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PROFESSOR JOHN GABRIELI: Last
time we discussed how people
can approach psychological
issues in terms of
experiments, and at least
correlations in some cases or
causal studies through
experiments.
And we discovered that
if you think
about money, what happens?
On average, you become more
self-reliant or less willing
to help, right?
We discovered that if you just
change the way that men and
women approach each other at a
dating event, you change their
internal feelings and their
external behaviors simply by
who's approaching whom.
So we learned all kinds of
things that you might or might
not have known unless you
did the experiments.
And for all these things that
are our mental life-- our
thoughts, our feelings,
they are all
supported by our brains.
And so for me personally as a
neuroscientist, I've always
thought that the brain is one
of the three amazing things
out there in the
natural world.
With the origins of the
universe, the origin of life.
And the brain that allow us to
think and feel, to see, that
remember, really everything that
we do comes from that.
OK.
So here's this device.
And I want to share with you
just this phrase that people
sometimes use, which is
that your mind is
what your brain does.
That your mind is what your
brain does And so the readings
from Oliver Sacks for today kind
of remind you of that.
So there are two women who have
seizures of various kinds.
And what happens in them?
So one is Mrs. OC, 88-year-old
woman.
And what starts to
happen to her?
She starts to hear songs.
And so powerfully, not just when
you have a little song in
your head, that it's hard for
her to hear conversations.
For her, a conversation like
we're having now, it's as if
the music stayed
on really loud.
Turns out she's having temporal
lobe seizures.
The temporal lobes are the parts
of the brain that are
terribly important
for hearing.
So music is something
that we hear.
And then she has a right
temporal lobe infarction.
She's had an injury in the
right temporal lobe.
Music, for most of us, is more
dependent on right hemisphere
processes than the left.
So that makes it unusual.
And how does she feel about
the whole process?
So what's generating
the songs, though?
What's generating the songs
that she hears?
Yeah, her memory.
Her brain, right?
Because in epilepsy,
what's happening?
Neurons are firing.
When neurons fire in organized
patterns, those are memories,
desires, physical actions,
thoughts.
When they're firing for no good
reason like an epilepsy
because of some brain
difficulty,
they just start firing.
But the neurons that happen to
be firing will drive certain
mental processes that they
normally support.
In this case, the neurons that
are firing away are ones that
are involved in memory
or songs and
perception for songs.
And when they fire, it's as if
you heard the song itself.
Because when you hear my voice
or when you hear a song,
you're never hearing the song.
You're always hearing what your
neurons are interpreting
the sound that comes
to your ear.
Your mind is what your brain
does in that sense, and in a
very central way.
If you had an injury in that
part of the brain, you can be
cortically deaf and never hear
a sound, even though all the
information came through
your ear.
So without your brain
interpreting the environment,
you wouldn't know what it is.
But if your brain starts to fire
on its own, that's just
as good a signal as if you
heard a song itself.
Because that is the stuff
of hearing songs.
So she enjoyed it, actually.
She declined taking
anti-convulsive medications.
Because she felt it was a portal
to her past, right?
The songs that she heard were
ones that reminded her of her
life and were kind of
pleasant to hear.
It was like being on a nonstop
highlight film of for life, or
a highlight MP3.
So now an opposite response to
a similar phenomenon comes
from a Mrs. OM in her 80s.
She hears songs, but she
also hears a lot
of ringing and hissing.
It's not limited to
the song itself.
She doesn't mention any
of this for how long?
Four years.
She's hearing ringing,
hissing, songs.
She knows because her mind is
fine that they're coming from
nowhere but inside her head.
But she doesn't tell anybody.
That's a huge burden, right?
And why doesn't she tell them?
Yeah, yeah.
And especially if you're in
your 80s, and you're going
around saying, I'm hearing
things, people go, OK.
Were putting you in the
old age home, right?
You're out of it.
So she doesn't want to
give up her freedom.
And she gets a short playlist,
just three songs, and hears
them over and over
and over again.
You may have had the experience
that some songs you
hear for a while.
You like them more, and then
you get tired of them.
If you had only three all the
time, every day, and a bad
version that was hissing and
ringing, you would get pretty
tired of the songs too.
That stops by anti-convulsive
medications and medications
that stops the seizures,
stop the songs.
And so it's sort of a beautiful
story, when two
opposite emotional responses for
how your mind is what your
brain does.
Now from this, the fact that
songs are played back as if
you had pulled out songs from
your computer or shelf
somewhere, you might think that
the brain retains these
records perfectly throughout
life and epilepsy
would just sort them.
But we'll come back to that
later on, and say that in very
much, we don't think
memory is that way.
But we do remember songs that
are important for us.
And if our brain just starts
firing in the same place where
we store those songs, we hear
them just as real as your
cortex hears it when it hears
the actual song itself.
Because that's the place
where you hear it.
So this is the kind of evidence
that at least in some
sense, your mind is what
your brain does.
And so here's this
amazing brain.
It's about two to
three pounds.
But every thought and feeling
you'll ever have, or every
physical movement, every desire,
every thing that
you're proud of or ashamed of
that crosses your mind will be
supported by this structure.
So I'm going to talk a little
bit about the neurons, just a
little bit about the neurons
that compose the brain, and a
little bit about a quick tour
through the gross organization
of the brain.
We'll come back to many of these
structures as they're
relevant to different things
like memory or emotion or
personality later
in the course.
Talk a little bit about the
enterprise of trying to say
which parts of our brain
support which
parts of our mind.
Missteps about that, famous
cases about that, that have
turned out to have roughly
the right message.
And we'll focus on hemispheric
specialization, the thing in
humans where our left hemisphere
and our right
hemisphere are organized to
accomplish different things,
to support different
mental functions.
And the surprise from split
brain or commissurotomy
patients, that these different
mental lives that support our
different parts of
the brain, that
they can live in isolation.
They don't even know they're
there one to the other.
So let me rephrase this.
