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PROFESSOR: Good afternoon.
In the last lecture we talked about the remarkable human
brain, and how it empowers our thoughts, or feelings, or
desires, or actions in the world, and how we began to
understand this remarkable complexity, or at least grasp
something of the complexity.
How we understand the potential for things like
moral character, and judgments.
The case of Phineas Gage, to produce language, to speak our
feelings and thoughts that's blocked in a patient like
Broca's patient, with Broca's aphasia.
We talked about the fact that split brain patients show us
not only to the left and right hemispheres of the human brain
mediate separate mental abilities, but that they also
seem to have almost independent forms of
consciousness, or they don't have to be
aware of one another.
And so my focus today is to say we would learn from very
unusual clinical cases.
And I'm going to focus today on tools we have to study the
typical human brain.
And what is it that we can do to understand how your brain--
without having a
hemispherectomy or a big stroke--
how does it operate, and what are the principles of human
brain function they gave rise to the human mind?
So what are the ways we can learn about the human brain?
And one thing we can't do is when animal researchers can
do, we can't literally go inside the brain except in
very rare clinical situations.
I'll talk about them, but it's a rare source of evidence.
So there's a million ways in which are trying to understand
which part of the brain is which part of the mind, and we
talked about the fact that phronology was a big misstep
in assigning the functions of mental life to different parts
of the brain.
And so we hope we can do a bit better than that.
And I'm going to review with you today some of the core
methods, and there's a number of them
studying the human brain.
The reason there's a number is none of them
are the magic answer.
All of them are limited in their own ways, and we sort of
need all of them to begin to grasp how your
brain makes your mind.
There's three huge ways in which we now have the human
brain organized.
Lesions, injuries to the brain, stimulation when you're
allowed to stimulate the brain--
rarer, but we'll talk about that.
And the most common, the one you see all the time in books
and magazines, recording, functional MRI, EEG, methods
where we record brain activity, and try to
understand how that relates to the life of the human mind.
And so we're going to go through these things a little
bit and show you how they're applied in some ways that I
hope that you'll find interesting.
We'll come back to many of these things as we go through
the semester, and as we talk about aging, or child
development, or personality, or other
topics, social cognition.
We'll use these tools to understand the brain bases of
those kinds of aspects of our mental lives.
So what's a big injury you can have?
You can have a stroke, where tissue in the brain no longer
receives its vascular supply that it depends on so greatly.
And a lot of different things like hypoxia, lack of oxygen,
the brain is very sensitive to oxygen.
Tumors can grow, you could have degenerative disorders
like Alzheimer's, Huntington's, Parkinson's, and
others, epilepsy.
So there's lots of different ways in which you can end up
with brain injury, and ultimately neuronal death.
What's the strength of this form of evidence?
Well first of all, it's causal.
We've talked about the difference between causal and
correlational sources of evidence, causal ones be more
powerful for scientific explanation.
A certain part of the brain is injured in you no longer can
speak, you change your character, you no longer can
make memories.
We're pretty sure that part of the brain in some way is
required, or causal, for that part of your
mental life to operate.
The deficits you see following brain injuries can be amazing,
we talked about Phineas Gage changing his character, unable
to produce language, unable to make new memories.
We'll talk a little bit about patients with Prosopagnosia,
it's a good big word to go home on spring break and if
your parents ask what have you learned about, you say
Prosopagnosia.
That just means a deficit in recognizing faces.
Patients with Prosopagnosia will be unable to recognize
their own spouse by their face.
They'll recognize it by the voice, by the physical
movements, but not by their face.
We learn amazing things about the brain that until it
happens we didn't know that could happen, what people like
to call counterintuitive.
So we'll talk later in the course in a couple times about
blindsight, patients who say, I see nothing, but their
behavior shows some part of their brain sees something.
We'll talk about category specific deficits where
patients all of the sudden can no longer name living things,
but they can name nonliving things.
So you wouldn't have thought of that if
you didn't see that.
And we get separations in the brain
between different things.
We talked about the difference between the left hemisphere
being important for local features,
the right for global.
The left thinking in terms of functional things in the
world, the right in terms of appearances.
We talked about that already.
We'll talk about other things, the hippocampus is important
for knowing that, knowing a piece of information but the
Basal Ganglia is important for learning how to do things,
mental skills and physical skills.
We'll come back to all of those, it gives us way to
organize things.
Much of our most solid understanding of the human
brain still comes from the history of
neurology and lesions.
But what are its limitations?
First, brain injuries don't follow anatomical boundaries,
they sort of crossover things depending on the injury.
So they're not going to selectively damage one part of
the brain and not touch an adjacent one they could be
doing something different.
People can be variable in their response.
Nearby systems, if you have two things in the brain that
are next door to one another, do quite different things.
Injuries are likely to injure them both, and you will have a
wrong conclusion about the architecture
of the human brain.
When we test a patient and ask them to do things after a
brain injury, we don't really test the part of the brain
that's not there.
We really test a part of the brain that is there, people do
the best they can.
So there's secondary degeneration to an injury,
there's recovery from injury, there's
compensation from an injury.
When you test a patient with a brain injury, you're testing
what the rest of the brain can do in the absence of one of
its companions.
And finally can offer limited views of
normal brain function.
Let me pick one and we'll come back in the course.
We're very interested in variation in people--
individuality--
what's the neurology of individuality?
That's very hard to study in lesion cases, because we don't
see enough of a lesion.
we don't have enough Phineas Gages to ask would that injury
look different if you grew up in one culture or another, if
you were outgoing versus shy.
Those kinds of things are very hard to
answer patient by patient.
But we can test large groups of people with imaging and ask
what's the influence of culture on your brain
organization?
What's the influence of personality on how your
brain's organized?
And you'll see later on in the semester evidence about those
sorts of things.
So let's go back to Paul Broca, the neurologist who
they gave a name to Broca's area, because he sought a
patient like this, like [INAUDIBLE].
That this patient had a big injury in this area could no
longer speak.
And every course you ever take about the brain almost will
include a discussion about Broca's area.
So I'm going to warp your world in a very narrow way,
but maybe a shocking way, and tell you we don't even know
how to think about Broca's area once we get more
scientific than that.
So because this is MIT so we're willing to
tell the truth, OK.
So some years later Nina Dronkers said the following
thing, she studied a large group of patients who had
Broca's aphasia by behavior.
That is they had trouble speaking, but the
comprehension was pretty good.
And then she made maps of their injuries and she
overlaid those maps.
And she said who has Broca's aphasia, and if you have
Broca's aphasia, what's the one part of the brain that
every patient with Broca's aphasia has damage to.
Because these patients--
what you see on these maps is, some patients have damage
here, or here, or here.
But you line them all up and you say, what's the one spot
that you have to have injured to have Broca's aphasia?
And it's not this area that you saw in the picture, it's
this area, in yellow, an area called the Precentral Gyrus of
the Insula.
The Insula is a fascinating, mysterious little structure--
you have one on the left, and one on the right--
that runs along from the temporal lobe, up to the
frontal cortex.
Just a couple years ago there was a paper reporting that
patients who had stroke in posterior insula instantly
gave up smoking, and never wanted to smoke again.
There's huge research efforts to help people quit smoking,
just because it's such a difficult health problem.
