﻿Imagine that you are a doctor in the distant future.
You have a patient that needs urgent attention. You soon realize that you cannot save the
patient’s body. It is beyond repair. Will this person soon be gone forever?
Well, our brains hold all our memories. Every emotion and every desire is contained within it.
What is a person if not a brain? Being the good doctor you are,
you take extreme measures to save your patient’s brain. You transplant it into a healthy volunteer.
Of course, a good doctor would never kill a healthy patient on purpose. So, when the
operation is complete two perfectly and completely connected brains now share a single body.
What does it feel like to be two minds in one body?
Is it complete chaos as two separate people battle for control? Or is the result a brand-new person?
This thought experiment is fiction. But split-brain patients are not.
And their experience demonstrates that we each might be two people occupying a single body.
Are you even real? The narrator’s personal opinion awaits you in the outro of this video. But until
then enjoy some interesting science history. Callosal Syndrome
The brain is composed of two hemispheres. Normally they are connected by a structure
known as the corpus callosum. Callosal Syndrome, also known as
split-brain syndrome, occurs when the corpus callosum is severed either completely or
partially. When surgeons cut the tissue on purpose the procedure is called a callosotomy.
Why would doctors permanently sever connections in the brain? The answer is epilepsy.
Some of those who suffer from epilepsy have extremely violent seizures. The only
effective treatment is to prevent the two halves of the brain from communicating with each other.
The lack of communication means the seizures cannot spread and are reduced in severity.
The good news is this treatment works. In many cases the patient’s health is greatly improved.
It isn’t uncommon for recipients of a callosotomy
to no longer require medication to manage their condition.
Drugs to prevent epileptic seizures can also have some nasty side effects. Vomiting, tremors,
weight gain, hair loss, and depression are a few that might be experienced. It isn’t hard to see
why patients suffering from this condition might be willing to undergo brain surgery.
Surgically severing the brain can cause its own set of strange side effects.
Once the two hemispheres are separated, they each have their own perceptions and impulses.
In most cases if the two are in conflict one hemisphere will establish dominance. Sometimes
they can’t agree, and the results are disturbing. One patient found his hemispheres were in constant
conflict. When he would try to dress himself in the morning one hand would
try to pull his pants up. The other hand would immediately try to pull them down.
One half of the patient’s brain also didn’t like his wife very much.
His left hand grabbed her and shook her violently. The right hand came to her rescue.
How did doctors discover this? What made them think cutting a brain in half was a good idea?
Brain Research It became apparent to
researchers in the 1950s that certain parts of the brain seemed to be connected to certain functions.
Most of this was discovered by studying people who had suffered brain injuries.
Doctors noticed that patients with damage to two specific regions of the left hemisphere
usually lost their ability to speak.
So, they became interested in figuring out which parts of the brain mapped to certain abilities.
Most of the early research in this area was performed by Roger
Sperry and his colleague Michael Gazzaniga. Roger Sperry began by studying animals.
By the 1960s he and Michael focused on split brain patients instead.
They wanted to know if each half of the brain had special abilities. Or could they function
independently. Furthermore, did people with split brains have any mental deficiencies?
Results of “The Split Brain in Man” experiment were published in Scientific American in 1967.
It contained the results of experiments the two scientists carried out on split brain patients.
The first important observation was that most patients didn’t show any change in
temperament or intelligence after the surgery. In terms of having a normal
conversation it was impossible to tell that the person’s brain was split in two.
Three tests were created to evaluate how the patients were functioning. The tests were visual,
tactile, and auditory. The main goal was to test each half of the brain independently.
The left hemisphere of the brain usually controls the right side of the body,
and the right hemisphere controls the left side of the body. The experiments were designed
around this. For example, they might show an image to only the right eye of the patient.
Then they would ask the patient to write down what they saw with the right hand.
The right hand was connected to the left eye and wasn’t aware of the image.
In most cases, the patient could only speak about something if the left hemisphere of the brain saw
it. Likewise, the right hemisphere could write information about something it saw while the
patient claimed to have no knowledge of it. The inescapable conclusion seemed to be that
after cutting a brain in half, both halves of the brain are conscious and aware.
Born This Way Although early research
focused on patients who had undergone surgery, some split-brain patients occur naturally.
The corpus callosum forms during the third trimester of pregnancy.