As you sit there, the thought is
you might have independent
parts of your mind supported
by independent
part of your brain.
And at any one moment, your
consciousness might be in one
part, and then it might
move to another.
And just like there's all these
people in this room,
your brain might be all these
things having their own
independent thinking lives.
They have to interact a lot.
But how much might there be
independent modules in your
brain that are doing
their own thing.
And now you're thinking about
music, and those turn on, and
that's where your consciousness
is.
Now you're thinking
about history.
Now you're thinking about
dinner tonight.
And different parts of your
brain turn on and that's when
your consciousness is moving
from one part of your
brain to the other.
But the other parts
keep going.
So we'll see how plausible
is that.
So it took a long time for
people to decide that the
brain actually is the
stuff of the mind.
Smart philosophers like Plato
said, well, it's part of the
body that's closest
to the heavens.
That's where the gods might
reside, so that's a good place
to have your mind and that's
where your brain is.
A sort of GPS approach
to locating where
the mind might be.
Aristotle said, wait a minute.
It's the warm and active heart--
the heart was very
impressive in post-mortem
examination of people who have
passed away--
that houses the mind.
And that it cools, and there's
an inner brain.
So the brain was kind of a
radiator that would sort of
cool stuff off to keep
the heart in optimal.
And even now, we talk
about people having
a big heart, right?
A cold heart, a warm heart.
We still talk about human
personality or character in
terms of heart.
Galen said that the brain
was surrounded-- there's
ventricles in the middle of
the brain that have fluid,
cerebral spinal fluid.
And he hypothesized that the
brain was the packing material
that protects that fluid.
Hang on to that fluid, that's
all your stuff.
We're going to cram a lot of
stuff around it, right?
Like the bubble pack that
comes in the boxes.
And of course now we know it's
the opposite way around.
The mind is in the physical,
the dense part of
the brain, not that.
And then ideas from Descartes,
the pineal body is one of the
very few structures that's in
the midline of the brain, that
doesn't have a thing on the left
and a thing on the right.
And so he thought maybe that's
where things get unified in
the whole brain.
It all comes together
as the place that
runs the whole brain.
And that's a wrong idea.
But people were trying to figure
out what was going on.
In modern neuroscience,
there's many levels of
analysis of the brain.
So if you go to any neuroscience
program, like
Department of Brain and
Cognitive Science, you will
actually see scientists who
study things like molecules
and synapses, molecular
neurobiology, how neurons
work, how neurons form networks,
little organizations
of things that solve problems
at a higher level, maps,
systems in the brain
as a whole.
In this course, we mostly have
to operate at this level.
That's the place where it's easy
for us to relate in some
ways parts of the mind as we
understand it, of human nature
as we understand it, and
physical parts of the brain.
It's very hard for
us to get that to
molecules at the moment.
But lots of neuroscience is
working to connect these
things at different levels.
And I can't resist talking for
one second, too, about the
fact that we know our
brains were not
designed from scratch.
You are not humans 3.0
or 98.0, right?
Everything in us in some way
evolved from other species
that were similar to us,
and far enough back,
dissimilar to us.
So there's lots of speculation
about how it is that we
balance parts of the brain
that are ancient in their
evolutionary roots, that are
more recent in their
evolutionary basis, and what
that means about us.
Another sense in which we're
comprised of multiple society
of brain systems in
between our ears.
So we know the cells in the
brain are glia support cells
and neurons, that a neuron--
and I know you all
know all this.
Oh, let me say a word
about notes.
So we sent PDFs of the lecture
notes from the first two
lectures and the third
one just recently.
Starting tomorrow, we'll send
you the PDF of each lecture,
the latest by the night
before the lecture.
So you will be able to
print it out or look
at it on the computer.
But neurons have a soma
or cell body.
Those make up the grey matter
when we look at the brain.
They have an axon that can be
covered with myelin that makes
the white matter.
The dendrite is the extensions
of the neurons that have the
input to the neuron.
We know that neurons
communicate by
neurotransmitters across
synapses, junctions between
different parts of neurons.
When you have a collection
of cell bodies,
people call it a nucleus.
When you have a collection of
axons, they call it a tract.
It's just vocabulary
and stuff.
And you know this from other
courses, just reminding you
about them.
And then you get these
unbelievably startling kinds
of numbers, which are always
huge estimates.
But they show you how amazing
your brain is, and how hard it
is for us to deeply understand
how the brain works.
I mean, we understand incredibly
more than we did 10
years ago, 20 years
ago, 30 years ago.
We're incredibly far from
understanding how your brain
accomplishes the amazing
things it accomplishes.
So it has about 100
billion neurons.
It has about 100 trillion
synapses, connections among
neurons and dendrites.
If you were to lay out the very
thin myelinated axons in
your brain, just the big axons
that get myelin, it's
estimated that you'd have
62,000 miles of axons.
That's pretty good, right?
Now you really want to wear
helmets when you go
skateboarding or anything,
right?
And about 100,000 miles of
dendrites in each of you.
So this is why the brain
is amazing and hard.
It's fantastic in
its complexity.
An average neuron may have up
to 15,000 connections, 1,000
synapses, and up to
1,000 neurons.
There's different ways
of thinking about the
computational power
of a neuron.
But they estimate that these
might have, each one the
computational power of
something like a
medium-sized computer.
So it's not the best computer,
but you've got
100 billion of them.
Now, that's the easy part.
Take 100 billion neurons and
your computer's in your head.
The hard part is to get them
all working together
efficiently.
And you're not sitting around
going, "Computer 33, get up to
speed here.
Something's wrong here." You
don't even think about them.
You just go about
your business.
The time for information to go
from neuron to neuron is
pretty slow compared to fast
computers, pretty fast for
biology, 10 milliseconds.
And everybody thinks the secret
of the brain, whatever
it will turn out to be in many
ways, is that you can run a
fantastic number of computations
simultaneously
and collaboratively.
