A vetrean of the Second World War, known only by his initials
W.J., suffered from a severe case of epilepsy. Worse, medication could not
stop his frequent and incapacitating seizures. There was, however, another
option: he could undergo a radical and newly conceived brain surgery. The
surgery would sever his *corpus callosum*, the tight bundle of neural
wiring that links the two hemispheres of one's brain. It was thought that
his seizures originated in one side of his brain and spread to impair the
other side. Severing the link would confine the seizure and prevent it from
impairing his entire brain. In 1961 W.J. elected to undergo this surgery
and by all accounts it was a succeess. His debilitating seizures were
eradicated. Yet, there were unanticipated side effects.
W.J. emerged from the surgery with his language and reasoning
abilities intact. But post-operative testing by Michael Gazzaniga, then a
graduate student under the neuroscientist Roger Sperry, revealed certain
deficits. Prior to the operation, Gazzaniga flashed images of various
objects in either the right or left area of W.J.'s visual field. Before the
operation, W.J. had no difficulty in identifying the objects regardless of
where in his visual field the image was presented. After the operation,
however, when an object was displayed to W.J.'s left visual field, he was
unable to say what he saw. When asked, he reported not seeing anything. It
seemed as though W.J. was blind in his left eye, but things were not so
simple.
After W.J. reported not seen anything, Gazzaniga asked him to
point out what he had just seen from a collection of objects. His hand
correctly pointed out the correct object. It seemed that part of W.J.'s
brain, a part that could not communicate verbally, possed the knowledge of
what was flashed on the left side. It had seen the object. These
experiments helped prove that visual stimuli received by one's left eye is
processed by the right hemisphere, and visual stimuli from the right eye is
processed by the left hemisphere. At the time it was known that each
hemisphere controlls muscles on the opposite side of the body, but a
similar reversal with visual processing was not known.
Later it was found that for most right-handed men the language
center of the brain is found predominently in the left hemisphere.
Left-handed men, and women, are more likely to have language capacities in
both hemispheres. This fact, together with the previous disoveries
regarding the reversal of motor control and perception fully explains
W.J.'s side effect. When the image was shown to his left eye only his right
hemisphere saw it. Lacking the ability to verbalize a response, the right
hemisphere remains mute when asked what it just saw. Yet the right
hemisphere is able to control the muscles on the left-side of the body.
Therefore his right hemisphere, using his left hand, could point out what
it has just seen. Later experiments by other "split-brain" cases lend
further confirmation to this explanation.
Thirty years after working with W.J., Michael Gazzaniga was
still studying split-brain cases. In one experiment involving a patient
named Joe, Gazzaniga flashed two different images simultaneously. The image
of hammer was shown on the right-hand side of the screen, while the image
of a saw was shown on the left. The exchange between Joe and Gazzaniga went
as follows:
Gazzaniga: "What did you see?"
Joe: "I saw a hammer."
Gazzaniga: "Just close your eyes, and draw with your left hand.
Just let it go."
With his eyes closed, Joe's left hand draws the image of a saw.
Gazzaniga: "That's nice, what's that?"
Joe looks at his drawing and answers "A saw."
Gazzaniga: "What did you see?"
Joe: "A hammer."
Gazzaniga: "What'd you draw that for?"
Joe: "I don't know."
This experiment makes clear that Joe saw both images, but his
experience is fractured. One half of his brain observed the hammer while
the other half observed the saw. It is as though two independent minds are
present in one skull. What was previously a singular consciousness is now
two. Another split-brain patient, Paul, helped demonstrate this.
Paul was unusual in that he possessed verbal capacities in both
his right and left hemispheres. This enabled each of his minds to be
interviewed concerning their thoughts, beliefs, and desires. When asked his
name, both hemispheres answered "Paul." When asked his location, both
answered "Vermont." But when asked what he wanted to be, his right
hemisphere answered "Automobile racer" while his left answered "Draftsman."
These experiments took place during the Watergate scandal, and so Paul's
opinion of President Nixon was queried. His right hemisphere expressed
"dislike" while his left hemisphere expressed "like." One wonders how Paul
would have voted. It might depend on which hand he used to pull the lever.
In addition to preferences, hemispheres can differ even on
fundamental beliefs. The neuroscientist Vilayanur Ramachandran recounted
the case of a patient with a right hemisphere that believed in God and a
left hemisphere that did not. Sometimes these conflicts manifest
physically. In a condition known as *alien hand syndrome*, split-brain
patients may find one hemisphere, and the limbs it controls, behaving
independently from and contrary to the will of the other. One patient
struggled to get dressed in the morning. While his left hemisphere (and
right hand) tried to pull his pants up, his left hand would pull them down.
On a separate occasion, this same patient became angry at his wife. His
left hand attacked her while his right hand tried to protect her!
Roger Sperry, who received a Nobel prize for his work on
split-brains, remarked "Although some authorities have been reluctant to
credit the disconnected minor hemisphere even with being conscious, it is
our own interpretation, based on a large number and variety of non-verbal
tests, that the minor hemisphere is indeed a conscious system in its own
right, perceiving, thinking, remembering, reasoning, willing, and emoting,
all at a characteristically human level, and that both the left and the
right hemisphere may be conscious simultaneously in different, even in
mutually conflicting, mental experiences that run along in parallel."
On Tue, Feb 3, 2015 at 12:01 AM, meekerdb <meeke...@verizon.net> wrote:
> I think "conscious" is ambiguous. From what I've read the two halves of
> the split brain are not both conscious in the sense of having an internal
> narrative; only one half is verbal. Both halves are conscious in the sense
> of processing information and influencing action - as my dog is conscious
> and Bruno's jumping spider are conscious.
>
> Brent
>
>
> On 2/2/2015 9:41 PM, Jason Resch wrote:
>
> What are your thoughts on split brains which develop two independently
> conscious minds?
>
> We're they always two minds, or do they become such when they can't
> communicate?
>
> Jason
>
> On Monday, February 2, 2015, meekerdb <meeke...@verizon.net> wrote:
> > On 2/2/2015 8:37 PM, Jason Resch wrote:
> >
> > You can no more assume those other parts of your brain are unconscious
> than you can assume other beings lack consciousness. You might even have
> solved it consciously but are amnesiac about it.
> >
> > Poincare's unconscious was pretty smart, it could prove theorems his
> consciousness couldn't. So JKC would say that proves his unconscious was
> conscious. I think that's what Bruno calls []f.
> >
> > I infer (not assume) other beings are conscious because they are very
> similar to me and act like I act when I'm conscious. Pieces of brain don't
> look much like me and they don't act like me.
> >
> > Brent
> >
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