Split Brain, Part 1

Our brains are composed of two hemispheres, but in what ways are they truly separate? In which ways are they one? In this bisected Stuff to Blow Your Mind exploration, Robert Lamb and Joe McCormick explore what we’ve learned from split brain experiments in animals and humans. 

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Episode Transcript

Speaker 1 (00:00):
The powers of Hide seemed to have grown with the
sickliness of Jackyal, and certainly the hate that now divided
them was equal on each side. With Jekyll, it was
a thing of vital instinct. He had now seen the
full deformity of that creature that shared with him some
of the phenomena of consciousness, and was co heir with
him to death and beyond these links of community, which

(00:21):
in themselves made the most poignant part of his distress.
He thought of Hide for all his energy of life,
as of something not only hellish but inorganic. This was
the shocking thing that the slime of the pit seemed
to utter, cries and voices, that the amorphous dust gesticulated
and sinned, that what was dead and had no shape

(00:43):
should usurp the offices of life. Welcome to stuff to
Blow your mind from How Stuff Works dot Com. Hey
you welcome to up to blow your mind. My name
is Robert Lamb and I'm Joe McCormick and Robert. Why

(01:03):
are you reading Robert Louis Stevenson at us Oh, Because
that's from the Strange Case of Dr Jackel and Mr
Hyde from eighteen eighty six, and it concerns the idea
of there being two entities within the human skull, two
entities within the mind, indeed two minds within the brain.
And I think this is an interesting place to start
because while it presents a very erroneous vision of the

(01:27):
lateralization of human brain function, it also, uh, it gets
some of the same like hair standing up on the
back of the neck, that the actual research we're gonna
be talking about today does, at least for me. Oh yeah,
I mean, Robert Louis Stevenson was a fabulous writer and
he's he's one of those authors that you can read
today and it holds up so well. Did they ever
make a good Jackal and Hyde movie. It's been a

(01:49):
very long time since I've saw it, but there was
an adaptation. It may have been a TV adaptation with
Michael Caine Michael Kine. Yeah, And I remember really loving
that and being quite disturbed by it as a child. Now,
I was thinking there had to be a Jekyl and
Hyde with Tim Curry as Jackal and Hyde. But I
think maybe I'm confusing that with the Muppet Treasure Island,
where he's You're thinking of the Muppet Jacky and High

(02:11):
he's long John silver Man, that scene where he tramples
Kermit to death is brutal. Well, yeah, so so we
are we are beginning with kind of an erroneous model.
But but I think helpful and because it is often
easy to think of the brain as the thing itself, right,
we fall into this center, our mode of of of
of you know, the thinking of the brain body relationship

(02:34):
as being a rider and its horse, when instead it
is more this idea of a centaur, this this this
one single entity, um, you know, and honestly, we see
this reflected in so many real and fictional scenarios. Uh.
Take for instance, the late physicist Stephen Hawking a brilliant
brain within a body that was gradually paralyzed by motor
neuron disease. Or just look to our dreams in which

(02:56):
the inner world of the brain runs wild while the
body goes un lockdown own. Uh you know, think of
our imaginings, our inner thoughts versus our outer smile. And
then there are all those disembodied brains and science fiction
right from Crying and his robot body and teenaging Ninja
Turtles to the Brain that Wouldn't Die Cane and RoboCop
to one of the best I know that's one of

(03:16):
one of your favorites as well, greatest of all time lovecrafts,
The Whisper and Darkness, and so many Doctor Who characters,
especially the Daleks brain guy from MST three Ky. We
just keep keep coming up with these these visions of
the brain as the just sort of the central human
thought experience. You know, I never thought of this until now,
but actually the brain guy from Mystery Science Theater is

(03:37):
kind of a great illustration of Daniel Dennett's short story
thought Experiment where am I I wonder if there was
any connection there. Someone have to have to have to
reach out to the the MST guys on that, you know,
there are those like plot lines where his brain gets
separated from him and somewhere else. Um. Of course, we
know that things are not this simple. No brain is

(03:58):
an island. It's affected by a host of outside influences,
including all sorts of environmental nervous stimuli. And we're learning
more and more about the role of our microbiome and
various parasites in human cognition. But even if we're to
just strip away all of that, if we're actually to
become a brain and a tank, you know, Kane's brain
in RoboCop two or or any of these sci fi

(04:20):
visions take out all that external stuff, just the brain.
We still have to contend with the fact that the brain,
like a government, is composed of different houses. The brain
consists of two cerebral hemispheres connected by the corpus colossum uh,
each each hemisphere with many different modules, all of these
acting in concert with each other, all of it interconnected. Yeah.

(04:43):
One comparison I've seen in some of the neuroscience research
we're looking at today is that the brain is often
described as a computer, you know, or by the metaphor
of a computer. You know. It's not that it is
a computer, but that Yeah, there's the analogy that the
brain is like a computer in the different parts of
the brain and are maybe sort of like different programs
that run on that computer. But at least one researcher

(05:06):
we were reading I said, maybe it's more accurate to
think of the brain not as a computer running different software,
but as a vast network of computers that are each
capable of operating independently, but most of the time operate
in in tandem. It's right. This is an example where
if you don't really have much of an understanding of

(05:26):
how computer works, the the the idea of thinking of
the human mind as a computer as technology is is
more harmful. But if you have, if you have a
better understanding of how computer actually works, it could perhaps
be a more helpful metaphor cuttle cats cuttle fish to
the second oil age and kingdom with or of darkness.