But we don't have a deep
understanding of how
that all plays out.
So here's a cartoon of this
amazing axon, the cell body,
and the dendrites to
get inputs to it.
The axon is the output signal
of a typical neuron.
Neurons can have these beautiful
arborizations,
tree-like properties
of dendrites.
Neurons have all kinds of
different shapes in different
parts of the brain, presumably
reflecting their different
missions, what they have
to accomplish.
An incredibly complicated
cellular factory inside all of
them is producing different
things.
This is a big overview.
This is not for you to learn
a specific fact.
And this, here's an actual
neuron that's injected in the
fantastic tree of connections it
makes within the neurons to
accomplish its mission.
Here's a cartoon of a synapse,
places where neurotransmitters
signal from one axon to one
dendrite, for example.
Here's an actual picture.
Here's the package of vesicles
that house the
neurotransmitters in them,
making a connection or a
synapse onto a dendrite.
And you just have a fantastic
number of these.
And as you're sitting in you
right now an unbelievable
amount of stuff is going on--
releasing them, cleaning them
away so they don't hang around
too long, building new ones to
get ready to go.
It's just an unbelievable story
per neuron, never mind
the whole of them.
So now we take a step back
to the brain as a whole.
Here's the front of the
brain, top of the
brain, back of the brain.
I'm going to say a word about
the cerebellum, which we'll
talk very little about
in this course.
The cellular organization
of the cerebellum is so
consistent that people estimate
that half of all the
cortical neurons in the brain
are in the cerebellum.
And if you see this cerebellar
size is small, not that large,
it's because it's packed
so tightly.
And it's so consistent in its
organization that people
thought, that's the first part
of the brain we'll crack.
Because the organization is so
clear that we'll be able to
figure out what it's computing
and how it does it.
And it's turned out to be
about as mysterious a
structure as any.
I can't tell you the number of
debates about what people-- we
know it's involved in motor
control, but in many other
things, as well.
The wiring diagram, knowing it,
what's connected to who,
turns out to be only a tiny step
in understanding how what
part of the brain does
what it does.
So here's this mysterious
cerebellum.
And then here's a basal ganglia
that we know is
involved in movement.
Parkinson's Disease
affects it.
Huntington's Disease
affects it.
It's also involved in learning
habits of all kinds.
It's also involved in the reward
systems of the brain.
What have we found delightful
and important?
What did we want to do
because the reward
system is turned on?
We'll come back to
that later on.
And then the limbic system, the
part of the brain that's
involved in emotion
and memory--
amygdala and hippocampus.
We'll come back to that.
If you don't have this structure
intact, you can't
form new memories ever again.
We'll talk about patients
like that.
And then we'll come to the
smarts of the brain, the
cerebral cortex, four lobes--
frontal, parietal, occipital,
and temporal.
You have four on the left
and four on the right.
These lobes are comprised
of gyri.
That's the part of the brain
that sticks out.
And then there's this sort of
indentation where it dives
deep into a sulcus.
Comes back up, it's the next
gyrus, dives deep into the
next sulcus.
A huge sulcus is called
a fissure.
Here's a Sylvian fissure that
separates the temporal and
frontal cortices.
And one of the reasons that
people have speculated about
why do we have a thing
like that?
Why do we have these waves of
a gyrus going up and then
plunging into the depths, then
coming back up like this again
and plunging from sulcus
to sulcus?
And nobody really knows.
But there's kind of
a speculation
that's fun and plausible.
One thing we know is that bigger
cortices are good, not
so much one person to another,
but across species.
Your smarts are in
your cortices--
language, higher-level
thought, and so on.
So on the whole, a species that
has bigger cortices has a
lot of opportunities for
thought and social
development and so on.
So you could imagine having
babies with heads this big.
They'd be really smart, maybe.
But what would be the problem?
What would be the big problem?
Think about it not from your
perspective, perhaps, if most
of you are sort of teenagers or
young 20s or something like
that, most of you.
So you don't remember your birth
experience directly.
But who remembers your birth
experience pretty well?
Your parents?
OK.
All right.
It's your mother, especially.
Giving birth is a
pretty painful,
specific, challenging process.
So if a head this big came
out, it would be
incommensurate with the
birth canal that
the mother can afford.
It's already pretty challenging
with your head as
big as it is when
it comes out.
That's the challenge of birth.
It's not getting the
arms and legs out.
Its the head that's too big.
So now we have a problem that
the mother's birth canal is
only so big.
We want as much brain and
smartness in our species and
in ourselves as possible.
So how are we going to get a
lot of neocortex in there?
We're going to fold it.
A lot of neocortex in there,
but a smaller volume to get
out through the birth canal.
And that's thought to be why the
brain has this elaborate
plunging from sulcus to sulcus,
and this sort of
convolved physical structure.
And if we think about the brain,
we can think about
things that go into our brains,
about the outer world.
So when you see, vision enters
through this area, or when you
hear, it enters here.
When you touch or when you move
your body, these are the
motor cortical neurons.
So it's either sort of major
inputs or major output.
That's in blue.
That's the areas that are
devoted to specific perception
or modalities or sensories.
And then we have areas
in yellow here.
They are the areas
that are sort of
closely tied to one modality.
But already, they're
interpreting what's going on.
And then you have areas in pink
here that are sort of not
tied to any modality and are
devoted to what we might call
abstract thought.
And you can see the prefrontal
cortex, the part of the cortex
that's in front of
the motor cortex.
There's a huge swath
like that.
We'll come back to that.
We think it's terribly important
for thinking,
problem solving, and
many aspects of the
highest human mentation.
Now we're a huge believer in
the end that form follows
function in the brain.
And if we understood the correct
relationship between
form and function,
we'd be very far.
And a neuroanatomist named
[? Broadbent ?]
made the following
heroic effort.
What he did is he sectioned
brains into
lots of thin slices.
And he followed them through
a microscope.
And every time the brain tissue
changed, the neurons
looked different, he would
change the number of the area.
