How Does Your Memory Work? Pt.2

You might think that your memory is there to help you remember facts, such as birthdays or shopping lists. If so, you would be very wrong. The ability to travel back in time in your mind is, perhaps, your most remarkable ability, and develops over your lifespan.

Horizon takes viewers on an extraordinary journey into the human memory. From the woman who is having her most traumatic memories wiped by a pill, to the man with no memory, this film reveals how these remarkable human stories are transforming our understanding of this unique human ability.

The findings reveal the startling truth that everyone is little more than their own memory.

>> -- to remember instructions
only for a short period of time.

And to find my way around
new places is hard, as well.

I might just not
remember that I wanted

to remember something
rather than remember

that I've forgot that I wanted to remember

such and such, you know.

And I just totally forget.

Narrator: John Forbes was
born prematurely,

and his memory circuit has
never fully developed.

These home movies show something
that John's mind never can,

because to this day, John
can still not bring his past

to mind.

John: This is the New Year's party? Mother: It's the New Year's Eve Party.

Narrator: John is now 30, and has just
left home to live alone.

Mother: What did you do to Steve?

John: I didn't do anything
to Steve.

Narrator: Still, his parents
spend countless hours going

through photos with
John in the hope

that they might instill
some of his past.

Mother: She's got all emotional here.

Dad was talking, wasn't he.

When he was little,
yes, I was his memory.

It was whatever I
repeatedly told him,

that's what he would
be remembering.

In effect, the photographs
are all his memories.

So, yes, it's kind
of a responsibility

that he relied on me heavily.

Narrator: It means that every day,
every moment is a struggle.

Every action depends on
remembering to take it,

and since John can't do this,
he has to write it down.

John: I never know what
I'm going to remember

and what I'm going to forget.

Learning something, I've
got to concentrate more

to have a better chance of
remembering it, so newer things,

I write things down and
I have to repeat them.

Narrator: John has to rely on
routine for everything he does,

external prompts from
notes and reminders,

because he cannot remember
to do these things himself.

Mother: I think routine is
really important for him,

and that helps to
keep him organized.

So if something different
happens,

he needs to write it down,
and if I'm ringing him

about something, I can hear
him writing it down, you know,

I'm just going to make a note
in my diary so that I know

that he's written it down.

He doesn't always remember
to look in the diary, though.

Other times he needs to.

>> Narrator: Because of this,
John travels by train.

He can rely on its
timetable without having

to remember where
to go and when.

Yet, despite the fact that
John has done the same journey

hundreds of times, he still
writes out directions.

John: Knowing what I'm doing

and where I'm supposed
to be is important.

I just would rather
read it in my diary,

just as a reassurance thing to
go from Harlow Town to London.

Narrator: He's on his way to see
Faraneh Vargha-Khadem,

a neuroscientist who
has been studying John

since his childhood.

She's particularly interested
in John's condition because,

almost uniquely, the damage
to his brain is specific

to the most crucial link in the
memory circuit, the hippocampi.

Vargha-Khadem: When we look at
the MRI scans obtained

from a healthy individual,

we can see the hippocampi
quite clearly.

They're almond-shaped,
they're full-bodied

and fleshy looking,
one on each side.

When we compare this to the
hippocampi that we can see

on the MRI scan of John, they
are approximately half the size

of the hippocampi in
the healthy individual.

Narrator: The hippocampi are
crucial to memory,

because without us even knowing
it, they receive information

about every single
experience we have.

Vargha-Khadem: The hippocampi
appear never to sleep,

because they register
every episode,

every moment as it unfolds.

This is the beauty of hippocampi
that work and work well.

But in the case of John,

even things that are
important are forgotten,

and his hippocampi are not
automatically registering every

moment of his life.

Narrator: Because the rest of
John's brain is intact,

his intelligence can
mask his memory problems.

Vargha-Khadem: Hello, John.

Narrator: So Faraneh devises tasks

which reveal John's
core problem.

