nature_wonder (nature_wonder) wrote,

В поисках своего тела

Your own body is a phantom, one that your brain has temporarily constructed purely for convenience.
-- V.S. Ramachandran (1, 2, 3)

Проблема выделения себя из окружающего пространства (первый шаг к развитию «я») непосредственно увязана с ощущением собственного тела. Какими бы привычными, устойчивыми и объективными ни казались человеку его границы, они «очерчиваются» мозгом в реальном времени и могут быть сенсорно изменены буквально за десятки секунд. Элементарно, путем прикосновений и постукиваний, можно, к примеру, «вынести» нос на полметра или распространить ощущение собственного тела на к.-л. предмет.

В книге Phantoms in the Brain (1998) V.S. Ramachandran рассказывает, как этого может добиться в домашних условиях любой желающий.

The experiments I've discussed so far have helped us understand what is going on in the brains of patients with phantoms and given us hints as to how we might help alleviate their pain. But there is a deeper message here: Your own body is a phantom, one that your brain has temporarily constructed purely for convenience. I know this sounds astonishing so I will demonstrate to you the malleability of your own body image and how you can alter it profoundly in just a few seconds. Two of these experiments you can do on yourself right now, but the third requires a visit to a Halloween supply shop.

To experience the first illusion, you'll need two helpers. (I will call them Julie and Mina.) Sit in a chair, blindfolded, and ask Julie to sit on another chair in front of you, facing the same direction as you are. Have Mina stand on your right side and give her the following instructions: "Take my right hand and guide my index finger to Julia's nose. Move my hand in a rhythmic manner so that my index finger repeatedly strokes and taps her nose in a random sequence like a Morse code. At the same time, use your left hand to stroke my nose with the same rhythm and timing. The stroking and tapping of my nose and Julia's nose should be in perfect synchrony."

After thirty or forty seconds, if you're lucky, you will develop the uncanny illusion that you are touching your nose out there or that your nose has been dislocated and stretched out about three feet in front of your face. The more random and unpredictable the stroking sequence, the more striking the illusion will be. This is an extraordinary illusion; why does it happen? I suggest that your brain "notices" that the tapping and stroking sensations from your right index finger are perfectly synchronized with the strokes and taps felt on your nose. It then says, "The tapping on my nose is identical to the sensations on my right index finger; why are the two sequences identical? The likelihood that this is a coincidence is zero, and therefore the most probable explanation is that my finger must be tapping my nose. But I also know that my hand is two feet away from my face. So it follows that my nose must also be out there, two feet away."

I have tried this experiment on twenty people and it works on about half of them (I hope it will work on you). But to me, the astonishing thing is that it works at all—that your certain knowledge that you have a normal nose, your image of your body and face constructed over a lifetime should be negated by just a few seconds of the right kind of sensory stimulation. This simple experiment not only shows how malleable your body image is but also illustrates the single most important principle underlying all of perception—that the mechanisms of perception are mainly involved in extracting statistical correlations from the world to create a model that is temporarily useful.

The second illusion requires one helper and is even spookier. You'll need to go to a novelty or Halloween store to buy a dummy rubber hand. Then construct a two-foot by two-foot cardboard "wall" and place it on a table in front of you. Put your right hand behind the cardboard so that you cannot see it and put the dummy hand in front of the cardboard so you can see it clearly. Next have your friend stroke identical locations on both your hand and the dummy hand synchronously while you look at the dummy. Within seconds you will experience the stroking sensation as arising from the dummy hand. The experience is uncanny, for you know perfectly well that you're looking at a disembodied rubber hand, but this doesn't prevent your brain from assigning sensation to it. The illusion illustrates, once again, how ephemeral your body image is and how easily it can be manipulated.

Projecting your sensations on to a dummy hand is surprising enough, but, more remarkably, my student Rick Stoddard and I discovered that you can even experience touch sensations as arising from tables and chairs that bear no physical resemblance to human body parts. This experiment is especially easy to do since all you need is a single friend to assist you. Sit at your writing desk and hide your left hand under the table. Ask your friend to tap and stroke the surface of the table with his right hand (as you watch) and then use his hand simultaneously to stroke and tap your left hand, which is hidden from view.