So he started in something
like Area One.
And the neurons look
pretty similar.
And he's moving,
moving, moving.
And then all of a sudden
they start to look
different, the neurons.
And then that becomes something
like Area Three.
Moving, moving, Area Four.
Moving, moving, Area Six.
So every time the neurons looked
different to his eye,
it gets a new number.
The idea being when the neurons
look different, they
have a different job to do.
And that part of the brain
does something different.
And there's lots of debates
about the best way to do this,
or different interpretations.
But something like this holds
true in a striking way.
The cellular organization of the
brain reflects in some way
what that part of the brain is
accomplishing, what part of
your mind it supports.
And then we have simplified
color pictures of this.
And we'll come back to
neuroimaging next time.
But it's turned out to have a
second life in neuroimaging.
Because when scientists across
the world want to compare
their neuroimaging results,
they'll talk about, well, I
got activation in Area 46,
or I got it in Area 21.
It's become a nomenclature for
the organization of the human
brain that allows you to
integrate all kinds of imaging
data about the human species.
And here's a view from the
inside of the brain.
And here's a structure chord,
the corpus callosum, that
we'll come back to in the
next few minutes.
So how much are functions
localized or distributed?
How much is--
you have a specific thing your
mind does, and it's in one
place in the brain versus it's
spread over a range.
And this idea of how much things
are distributed or
localized for mental functions
in the brain has been a source
of huge debate.
And I'll show you a misstep,
and then I'll show you some
things where we think we
have it more correctly.
The misstep is a phrenology.
And the most famous name
in this is from Gall.
Spurzheim is another one.
And in the 19th century--
that's the 1800s--
the phrenology took
hold a lot.
And there's a sort of
a Freudian story.
If you want to call it that,
of Gall, which is that
apparently when he was a
student, he viewed himself as
a very effortful and fastidious
student who took
all the notes you're supposed to
take, and worked very hard
for exams and did everything
you were supposed to do.
But shock of shocks,
some students did
better than he did.
And he looked around
the classroom.
He said, who are these
students doing
better than I am?
Because I'm trying
as hard as I can.
And some students are
doing better.
And he said, hey, one thing I
notice about these students is
they all seem to have
big foreheads.
OK?
[CHUCKLES]
Now, I don't know how accurate
he was scientifically.
But apparently, this was a
emotionally transformative
moment for Gall.
And you'll see in what
way this ended
up guiding his science.
So Gall and Spurzheim were
actually good neuroanatomists.
They describe lots of things
about the brain that were
correct that were kind of
unknown at the time.
For example, the pyramidal
tracts, the tracts that move
from your motor cortex-- say on
your left to control your
right hand, or on your right
to control your left hand--
they describe those very well.
But here's where they
got kind of funny.
They said, OK, we can describe
the physical
organization of the brain.
But now let's say which
part of the brain is
which part of the mind.
And in a way that we now
consider a bit willy-nilly,
they began to assign different
mental processes to different
parts of the brain.
And the way they did it was they
said, I'm going to look
at somebody.
And let's pretend somebody you
know is very combative.
What they began to
figure was this.
Well, maybe the part of the
brain that's involved in being
combative--
the more combative you are,
the more you have of it.
So if I feel your skull above
the part of the brain that I
think goes with being combative,
if you have a big
rise there, if I feel your
head-- and most of our heads
are a little bumpy--
the person who's really
combative is going to have a
lot of bump there.
And the person who's very
meek will have none.
OK, does that make sense?
They have these little
categories as they just
thought about people.
And they developed this idea
that they could find where
cautiousness was, or
precociousness, or
secretiveness.
You'd give it a big
bump there.
Let me show you this picture.
Here's a device you would step
into that would have springs
go down, and then it would go
up, and they would say, where
do you have the high bumps?
And where do you have
the little bumps?
Now all of this is wrong.
Because it's a naive way and not
a scientific way to do it.
Weirdly enough, look at what
they put below the eye--
language.
Now that's a weird
place to put it.
And what they saw was a soldier
who had a wound that
went his eye and
into his brain.
And they said, OK, he had
trouble producing language.
And they said, well, that's
where language is.
Language is not below
your eye.
But they didn't realize that the
wound went up into what's
something called Broca's area.
We'll talk about that
in a couple minutes.
And so they weren't
that wrong.
They just didn't think
through where the end
of the injury was.
All the other ones, we
completely dismiss these days.
But we have to worry about naive
ways in which we link
the life of the mind to the
stuff of the brain.
And they did a control
experiment. "The famous
physiologist, Magendie,
preserved with veneration the
brain of Laplace," who's
a big name in
the history of chemistry.
"Spurzheim had the natural
wish to see the brain."
Spurzheim was the
phrenologist.
"To test the science of
phrenologist, Magendie showed
him instead the brain
of an imbecile.
Spurzheim, who had already
worked up his enthusiasm,
admired the brain of the
imbecile as he would have
admired that of Laplace."
So this was a control assess.
I give you a brain of somebody
who's not a genius in
chemistry, and you
go, oh my gosh.
This chemistry part of the
brain is unbelievable.
And this is the old idea we
talked about, that if you have
an idea you believe in as a
scientist, you will always
find positive evidence for
it everywhere you look.
Back to the brain, and let's
talk about this part, the
lower part of the orbital
frontal cortex.
It sits right above your eyes.
Your eyes would be something
like here.
And we know something about what
that part of the brain
does from the famous case
of Phineas Gage.
He was involved in railroad
construction in Vermont.
And that involved exploding
rocks to level the area so
they could put in
train tracks.
They would drill a
hole, put in some
fuse, put in the powder.
And they would use a tamping
iron to push down the sand and
powder so there would be a big
explosion to flatten the rock.
And at age 25 in 1848, he has
a mind who was described as
well-balanced, energetic,
and persistent.
He was the ideal employee,
resourceful, hardworking.
He was made a foreman,
a leader.