(05:48):
I don't dispute the eurostata, but if he's down here,
we know not blood but darkness, the earth's black riches.
No I could taste it on my lips. Today, I
want to talk to you about the science of transgenesis

(06:13):
tens genesis dot show now I wanted to to I
think it would be helpful to just go ahead and
consider one particular question right up top now. And we've
certainly received questions like this following episodes in which brain
hemispheres are discussed, such as our discussions on the bicameral
mind hypothesis or the alphabet in the Goddess. Because there's

(06:36):
this kind of pop understanding, right that each side of
our brain controlled certain aspects of being, and that certain
individuals have certain leanings that you know you have, right
brain people left brain people, and that when that we
can reconnect with our less favored hemisphere. Now, there certainly
are some pieces of evidence that we're gonna look at
in this episode that certain functions of human life are

(07:00):
strongly lateralized in one half of the brain or the other,
but they're not necessarily these functions or personality traits that
are understood in popular consciousness like logic and creativity, right
like taking or that you're gonna take some sort of
a quiz online and find out if you're a right
or lefty in terms of your brain. Now, a lot
of these ideas apparently were popularized by nineteen seventy nine

(07:22):
book title Drawing on the Right Side of the Brain
by Betty Edwards. Uh, and the downstream myth that kind
of uh, you know, took over a popular culture for
a little bit. There is that, yeah, you had left
side logic, right side creativity. And even in people who
know better people, we still talk like this. I've noticed
that I use this metaphor even though I know it's wrong,

(07:43):
Like I will sometimes think of people as being very
right brained or very left brained, even though that I
know that that I've read before about how that's not correct. Well, likewise,
if I hear it mentioned saying a yoga class, I'm
gonna be less inclined. I'm not going to be the
jerk in the yoga class that like perks up and
says act l A, there's some interesting you know, I'm
I'm gonna set back and enjoy the class because because

(08:05):
it's one of those things that can can feel true. Right.
But the idea goes back further than this particular book here.
I mean, it goes back to some of the earlier
discoveries that we're going to discuss here about hemispheric division. UM.
You know, the ideas of neurologist Paul Broca who lived
eighteen four through eighty French neurologist or Carl Vernica who

(08:29):
lived who lived eighteen forty eight through nineteen o five,
a German. They studied patients who had communication troubles due
to brain injury UM, such as you know, left temporal
lobe injuries, and they figured that this was the language center.
Thus language was left hemisphere focus. And this is one
thing that actually has been more born out by good

(08:49):
research in in the history of neuroscience, is that one
thing it's very clear the left hemisphere of the brain does,
is it is dominant in language function. It's not that
the right brain can't do any language, but it can't
do a whole lot of language certainly can't do what
the left hemisphere can do. Right Uh now we we
kicked off the episode with reading from Robert Louis Stevenson

(09:11):
against Scottish author He lived eighteen fifty eight and according
to neuroscientist Elizabeth Waters, who's put together some you know,
wonderful ted talks and ted ed videos about this, uh this, this,
uh this topic, she points out that Robert Lewis Stevenson,
in his book Strange Case of Dr Checkl and Mr Hyde,
presented the notion of a logical left hemisphere that is

(09:33):
in combat in you know, in in in in this
uh this struggle with an emotional right hemisphere, and uh
it's It's also worth noting that Robert Lewis Stevenson was
also inspired by two popular French cases of individuals who
exhibited dual personalities, uh their name. They were credited as
being uh Felida X and Sergeant Fay. And these were

(09:55):
apparently cases that were really you know, well covered in
French and British press at the time. You know, it's
kind of popular science influencing, uh, popular science fiction. Do
you have any sense of whether what was presented to
the public about these cases was largely accurate or was compleating.
I don't, but I'd love to go back and look
at it, because you know, this is a case where
you can the science influences the science fiction, and the

(10:16):
science fiction influences, uh to a certain extent, how the
public thinks about a given topic. Now, other another influence
on Robert Louis Stevenson. Apparently he had a just a
terribly high fever, uh at one point during which he
claimed to have experienced a split into which he experienced
quote myself and quote that other fellow. Yeah, so this

(10:40):
apparently had a big influence on him. An according to
biograph for Claire Harmon, author of Myself and the Other Fellow,
duality and the idea of the double self turn up
again and again in Robert Louis Stevenson's work. Well, maybe
I'm over interpreting here, and this could be just kind
of a mundane parallel, but I mean I see stuff
like that even in Treasury, and you know, his Space

(11:00):
Adventure where long John Silver is at the same time
a a patient and sort of good father figure and
also an evil pirate. Yeah. Yeah, this is the the
argument here is, Yeah, that this is the type of
duality that that he was obsessed with and and so
much of it, so many of his works, I mean
essentially had a fever induced psychedelic experience and then this
lining up with various elements of his of his life.