Nobody is doing insula lesions to help people
stop smoking, OK.
But it just stopped the smoking, and their desire to
smoke, just like that.
This is now more towards the front of the brain, this is
not what anybody in a book or a course will tell you is
Broca's area, that's out here.
But it turns out this is the hot spot, and you could say,
well what about the original patient?
So kind of creatively Nina Dronkers went back and they
did an MRI of the brain of the deceased original Broca's
aphasic patient.
They still had his brain, they put it in a scanner and they
ran a structural MRI.
And what they found was sure enough he had damage way
inside the exterior limit of this damage, in as well as in
white matter that connects to it.
So even now imaging evidence lets us rediscover what is the
true basis of your ability to speak, or its
vulnerability to injury.
And it turns out not to be exactly what
Broca thought it was.
He saw big lesion and he said, this is the part of matters.
It turns out, as far as we understand, it's a slightly
different part that he thought was just at the
edge and not important.
So we can get better even going back to 150 years of
imaging a brain, we don't have many of those brains around.
Stimulation, so you like to go in the brain is stimulate.
People who do animal work will go in and stimulate a neuron
and see what happens.
It's rare, you only get into the patient's brain when they
have a neurosurgical procedure and they're considering a
resection, or removal of tissue.
You can also do recordings by putting grids on
top of those brains.
And Penfield did famous studies for patients with
epilepsy, where he would stimulate and map things that
contributed a lot to our thinking about the brain.
But that's a rare source of evidence, as you can imagine.
Another one that's much more common-- there's one of these
devices down the street in building 46--
is Transcranial Magnetic Stimulation, or TMS.
So this is one in which people are allowed ethically, and
responsibly to give you a virtual lesion for a few
moments, if you volunteer to do so.
So they put some sort of wire, there's different
configurations, over your head in a targeted location.
It generates a magnetic field that passes through the skull
and induces a current.
And what happens is the current drives lots
of neurons to fire.
Turns out, this is kind of interesting, if all your
neurons are firing at the same moment, in one sense it's as
if none of them were, because there's no information.
There's a lot of different ways you could think about
that, but for example if on your 300 channel television
you had all the channels on simultaneously on the same
screen, it wouldn't be very easy to watch,
something like that.
All the neurons firing pretty much wipes out the
function of that area.
People do feel a little bit of a physical sensation, if
you're prone to epilepsy it's not a good idea to try this,
so it does require some careful supervision
experimentally.
But you can do this with healthy people, and if for
example you do it on this side of the motor cortex, people
twitch or say they felt somebody touch them.
Nobody touched them, but the part of the brain that codes
for touch just got turned on.
If you put it on the occipital cortex, visual cortex, and you
turn on at a certain moment, you could put a word up and
word down, and the person will say they saw nothing.
You'll make them functionally, cortically
blind for a few moments.
People have done experiments like this to suppress
activity, to enhance activity, sometimes it makes people even
faster, like naming pictures.
And it's also been used there's still experimental
studies of whether it can be helpful for treatments of
neuropsychiatric disorders.
It's not invasive, in a sense of you're not going literally
inside, you have a causal thing because turning the
brain on or off.
It's not very well targeted, it can't go into subcortical
areas, but it's a very interesting tool.
Let's talk about recording brain structure for a moment.
It's really important to separate this concept between
recording structure, which is a picture of anatomy, or
function, which is a picture of physiology.
So there's old ones angiography, and things like
that, I'll show you two.
Computed Tomography, and MR and a really cool measure
called Diffusion Tensor Imaging.
And then, dysfunctional measures, and we'll talk about
those, EEG, PET, fMRI, MEG.
So here's some different images you can
get from the brain.
This is a post-mortem brain, this is a cut brain, here's
the front, here's the back.
If a brain was open in front of you, this is
what you would see.
So here's an MRI, Magnetic Resonance Imaging, and it's
pretty good, and I'll show you some more pictures, in showing
you lots of information.
Not as good as if you were in there, but pretty good.
Here's a CT scan, Computed Tomography.
It's not as good, it's more blurry.
And this thing that looks really sad, it looks like get
your camera to focus, that's actually the quality of the
picture that we see that underlies maybe the most
widely used tool these days for understanding the human
mind and brain, Functional Magnetic Resonance Imaging.
It's a very smudgy picture, but it has some really
interesting properties.
So here's the kind of thing you go into for an MRI, both
structural or functional.
Some of you have almost certainly been participants in
research or experiments, or studies, stick up
your hand if you have.
Oh, a lot of you, OK, so you'll speak up on this, is it
quiet or noisy?
It's super noisy, so you have to have ear plugs in.
And this is why people doing experiments with this
Functional MRI want to do visual studies, because
auditory ones are tricky.
So Tyler, your head TA, likes auditory stuff, it's 10 times
harder to pull off those experiments.
Everybody tries to do visual stuff, so you don't have the
noise problem.
But you get some beautiful pictures, here's Computed
Tomography.
And here's an MRI structural scan from the brain, the
ventricles, here's Basal Ganglia.
With an MRI, beautifully you can see the difference between
white and gray matter.
I'm always impressed that the gray matter is
just this thin ribbon.
Cortex really means bark, it's just like
the bark on our tree.
And when you look at the brain this way, look at how much
white matter there is.
Here's your frontal cortex, look at all that white matter
and then this thin, cortical mantle, or ribbon, or bark.
That's what we think of as the smarts of language, and social
planning, and things like that.
So that's a structural picture.
And then these two pictures are sort of fun.
This is just recorded down the street, we're going to fly
through your brain from one ear to the other.
And you get amazing resolution, it's not the same
thing like being inside the brain.
There's things that you don't see, we know that,
but you see a lot.
Isn't that cool?
Let's examine what you can see now.
Only about 40 years ago, you would have to have a person
die to see this.
This is a patient with Huntington's disease, we'll
come back and talk about that disorder.
Here's a healthy person, top of the brain.
This is the caudate here, part of the Basal Ganglia.
And you could see in a patient who has passed away that part
of the brain is completely withered away in
Huntington's disease.
You would have to wait until person passed away to see
something like that.
Here's a healthy person top of the brain,
again lining the ventricle.
This is the caudate.
And here in a living Huntington's patients you can
see the great withering away.
Some of cortex 2 in later stage of disease, but
especially in the Basal Ganglia.
Here's a healthy older person, about 70 years of age, top of
the brain, bottom of the brain, the ventricle.
Here's on the left and right of the hippocampus, the
structure we'll talk about, without which you can cannot
learn any new fact, or remember any
event in your life.
So powerful for almost every sense of learning.
And look what happens the structure in the same aged
patient with Alzheimer's disease.
It's virtually gone, it's greatly weathered.
You see it's much wider here, because the tissue's greatly
shrunk in the Alzheimer's patient.
So we can see these kinds of changes in living people, for
both research purposes and clinical purposes.
Here's one that's more cheerful, and more reflecting
your experience.
Here are studies of brain changes from age four to 21.
So they follow a large number of people at NIH
from age four to 21.
And what this shows is this color coding is the thickness
of the cortex.
And you might imagine that as you get older, and smarter and
go through grade school, and middle school, and high
school, and MIT college, and as you head towards grad
school, your brain will get thicker, and
thicker with cortex.
