that we agree with.
And so we'll add that to our memory.
We're also as human beings, natural born storytellers.
So if there are pieces of information missing in my story
or if there's a way I could embellish
and make the story better,
give it a nice beginning, middle and end,
I might supply that,
not knowing that I'm consciously lying.
I'm just providing information that makes sense,
to tell you the story of what happened.
Here's the weird thing that happens,
if we've revised the memory in any way whatsoever,
when we recall it, we store this version,
this 2.0 version of the memory,
over the old version in our brain.
It's like hitting save in Microsoft Word.
So you can imagine that with each retelling,
the memory for what happened has the possibility
of drifting further and further away
from what you stored his memory to begin with.
There's another kind of memory called prospective memory.
This is your memory for your future you.
This is your brain's to-do list.
Pick up the dry cleaning, pay the bills,
oh, I need to remember to call my mother later.
And our brains are not designed to do this.
Prospective memory is fraught with failure.
Unless the proper cue is there and available
for you to notice at the right time, in the right place,
you will forget to do this.
And so the more that we understand
about the biology of memory, the science of memory,
the more we can develop a better relationship with it.
Your identity is so closely tied
to your ability to remember.
If someone meets you,
the first question people often ask is, "what do you do?"
"Where are you from?"
"Tell me about your family."
The answers to all of those questions, rely on memory.
Your ability to remember what happened,
the story of your life,
is really who we say we are.
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