(11:22):
I mean, that is the meat he chewed upon. But
of course, this popular understanding of the left right division.
You know that that like the side ruled by passion
and the right brain and the side ruled by logic
and reason and the left brain. That's not exactly right, right.
You know, as we'll explore, doctors actually looked to patients
with missing brain hemispheres or separated hemispheres and is appealing

(11:44):
as this notion, maybe it didn't really hold up. I mean,
they were all still logical and creative beings. You didn't
just end up with us, you know, as a Spock
or whatever the opposite of Spock would be in the
Star Trek universe. To be clear, though, Yeah, the brain
is divided into two hemispheres in internal regions like the striatum,
the hypothalamus, the thalamus, and the brain stem. They're also

(12:07):
organized with left and right sides as well, despite appearing
to be continuous when you when you sort of look
at illustrations of them. Yeah, and for the rest of
this episode, in fact, this is gonna be the first
of two episodes we're going to be looking at ways
that despite this, uh, this like emotional versus logical split
being wrong, there are very interesting ways that the brain

(12:27):
hemispheres are different and do different things. In fact, well,
we can start with the mundane ones I guess, right,
like mundane motor control differences. Exactly. We can look to
the two two arms and legs. For instance, the right
hemisphere of the brain controls the left arm and leg,
the left hemisphere controls the right arm and leg. Now
I have read that in a way like both hemispheres

(12:50):
can in some way to some degree control both arms.
But that when it gets done to like fine motor
control of like controlling the actions of the hand and
especially that's where he gets really lateralized and like it's
really going to be your right brain that's controlling what
your left hand does with its fingers. Now, a more
complex example is, but one it's extremely important is each

(13:14):
eye has a left and right visual field, with the
left visual field sent to the right hemisphere and the
right field sent to the left hemisphere. Now this can
also be misunderstood because I've seen it represented in the
press in places that where like the left eye goes
to the right hemisphere and the right eye goes to
the left hemisphere. And that's not quite right either, because

(13:35):
both hemispheres can get some information from both eyes. But
it has to do with the side of the visual
field that you're talking about. So like stuff that you
perceive over to the left part of what you're looking
at that goes to the right hemisphere, and stuff you
perceive over in the right area of what you're looking
at to the right of your center of vision that

(13:57):
goes to the left hemisphere. And then our visual experience
of reality it comes together from these two feeds. Movement
and vision depend then on this uni hemispheric relationship. Now,
why do our brains work this way? Yeah? Why the crossover?
Why don't we just go straight up parallel? It's one
of those things about the human vice seems needlessly complicated, right, um,
And the thing is we're not entirely sure. One theory

(14:20):
that has been discussed is that animals developed more as
as animals developed more advanced nervous systems, there was an
advantage in escaping to the right if something came at
you from the left. So these are examples where we
can actually look to specific hemispheres and say here, here,
here's where they are most active. But we can't easily
extend this idea to other aspects of cognition, and certainly

(14:41):
not to the overall human experience or things like pure
logical thinking or creativity. No, not that, But there are
some cognitive functions that do appear to be pretty strongly
lateralized in one way or another, And one of them,
obviously is language. We mentioned this, Yeah, that's localized to
the left, especially complex language and the power of speech.

(15:02):
There's some research indicating that like the right brain might
be able to have a sort of simple lexicon or
understand very simple bits of language, but if you want
to generate a sentence like speak one out loud, or
understand complex instructions in language, this is usually going to
be dominated by processes in the left hemisphere. Oh and

(15:22):
we should also say that everything we say about hemispheres
in this episode is going to be for most cases.
There there cases where this is reversed, where people have
like the switching of which hemisphere is dominant, but we're
talking about the majority of cases here right now. Meanwhile, attention,
we see that more localized to the right hemisphere. Yeah,
and this would be especially things like visual and spatial reasoning,

(15:45):
Like the right hemisphere is going to be very important
if you need to imagine a map in order to
give directions. So, brain activity unbalancing, where one one side
is more active in a given task than another. This
this occurs based on which system is being employed in
a given task, rather than anything about an individual or

(16:08):
their background. Of This is all, of course, assuming a
healthy brain. Obviously, if one side of your brain is missing,
there's going to be more activity beside it's there. Now,
no evidence suggests that individual individuals have truly dominant sides
of the brain when it comes to their you know,
their personality makeup right, you're not like creative right brained
or logical left brain right and likewise that the logic

(16:31):
and creativity split idea. Uh, you know again, you'll have
individuals that are certainly more logical, perhaps or more creative.
But as as neuroscientist Elizabeth Waters has pointed out among
many others, logic and creativity are not these two distinct notions,
you know, they're deeply interlinks, Like being good at logic

(16:52):
is in many cases being a certain type of creative. Yeah.
I mean, what you might dismiss is just a really
logical exercise, like safe solving a complex math problem that
may well require that will require some creative thinking. Likewise,
a creative endeavor like say, writing a poem, finishing a novel,
coming up with a cool joke, whatever, you know, those

(17:14):
are gonna gonna be activities that also involve logic. In fact,
some of what we're going to discuss in this pair
of episodes in in the neuroscience research turns this whole
thing on its head in a way, because the left
part of the brain that's more dominant in exercises involving
speech and language often tends to be the more creative
one in explaining behaviors. Right it's the one that tends

(17:35):
to interpret and come up with explanations for things as
will as we'll talk about later on, which is a
creative exercise. Whereas the right brain tends to more often
be the part of the brain that records experiences accurately
without creating explanations for them exactly. And but but certainly,
if I'm gonna you know, drive home anything, we want

(17:57):
to point out that that the creativity law, anything that
employs these these two loose idea, you know, buckets of
of of of cognition. You know, these are going to
be products of whole brain cognition. Like our our the
brain is all these areas of the brain are working together,
uh to create this effect. Now, ultimately in this episode,