He was the most efficient and
capable in the group.
And on September 13, 1848,
something big happened.
There was a miscommunication.
An iron that was three feet,
seven inches in length--
I'll show you a picture in a
moment, because even if you've
heard this story, until you see
a picture of it, you can't
grasp how big this was compared
to a human being.
There was a miscommunication,
the explosion went off early.
He was directly over it.
The rod flew up, went through
his head, all the
way through his head.
And it had the power to land 30
yards away after exploding
up into the air.
And by March of the next year,
he was back at work.
Not too long a vacation, a
recovery period for that big a
thing going through your head.
But his personality had
fundamentally changed.
So here's his cast of his actual
head and his skull.
Here's where it shot
up through here
and out this hole.
Here's the actual rod
compared to that.
So if you haven't seen this,
you can underestimate the
amazingness of this thing.
And at the time he was famous
not for the reason we now
think of him.
He was just a Ripley's believe
it or not story of that a
human survived at all.
So Antonio Damasio has attempted
to reconstruct by
computer where this rod shot up
through here and out into
30 yards away.
They're that big compared
to him.
And the amazing thing, and
described by a physician who
worked with him at the time,
is "the equilibrium to his
intellectual faculties and
animal propensities seems to
have destroyed.
He is fitful, irreverent,
indulging at times in the
grossest profanity.
Little deference for his
fellows, impatient of
restraint, conflicting
with his desires.
At times pertinaciously
obstinate, capricious and
vacillating, devising many plans
of future operations,
which are no sooner arranged
than they are abandoned in
turn for others appearing
more feasible."
Exactly the opposite of
who he was before.
He was a responsible,
efficient leader.
And now he's a totally
irresponsible person doing all
kinds of things that
make no sense.
"A child in his intellectual
capacity, he has the animal
passions of a strong man."
So he completely
changed who he was.
In this regard, his mind was so
radically changed that his
friends and acquaintances said
that "he was no longer Gage."
So here's a physical insult to
the brain that changes the
character of a person, that
changes what we would think of
as the moral judgments.
Of when is it right to tell the
truth, having plans and
being a responsible, trustworthy
person, completely
changed by this injury.
One interpretation is this part
of the brain is essential
for making moral judgments and
being of good character.
What would be another
interpretation of why he might
have changed, just common sense
besides that this part
of the brain does that?
We want to not be for
phrenologists, OK?
So the first thought is, this
part of the brain supports
what we think of as moral
reasoning and character.
Well, what else could you
imagine might have happened?
Yeah.
AUDIENCE: He had a giant spike
driven though his skull and is
upset about it?
PROFESSOR JOHN GABRIELI: Yeah.
I'll make up something
like that.
But a more psychological and
different interpretation, let
me try this one.
He was getting ready
for the future.
I'll be a foreman today, and
then next week, I'll be
executive vice president, and
then I'll be associate
executive president.
And a rod goes through
his head, and he
goes, wait a minute.
Life is short.
It could end at any moment.
Why not just do what I want
to do all the time?
Because the next rod could
come who knows when.
And I had all these plans, and
I was promising people things
next week that I delivered on.
But that's a sucker's life,
because your life
can end like that.
So forget all the stuff about--
just enjoy the moment.
That's a possible thing, OK?
You see movies like that, where
people are told, you
have so long to live,
and they change.
What would you want to convince
yourself that it
wasn't something like that,
which is not an unreasonable
interpretation?
What you would want to see, at a
minimum, is that if you have
brain injuries other places in
the brain, you don't see that.
And if you have other people
with brain injuries in the
same part of the brain, you
see that consistently.
At a minimum, you want
to say it's not
just a big brain injury.
But it's consistently a brain
injury in this part of the
brain that leads to this
kind of behavior.
And for at least this example,
that's true.
Other patients with similar
injuries behaved similarly.
People with very big injuries
elsewhere in the brain don't
behave similarly.
So there's a lot of reason in
the end for us to believe that
this part of the brain is
essential for something that
we consider almost
metaphysical.
Character has this incredibly
physical dependence.
And relatively recently, just
a few years ago, they
discovered a picture of
Phineas Gage himself.
Here's the rod.
Here's the injury to his eye,
his eye is damaged.
So one more example, and then
we'll switch this refrain.
Paul Broca.
And Broca's area in the brain,
here's Paul Broca.
Here's a brain of a patient
named Mr. Tan.
And let me say a word
about the story.
So in France, a number of people
observing patients with
injuries had talked about that
the left side of the brain is
important for speech.
Until then there had not been
much ideas that the left and
right were fundamentally
different.
So there's always sort of a
background before the discovery.
And there's a talk in 1861 which
describes a man who lost
his speech but understood
everything said to him.
He couldn't produce speech.
He could understand speech.
His intelligence is
still unimpaired.
His speech is gone.
And then Broca heard that talk,
and he went back, and
five days later a patient named
LeBorgne, who had lost
his speech-- he could only say
two things, "tan," and he
could swear like crazy.
And our current thought about
that is swearing that's
emotional and intuitive, not the
one where you think, OK,
I'm going to swear now
to scare somebody.
But the one-- you stub your
toe in the middle of the
night, and you really
let out a curse--
we think that's guided
like an animal cry
by the basal ganglia.
Those heartfelt, really
emotional cursing is not
really language.
It's actually the same cry an
animal makes on injury.
And it uses some of the
same neurocircuitry.
But for higher level cortical
stuff, the only word he could
say was "tan." He
died in 1871.
They looked at his brain, and
they found this change in the
left frontal cortex.
And we now call that Broca's
aphasia, the inability to
speak despite the
presence of--
your mouth can move, and
you can understand
language pretty well.
We'll come back to that.
So we talk about Broca's area,
and then Wernicke--
the Broca's area's important
for production.
And here's the kind of damage.
And we'll come back to Broca's
aphasia later in the course.
So this was a big hint that
there's something different
between the right and the
left hemispheres.
