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When it comes to blindness, people generally think that blind people can't see anything. What is shocking is that some blind people can actually "see", but they just don't realize it. The scientists who discovered this phenomenon were questioned at first, but now it has been accepted by most researchers.

Let's take a look at this video first.

The blind man (light-colored trousers) can "see" and avoid obstacles. (photo source: doi.org/ 10.1016 / j.cub.2008.11.002) there seems to be nothing wrong with this video, isn't it just a person bypassing the sundries in the room? But you should know that the man who can get around the obstacle is blind, and this video was filmed by his researchers.

How is it possible that the blind can see?

Yes, not only you, but even the blind man himself thought it incredible, because he really didn't "see", but just walked with an unspeakable feeling.

If the researchers hadn't filmed the video, conducted detailed research, and published the results in top journals, I believe many people would have thought this was bullshit.

It starts with how the blind man went blind.

(photo source: wikimedia) the blind man, who goes by the pseudonym TN, is actually a doctor from Burundi, Africa. Before he went blind, he worked for the World Health Organization in Switzerland. In 2003, TN, who was in his early fifties, suffered two strokes in just a few weeks.

The two strokes completely destroyed the visual cortex, the part of his brain responsible for "seeing". Although his eyes and other brain areas were not injured, he went blind because the "graphics card" in his brain was broken.

The pathway between the visual cortex and the eyeball. (photo source: see watermark) TN went to the affiliated hospital of the University of Geneva in Switzerland, where he met researcher Alan Pegna. Pegna did a lot of experiments for TN. He was surprised to find that although the blind man was blind, he could read the frightened expression in the picture and showed fear like ordinary people.

Pegna published this magical phenomenon. Beatrice de Gelder, a neuroscientist at Harvard University and the University of Tilburg in the Netherlands (Tilburg University), saw the study and found it so interesting that she invited TN to fly to the Netherlands in 2007 to participate in her research.

(photo Source: wikimedia) at first, walking the maze of obstacles was not part of the experimental plan. One day, however, careful researchers found that TN could actually avoid obstacles, so he came up with the bold idea of walking through the maze of obstacles.

TN himself initially rejected this experiment of "touching the elephant for the blind". "at first he was nervous and didn't know what to do, because he was blind after all," de Gelder recalled. But then he agreed. It turned out that he could actually bypass the dustbins, tripods, a stack of paper and several boxes in the room.

Is it possible that TN is not actually blind?

To make sure he really can't see, the researchers gave him a lot of brain imaging and matching experiments. The results showed that there was no vision-related activity in his visual cortex. The researchers also point out that there is no evidence that the blind man can look around through echolocation like a bat.

De Gelder laboratory nuclear magnetic resonance imaging experimental equipment. (photo source: see watermark) there is only one possibility left, that is, his brain sees it, but his mind does not see it.

Whatever the reason, this is the first time that researchers have found that people with completely damaged visual cortex still have visual ability. This ability is called Blindsight, and the study was published in the 2008 issue of Current Biology. In the same year, Nature also reported on this strange phenomenon.

So why on earth can TN be "blind"?

The current mainstream theory is related to an ancient visual system in the human brain.

I just said that the "video card" of TN's brain is completely dead. this "graphics card" is located in the occipital lobe, the back of the head, which is called the primary visual cortex (or striate cortex).

Primary visual cortex (red) (photo source: wikimedia) however, there are two "graphics cards" in mammals, in addition to the more advanced one above, there is also an original one. This low-equipped "graphics card" is common to all vertebrates, including fish, amphibians and reptiles. It is located in the optic tectum (optic tectum) of the midbrain and can also receive signals from the retina.

Mesencephalon (red) (photo: physiopedia) the optic tectum is one of the most conservative "hardware" in vertebrate brains, both in primitive vertebrates (such as lampreys) and humans. Because the function is too basic and hard core, all vertebrates have not eliminated it.

What is the function of the visual top cover?

With the help of internal landmark-recognizable location cells (Place cell), head orientation cells (head-direction cells) that can track the orientation of the head, and boundary cells (border cells) that recognize boundaries, the optic tectum can help vertebrates hunt, escape and turn their heads.

The optic parietal cover of the tadpole (referred to by the pink ball) causes it to evade. (photo source: blogs.brown.edu/ aizenmanlab / projects/) however, different vertebrates have different degrees of dependence on the optic tectum. Richard Held, a professor of brain science at the Massachusetts Institute of Technology, points out that in lower mammals, the midbrain visual system plays an important role. Small movements on the optic roof can even manipulate some simple vertebrates, such as zebrafish, to make them hallucinate.

Zebrafish are more primitive than humans, and their behavior is dominated by the optic tectum. (photo: wikimedia) primates that are nearly human in evolution are not completely manipulated by the optic tectum, but can also navigate through blindness.

This was confirmed by a classic study in 1965. In this experiment, Lawrence Weiskrantz, a psychologist at the University of Cambridge, and colleagues removed the primary visual cortex of Helen, a macaque. Helen couldn't see anything after the operation.

Helen, a blind macaque, can avoid obstacles and pick up food. (photo: Nicholas Humphrey) Nicholas Humphrey, who was involved in the study at the time and later became a professor of psychology at the London School of Economics, was surprised that he did not believe that the optic tectum had no effect on mammals, so he continued to experiment with Helen.

In his interaction with Helen, he found that Helen could accurately remove food from his hands and even touch his flashlight. Seven years after the operation, Helen was able to bypass the obstacles and grab peanuts on the ground as shown in the video.

Helen, a blind macaque, can "see" food. (photo source: Nicholas Humphrey) Weiskrantz found it very interesting. Later, he found a blind man under the pseudonym DB. In this patient, the visual cortex of the left hemisphere was partially damaged, so he could not see the right visual field (the left hemisphere corresponds to the right visual field, and the right hemisphere corresponds to the left visual field).

For patients who are blind on one side, the researchers usually give different information to their different horizons. (photo source: see watermark) DB thought he couldn't see anything in the right field of view, but Weiskrantz asked him to guess. Surprisingly, DB's blind guess rate reached 100%, which even surprised him.

In 1973, Weiskrantz named this phenomenon of visual perception, or "seeing" by the blind, in the absence of visual cortex processing, as blindness for the first time in the literature. At first, however, blindness was controversial, but with more and more cases, no one will doubt its existence now.

So, can normal people also be blind?

De Gelder believes that ordinary people also have the ability to be blind, but we just don't realize it. In a 2010 review published on Nature Reviews Neuroscience, De Gelder and colleagues explained that because of the existence of the optic tectum, healthy people can actually unconsciously surge in emotion about what they see.

Blindness may be the "sixth sense" that we have been ignoring.

It lets the heart see, but the heart does not see it.

Cover source: pxhere

Reference:

Https://docs.qq.com/doc/DVHNTT1ZseWpuenV4

This article comes from the official account of Wechat: take Science Home (ID:steamforkids), write | Seven Jun

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