(18:19):
we're going to be asking what happens when you cut
those two hemispheres of the brain apart. Yes, but I
guess we'll have to get to that after a break.
All Right, we're back now. Before we get to the
idea of severing the brain hemispheres, we should probably talk
about a little more about Broca and Vernica. Yeah, these

(18:39):
are just two really key individuals to this whole discussion
and even just the idea of understanding the human brain.
Um So Paul Broca will start with him again eighteen
eighty He was a French surgeon, neurologist and anthropologists and
he is also for anyone who hasn't read the book
but has seen the title. He is the namesake for
Karl Sagan's book Broke His Brain. Sagan describes at one

(19:03):
point point holding a jar containing the noted scientist's brain. Wait,
like imagining doing this literally doing literally doing it? Okay,
holding holding the jar that contains his brain and thinking
about like what you know, talking he talks a bit
about Broca and and and you know, his his work,
his personality, but also just sort of meditates on what

(19:25):
you're doing when you when you hold this brain in
your hands. I want to imagine that, having not read
this book, it is in fact just like a caper
story with Broker's brain as the MacGuffin and it gets
traded around and their car chases. Sagan is trying to
get it back from the KGB spies. Uh no, not quite,
but Dante Skull shows up as well. O nice So

(19:46):
brokea though he made important contributions to our understanding of cancer,
the treatment of aneurysms and aphasia and his Sagan pointed out,
Broca was also quite concerned with the medical care of
the poor. He was you know, he was he was
a free thinker. He was a strong Darwin supporter, and
above just about everything, he was the founder of modern
brain surgery, and Broco was influential in identifying regions of

(20:10):
the brain as being especially responsible for certain cognitive functions. Right. Yeah,
he investigated the rheinan cephalon the smell brain. But his
name actually goes to a small region in the left
frontal lobe of the cerebral cortex what we call Broca's area. Uh.
This is left hemisphere, third frontal convolution. To be specific,

(20:31):
this is the area where articulate speech is largely localized
and controlled. And his Segan pointed out, given the importance
of language and articulate speech and human evolution, this portion
of the human brain may be considered, in Sagan's words,
the seat of our humanity and some respects. And it's
also something anatomists have looked for in the remains of

(20:52):
our hominid ancestors, such as Homo habilish. Columbia University anthropologist
Ralph Holloway Sagan sided Uh's you know, studied and claimed
to have found evidence for its development of a Broca's
area some two million years ago, and this would have
been around the time early tool use was beginning uh.
Also South African palaeo anthropologist Philip Tobias also made this claim,

(21:16):
though according to Susanne Kemer, Associate professor of Linguistics at
Rice University, quote, these claims have been controversial. Many see
no regular impressions that could be ascribed to brain structure here,
and I can imagine it's probably difficult to just look
at skulls and figure out what brain regions were evolved when, right,
but broke as a discovery here broke a's namesake here

(21:39):
is the first of many discoveries that illuminated hemispheric separation
of function in the brain. And you know, and really
driving home the idea of that specific brain functions might
be isolated to specific parts of the brain. Yeah, if
there's a certain part in the left hemisphere that seems
especially important for language, what else could be lateralized? Right
now is to throw in the Nowadays, you hear more

(22:02):
talk of networks as opposed to regions. You know, again
getting into this idea that that that that we're looking
at at a network of of of different systems and
not individual areas that are just doing all the heavy lifting.
Your brain is less like a computer. Maybe in more
like the Internet, right, but a conscious Internet. That's scary.

(22:24):
Uh so horror movie pitch the conscious Internet. Uh yeah,
and then it takes physical form via three D printers. Right,
But let's also talk about about the German Carl Vernica
okay live eight five a German? Yeah, Well, thus the
Vernica uh he was. He has another area of the

(22:45):
brain's name for him, the Vernica area, and he first
described this area in eighteen seventy four, and it's found
in the posterior third of the upper temporal convolution of
the left hemisphere of the brain. It's close to the
auditory cortex and seems to play a unique role in
the comprehension of sound and language reception and comprehension. So
the stage is set to discuss the lateralization of certain

(23:08):
brain functions. But we mentioned earlier that this episode was
really gonna end up focusing on cutting brains in half.
And I know you're out there saying, when are you
going to cut the brain in half? Robert, I think
it's time. We've got to make the incision, that's right,
And what better time to just slice the human brain
in half than the nineteen sixties and seventies it's really
really perfect. I mean, you could really almost it's tempting

(23:29):
to just want to think like a left brain, right brain,
old fashioned idea and have like the nineteen sixties hemisphere,
in the nineteen seventies hemisphere. Right, there's just something something
perfect about the post revolutionary hemisphere. Uh no, no, So
we're gonna be talking about the research of neuroscientists named
Roger Sperry and Michael Gazzaniga, and so actually the brain

(23:51):
cutting started in the nineteen forties, but it was in
the nineteen sixties that the research on people with severed
hemispheres really got going, that's right. And they they discovered
something that's that was seemingly amazing that if you split
the brain, you you essentially split the person as well
in a certain sense and not in another sense. And
well we'll have to define that as we go on.