It's exactly the opposite.
Ever since you were about five years old, you've been
shedding neurons by the millions, and connections
among them by the trillions.
And you're still going to do that until your
probably about 22 or 23.
Then you peak, and you decline and become faculty members.
But that's really interesting, we'll come back to this, that
what happens as your brain get smart, experienced,
knowledgeable, all the differences between you now,
if you're 17, 18, 19, 20, and when you were four, it all
goes with your cortex getting thinner.
And we'll come back to that and how people think about
that, but let's see if I can get this next movie to run.
There's also an ordering-- and we'll come back this but I
want to show you this movie.
So the more blue you are, the thinner you are, the more
advanced you are in terms of ultimate young adult
development.
Here's visual cortex, vision coming in.
This is Somatomotor Cortex, how you feel, your body, and
how you move yourself.
And what you see is, as you go from age four to 21, the blue
spreads, that spreading is your brain maturing in higher
thought areas.
So we're going to review your life on average right now,
here you go.
And now you're ready to graduate.
It's kind of an amazing story of fantastic brain changes
that move you from what you could do and not do at four,
to what you can do and not do at age 21.
And we couldn't see these things, we couldn't begin to
see these things, until just a few years ago in any
scientific sense.
All these things are like miraculous sources of
information.
So let's pick another thing, and we'll tie
it to school work.
Here's the structure we said, the hippocampus.
So important for the formation of new memories on an everyday
basis, everything that's important and that you learn.
So here's a fun study they took, and as you hear it,
think about its scientific limitation, but it's fun as
students to think about.
They looked at students in medical school in Germany.
They looked at the measure of an anatomic thickness of the
hippocampus before and after they studied like crazy for a
huge exam over some number of periods.
This is the difference between the two, and what they're
showing you is that as you study, your hippocampus got
thicker as you crammed for your test.
So will there be a day where instead of having to give you
tests we could just measure the thickness of your
hippocampus to know how much you studied, and you could
just zoom in and out of a scanner, I don't know.
But one cool thing about it is it's showing you that we can
see structural changes not just on a giant scale from
when you're four to 21, but from some number of months of
experience, we can see a physical change in your brain.
Now that's trivial for animal researchers, they can show
amazing things in seconds, but you see the human brain
physically changing.
So let's take a look at another one, slightly more
controlled, we'll look at two more examples.
London taxi cab drivers.
If you've travelled in various cities, and have gone in
various taxis, you may have had better or worse
experiences whether the taxi driver knows where he or she
is going exactly.
London is famous for having a very high code, taxi drivers
have to take big exams to get their official taxi license,
they create a very demanding thing.
And when they ask this in the hippocampus if you learn lots
of routes, if you know tons of routes in London, what happens
to the hippocampus as it's memorizing all
these special routes?
And what they saw, that taxi drivers had bigger hippocampi,
and the longer they drove, the bigger it was.
So is this a causal or
correlational source of evidence?
It's correlational right?
So let's start with this, they have bigger hippocampi, and
now maybe that's simply because, what?
Maybe somebody who has an awesome hippocampus is ready
to go to be a taxi driver.
Maybe they pass the test, and the one who got lost all the
time, and was driving to the wrong airport and stuff, small
hippocampus, never became a taxi driver.
So the size of the hippocampus is the cause of your success,
not the consequence.
Because the longer you drove, the bigger it got, that kind
of goes with that.
But you could do a causal experiment this way.
They taught people to juggle three balls, they practiced
every day for three months.
Three months juggling every day.
What you see in yellow are parts of the brain-- that's a
statistical map--
parts of the brain that significantly got thicker in
three months of practice.
So they could compare directly before and after, it's a
causal experiment.
And these are areas that are involved in the visual motion,
and it makes sense that areas involved in visual motion
would somehow change.
But the fact that we can see three months of experience
change the structure of your brain, it's kind of remarkable
in they way that we can measure and scientifically
scrutinize.
You might be curious if you did three months of this and
you were a pretty good juggler, you're impressing
your friends at parties, your brain scan is different.
What do you think happened--
they followed these people up-- after the juggling
requirements stopped?
They kind of stop, most of the people, they were too busy.
They would show off here and there, but that was it.
They measured their brain's again about six months later,
and this change was gone.
It came in, and it went out with the activity, it's
activity dependent.
So depending on what you do, you could think about every
activity you do-- mental and physical that you do-- is
constantly slightly changing your brain.
And if you do a lot of it, you're fundamentally changing
it like in these individuals.
But if you stop doing it you go right back to where you
were, because you're going to be doing something else.
And another fun measure that's kind of beautiful and
intriguing is Diffusion Tensor Imaging.
Now every [INAUDIBLE] we talked about so far has been
gray matter of the brain, the neurons and then the
circuits they form.
We're going to turn to white matter, which is the
myelinated axons that are the super conducting
highways of the brain.
And what Diffusion Tensor Imaging does, it shows you
something about the organization of that white
matter, measuring directly the movement of water at very,
very tiny distances.
This is a cross-section of a myelinated nerve fiber.
Those are the fibers that are covered with white matter that
have to go some distance.
And the myelin protects the quality and speed of that
signal through your brain.
And you could see at the level of, if you're a tiny, tiny
drop of water, or smaller than that, this is a pretty big
bump in the road.
So imagine you're a little drop of water moving a little
bit, and you bump up against the myelin, you go oh, can't
go that way, and you go back this way, and
you go with the flow.
You go parallel with a myelin, it's hard to cross it at that
microscopic scale.
But we can measure that movement in areas where it's
highly constrained, and that's a property of the water.
Here cerebral spinal fluid, things can go anywhere.
Here's where there's a lot of white matter, and the water
tends to flow along parallel with the white matter, just
for physical reasons it can't cross it over.
And here for example, is a statistical map comparing this
measure of white matter organization between adults,
who either in their childhood had a diagnosis of dyslexia,
reading was difficult for these individuals.
Or people who typical reading development, where you learned
to read and wasn't particularly difficult.
And you can see that in this area around the Temporal
Parietal Cortex, there's a significant difference.
But we can do one more thing.
These are reading scores this way, this is the measure of
the white matter organization from the
Diffusion Tensor Imaging.
Each of these as an individual person now.
So the open dots are the people who had typical reading
development.
The filled dots are the people who had poor development, and
you can see it's pretty continuous.
Even in the people with the open circles who never had a
problem, the better they read, the more the
organization is here.
So this is not just the difference between good and
bad readers, it's a difference between really good readers,
and medium readers, and poor readers, right, continuous.
So now, cause or effect?
Were those of you who at three, who had awesome myelin,
were you going, reading's a snap.
I love this stuff, where's War and Peace, mom?
Or, were you like the jugglers, and you were reading
a lot, and you were exercising this part of the brain, and
altered its physical structure.
And the answer is we don't know.
How could we know?
If you were scientists and were given a pot of money to
do this, how could you know?
Well--
yeah?
AUDIENCE: Track the entire lives of multiple people.
PROFESSOR: Yeah, do a longitudinal study and start
like, before people read.
And you could see is it different then?
Are we born to be big readers, or by being big readers do we
alter the architecture our brain.
What's the effort, and what's the talent, or what's the
predisposition at birth, and what's the time you put in
creating this part.
