Revealing the split-brain experiment and uncovering the mystery of the left and right brains

Left-handers are smarter, the left brain is good at analysis, and the right brain is good at processing images...

These words may be familiar to you.

But do they have any scientific basis?

Come, let me find out with you.

The concept of split-brain originates from the treatment of epilepsy.

The human brain is divided into left brain hemisphere and right brain hemisphere. This concept has become people's common knowledge in the era of the rise of anatomy.

The white matter band connecting the two hemispheres is called the corpus callosum (piǎn zhí tǐ). It contains 200 to 250 million nerve fibers and is the channel for communication between the left and right brains.

The brain will discharge during severe epileptic seizures. Cutting off the patient's corpus callosum can prevent the current from spreading between the two brain hemispheres, reduce the frequency of seizures and relieve seizure symptoms. This operation is generally successful, and the patient's behavior after surgery is normal in most circumstances. These epilepsy patients are called "split-brain people" because of the "separation" of the left and right brains. Because the corpus callosum is severed and the left and right hemispheres of the brain are independent of each other, the right side of the body in these split-brain people is mainly controlled by the left hemisphere alone, and the left side of the body is mainly controlled by the right hemisphere alone.

The leaders of split-brain research are American psychologist Roger W. Sperry (1913-1994) and his student Micheal Gazzaniga (1937~).

Sperry was the first to conduct experiments on animals. He once surgically severed the corpus callosum of a cat and changed its optic nerve so that the cat's left eye could only transmit information to the left hemisphere, and the right eye could only transmit information to the right hemisphere. After surgery, the cat behaved normally.

During the experiment, cover its right eye and let it learn a new behavior, such as walking through a small maze to find food. After the cat is able to pass the maze skillfully, release its right eye, cover its left eye, and put it into the maze again. At the beginning, it couldn't pass the maze. Its right brain had no memory of where to turn, and it had to start familiarizing itself with the entire maze again.

Sperry and Gazzaniga's split-brain experiments began in 1962. Four epilepsy patients whose corpus callosum had been surgically severed successively participated in their experiments.

This experimental project is mainly conducted from three aspects: vision, touch and hearing.

Sperry’s team used the following method to make information only project to the left or right visual field: the subject stared at a certain point, and then presented images, text or other information only in his left visual field. Make sure information is only delivered to the right hemisphere and not vice versa. To prevent subjects from peeking, each piece of information flashed by, lasting about a tenth of a second or less.

In one test, a row of light bulbs was arranged horizontally on a wooden board. The subjects sat in front of the board and were asked to stare at a light bulb in the middle. The researchers controlled the light bulbs to flash in sequence in their left and right visual fields. The subject verbally reported that only the light bulb on the right side of the board flashed.

Afterwards, the researchers flashed only the light bulb in the subject's left visual field, and the subjects said they saw nothing.

The light bulbs flashed again in the subjects' left and right visual fields, and this time the researchers asked them to point to the flashed light bulbs. Although they reported seeing only the lightbulb flash in the right field of view, they were able to point to all the lightbulbs that flashed in both fields of view.

In another experiment, the word "FACE" flashed rapidly in the subjects' right visual field, and they could accurately say the word they saw; when "FACE" was in the subject's left visual field, The vision flashed rapidly and they said: they saw nothing, but they could draw it with their left hand.

Also, when an image of a spoon was projected into the subjects' right visual field, they were able to pick out a spoon from a set of invisible objects with their left hand; when they held an object in their left hand ( out of sight), they can point to a card with the object's name on it, although they cannot name it or describe it.

These experiments show that:

1. Both the left and right hemispheres can recognize images and text information;

2. The language center is located in the left hemisphere ;

3. The right hemisphere cannot speak but can express through movements.

As the research deepened, Sperry's team discovered more functions of the right brain.

In one experiment, the researcher verbally asked the subjects to put their left hand into a bag mixed with different items that they could not see, and take out a specific item (a watch, a glass ball, a comb), they did not have the slightest difficulty.

Even if the researcher only describes a certain feature of the object and asks the subjects to find the object, they can find it accurately.

Gazzaniga gave an example: When the subjects were asked to use their left hand to find "the monkey's favorite fruit" in a bag filled with different plastic fruits, they took out one Bananas; when subjects were asked to use their left hand to find "something Sunkist sells a lot of," they pulled out an orange. However, when the same fruit was placed in the subject's left hand, they could not tell what it was.

This experiment shows that the right hemisphere of the brain can understand language and express it non-verbally.

In another experiment, a picture of an item (such as a cigarette) was shown to the right hemisphere of the subjects. They were allowed to touch 10 items behind the screen, but there was no cigarette inside, and they were asked to choose the best one. An object close to the picture - an ashtray. They successfully located the ashtray, but they were also unable to name or describe the object while holding the ashtray in their left hand.

This experiment shows that the right hemisphere is better at thinking and analyzing objects.

Researchers also revealed the emotional responses of the right hemisphere of split-brain patients.

While conducting a visual experiment, Sperry and Gazzaniga suddenly presented participants with a picture of a naked woman. For example, they projected this image onto the left hemisphere of a female patient's brain.

She laughed and was able to verbalize that it was a nude photo.

When the photo was later presented to the right hemisphere of her brain, she said, she saw nothing, but a sly smile flashed across her face and she began to giggle. When asked what she was laughing about, she said: "I don't know...it's nothing...oh, that machine is so funny".