(24:12):
But but but just think about it for a second.
Just the the the promise that the you know, the
tease of this idea that there would be one person
per hemisphere of the brain, this division of the self.
Getting back to this idea in a certain sense of
myself and the other guy, right, yeah, oh, that's right. Uh,
the Robert Louis Stevenson and h and this was work

(24:34):
they would have eventually earned Sperry the Nobel Prize in
Medicine in now. During this this these decades of research,
Sperry performed experiments on cats, monkeys, and humans and focus
a lot of attention on the neuron packed corpus colossum
that bridges the hemispheres. This is often described as sort
of like a broadband Internet cable, like an Internet backbone,

(24:58):
fiber optic or something that connects the two hemispheres together
and enables most of the exchange of information between them.
Right now, with non human animals, he surgically split the brains,
producing what he called a split brain, in which each
side seemed to function independently of the other. And he
also found that an animal with a split brain could

(25:18):
memorize double the information. Oh I didn't read that. Yeah,
that was a tidbit I ran across creepy now obviously
him not being a mad scientist villain in like a
serial in a comic book or something. He didn't split
human brains just for experiment, that's right. Fortunately for him,
there were already humans walking around with split brains because
they had had because there were patients who had their

(25:40):
corpus colossum separated uh severed as a treatment for epilepsy,
and so he was able to get a number of
these individuals to volunteer for his experiments. Yes, so this
procedure was not done for experiments, obviously, it was done
as a medical treatment, and it's known as a corpus callosodomy,
and so the theory behind it is that an epileptic

(26:01):
seizure is sort of like a storm of activity in
the brain with too many neurons firing and triggering chaotic
activity all throughout both hemispheres. And the idea was if
you cut the corpus colosum, if you sever that broadband
internet connection between the two hemispheres of the brain, you
limit the ability of one of these seizures to spread

(26:21):
from one hemisphere of the brain to the other. And
in many cases where severe epilepsy could not be treated
by any other means, the surgery actually was considered effective,
I think, especially later versions of the surgery, less so
in the forties, more so I think in like the
sixties on. But this surgery generally isn't used today because
we have on on the whole safer, better, less radical

(26:43):
treatments for epilepsy. Now they're they're drugs that are pretty effective,
and there are less radical surgeries you can do. And
it's not known exactly how many patients ever received a
corpus colisotomy and history I've seen estimates including somewhere between
fifty and a hundred total patient. I read Michael Gazaniga
estimated that there were over a hundred patients who had

(27:04):
received one. Now, obviously not all of these patients volunteered
for split brain neurology research, but some did. And one
of the really interesting things to point out is that
we'll have to keep coming back to this is that
despite the radical nature of this surgical intervention, cutting the
two hemispheres apart and basically preventing them from communicating with

(27:25):
one another, most patients reported that their lives were generally
normal after the surgeries. Their families did not usually report
any major changes in behavior, personality, or cognitive ability. Uh.
Michael Gazaniga says that generally, quote, you wouldn't know it
if you were talking to such a patient. Yeah, I've
read that the really the only notable results of this

(27:48):
outside of you know, perhaps some experimental stuff that's gonna
come up, was that they didn't have the seizures anymore. Yeah,
like that. That was the goal, and that was the
the the primary experiential difference. By and large, people underwent
this procedure. It cut the two halves of their brain apart,
and they seemed mostly unchanged. Now. On the other hand,

(28:08):
I have read some anecdotes about changes certain patients faced,
especially right after the surgery, during like an adaptation period.
For example, a article in Nature News by David Woolman
recounts the experiences of a patient named Vicky, who received
a calisotomy in nineteen seventy nine to treat terrible caesar
she was having. There's a story that her seizures were

(28:30):
so bad that one time she like fell on a
stove and burned her back while she was having one.
Um And so she says that for the first few
months after her surgery, she would stand in the grocery
store trying to pick items off of the shelf, but
having severe difficulty just picking up items. She says, quote,
I'd reach with my right right hand for the thing

(28:51):
I wanted, but the left would come in and they'd
kind of fight almost like repelling magnets. Uh. And she
would apparently have similar troubles when trying to get dressed
in the morning. Woolman writes, quote, Vicky couldn't reconcile what
she wanted to put on with what her hands were doing.
Sometimes she ended up wearing three outfits at once. And
then Vicky says, quote, I'd have to dump all the

(29:14):
clothes on the bed to catch my breath and start again.
And I've read other accounts along these lines that a
few split brain patients described things like that this was
one image one hand buttoning up a shirt and the
other hand following immediately behind it and unbutton ing all
the buttons. But these kinds of these type of descriptions
are apparently not typical. Most reports indicate that people's behavior,

(29:37):
cognitive ability, personality, all that is mostly unchanged. And even
in Vicky's case, after about a year, she was mostly
back to normal in terms of everyday activities. She says,
she could, you know, slice vegetables, to cook and and
operate machines and all that. And this is in line
with other reports. Amazingly, you can completely sever the connection
between the two hemispheres of the brain and most of

(30:00):
the people you do this to function normally in day
to day life afterwards, before we even get to the
other strange stuff we're talking about that in itself seems crazy. Yeah,
I am just always amazed when you when you hear
about the things that can be done to the brain
and the ways that the brain can can can bounce
back and and behave just relatively normally or just or

(30:23):
seemingly completely normally. Even in the face of catastrophic injuries.
The brain can often find a way. The mind, uh
finds a way. But of course, despite these reports that
people are generally unchanged, what we're about to talk about
is that if you and what Sparry and Kazaniga discovered
is if you apply some special conditions in the lab,
you can see some really strange and thrilling things at