We don't know that yet, but we have a place to look at that.
And then you can create these kinds of beautiful pictures,
and I'll say a word about this.
So this is an individual person's white matter
organization.
So we could take this picture of you, or anybody you know
who wants to go in a scanner.
And what's color coded here in blue are fibers that are
running up or down, we can't tell with the fibers which
direction they're going, but we can tell other
orientations.
Up and down, left and right in red, up and down in blue, and
green is front to back.
Pretty cool, huh?
I can tell you that I'll say a word about this.
Should we do that again?
I like it, but I work in this area.
This is fantastic, this is an individual person's white
matter organization.
As information is flowing around in your mind, here's
the paths that it's flowing around in as you just do
anything that's interesting in your feelings
or thoughts or anything.
It's fantastic.
I can tell you that the algorithms that are used to
create these maps, there's some debate
about the better ones.
So the last steps of this are a bit debated, and a bit
depending on how cool you are as a visual engineer.
But there's a lot of things that's right about Diffusion
Tensor Imaging, there's a lot of things that
are right about it.
Function, so most of all we're interested in structure, not
just for itself, but how is it makes your mind do the things
you could do.
And when we think about different functional measures
that are available to neuroscientists or
psychologists, we often think in two dimensions, Spatial
Resolution, and Temporal Resolution.
How precise are we where we are, and what's the time scale
that we're measuring in, milliseconds, are we averaging
over many seconds, many hours.
We know mental operations, roughly speaking, occur at the
millisecond level, or maybe 10 milliseconds.
There's no answer to that, but we know lots of things happen
that fast in the mind.
So if you look at this here you can see that, for example,
if you're in animal work, looking at size, you can get
down to the Synapse or the Dendrite.
We can't touch that in humans, we can't touch
that cellular stuff.
And it's not until we get up to here, which is like big
patches of the brain, that we can state things about people.
That's why it's always going to be fundamental in
neuroscience to link the human work to the animal work,
because we can't get to the neurons or anything like that
in a person almost ever.
That has to come from animal work, where you can do
invasive work.
So we have to look at a pretty big patches
of the human brain.
How about time?
Well, we can get down to milliseconds in time in the
human brain.
Functional things like PET and MRI are here and in the order
of multiple seconds, I'll come back to this.
But you can see all these things have strengths.
Now you don't always want to be down to a single synapse,
it's not clear that we would understand much of the
organization of the brain at the level of the synapse.
There's things happening in the synapse, but a thing like
knowledge, or love, or something like that probably
we can't study at the level of the synapse.
Effectively, yet.
Bigger units are probably more interpretable.
So here's a fun one, EEG's, Electroencephalography.
So they put on your head some sort of a cap with electrodes,
and they measure changes in electrical activity that are
being picked up through the skull.
And you're picking up huge changes in hundreds of
thousands of neurons, but you're able to do it
millisecond by millisecond at the speed of thought.
The same electrical signal for EEG and ERP, that evoke
response potentials, with EEG you just watch it over time.
So you can see these different rhythms that go with a person
in coma, or in deep sleep, asleep, drowsy, relaxed.
You can see these characteristic rhythms that
people can measure.
If you do an experiment, you can time lock these moment by
moment to some stimulus or task you give the person.
So here we're going to time lock these, and then you get a
thing like this that says, here's a response, maybe the
first moment after I see a word, a second moment after I
see a word or something like that.
So you can time lock large electrical
responses in the brain.
And you get some studies like this, and we'll come back to
this, but here's a fun one in language for example.
You read a sentence like, It was his first day at work, OK
that's the baseline condition in purple, not a particularly
exciting sentence.
Although, your first day at work is actually pretty
interesting-- but to read the sentence.
How about this one: He spread the warm bread with socks.
You go, Socks?
I'm shocked, that makes no sense at all.
What happens as you read it, here's in broken blue line,
you go wow, and that's called the N400.
But that's kind of cool, that's 400 milliseconds after
you saw that word you said, I get it's socks but it doesn't
make sense.
So you're violating semantics.
And then they have to do a control experiment.
And a lot of psychology, in a course like this, we can't
devote enough time to this.
But I can tell you high quality research in psychology
is high quality thoughtfulness like in any other field.
You could say, well maybe it's not the word "socks" that's
bothering you, maybe just because it's odd, just like a
weirded out signal, it's a weirded out signal.
So they do this, She put on her high-heeled shoes, but
they put shoes in big print that you didn't expect.
So now you're weirded out, but it makes sense.
So what happens in your mind, you a very
different response here.
So here the meaning is wrong, here the size is wrong.
And see you can read a person's mind in this sense,
millisecond by millisecond as they understand something like
a sentence.
You can do it with babies, which is pretty cute, and
incredibly exciting too.
So we can measure to the milliseconds.
Lots of people can take doing it, it's relatively
inexpensive.
Why don't we just run around and do that?
And we do that at MIT, and lots of places do this too.
Well, Spatial Resolution is really problematic, we don't
know where in the brain the signals are
really coming from.
We know where the electrode is on the head, but that's
picking up a lot of stuff below it, we don't know where
the brain is coming from.
The way I think about it a little bit, imagine you went
to a football game, and you were on the outside of the
stadium, and you heard big cheering on the side that you
knew was MIT.
You might think something good happened to MIT, then you hear
big cheering on the side where CalTech team is sitting, and
there's fans, it'd be the usual Rose Bowl.
You might figure something good happened at CalTech, but
you don't really know exactly what happened, and exactly
where it happened.
So we don't know where the signals are coming from in a
very precise way.
There's another method that's sort of very intriguing too,
and we're just installing it at MIT, and you could be
amongst the first generation of participants, if you so
choose to be.
This is called Magnetoencephalography, active
neurons produce small magnetic fields.
You can use a superconducting quantum device to measure this
tiny, tiny change to the magnetic field, they're
secondary to the neurons firing.
These signals are problematic to measure because they're
estimated to be 100 million times smaller than the earth's
magnetic field.
And all these measures we have in human brain function, all
of them, the signal is terrible compared to the
noise, it's terrible compared to the noise.
And MEG might be the worst, there's a number of places
that installed MEG, and had to take it out because the local
traffic on the road was too big relative to the difference
between the earth's magnetic field in the signal they get.
Signal to noise is terrible in every noninvasive human brain
measure we have.
But you get something beautiful.
Now, any mental thought we have of any interest of any
kind, we pretty much understand to be the property
not of a single part of the brain doing its thing, but a
remarkable concert, different parts of your brain playing or
interacting with one another.
It's a symphony orchestra doing anything interesting in
the human mind, and MEG can show that beautifully.
So here's an individual's structural MRI that's been
inflated, they've sort of blown it out like a balloon so
it's sort of easy to look at.
And what you're going to see now from Dale & Halgren in an
MEG measurement millisecond by millisecond of what your brain
does, roughly speaking, when you read a single word, OK
here we go.
See, back and forth, back and forth, and there's all this
interaction feeding forward from when you see it, feeding
being backward from parts of your brain that say, I think I
know what it is, let's double check.
Back and forth, back and forth.
Let me do it one more time, because I think
it's just so cool.
Anything interesting that your brain does is an incredibly
complicated millisecond by millisecond interaction
between large scale brain networks.