Although the right hemisphere of the brain cannot verbally describe what it sees, they can still elicit emotional responses in the right hemisphere of the brain just as they can in the left hemisphere.

Have you noticed: There are more experiments on the function of the right hemisphere. Why does Sperry do this?

As early as 1836, brain scientist Dax clearly pointed out that the left hemisphere is related to aphasia.

Then French surgeon Broca dissected the brain of a patient who had suffered from aphasia for 30 years and found that an area on the left side of his brain was damaged.

Broca immediately published a paper, locating the human language mechanism in the left brain hemisphere, thus developing the logic that "the left brain hemisphere is the dominant hemisphere."

This idea has been continuously supported by other studies in the subsequent years.

*Note: The dominant hemisphere refers to the hemisphere that occupies a dominant position in human brain activity.

Almost everyone has confirmed a point of view: the left hemisphere is more intelligent and advanced, while the right hemisphere is a backward and low-level primitive brain.

This prejudice became the dominant view of the period.

Sperry’s team’s research on split-brain people directly subverted this concept, and it was like a thunder that resounded in the field of brain research.

Previous experiments have proven that the right hemisphere has advanced functions. This discovery also surprised Sperry and Gazzani.

They are curious, does the right hemisphere have any advantageous skills compared to the left hemisphere?

In one study, Perry and Gazzaniga found that the left hand performed better on visual tasks involving spatial relationships and shapes.

As you can see in the picture below, the left hand performs better when copying 3D images.

Original picture Picture drawn by the left hand Picture drawn by the right hand

Gazzaniga also designed another experiment that reflected the ability of the right brain.

He gave the subjects four blocks with six different patterns on each side and asked them to place them according to the model.

The left hand, which is controlled by the right brain, can always complete the task well, but the completion degree of the right hand is always unsatisfactory.

After that, Sperry's team designed a series of similar experiments for the left and right brains targeting different abilities.

In the end, Sperry proposed a new theory of lateralization of left and right brain functions, which was also his main contribution in winning the Nobel Prize.

All evidence shows that the two separate brain hemispheres have their own independent fields of consciousness, and each hemisphere has advanced psychological functions. When one hemisphere plays a major role in completing these functions, functional lateralization is considered to have occurred. Speech—the ability to produce complex language—may be the most highly lateralized of all functions. Neuroscientists have found that only 5% of right-handers and 15% of left-handers have language controlled by the right hemisphere; in addition, 15% of left-handers have language processing in both hemispheres.

Each hemisphere has its own style when it comes to processing the same information. The left hemisphere tends to be analytical: processing information bit by bit, such as speaking, logical reasoning, calculations, etc. The right brain hemisphere tends to have a holistic style: processing information from a holistic model, such as spatial relationships, artistic activities, intuition, etc. One should not assume that the left hemisphere is superior to the right, it is the combination of the left and right hemispheres that enriches your experience.

The theory of cerebral hemisphere functional lateralization proposed by Sperry breaks the previous mistaken view that the right brain is an appendage.

Gazzaniga and his students later conducted an interesting experiment.

They repeated the experiment of teaching the right brain to read, but this time, he asked the subjects to act on the information received by the right brain.

When Gazzaniga showed the word "wave" to the right side of the subject's brain, the subject waved.

Perhaps it was Gazzaniga's flash of inspiration that he decided to pose a problem to the subjects' left hemisphere, which was unclear about the situation. He asked the subjects to explain why they waved.

The subject hesitated for a moment and said that he waved because he thought he saw a friend.

This incident gave Gazzaniga a conjecture, and he designed an experiment again.

He asked the subjects to see a snow scene with their left eye and a chicken foot with their right eye, and then asked them to select a card related to the image they saw with each hand from a pile of cards. .

The subject picked a shovel for shoveling snow with his left hand, and a chicken with his right hand.

But this time the subject’s explanation was: they picked the chicken because they saw the chicken feet, and they picked the shovel because they wanted to use it to clean the chicken stable!

Gazzaniga immediately understood that the left brain not only has the ability to speak, but it is also a "storytelling brain."

Although the left brain cannot understand the information obtained by the right brain, it can guess the meaning of the right brain's behavior through the existing information.

Thinking: Are your thoughts true and objective? Could it be your left brain "telling stories"?

The article has a lot of knowledge points, I have sorted it out for you:

1. The split-brain experiment originated from the treatment of epilepsy, and Sperry and Gazzaniga led the split-brain experiment. Brain-human experiment;

2. There is no distinction between high and low levels between the left and right hemispheres, but there is an emphasis on specific functions. This is called lateralization of cerebral hemisphere functions.

3. The left hemisphere tends to be analytical - processing information bit by bit, such as speaking, logical reasoning, calculations, etc.;

4. The right hemisphere tends to In the overall division - processing information from a holistic model, such as spatial relationships, artistic activities, intuition, etc., the perception of vision, touch, hearing, and emotion is no different from the left hemisphere;

5. The associative ability of the left hemisphere may make our ideas inconsistent with the objective situation.

PS: Hello, I am studying "Forty Studies in Changing Psychology" and I will export the study articles of these studies to . Welcome to pay attention, let’s learn psychology together, practice it together, and grow exponentially together:)

References:

Roger Hawke, Forty Studies in Changing Psychology , Chapter 1 'One brain or two brains'

Gazzaniga,The split brain in man.

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Zimbardo, Grieg, Psychology and Life, P78-81