(30:46):
work in the split brain patients. Yeah, the crux of
this comes down to the very visual processing we discussed earlier.
Left visual field, right side of the brain, right visual field,
left side of the brain. So in a split brain,
the left side of the brain can't see the left
field of vision and the right side of the brain
can't see the right visual field, or generally can't generally yeah,

(31:08):
generally speaking, and we'll we'll get into the meat of
this in a minute. But but it's going to lead
to split brain cats with eye patches and split brain
monkeys with memorization, because, as we mentioned again, he did
conduct animal experiments to see how this uh to to
to reveal what was going on, and the animal experiments
were very they produced very strange and fascinating results. But

(31:30):
you always wonder, well, okay, you know, animal brains are
just different than human brains, so so what happens with
the actual human So I was reading an account of
their very first patients, very in Gazaniga's very first split
brain patient, uh in that that David Wollman article, and
it was a man known as w J. A lot
of times these patients are known just by a first
name or by initials, you know, to protect their their identity.

(31:53):
And apparently w J. Had served as a paratrooper in
World War two and he suffered a head engine read
during the fighting, a Nazi had smashed him in the
head with the rifle butt, and afterwards he experienced severe
seizures and was treated with the callistotomy. And so in
nineteen sixty two after the surgery, Becazanega ran visual field

(32:15):
experiments with w J. And what he found was amazing.
So the standard set up of one of these experiments
is that you have the patient focus on a dot
in the middle of a screen and then you flash
a visual stimulus in the peripheral visual field on one
side or the other. And the scientists knew from previous
research that this would mean stimuli shown to the left

(32:37):
visual field, as we've been saying, would usually be perceived
only by the right hemisphere, and stuff shown in the
right visual field would be perceived only by the left hemisphere.
But now that the hemispheres can't talk to each other anymore,
what happens? So w J was shown images in his
left or right visual fields and then asked to press
a button and then asked to say what he saw.

(33:00):
And when an image was shown to his left hemisphere,
the part we know is primarily responsible for language, he
had no problems at all. Right, you show the left
brain whatever you want, a cat or you know, show
him RoboCop, and then they'll press the button to indicate
they saw something, and he'll say, I saw robo cop.
But when they showed an image to w j's right hemisphere.
What he said was that he saw nothing, but strangely enough,

(33:23):
his left hand, which remember, of course, the left hand
is connected to the right hemisphere. His left hand pressed
the button when he saw the image, even though the
part of his brain responsible for speech was saying out loud,
I don't see anything. I mean, take take a second
to think about that. Like when I first read that,
I was like, oh, okay, oh, and then it hit

(33:46):
me and I got the chills. I mean, you know,
the hair stands up on the back of my neck. Literally. Yeah,
Because what we're we're imagining here is we we read
this and discussed it is. It's not a complete sle
like separation of self, but it's like a temporary, very duality,
like a flash of duality, where in the very place
where we we want and expect to find some sort

(34:09):
of continuity of self, well, it's yeah, it's like peeking
in and seeing a quick glimpse of a reality that
may be far more true and accurate a description of
how the brain is than we would like to admit,
or that normally seems true to us. Because again, we
always feel unified and the split brain patients feel unified

(34:30):
will revisit this a little more, but they don't report
feeling like two different people. They just feel normal. This
is just how I am. And yet from an objective
outsider's point of view, it's almost as if you've got
two different people taking the test at the same time.
One is registering I see something with a hand and
the other is saying he doesn't see anything. And yet

(34:50):
it only seems this way under certain conditions, and only
from the outside. Now, if you want to see an
example of this, you can actually see one of these
experiments demonstrated on film. And there's like a short documentary
segment feature that I think he's up on YouTube. Still
there's a patient name to Joe who is working with
Kazanega and this looks like it's the nineties or so,

(35:11):
and uh, it demonstrates a typical experiment. So you show
either words or pictures to the left brain only, and
Joe can name them out loud just fine. So he
you know, you show him the word car or a
picture of a car. He says car. Show him the
word grapes or picture of grapes. He says grapes. Everything
seems normal because it's all going to the left hemisphere,
and that's the hemisphere that talks. You show a word

(35:33):
to the right brain, only in this case, the word
pan flashes on the far left side of the screen,
and suddenly Joe is stumped. Uh just based on my read,
it looks to me like he seems to be aware
that he saw something, Like there's a kind of recognition
that it looks to me at least like he is

(35:54):
aware something appeared but can't say what it is. And
with a little shrug and a shaking of his head,
he says, I didn't see it. But then Gazzaniga has
him close his eyes and draw with his left hand,
which is controlled mostly by the right hemisphere, and his
left hand draws a pan. Again legitimate chills, And of course,

(36:15):
after he draws it and looks at it with both eyes,
he can say, yeah, I saw a pan, But the
part of his brain that talks didn't seem to know
he'd seen a pan until after his left hand drew it.
Another type of experiment they carried out. You take a
split brain patient and simultaneously show two different pictures on
the two to the two different hemispheres. You show a

(36:36):
hammer to the left hemisphere and you show a saw
to the right hemisphere and you ask what did you see.
Of course, the speaking part of the brain says hammer.
The person says I saw a hammer. But then when
asked to draw with the left hand, the patient draws
a saw and you ask them why did you do that,
and the patient in this one case, the case of Joe,

(36:56):
says I don't know. Now. In other cases like this
version of this test, sometimes the speaking part of the
brain will not just say I don't know, but will
actually seem to make up stories about why their brain
produced a certain output that the left part of the brain,
the speaking part, doesn't seem to understand, and they'll just
confabulate an explanation. Well, you know, they might say, well,