So here we go again, reading a single word, arrives in the
back of the brain, front's thinking about back, front,
back, front, back front.
We read the word.
It's just amazing, and MEG is one of the better measures for
us to see this time based way in which your mind
accomplishes things.
The strengths are it has great temporal resolution,
noninvasive, Spatial Resolution is it maybe better
than EEG, or perhaps better, not as good as a fMRI, we'll
come to that.
And it only can measure neurons in the cortex that are
parallel to the skull, so we can't see lots of things like
support local structures like the hippocampus.
So now we're moving to the measures that you most often
see, but these other ones all help us a lot.
And they are all derived from the following things.
Sadly, for PET or fMRI, the most widely used studies to
understand how your mind works, we can't interrogate
the neurons to compute your mind, we can't, they're off
bounds to us.
The other measures you just saw are based on neurons.
What we have to do is we have to look for gossipy neighbors,
that is the vasculature that surrounds and supports the
neurons that compute the mind.
And we know the neurons require oxygen and glucose,
metabolically to do their work, the cellular life.
And the brain area's active, there's increased blood flow,
and increased energy supplies that come to that.
So it's all the sort of inference by the secondary
consequence of neurons doing their business.
So the brain is about 3 and 1/2 pounds, it's about 2% of
your total body mass.
So it has a tenfold, 20% extra demand of body oxygen, your
brain cries out for oxygen at every moment.
So 2% of your body, but 20% of the oxygen demand.
And it's so sensitive that only 10 minutes of loss of
oxygen can often cause irreversible brain damage,
especially in structures like the hippocampus.
The first discovery that blood changes that are going with
brain changes, blood changes that are the sort of the
echoes, if you will, a secondary consequence, is low
tech character current machines.
This is work from Angelo Mosso in the late 1880's, and he saw
a patient who had a unusual sort of malformation, so he
had almost no skull here.
And he put on it something that measured the pressure
there, and he also measured-- and what's shown here in red
is this pressure as a control thing, that's pretty clever--
pulses of blood in the forearm, so those are in blue.
That's the control, that's not just blood everywhere.
And what he did is, the guy's still sitting there, nothing
happening, and he noticed that when the church bells rang
nearby, boom, this device picked up increased pressure
over this part of the head.
That's pretty cool, it has to be blood, it's not neurons,
OK, it's blood.
But now he has the signature of mental life in your brain,
the blood consequence of a thought, which
is I hear the Church.
They asked the guy, does it have to be something that you
hear, he says, did you make your prayers
today, your Ave Maria?
Again nothing happening peripherally, but boom, as he
gives his answer, a change in blood pressure there.
Or do math problem, boom, a change there.
So all of the sudden, blood changes of a part of the brain
become the witness to that part of the brain supporting
the mental operations to do that task.
And here's a PET study, the first weighted Positron
Emission Tomography, which is basically used to measure
local brain activity by looking at the consequences of
photons disintegrating as they're measured in this sort
of a device.
And here's the way they use this task to discover which
parts to map the neural organization
of the human mind.
So I need somebody who's willing to do a task at their
seat, and it's just going to be reading words, or coming up
with words.
OK, thanks.
Here you go, ready?
Look at that, in our field we call that fixation, you're
just looking, OK, just looking.
Alright, good job.
Ready for something else?
Alright, now just look at these things,
OK, you see the words?
The technical word is reading.
Alright, now imagine we did one more thing with you-- and
actually if you were in a PET scanner
here's what would happen.
If in a PET scanner, you'd be sitting down there like that,
there'd be a physician in their lab coat like this.
There'd be physicist in the basement making up some sort
of a tracer they're going to inject into you
every round of this.
Because that's what they need to sort of track this, and it
comes up an elevator, and people take turns running down
the hall with it, because it has a pretty short half-life.
The shortness of its half-life is what makes you able to do
these multiple measures.
This is a pretty big deal process, and in fact the one
or two PET sessions I ever attended, you would rotate who
would run down the field with the radioactive substance, so
you would share the radioactive substance.
So now you've done that, and you feel like, I'm doing
pretty good.
So now they come and they say, are you
ready for another injection?
They have a catheter running into your arm, and they inject
you again, here comes the radioactive stuff, the oxygen.
And now they ask you to read the words aloud presented one
at a time, why don't you just read aloud one
at a time, go ahead.
AUDIENCE: Rose, cat, apple, pen, plane.
PROFESSOR: OK, and they say thank you very much, and we're
going to do one more injection if that's OK with you, of
radioactive substance.
And now we're going to ask you to do one thing, and this is
harder, as you see each word tell us a verb that describes
what you might do with that object, or what a person might
do, so go ahead, for rose tell us.
AUDIENCE: Smell, pet, eat, write, fly.
PROFESSOR: Perfect.
Yeah, I can tell you that in the experiment they present a
lot of these, and a lot of subjects after while just go
use, use, use, use, hold, hold, hold, hold.
But you did a good job, OK.
This is just looking at something, this is looking at
a word, which is reading.
Now don't forget, we're the only species that ever read,
reading has been around in our culture only for about 700
years on any scale, and reading is an incredible thing
to work correctly.
And you saw the whole brain flicker to get it right.
But now you're going to say the word in the next
condition, so you're not just looking at the word, but
you're also saying it.
And now finally you're not only saying a word and looking
at it, but you are thinking about it to come up with
smell, or pet.
So they say, what we're going to do is we're going to do a
hierarchy of your mind, just looking, reading, reading and
talking, reading and talking and thinking.
And by comparing those different conditions, we'll
subtract them against each other, and pull out the part
of your mind that sees a word, that speaks a word, and that
thinks about a word, and we'll separate
those out in the brain.
So basically the subtraction method.
So when we compare looking at fixation versus looking at
words, we'll see what part of your brain discovers that it's
a word, knows how to read words, looking at words versus
repeating them.
We'll discover the basis of speech, speaking a word versus
coming up with the verb, thinking about stuff, their
meaning, and coming up with an answer.
So again the idea is if you're saying something like pet for
the cat, you're doing all these things.
Or you might just be reading it aloud, and
we'll subtract them.
In both these conditions, here you saw a word and read it,
here you saw a word and came up and produced a verb, you
subtract these two and you end up with a
statistical image like this.
This is not a raw image of blood, all these you ever see
those are statistics of the areas that differed by some
statistical criterion between one condition and another.
They're all statistics, they're not blood, or raw
blood, that underlies it, but what you see is a statistic,
and here's the statistic.
Now in both of these cases, you saw the word.
In this case you simply read it, in this case you read it
in your head and you came up with a verb.
But why don't we see anything back here?
Why don't we see the seeing of the word, even though the
seeing occurred in those conditions?
Why isn't it visible in this brain picture?
Because it's been subtracted out.
So always in these brain imaging experiments, for
reasons I'm about to tell you, we almost always have to do
some kind of subtraction.
And I'll tell you why, but that subtraction is very big.
Because what you subtract out, that's the heart of the
experiment, and your decision about what's a legitimate
subtraction.
And the reason we have to do it is this, look
at these two things.
Here's one condition, and here's the other condition.
Do you see that they look pretty similar?
Again, signal to noise.
Your brain is busy all the time, now we ask you to do
something and see the difference.