There are several risk factors that can cause birth defects.
Drugs, alcohol, and viral infections are some of the more common ones. Some of these defects
can prevent the connective tissue between the brain hemispheres from forming at all.
Children that are born with this condition may have other brain abnormalities as well.
If those are not present, then the physical structure of their
brain resembles that of split-brain patients who have undergone surgery.
There are some common problems that those born without a corpus callosum experience.
Problems with coordination are common, as well as trouble relating with other people
and separating fact from fiction. There is some overlap with the symptoms for autism.
Testing found that unlike patients who undergo surgery to separate the two halves of the brain,
children’s brains are much better at compensating.
Tests on these patients demonstrated that there are low level connections between the hemispheres.
Scientists aren’t sure how it is happening, but they clearly share
information between the brain hemispheres. Children born with separated brains form new
connections as they develop. Adults whose brains are separated seem unable to do the same.
Hemispherectomy When trying to determine if
each half of the brain is conscious, there is a more direct way to answer the question.
Finding people that only have half a brain simplifies matters greatly.
In some cases, the only way doctors can save a patient is to remove half of the brain. In the
past this was sometimes done to address problems with seizures. For these cases simply severing
connective tissue wouldn’t fix the problem. The results are amazing and perhaps disturbing.
In 1996 Christina Santhouse, who was then eight years old, underwent a hemispherectomy
because she was having around 150 seizures per day. Incidentally, the doctor that performed
the operation on her was Ben Carson. The medical community informed Christina’s
family that she would probably never be able to live a completely normal life.
Driving a car, having a normal job, or even living unassisted may be impossible.
She surpassed expectations in almost every way. Christina went on to earn
a Master’s degree in speech pathology. She even married and had children of her own.
Children’s brains are very malleable even into adolescence.
In 1987 14-year-old Aha Israfil suffered a gun related accident.
The firearm discharged into his brain taking out most of the tissue on the right side.
Doctors had to remove that part of his brain and didn’t expect him to survive.
Imagine their surprise when he started trying to speak after waking up from surgery.
Although he had to use a wheelchair, Aha Israfil regained most of his abilities.
He acquired a degree and appeared on various television shows. Unfortunately,
he did pass away in a nursing home in 2019. Both patients demonstrate quite clearly
that only half a brain is needed to create a fully conscious human being.
Deficits Although it only takes half a brain to function,
it turns out that natural selection developed two brain halves for a reason.
A significant amount of research over the past few decades has been dedicated to finding out
if the abilities of split-brain patients differ significantly from their whole brain counterparts.
The evidence seems to indicate that split brain patients are diminished in some important ways.
For example, those with altered brains appear to have memory problems. Tests on these patients
indicate that by itself each hemisphere isn’t great at forming new memories. Researchers think
the connections between brain hemispheres might be necessary for efficient memory formation.
Also, each hemisphere of the brain appears to have different ways of paying attention.
The right hemisphere is better at rotating images in the mind whereas the left is better at creating
new images. There is a similar disparity concerning spatial awareness. When the two
hemispheres are unable to communicate then they are no longer able to combine these functions.
In one split brain patient researchers even found that one half of the brain was good
at subtraction, multiplication, and division. But the other half was good at addition. So,
it appears that both parts of the brain must work together to be good at math.
Those who are living without a corpus callosum can function just fine in day-to-day life.
But there will always be some things that they can’t do.
The fact that people with separate brain hemispheres are still conscious and still
have a sense of identity says something interesting about conscious experience.
Your conscious awareness is mostly a function of the present.
If you have enough functional brain tissue, then you will always feel like the inner “you” is still
there. Or to be more specific, if one half of your brain survives you are still in there somewhere.
But if two halves of the brain are still alive and thinking and they both feel like they are “you”,
which one is right? Is there a real “you” in there?
We don’t have the answer for you. What we can say is that if you have a choice,
try to keep both hemispheres of your brain. Side note from the narrator: Personally,
I don’t think you’re any more real than I am, and I’m a fictional character brought
to life by a voice actor & some guy with really expensive software. Taking some of
the antiquated metaphysics with a grain of salt, I’m partial to Theravada Buddhism’s
practical commentary on the self and how to make use of it during a brief human life.
What do you think about split brain patients and the elusive nature of consciousness?
We’ll accept comments below from either hemisphere of your brain.
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