(37:19):
because you know, I I was thinking about this other thing,
or because you said this thing earlier, or something, well
that makes sense. I mean, it's almost like a supernatural experience, right,
and uh. And you know, logically you can, you know,
try and find some sort of answer to it. But
the answer you give, and apparently the I mean, there's
no indication that these people were just consciously lying about
their motivations. The answer you give, and apparently the answer

(37:42):
you seem to believe is not true. It is just
like you. You can come up with explanations for your
own behavior that are completely wrong, and we can show
why they're wrong, but you are not aware that they're wrong.
You can be wrong about your own mind. And even
without a split brain, of course, humans are are very
capable of of of coming up with false reasons for

(38:04):
whatever they believe or whatever they did. Oh, absolutely, yeah,
I think that's entirely correct. And that's sort of what
I what I'm thinking we might be able to extrapolate here.
So one of the most amazing things to me about
this kind of research is uh is that this can
happen to the brain. For the most part, nobody seems
to notice. It takes a lab experiment like this to
draw it out. Like not the people who interact with

(38:26):
the split brain patient. Remember that family members usually report
no major changes in personality or cognitive ability. As David
Wollman points out in his Nature article, the patients themselves
say they quote never reported feeling anything less than whole,
and in the words of Michael Gazzaniga, the severed hemispheres
do not seem to notice that they have been severed.

(38:48):
And they don't report missing each other. So this raises
so many questions. First of all, why are they connected
in the first place If they can be severed like
this and not seem to notice that, that's an interesting thing, Like,
what's the reason for this this connection? Second, how is
this possible? Like, how is it possible to cut a
brain in half and have it not seem to notice

(39:09):
anything's different and not behave much different? Indeed, I mean,
even in a light of everything we've talked about, it
seems it seems kind of impossible. It seems seems like
it's a like like like it's a magic trick, a
grotesque magic trick, but a magic trick in the west. Well,
maybe we should discuss a possible explanation for this after
a break, thank thank Alright, we're back. Okay, So we're

(39:31):
asking the question of how is it possible given these
split brain experiments where uh, you sever the corpus closum,
the two hemispheres of the brain are separated, and now
functions that are dominated by one hemisphere of the brain
or the other can can take place, can go on
independently without the other part of the brain seeming to
be aware and This even leads to stuff like the

(39:53):
right brain being aware of a piece of information that
motivates action. Like say you show the right brain a picture,
the left hand, which is mainly controlled by the right brain,
can draw a picture of that thing, and the left
brain doesn't know why it happened, and the person speaking
gives a maybe a made up explanation of where that
image came from. How is this kind of thing possible?

(40:14):
Gazanica explains it in terms of what he sort of
calls interpreter theory. The interpreter is the idea of the
part of your brain. Gazaniga thinks this is localized in
the left hemisphere that comes up with this contrived explanation
for why your your brain did something that it doesn't
actually understand. Uh. And we can know in many cases

(40:37):
that this explanation is bunk because we know where the
actual stimulus for the behavior came from. It was shown
to the other half of the brain that the speaking
part of the brain doesn't know about. And so Gazanica's
idea is that this interpreter function, its main role is
to create a sense of self, to sort of weave
an autobiographical narrative about the self that makes sense, even

(40:59):
if it makes sense in a completely false way, that
does not actually explain the real things that happened in
the real motivations for behavior. It just comes up with
post talk explanations for behaviors. And you know, this reminds
me of Um, I'm sure you've read about this before.
There's a metaphor that's often used. I don't know where
it comes from in the first place, but sometimes the

(41:21):
psychologist Jonathan Height invokes it of the elephant and the rider,
you know, to explain the conscious and unconscious brain. So
in the case of the unconscious versus the conscious brain,
the conscious mind is a person is like a person
riding on top of an elephant, and the elephant is
the unconscious mind. And the writer thinks they are driving,

(41:41):
steering the elephant around, but actually the elephant goes where
it wants, and the writer is just writing right there
along for the ride wherever the elephant goes. Nevertheless, the
writer will always be able to come up with some
explanation for why they meant to steer the elephant in
the direction it went right, Like oh yeah, yeah, I
actually wanted to go over to that mud hole and

(42:01):
get showered in mud because because I was hot and
the mud is cooling me off. Now. But in this scenario,
the elephant, of course is the one calling the shots,
actually right, I mean, yeah, elephants love mud holes right now.
Of course, not to be a stickler here to complicate
the issue, but you could have a mahoot in there.
I believe the term is is mahoot the individual who
who will sometimes stand to the side and using a

(42:25):
stick to touch different parts of the elephant, um naked
go where it needs to go. Oh well, we know
quite well that often the unconscious mind of a person
can be controlled by manipulation from the outside without the
rider being aware that they're not driving. I mean, think
about the ways people are are manipulated in their unconscious

(42:45):
drives and desires by advertising, by media, by drugs, by
so all of these things are the stick of the mahoot,
which I'm sure has a particular name that I'm not
aware of. And then the mahoot is it represents the
interests of corporations and governments and uh and religious groups, etcetera.