And the difference is very tiny by the way we measure it.
It's not tiny mentally, it's not tiny in terms of the
consequences for civilization in the world.
It's tiny because of the weird way we have to measure it.
I can tell you that if I've put on an optimal
checkerboard, the psychophysicists have said,
this turns on your visual cortex.
I'll get about a 3% to 5% change in your brain signal.
If you wave your arm, I can get 3% to 5% signal change in
your cortex here.
If I ask you to do everything in between seeing something
and moving your lips or hand, everything about thought,
emotion, memory, desire, motivation, everything that's
big in our life will get something like that one tenth
of 1% of the signal change.
One tenth of 1% of the signal change.
Yeah, Tyler's like yeah, that means you have to test a lot
of subjects, and work 40 years on your Ph.D.
So we have to do that subtraction, because if we
just take a picture of what's going on in your head, it's so
much that we can't tell what's going on at all.
And if we have you do something that's pretty big,
like seeing like a really provocative picture, we'll
just get one tenth of 1% of the signal change.
So we have to do the subtraction to have a hint.
And then we do one other weird thing, we don't have to but we
often do it.
We want to average people to make some general statement
about humanity, as far as we can do it, based on the 10 MIT
students we test.
So we scrunch everybody's brain into common space,
everybody's brain's a little bit different, like their
bodies are a little bit different.
We scrunch everybody to line them all up so we have a
common physical space.
So by the time you see this picture, it's a statistic on
an average of people in most cases, but you
get an amazing story.
Which up until these pictures--
about the late 1980s, it was unimaginable that you could go
inside a living person's brain, and see what it is that
allows you to hear a word in auditory cortex, to see a word
in visual cortex, to move your mouth to speak, or to think,
what's the verb that goes with that word?
Unimaginable at your--
OK, now I have to do the quick math, but you'll help me out--
what year were you born in?
'82?
'92?
I know, at my age it all blends. '92?
OK, so just a year or two before you were born-- this
was 5 years before you were-- unimaginable that you could
see such a picture.
When I was a graduate student at Harvard, and the people at
Washington St. Louis University--
who did the first of these--
did an incredible service to the field.
Here we saw, oh my gosh, it was like landing on the moon.
Going inside the human brain, and knowing which part of the
brain endows us with human capacities.
Now, we can be appreciative or we can be skeptical
scientists, and we can say this, let's pick this one.
Let's compare seeing a word like "board,"
versus seeing a fixation.
We do that subtraction, and that's seeing a word.
Just by common sense, what's wrong with this comparison?
It's OK it's not terrible.
How can you control it better?
To understand what this part of the brain is really doing?
I heard something?
Well partly it's a meaningful word, versus something that
doesn't mean anything to a plus.
But what else could you say is different between them?
Yeah?
[INAUDIBLE]
GUEST SPEAKER: [INAUDIBLE]
PROFESSOR: In this case, oh my gosh, yes, and I'll come back
to that, but let me not do that one for the moment,
because that's a giant story which I can't fit in today.
Yes your mind can be all over the place.
So that's definitely the case, so that's a good one.
Yeah?
GUEST SPEAKER: You could replace the plus, which is
like really small, with [INAUDIBLE]
PROFESSOR: Yeah, that's perfect, OK that's the way I
was going-- the other one's great too, two great comments.
Yeah you could say like, maybe this is a part of your brain
it goes with five things, or something this
big versus this big.
No you go, that's not so interesting, the part of your
brain that looks at something this big, versus this big.
But that's just as legitimate a conclusion here.
How about this, five different things, versus only this.
There's a lot of different ways in which you could say,
what is the mental operation that I've discovered in the
human brain and mind, it all comes down to the comparison.
So here's what they did to try to do a better job.
They showed you a more complicated thing that doesn't
mean anything.
A bunch of letters that you can't pronounce, a bunch of
letters that you can pronounce, but it's not a real
word, and here's the real world itself.
So if you want to say, what do you think this part of the
mind is doing?
What part the mind does this part of the brain allow to
happen in humans, and only humans on this planet?
And every word you ever read only happens because this part
of the brain does what it does.
What is that part of the brain doing?
Is it just simply responding too complicated
things, five of them?
No, not much, a little bit, but not much.
How about letters, letters are pretty interesting, but there
can't be a word by English, you can't pronounce this.
Not too interested?
A word, a set of letters you've never seen together
before, but you can pronounce by the rules of English.
Boom.
That's what I do, says this part of the brain,
that's what I do.
I say, I see something, and it's possibly a word and I can
say it by the rules of English.
And by the way, if it's a word I've done
before, I do that too.
I'm pretty flexible, I can do new words, I can do words I've
known before.
It matches what you see with language, that's reading.
Only our species can take our visual system, and the
language you learn as a child, and put them together, and
allow our civilization to read.
And this is a part of the brain where those roads meet.
And by the way, we talked about local and global, the
forest and the trees.
And consistent with what we talked about the split brain
patients, looking at global stuff right hemisphere, if
you're looking at local stuff, left hemisphere.
So we like it when the information we have from
split-brain patients, or stroke patients aligns with
healthy people doing a task as they typically do.
Because then we sort of believe there's something
right about that.
So PET, pretty good spatial resolution, I mean, depends
what you mean by good.
My neuroscience colleagues dismiss everything we ever do
as sort of pathetically imprecise.
But 5 to 10 millimeters, not as good as fMRI.
The temporal resolution is very poor we can only take one
picture that lasts about a minute, and averages
everything across that.
You have to inject people with radioactive stuff, and it's
correlational.
But it has one other thing that's really, really
interesting, Positron Emission Tomography.
Because you're injecting a radioactive label, you can
create different kinds of labels that go to different
parts of the brain.
So here's Parkinson's disease, which involves damage the
Substantia nigra, and the Basal Ganglia.
Here's a healthy persons Substantia nigra, and here's a
person with Parkinson's disease, where these cells
have died away.
Typically, at least 80% of these have to die before a
person shows Parkinson's disease symptoms clinically.
Here's an injection of radioactive stuff using PET
that binds to Dopamine receiving neurons.
And you can see that in the living Parkinson's patient,
this tremendous reduction in these
receptors waiting for Dopamine.
In a living patient
specifically Dopamine receptors.
So that's a disease.
Here's why video games are taking over the world.
Oh no, not yet.
We can do one more thing.
We can track the disease from a typical person, to a person
with moderate Parkinson's disease or severe.
Within the disease, we can see differences.
But here's why video games are taking over the world, because
if we take a healthy person, young adults, give them this
kind of Dopamine binding tracer, and have them play a
video game, two things happen.
A, the parts of your brain that are involved in reward,
Dopamine, is the strongest to reward
neurotransmitter that we know.
Things go crazy, and what this graph is showing you is the
better you do, the more rewarded you are.
This is why you will go for the next level, because to get
that dopamine fix, you got to keep going.
And we think these reward mechanisms underlie
everything, in many ways they relate to everything.
Why do you do whatever you do, because at some level, in some
way, you find it rewarding.
And the data is very compelling that way.
The last method I'll talk about is functional MRI, and
it's the one that's most widely visible.
So you sit in a scanner, stimula are presented to you
to perform a task.