Vargha-Khadem: I've prepared a couple of
things for you to do today.

John, if you don't mind looking
at this picture and trying

to copy it as best as you
can, would that be possible?

John: Yes.

Vargha-Khadem: John had not seen this
particular design before.

And when we left the model in
sight and asked him to copy it

with the model in place,
he produced this copy,

which is actually
not bad at all,

because it captures all the
features that you have here,

and, of course, he
wasn't given a ruler.

Narrator: One hour later, John is
asked to draw the same design,

but this time from memory alone.

Vargha-Khadem: Can you see it
in your mind's eye?

John: No.

Vargha-Khadem: You can't, huh?

John: It's not there,
otherwise I'd just copy it.

Vargha-Khadem: Yes, of course.

Narrator: John's ability to
recall the design is

completely compromised.

Vargha-Khadem: Those features that he does
remember, they are inaccurate,

both in terms of the
reproduction of the actual part,

but they are also
placed in the wrong order

or in the wrong location.

So he doesn't get full points
for anything except the outline

of the square and
the cross inside it.

Everything else,
he gets it wrong

or he has failed to remember.

Narrator: But there is another,

more unexpected consequence
of John's amnesia.

It's not just the past
he can't bring to mind.

[ Music ]

At Harvard University in Boston,

Donna Addis is exploring
whether there's any link

between the way you
think about the past

and how you imagine the future.

Addis: Okay, we're going
to be putting you

into the scanner
today to take pictures

of your brain activity,
all right?

Narrator: She's examining which
parts of the brain is are used

for remembering versus
those used for imagining.

Addis: Hold this in your hand,

and if at any time you're
feeling uncomfortable and you'd

like to get out of the
scanner, you can touch this

and we'll come and
get you out, okay.

Narrator: First of all, Donna
asks Ling

to recall memories
from her past.

Addis: Close your eyes for a moment.

Okay, so our volunteer
today, Ling,

is in the scanner right now,

and we're recording her brain
activity while she's responding

to words that are
shown on the screen.

And, as you can see here,

the word that she's seeing
right now is "party."

And she's been instructed
to recall a memory to do

with party, so to think about
a party that she's attended

or that she's thrown
in the past.

Narrator: Next, she asks Ling to
imagine events in her future.

Addis: Okay, Ling, please
squeeze the squeeze ball.

[Beep] Excellent.

This time she's been asked
to think of a wedding,

and so she may be
imagining her own wedding

or somebody else's wedding

that may occur some
time in the future.

Narrator: After repeating this
procedure with 16 people,

the results are surprising.

Addis: As we look through
the brain here,

you can see just how remarkably
similar the neural activity is

when people are thinking about
either the past or the future.

And this is quite a
striking finding simply

because the patterns of activity
are so remarkably similar.

We never expected,
when we started this,

to see such similar
patterns of activity.

Narrator: Exactly the same
parts of brain were used,

and Donna believes that this is

because we piece together
fragments of memory

to create an idea of the future.

Addis: You know, traditionally
memory has always been thought

about as something that's
important for the past.

However we're now
starting to realize

that memory is much
more than this.

We need to be able to
draw on information,

so if you're imaging some
scenario that might happen

in winter, you see
yourself in your winter coat

with your favorite scarf.

You know, you're not just
drawing things from thin air.

Narrator: So from the age of five,
as we get better at thinking

about the past, we also
develop the ability

to think about the future.

This allows us to move along
an axis of time in our minds

to travel backwards
and forwards at will.

Addis: Mental time travel refers
to the ability of humans,

the presumably unique ability,
to project ourselves over time

such that we can
project ourselves back

into our personal
past, and then also

to project ourselves forwards
in time to imagine scenarios

that could occur to us in the
future, and so in essence, then,

from the present, we are able
to be like a time traveler

within our personal lives.

Narrator: For John, the
implications are bleak.

[ Music ]

Because he can't draw on any
past experiences, he is unable

to mentally time
travel into the future.

So John is trapped
in the present.