Simplified Flow-Chart of a
Split-Brain Experiment
as carried out by
Sperry and Gazzaniga
In the 1960s, patients with severe epileptic seizures
sometimes underwent a surgical procedure that had
been found to allay the problem. During the
surgery, the connection between the two cerebral
hemispheres was removed.
When the band of nerve tissue between
the two cerebral hemispheres,
called the corpus callosum, was cut
through, all communication between the
two hemispheres of the brain was severed.
corpus callosum
Oddly enough, the patients were able to
live quite a normal existence after
undergoing this daring and risky surgery.
Furthermore, their problems with
epileptic seizures were dramatically
reduced.
In a series of ingenious studies with
these patients, Sperry and his
colleague, Gazzaniga, discovered
many then unknown details about the
functions of the two hemispheres.
left visual
field
right visual
field
The patient was
asked to focus on
a dot in the
middle of a
screen set up in
front of him or
her.
A word, picture
or even a
mathematical
sum was
shown on one
side of the dot.
I see an
apple.
In this case, the
information
about the apple
displayed in the
right visual field
would be relayed
to the left
hemisphere.
The patient
could name the
object, just as
one would
expect.
When an object
was displayed in
the left visual
field, the
corresponding
visual information
was relayed to the
right hemisphere.
Yet this time, the
participant could
not name what was
displayed and was
not consciously
aware of having
seen anything at
all.
I
don’t see
anything.
The left side of the
brain is
responsible for
speech. The
“mute” right side,
unable to
communicate with
the left side, could
not form the
required words.
I
don’t see
anything.
s
p
e
e
c
h
n
o
c
o
m
m
u
n
i
c
a
t
i
o
n
Yet the participant,
using his left hand,
which was
controlled by the
right hemisphere,
was able to…
… reach behind
the screen and…
…select the object
he had actually
seen, despite
having no
conscious memory
of it!
In another
variant of the
experiment,
the patient was
able to draw
the object with
his left hand.
In this way, the split-brain patients,
through the medium of Sperry and
Gazzinaga’s creative experiments,
were able to reveal a great deal
about hemispheric specialisation in
the human brain.
Useful Links
Video of a Split-Brain Experiment
https://www.youtube.com/watch?time_continue=3&v=ZMLzP1VCANo
Description of the Split-Brain Experiments and Game
at Nobelprize.org
http://www.nobelprize.org/educational/medicine/split-brain/
background.html
http://www.nobelprize.org/educational/medicine/split-brain/
splitbrainexp.html
Description of the Split-Brain Experiments at
Neuroscience for Kids
https://faculty.washington.edu/chudler/split.html