We do a lot of stuff in our lab with children, we show
them how the frog would do it.
For those of you who've done a functional MRI experiment,
because there were so many hands that were put up.
Do any of you want to say a word about your experience
doing that?
What was it like, easy, huge fun, recommend,
no, not so much fun.
It will vary a little bit.
We said noisy.
Some people find it claustrophobic.
GUEST SPEAKER: I dont know, I didn't really do anything.
I just had to sit there for a really long time and not move.
PROFESSOR: Oh, so they didn't ask you to do a task, maybe.
GUEST SPEAKER: Well, for a big part of it, I
was watching a movie.
PROFESSOR: So for the student they were watching a movie not
doing anything,
GUEST SPEAKER: [INAUDIBLE]
PROFESSOR: You were doing yes or no clicks.
So that would be typical functional MRI kind of
experiment, some of them are more obnoxious, some are less,
some are funny, some are not as funny.
Any other experiences?
Was it comfortable, not so comfortable, medium.
Anybody else want to share?
No, OK.
OK.
So how does this work?
Functional MRI takes advantage of MRI but it focuses on
hemoglobin, the stuff that carries oxygen in your blood.
And it rests on the fact that after oxygen has been
extracted it's more sensitive to the magnetic field than
oxygenated hemoglobin.
So it's like this.
Here's basically capillaries and veins, arteries and veins.
And as you go through the capillary bed, the smallest
vessels, neurons are extracting oxygen to support
their physical life.
What happens when this part of the brain gets active, is that
more oxygen is extracted to support the active neurons.
So we call this BOLD effect, blood oxygen level dependent.
So we're measuring the change in blood, changes the ratio of
oxygenated to deoxygenated hemoglobins, that changes the
magnetic field as we measure it.
And that's what we directly measure, not the neurons.
So if the neurons are using up oxygen, why does the BOLD
signal increase, why does this ratio go up?
Because intuitively you'd think it would go down,
because oxygen is being extracted at a higher rate.
If you look at oxygen being extracted, right after
something happens, 10 seconds, there's an
initial dip of oxygen.
That's the neurons extracting oxygen to replenish themselves
from their activity, their activity has been to give your
mind its life.
Then what happens is there's this vast oversupply for much
longer time.
Intuitively, it's as if we said it's so important to
metabolically support the neurons that make up our
minds, that if some areas demanding a lot of blood, we
send over way too much extra as soon as we can, from a
distance to make sure everything's OK.
And because our measurement is so sad, we almost can never
measure this initial dip.
We almost always measure the sustained oversupply of oxygen
to that part of the brain.
So you could say it's such a house of cards.
The oversupply of the blood going to a part of the brain
changes the balance of oxygenated to deoxygenated
hemoglobin that changes the magnetic property.
And that's how we try to figure out what that part of
the brain is doing for your mind.
But it works pretty well in some cases.
Decent Spatial Resolution, no injection, you can zoom in a
scanner and do a lot of different things.
Modest Temporal Resolution, because it's not milliseconds,
it's always on the order of seconds, that's correlational,
not causal.
But you get some amazing results, I'm just going to
present to you two or three.
So here's one, a thing we're very interested about humans
is empathy.
How much we understand and feel other people's happiness,
or sadness, or pain.
So the "observation or imagination of another person
in a particular emotional state automatically activates
a representation of that state in the observer," empathy.
And how do we understand how another person feels, and we
think that's a big thing in how we relate to
one another as humans.
So Tania Singer did the following experiment, we
talked about this before a little
bit, embodied cognition.
That we understand others out there by the feelings
we know within us.
We don't know their feelings, but we know our
feelings inside us.
So here's what she did, she brought in pairs of people who
were friends, or romantic partners.
And she either had them get some pain, it was a shock,
within ethical boundaries, but not pleasant, that's the pain.
Or, you got to watch through a video camera, while you're
being imaged, your partner getting the shock.
So think about somebody you care about and think about
them getting something painful, and how you would
feel at that moment.
And they asked in the brain, what's similar and dissimilar,
and we'll focus on what's similar right now, between
feeling pain yourself, and observing pain in somebody you
care about, emphasizing with the pain you see them having.
And what they found is two areas, something of an
Anterior Cingulate, and something in the Insula, which
we talked about before, where there was a lot of overlap.
So this phrase, I'm feeling your pain, in your brain when
you feel for somebody else's pain in this physical sense,
you turn on some of the same brain areas as when you feel
physical pain directly.
It's as if the basis to imagine another person's
feelings is the feelings you know so well yourself.
And this is literally shown now by the brain imaging.
It could've been a story, a metaphor, an argument, this is
scientific evidence that supports that likelihood.
So we're going to expend it in a slightly fun way.
There's been a lot of study in neuroeconomics thinking about
how we think about, for example, things like trust.
So one game, and there's a number of them, is called the
ultimatum game.
And many people probably know this, but let me
remind you of this.
This version of it has two players, a
proposer, and a responder.
And what they do is they give to proposer a certain amount
of money, and the proposer is allowed to make an offer to
the responder.
If the responder says, No, nobody gets any money.
Usually people offered about 50%, so let's make this
concrete just for a moment.
Can I pick you for a second?
You can decline.
Imagine if Tyler came over to me and give me $10, and I
said, how would you feel if I gave you five and I kept five.
What do you think?
Might you go for It?
GUEST SPEAKER: Yeah, sure.
PROFESSOR: I mean, you go, I'm $5 dollars ahead, you're $5
ahead, Tyler won't eat this month because graduate student
stipends are modest, but it's a zero sum game in the end.
So now Tyler comes over hands me 10 more dollars, and I
offer you one.
What's your first feeling assuming that I wasn't your
teacher grading you?
He saw me get ten, I say here's one.
What's your feeling?
Think about it just for--
GUEST SPEAKER: You'd feel kind of cheated.
PROFESSOR: --yeah.
You don't have to, by purely economic perspective, would
you be ahead by taking that dollar?
Yeah.
A dollar's a dollar, $2 is $2, but people
have a sense of fairness.
Even to their own detriment, if you offer $2 and lower.
Even knowing that you're just ruining $1 or two you would've
gotten for nothing, except saying yes, people half the
time will say no.
It's like, you are so unfair--
you were saying to me, I would never say this to you-- you
are so unfair, that we're going to take us both down,
rather than you have the pleasure of the $8.
OK It's so unfair, that my sense
of fairness is disturbed.
It's an interesting way to think about it, imagine a
friend of yours is handed $10, and they offer you half, and
if you say no, nobody gets anything, so
it's a trust game.
They had the people in the scanner playing this game with
two people they saw on a video monitor.
The two people they're playing with are set up.
The person in the scanner is the real participant, the
people out there they see, are confederates,
they're play actors.
And one is a fair person, here's $5, thank you, here's
$5, thank you.
Here's $6, oh, you're awesome, we can get along, And then
there's an unfair player, here's $1.
And you go, why is this guy a jerk?
How about $2?
And after a while, you go the fair player was very decent,
this unfair player--
who you believe is part of the experiment, but is a set up--
and you're just thinking, why is this person such a jerk?
They're constantly getting $10, and constantly giving me
one or two.
No, no, no thank you.
Now, you get a shock, and you see these two strangers, one
of whom was a wonderful, fair player, and one of whom was an
absurdly unfair player.