(43:06):
It's driving somebody's unconscious mind around while they think they're
the driver. I mean, no matter you know, the elephant
is going to be calling the shots. See whether it's
being manipulated or it's just following its nature. But either way,
the driver is always going to be able to come
up with the story saying, yeah, this is why we
went over here. I have planned it this way all along.
I wanted to buy this product. Now, this is a

(43:28):
kind of different case, But the analogy here is that
the talking, explaining, interpreting part of the left brain, according
to Gazaniga's theory, is making up stories about why the
now alien right brain does what it does, which, of course,
it still shares a body so it controls some of
the same limbs and stuff, when the interpreter really has

(43:50):
no idea why the other part of the brain did
what it did. Now, I think we should probably take
a minute to emphasize like the drawbacks and limitations of
split brain research. One of them is that, as riveting
as I feel like, this kind of thing is um
I think, for one thing, due to the necessity of
the small sample sizes and the unusual history of the

(44:11):
patients involved, this is the kind of research that's better
thought of as a jumping off point to inspire questions
and hypotheses that you should really try to prove through
other means if possible. Like a lot of modern neuroscientists
would probably say that you can learn more with more
confidence from brain imaging studies like f m R I
and stuff, then you can from a very small cohort

(44:33):
of people with calls. Otomy's right, right, But at the
same time that that may be true. But I do
think there's real value in these kind of experiments, specifically
mainly because you can see it, like you can see
the human behavior in reality. You can see the implications
of a strange discovery in neuroscience instantiated in the real world.

(44:55):
It's one thing to learn through fmr I. That's something
like different brain reach can function somewhat independently of one another,
almost as multiple brains within the same head that don't
understand what the other one is doing. You could probably
show that in some ways through fm R I, But
the split brain experiments show you the texture and the
drama of the experience of a real person dealing with

(45:18):
these facts about the brain. Other studies could probably find
ways of indicating this, but but it is I think
valuable how these experiments showed the experience of it right,
like you can actually see somebody in real time dealing
with the fact that they don't understand why their left
hand just did what it did. I was reading a
little a little bit about this. I ran across uh

(45:40):
some material written by a cognitive psychologist, Year Pinto, an
assistant professor at the Psychology department of the University of
Amsterdam in the Netherlands. And uh Pinto and their team
tested to split brain patients in to see if they
could respond accurately to objects in the left visual field
perceived by the right brain while also responding verbally or

(46:03):
with the right hand controlled by the left brain. And
Pinto uh Pinto also wrote about this in a piece
for Ian magazine as well. So Pinto and the and
and the team found that they could be that the
individual could perceive stimuli and presence in either side of
the visual field, but that they couldn't compare stimuli across
the midline of the visual field. When the stimulus appeared

(46:25):
in the left field, they were better at indicating its
visual properties attention, and when it appeared in the right
visual field, they were better at labeling it. So, you know,
coming back to a language, here's how Pinto summed it
up in Ian magazine. I just want to read a
passage from this because I think it it punctuates a
lot of what we're talking about here. Quote. Based on

(46:45):
these findings, we have proposed a new model of the
split brain syndrome. When you split the brain, you still
end up with only one person. However, this person experiences
two streams of visual information, one for each visual field,
and that person is unable to integrate the two streams.
It is as if he watches an out of sync movie,
but not with the audio and video out of sync. Rather,

(47:05):
the two UNSYNCD streams are both video. And there's more.
While the previous model provided strong evidence for materialism, split
the brain, split the person, the current understanding seems to
only deepen the mystery of consciousness. You split the brain
into two halves, and yet you still have only one person.
How does a brain consisting of many modules create just

(47:27):
one person? And how do split brainers operate as one
when these parts are not even talking to each other. Now,
this study, I think, does add some interesting nuance to
what we've been talking about before. One thing, I feel
like I don't maybe I'm just missing something. I feel
like Pinto is setting up this model as like, uh,
as like a counterpoint to the idea of of what

(47:49):
Spery and Gazzaniga discovered. But it seems actually to me
kind of in line with what they discovered, like the
idea that that our consciousness is very mysterious. I mean,
I think Spery Gazaniga would say that despite being able
to produce these behaviors that look from the outside like
as if they're from two different people. Uh, the experience
of the patient, as they've always reported, is that they

(48:11):
feel like a normal, whole person that nothing seems to
have changed to them, right. I think in both cases though,
it just you end up in this weird conundrum almost,
this paradox, this idea that the single person we feel
that we are is in some ways too And in
these cases where we see evidence of of seem to

(48:32):
see two evidence of what you could you know, call
two minds within one brain, they're still functioning as one.
They are still one. And so yeah, the paradox of
that which is one seems too and that which is
too seems one or more than two. Yeah, I mean
that we've got the two hemispheres of the brain but
remember that the hemispheres are each full of you know, modules,

(48:55):
and like they're full of millions of neurons and they're
that are working in different networks and jules to accomplish
different goals. And so I think one of the lessons
is that definitely different parts of the brain can behave
and generate behaviors independently. And somehow you are here and
you end up thinking I am a person. There's one

(49:15):
of me, but there's a lot of different independent stuff
going on inside whatever makes you. Yeah, I come back
to that Hunter S. Thompson Warren Yvon quote, you're a
whole different person when you're scared. Uh and in because
in some because in to some extent, as we've discussed,
you are a different person. You're at least a different
version of the person. Uh So, yeah, how many how

(49:37):
many us are there? Really? Well? I think we can
explore this more in the second episode, but this really
should give us some questions to think about, questions about
whether our idea of a person or a self is
really an accurate understanding of what brains are like, or
is it just a is it just a convenient illusion?

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