Now in what percentage of people
is language, especially
speech production, predominantly
in the left?
And our best answer for that
comes from a thing
called the Wada Test.
So this is a test given to
patients who are undergoing
neurosurgery for something
like epilepsy,
sometimes for tumors.
And they want to know for you
personally with great
certainty, which hemisphere is
the eloquent or speaking
hemisphere?
Because they want to remove more
tissue if they're away
from your language areas, and
less tissue if they're near
your language areas.
Maybe they won't even do a
certain surgery if they're too
much in the middle of
your language areas.
Because in many cases, it's so
frustrating for people to lose
their ability to speak their
thoughts, that they'd rather
have the seizures, for
epilepsy, than
be unable to speak.
So physicians and neurosurgeons
are very worried
about that.
So what they give you is, they
give you a test where they put
in a drug called
sodium amytal.
And they inject it into your
femoral or carotid artery.
It feeds up.
And the way that the
vasculatures between the two
hemispheres-- it mostly shuts
down the operation of one
atmosphere.
If you're injected in this
femoral artery, it'll mostly
shut down your left.
In this one, it will mostly
shut down your right.
And while the patient has one
hemisphere turned off, and
they know this because for
example, let's say they shut
down this hemisphere
with the injection.
You're waving your arm.
It falls down because your motor
system can no longer
control your arm.
You're blind in this field.
We'll talk about that.
Many of the mental processes
done by this half of the brain
are shut down.
And then they'll test you like
crazy to see if you can talk.
They'll say, what are the
days of the week?
What's your name?
Name these pictures.
OK?
Until the drug wears off.
And then you come back two days
later or a day later, and
they'll inject the other side.
And they'll know with near
certainty in you which is the
side of your brain that
does the speaking.
And best estimates are that
something like 90% to 99% of
people speak from their left.
Even left-handers mostly speak
from the left hemisphere.
Because these are patients with
epilepsy, we're not quite
sure how they generalize
to everybody.
We wouldn't do this with
typical people.
Because these kinds of tests are
invasive and a bit risky.
But our best estimates are that
if you're right-handed,
it's almost certain you speak
from your left hemisphere.
And if you're left-handed,
about 80% of left-handed
people also speak from
the left hemisphere.
So it doesn't go by handedness,
which makes
handedness a bit more
of a mystery.
So now switch from grey matter
discussions to white matter.
In the middle of your
brain is something
called the corpus callosum.
Here it's viewed from the
middle, if we cut
the brain this way.
200 million myelinated fibers
that connect the similar areas
from the left and the right.
This is what hooks up the left
and right hemisphere
from spot to spot.
Here it is connecting--
and this is from the side view--
so it's a huge white
matter area.
Corpus callosum.
And people noticed it because
it was so striking.
But they couldn't figure
out what it does.
And it kind of started to
figure a little bit in
philosophical debates.
Would a divided brain--
if you cut the
brain down the middle--
would it read to separate
stores of mood,
predisposition, knowledge,
and memory?
That is, if your two halves of
your brain were divided from
one other, would you be
sort of two people?
Now, we're not going
to do that to you.
But the fascinating thing is,
are you two people to start
with, who talk to one
another sometimes
across your corpus callosum?
And William McDougall said,
well, the unity of
consciousness does not
depend on the unity
of the nervous system.
And he volunteered for
commissurotomy to cut the
corpus callosum.
Erickson noted in 1940 that
epileptic seizures would
become generalized convulsions
often in animal models--
if the seizure began here,
it would spread to the
corresponding part of the
opposite side of the brain,
and become a much
worse seizure.
So they got the idea that if
they cut the corpus callosum
in patients with severe epilepsy
who did not respond
to medications that maybe
that would make the
seizures less severe.
Does that make sense?
Because you wouldn't transmit
the seizure from the left to
the right or the
right to left.
But people were sort of
almost making jokes
about the corpus callosum.
Because they couldn't figure
out what it does.
They said, "The corpus callosum
is hardly connected
with the psychological
functions at all.
It is for transmitting seizure
activity from one hemisphere
to the other." That's kind
of a neurology joke.
Or Karl Lashley at Harvard,
"to keep hemispheres from
collapsing into one another."
You do have to have structure
to keep things from
collapsing.
So now I need to tell you a
word for the next couple
minutes for this to make sense,
about how your visual
system is organized.
So here's the world out there.
And if you're looking straight
ahead, everything to the left
people call the left visual
field, everything to the right
people call the right
visual field.
And we'll look at this more
next week a little bit.
But weirdly, your eyes are
not set up in that way.
You could think this eye looks
at this half, and this eye
looks at that half.
The way it's set up, each eye
looks at both fields.
Each eye looks at both fields.
And then the neurons that leave
the eye get organized
here in the optic chiasm.
So by the time they move out
towards the brain, everything
in the opposite half of the
world is reflected.
So everything that's in the
right visual field starts in
your brain in the
left hemisphere.
Everything that's in the left
visual field starts in your
brain in the right hemisphere.
Does that make sense?
So the first part of your smart
neocortex that knows
what's out there as you're
looking at a face, a word, a
scene, anything--
the right occipital cortex
notices what's on the left,
and the left occipital cortex
notices on the right.
Things are so seamlessly
integrated in the brain that
you don't ever have
that feeling.
You almost never have like,
we're getting bad signals on
the left here.
If you didn't have a course like
this, you wouldn't know
that exists.
And you could wonder, why on
Earth is it like that?
Is it just to torture students
and confuse them about fields,
eyes, and brains?
And people debate about
some evolutionary
history behind this.
But it's a great big mystery--
why we don't organize things
much more simply and just go
all the way this way.
Quite the opposite.
We have in the left posterior
areas, that's where we see the
right half of the world.
And then things get
integrated.
Is that OK?
Keep in mind also that our
left hemisphere moves our
right hand, and our
right hemisphere
moves our left hand.