You see them get a shock.
And they had both men and women in the scanner watching
these things happen.
And here's what happened, and it's kind of
funny, but you know.
For the women they had overlap again between the parts of the
brain to turn on in here in the insula, when they got a
shock, and when either the fair player got a shock, or
the unfair player.
They felt bad for both by this measure.
Look at the men in the study.
I feel bad if the fair guy gets it, but this part of the
brain's like, yeah, give it to 'em, can
you push up the voltage?
It just came out this way, whether it would work that way
under all circumstances, all ages, all societies, other
groups of men and women, don't know.
But in this sample in the United Kingdom,
the men had no empathy.
It's worse than that, it's worse than they had no
empathy, let me show you this.
If they asked to indicate their
desire for revenge against--
this is a behavioral response-- their desire for
revenge against the bad player.
I don't think they pursued the unfair player down the street,
but just that feeling.
And the women said, a little bit, the men said yes, if only
I could take down this person, that would be great.
And here's the amazing thing, we'll come back to the
structure called a nucleus accumbens.
It sits in the bottom of the Basal Ganglia.
It's the structure that in the human brain is most identified
with reward and pleasure, most identified with reward and
pleasure by fMRI imaging.
Look at the nucleus accumbens when the
unfair player gets zapped.
The women, nothing much, the men boom, big reward.
Revenge is rewarding in their brain.
No sympathy, and lots of revenge satisfaction for the
unfair player.
Now you can decide on your own life who this applies to or
not, but it's sort of fun to explore
these different things.
How we form ideas about empathy, trust, whether they
are in a society we grow up in.
Somewhat different on average men and women, huge ranges
within men huge ranges within women.
So it's a sort of fun thing to explore.
Let me end with something that's much more difficult and
disturbing, but another place where imaging is giving us
insights that you could not imagined having some time ago.
So this is a very difficult case, I don't know if any of
you gone through it, I don't wish it for you.
Some of you probably have, and many of you will at sometime
in your life, when you have to make an end of life decision.
And amongst the most famous of these cases was Terry Schiavo.
Now I don't know that name even rings a bell for you, but
it got very, very famous amongst these kinds of cases.
So she had a cardiac arrest, she had took a lot of diet
pills, and that may have contributed.
In February 25, 1990, she went into a coma, and then a
vegetative state.
So a vegetative state is when a person seems to be kind of
awake, but when you talk with them, they're not very aware,
they're not responsive, they're not noticing, they're
not talking.
But their eyes are open, and they're awake, their eyes are
not closed, so that's what she is.
And they put in her a feeding tube, because without that she
wouldn't live, she couldn't eat and feed herself.
It was a heartbreaking difference of opinion between
her husband and her parents.
Her husband petitioned some years later, actually eight
years later, to remove the feeding tube and
let her pass away.
The parents opposed that, they said that's not her wishes,
she would want to keep on going with the feeding tube.
The husband said no, I don't believe that's her wishes.
So you have this very tragic confrontation between the
parents who loved her, and the husband who presumably loved
her having different ideas about what to do with her,
whether to end her life or not.
So finally her tube was removed, but then the parents
went to court, and a judge reversed it, and they
put the tube back.
She became, sadly, kind of back and forth, living
nonliving, on judicial decisions.
Her case became particularly famous, for a bunch of
reasons, and it went back and forth from court, to court.
Moving up in the state courts, and there were several US
Supreme Court decisions about whether to remove the tube, or
keep the tube in.
And it's a tragic thing, it's a tragic choice between the
parents and the husband.
It got to the US Congress, in the US Senate.
President Bush signed a bill to keep her alive.
Everybody got involved, with various opinions, finally the
Supreme Court made a series of decisions.
It was disconnected in 2005, and she died in
March 31 of that year.
So tragic difficult decision, and a tragic family situation
that became kind of a political,
and judicial football.
So what's going on in the mind of somebody like this, and how
could we even begin to interpret it for a person who
can't speak for themselves and can't respond.
So let me tell you about a different case, we
don't know her case.
So, again a vegetative state is one where you appear to be
awake, but there's no sign of awareness.
Eyes are open, but the person's not talking or
responding to anything in their environment.
So here's a different woman, 23 years old, in 2005 she had
a road traffic accident, severe traumatic brain injury.
Five months later she's un-responsive, but she has
preserved sleep-wake, like she's waking up going to
sleep, waking up going to sleep.
Eyes open, but un-responsive in every other way.
They put her into an fMRI scanner, as well as healthy
comparison people, and they have them do to
mental imagery tasks.
they read instructions to her.
But you go into scanner, and you're told to imagine two
different things.
Playing tennis, so imagine in your mind's eye you playing
tennis for a moment, imagine that.
Or imagine visiting all the rooms of your house starting
with your front door, in the house that you are living in
now, or where you grew up.
Imagine those two things in your mind.
First of all, just a pure cognitive neuroscience level,
and we'll come back to that, imagination is a really
interesting thing.
And it turns out when we imagine things, again we use
the parts of our brain that does them, imagination is
perception run backwards.
We can see imagination in the human brain.
And depending on what you're imagining, you use the same
systems that you see with.
If you imagine something you're looking at, it will
turn on your visual system, it's even more
specific than that.
So let's first look at what happens with the controls.
When they imagine they're playing tennis, they turn on
the supplementary motor area, that's a part of your brain
that plans your physical movements.
You're not moving, but you're thinking about it, this is
imagination of movement.
When you plan a movement., you turn that on.
When you go around your house, you turn on spatial areas that
are in the parahippocampal cortex, and similar areas,
parietal cortex, and parahippocampal cortex.
They're turned on if we show you a movie where you're
moving around in spaces.
If you see spaces, you turn those on, if you imagine
spaces, you turn them on.
So imagination in the brain is perception run backwards, or
physical action run backwards, you're not actually doing it.
But look at this patient who got in the scanner, who was
non responsive, you read her the instructions, and see what
she does, and look at her brain.
Asked to imagine tennis, asked to imagine the
rooms in her house.
It looks just like that.
What does that mean, just in a common sense,
what does that mean?
Did she understand the instruction, at some level
yes, she wouldn't turn on those parts of the brain if
she didn't understand the instruction, she imagines the
thing you ask her to instruct.
So this guy on the front page of the New York Times said
fMRI could tell you the internal mental life of a
person could no longer speak, or communicate
with any other way.
Now it's turned out since then, that when they put in
other patients into the scanner, most of them don't
show this pattern.
So it's not that every patient in a vegetative state this is
full of mental life like this person.
And a deeper way, we don't really understand what this
mental life is like.
We don't know whether she simply understands some
things, but doesn't have feelings, or plans, or
desires, or whether she has those too.
We don't understand really the full range of mental life, but
we know that she can understand an instruction, and
her brain follows through with it.
Most patients, it turns out, don't look like that in
vegetative states.
So again, brain imaging has taken us inside the mind of
somebody who cannot communicate for themselves and
let us say something about what it is that's
going on in that mind.
In conclusion, we've talked about different ways of
learning about the brain, different methods to record
structure and function that vary in their temporal and
spatial acuity.
And incredibly different ways in which we can understand the
organization in time and space of how the brain supports the
human mind.