It is absolutely critical that you not see the movements of his left hand as this will ruin the effect (use a cardboard partition or a curtain if necessary). After a minute or so, you will start experiencing taps and strokes as emerging from the table surface even though your conscious mind knows perfectly well that this is logically absurd. Again, the sheer statistical improbability of the two sequences of taps and strokes—one seen on the table surface and one felt on your hand—lead the brain to conclude that the table is now part of your body. The illusion is so compelling that on the few occasions when I accidentally made a much longer stroke on the table surface than on the subject's hidden hand, the person exclaimed that his hand felt "lengthened" or "stretched" to absurd proportions.

Both these illusions are much more than amusing party tricks to try on your friends. The idea that you can actually project your sensations to external objects is radical and reminds me of phenomena such as out-of-body experiences or even voodoo (prick the doll and "feel" the pain). But how can we be sure the student volunteer isn't just being metaphorical when she says "I feel my nose out there" or "The table feels like my own hand." After all, I often have the experience of "feeling" that my car is part of my extended body image, so much so that I become infuriated if someone makes a small dent on it. But would I want to argue from this that the car had become part of my body?

These are not easy questions to tackle, but to find out whether the students really identified with the table surface, we devised a simple experiment that takes advantage of what is called the galvanic skin response or GSR. If I hit you with a hammer or hold a heavy rock over your foot and threaten to drop it, your brain's visual areas will dispatch messages to your limbic system (the emotional center) to prepare your body to take emergency measures (basically telling you to run from danger). Your heart starts pumping more blood and you begin sweating to dissipate heat. This alarm response can be monitored by measuring the changes in skin resistance—the so-called GSR—caused by the sweat. If you look at a pig, a newspaper or a pen there is no GSR, but if you look at something evocative—a Mapplethorpe photo, a Playboy centerfold or a heavy rock teetering above your foot—you will register a huge GSR.

So I hooked up the student volunteers to a GSR device while they stared at the table. I then stroked the hidden hand and the table surface simultaneously for several seconds until the student started experiencing the table as his own hand. Next I bashed the table surface with a hammer as the student watched. Instantly, there was a huge change in GSR as if I had smashed the student's own fingers. (When I tried the control experiment of stroking the table and hand out of sync, the subject did not experience the illusion and there was no GSR response.) It was as though the table had now become coupled to the student's own limbic system and been assimilated into his body image, so much so that pain and threat to the dummy are felt as threats to his own body, as shown by the GSR.

If this argument is correct, then perhaps it's not all that silly to ask whether you identify with your car. Just punch it to see whether your GSR changes. Indeed the technique may give us a handle on elusive psychological phenomena such as the empathy and love that you feel for a child or spouse. If you are deeply in love with someone, is it possible that you have actually become part of that person? Perhaps your souls—and not merely your bodies—have become intertwined.

Now just think about what all this means. For your entire life, you've been walking around assuming that your "self" is anchored to a single body that remains stable and permanent at least until death. Indeed, the "loyalty" of your self to your own body is so axiomatic that you never even pause to think about it, let alone question it. Yet these experiments suggest the exact opposite—that your body image, despite all its appearance of durability, is an entirely transitory internal construct that can be profoundly modified with just a few simple tricks. It is merely a shell that you've temporarily created for successfully passing on your genes to your offspring.


Сенсорно-моторный гомункулус Пенфилда – представительство частей тела в коре головного мозга.

Photograph taken at the London Natural History Museum

P.S. Phantoms in the Brain – выдающаяся книга выдающегося специалиста. Яркость и доступность изложения сочетаются у Рамы с научной строгостью и глубиной анализа. Настоятельно рекомендую всем интересующимся работой мозга и сознания. Подобных книг мало. [Скачать]


Foreword by Oliver Sacks, M.D.


Chapter 1: The Phantom Within
Chapter 2: "Knowing Where to Scratch"
Chapter 3: Chasing the Phantom
Chapter 4: The Zombie in the Brain
Chapter 5: The Secret Life of James Thurber
Chapter 6: Through the Looking Glass
Chapter 7: The Sound of One Hand Clapping
Chapter 8: "The Unbearable Likeness of Being"
Chapter 9: God and the Limbic System
Chapter 10: The Woman Who Died Laughing
Chapter 11: "You Forgot to Deliver the Twin"
Chapter 12: Do Martians See Red?

Upd. появился перевод благодаря zhezhera
Tags: books, brain, human, images, neuroscience

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