So at least that's
the same story--
opposite hemisphere seeing the
opposite field, controlling
the opposite hand.
So imagine these kinds of
patients who had the surgery
that divided the corpus
callosum or
treatment of epilepsy.
Let me tell you a
couple things.
Clinically, it was pretty
rarely done.
There weren't that
many of them.
It's pretty rarely done
nowadays, first.
Second, the first thing that
people noticed was, it didn't
have much an effect
on the patients.
It's a fascinating story.
Nobody noticed anything
for decades.
Because they didn't have the
right questions to ask.
So these patients are not like
astounding patients, I can't
believe when I see them.
They seem pretty much like
the same as they were.
I'll show you a video in a
couple minutes of two of them.
They're not looking unusual
in most ways.
But when people figured out what
to ask of them, they saw
remarkable things.
They saw two minds
in one head.
And here's how they saw that.
If they showed them a picture,
let's say of a spoon and a
picture of a cup simultaneously
in the two
fields, they would be
up briefly and go.
But it's easy for you to say, I
saw a spoon and I saw a cup.
They would say, what
did you see?
And the person would
say, a cup.
And that would be it.
What did you see?
A cup.
Because the information in the
right visual field goes into
the left hemisphere.
That's the speaking
hemisphere.
So left hemisphere says,
I saw a cup.
The right hemisphere saw
this perfectly well.
It's typically not the
speaking hemisphere.
So that information is locked
in the right hemisphere, and
it doesn't have access to the
speaking part of the brain in
the left hemisphere.
So each hemisphere had its own
experience, and only the left
hemisphere could speak.
You would integrate this
information instantly via the
corpus callosum.
But each hemisphere only
knew what it saw.
And so here's another example,
which is not only that each
hemisphere only knows
what it knows.
But it's completely
ignorant that the
other one knows anything.
It's as if the two of you were
sitting next to each other and
don't know each other,
are not passing notes
or tweeting or whatever.
It's as if like, do you know
exactly what the person next
to you is thinking?
No, not necessarily.
So that's exactly what it is
like, like you're in one
person in their brain,
in their skull.
So they would show them a square
in the left visual
field and a triangle in the
right visual field.
You would say, I saw a square,
I saw a triangle.
What do you want?
Here's what happens.
If they're asked to say,
say what did you see?
And then behind a board,
draw what you saw.
The board is there so it's
not confusing them.
So here's what they say.
What did you see?
I saw a triangle.
Because it's in the right field,
it goes into their
visual area in the
left hemisphere.
That's the speaking
hemisphere.
But if they're drawing
with their left hand,
what do they draw?
The square.
Because the right hemisphere saw
a square, so the left hand
is drawing, it draws
the square.
So simultaneously they will say,
a triangle, and the hand
behind the board will
draw a square.
And the patient is not bothered
in the least.
Because each hemisphere only
knows what it knows.
The reason they have the board
there is if they didn't have
the board there, then the left
hemisphere would see you
drawing a square.
And you go like, why am
I drawing a square?
I saw a triangle.
And the person would
be weirded out.
Does that make sense?
But here's the thing.
The amazing thing is both of
them have a lot of smarts by
themselves.
And they're completely
unaware of what the
other hemisphere knows.
Again, the idea is in you,
the hemispheres are
talking all the time.
But at lots of moments,
different parts of your brain
might be knowing different
things.
And we have a lot of
belief for that.
But this is the most striking
demonstration.
So here's a patient who was
asked to say what he saw and
pick it up.
He had one instruction.
Read what you see, and pick
it up with your left hand.
So he sees the word ring.
In the speaking hemisphere,
he says ring.
His left hemisphere sees the
word key, has enough language
to read that.
And it picks up the key
behind the board.
And it never says, I saw two
things or anything like that
in most cases.
So let me stop here.
And can we do the first video?
So you're going to see an
example of a patient named
Vicky who's going to be tested
by Mike Gazzaniga.
You're going to see two videos
with Mike Gazzaniga when he
was younger and when
he was older.
He did a lot of the work with
these split brain patients.
Plus, Alan Alda from MASH will
visit Mike Gazzaniga in the
second one.
So one of the really interesting
things is these
split brain patients have given
us a chance to ask, you
and I, what are some different
ways in which the right
hemisphere and left hemisphere
are your own minds?
And what are the things they
seem to care about, and that
are useful?
So here's one example
from Jerre Levy.
It's a very clever experiment.
She would show in the left
or right visual field
something like this.
And then say, in free view,
which of these two things is
more similar?
And on purpose it's ambiguous.
On purpose you could say, well,
this is more similar
because it has a similar
shape or appearance.
This is more similar because I
use a spoon and a fork to eat
a piece of cake.
And if this was seen by the left
hemisphere, people would
pick by function.
If this was seen by the right
hemisphere, the patients would
pick by appearance.
So the ideas is that the left--
and this is the power
of having two hemispheres in
parallel figuring out what's
going on-- one is figuring out
what's the information I need
about shape and things like
that in the world?
And what's the information
I need about function?
And because you have two
semi-independent brains in
you, you're constantly figuring
out form and function
and then using whatever you
need to use to solve the
problem in front of you.
Does that make sense?
So here's another nice one.
Here's scissors projected
into left visual field.
The right hemisphere,
that would pick the
spoon and the fork.
Because the crossing shape
is resembling that.
In the right visual field, left
hemisphere, people would
pick the needle and thread.
Because that functionally
goes with scissors.
So your mind is seeing the same
thing, but in one case
it's tuned, in the left
hemisphere, to functions, and
the right hemisphere
to appearance.
So these are just notes for you
going over what I said.
So they talked about, would
you have two different
consciousnesses in you?
It's hard really to tell.
They did one experiment with
Vicky, where they would
present a nude picture in
the left visual field
unexpectedly--
and this was a long time ago,
it was a shocking thing.
And the patient would
blush and giggle.
When asked to explain why you
were blushing and giggling,
all she could say is, oh doctor,
you have some machine.
She knows something funny
happened and inappropriate.
She can't tell you just in the
language in the hemisphere
that saw it.
And so she gives this other
kind of description.
Another kind of a favorite
one is the dresses one.
There was one patient who went
back to work in his father's
grocery store.
And this could be frustrating,
early on after his treatment.
He would stock things onto a
shelf with one hand and remove
it with the other.
You could imagine that would
be a slow work day.
These kinds of weird behaviors
pretty much
clear up within weeks.
After that, you have to test
to see the difference.
Another one, they presented
the instructions -- walk
across the room to the left
visual field, right
hemisphere.
Person gets up, walks
across the room.
That person's asked, why did
you walk across the room?
Person doesn't know why.
Because their speaking
hemisphere didn't see it.
And they'll just say something
like, I was thirsty.
So interestingly, they
fill in motivations.
They don't say, I don't know
why, or I have a split brain.
What do you expect?
I mean they're being tested
for that, right?
But they seem like they want
to fill in some other
explanation.
And I'll show you another
example for that.
And social psychologists
have said--
because they like this--
they said, this is an example
that people are desperate
rationalizers for ourselves.
We'll come back to this
in social psychology.
You could think about whether
it's true for yourself or not.
That when things are
contradictory, we don't say,
oh, things are contradictory.
We say, well, here's why, as we
explain our own behavior,
that we have to rationalize
our own behavior.
So here's the example.
Here's the picture.
So here's a split
brain patient.
And he's shown pairs of pictures
in visual fields.
And he's supposed to pick two
of them in free vision, then
relate to what he sees.
Here's the picture
that he sees.
Boom, this goes up
and goes away.
Now both hands go and pick
something related to what the
person just saw.
OK So this is shown briefly.
It disappears.
This hand--
let me do this right--
the chicken went to this
part of the brain that
controls this hand.
So the claw goes
to the rooster.
This hemisphere saw a snowy
scene, controls this hand and
it goes for the shovel.
So now they're going to make
the patient confront the
weirdness of what he just did.
His hand went out.
Each hemisphere points
to what it saw.
And again, his answer could
be, I'm in an experiment.
You're constantly tricking me.
I know that.
Basically they know that,
they're in an experiment.
But his answer is,
I saw a claw--
that's the speaking
hemisphere.
I picked the chicken.
OK, that's fine, left hemisphere
is speaking.
And then you have
to clean out the
chicken shed with a shovel.
OK You understand?
He's creating a story to make
his behavior seem coherent.
Rather than just saying, I'm
an experimental subject and
that's why you're testing me.
Here's the last thing I want to
show you for two minutes.
And then I'm going to show you
a film that touches on this.
Psychologists are interested in
understanding also in what
way we see the forests
and the trees.
You see the bumper stickers,
think globally, act locally.
Let's talk about global and
local, or parts and wholes.
So the whole here is H. And the
locals are S. Does that
makes sense?
It's a way to operationalize an
experiment looking at the
forest versus the
trees of S's.
Here the whole is the C, and
the local elements are O's.
And there's a painter who
did beautiful pictures.
You'll see another example.
But he made whole faces out
of vegetable parts.
OK, do you see that?
Every part here of this face,
if you look at it piece by
piece, is a different
vegetable or fruit.
So it's a sort of play on this
thing, and you'll see the
movie that way.
He made the whole face
of the parts of this.
But here's what split
brain patients do.
And I'll show you something
else in a moment.
They're asked shortly after
surgery to copy this.
It's right in front of
them all the time.
It's right in front of
them all the time.
Just copy what's right
in front of you.
If they do it with their left
hand, right hemisphere, you
see that you get the forest
but not the trees.
Here's the trees, and
then they don't
look that good, honestly.
But still, there's some
Y-ish thing there.
Copy this.
It's right in front of you.
If it's the left hand, you get
the forest but not the parts.
If it's the right hand,
you get the
parts but not the forest.
Does that make sense?
It's as if each hemisphere is
one hemisphere-- the left
hemisphere is seeing the
parts, and the right
hemisphere is seeing
the whole.
So that's awesome.
Because you don't have to
be global or local.
Your mind is simultaneously
figuring out the local parts
and the global parts.
And then you can use whatever
is the useful information.
Your mind, because you have
multiple brains in you, is
sort of figuring out what
it needs to do.
Last thing I'll show you, and
then we'll do one more video.
Here are patients who have
injuries after stroke.
It's the same idea, though.
So here's what they
have to copy.
It's right in front of them.
Just copy it exactly.
That's all they have to do.
If the patient has damage on the
right, he loses his sense
of wholeness.
You see there's lots of Z's,
that's the parts perceived by
the intact left hemisphere.
But the right hemisphere
is not giving very much
information about the whole.
Here's another patient with
left hemisphere damage.
That person fails to appreciate
the parts,
but gets the whole.
Here's the same thing
down here.
A patient with right hemisphere
damage appreciates
the parts in the intact left
hemisphere, but doesn't
appreciate the whole in the
injured right hemisphere.
Conversely, here's the injured
left hemisphere.
That patient copies the whole.
The right hemisphere gets
it, left hemisphere
is missing the parts.
The amazing thing?
It's right in front of them.
They're copying it.
But if your brain is injured, it
no longer appreciates that
the whole exists or that
a part exists.
It's as if it wasn't there.
So that's how much our mind
is what our brain
does in this regard.
And so if we do the last video
you'll see that again.
Any questions on what you saw?
So I would say neurons
are unbelievably--
we can't even begin to
figure out your brain
at the neuron level.
We're so far from that.
The big message from this last
part besides hemispheric
specialization is that
your brain--
and we'll show you this
over and over
again in this course--
is a society of semi-independent
brains doing
their own thing, sharing
information as needed.
And the more we study the brain,
the more we understand
how many parts of you there are
that are semi-independent
and autonomous.
Thanks.
