I just spent an hour composing this, only to have it inexplicably dissapear. So I'll try again.

When I was a kid, I used to wonder why I was me, why couldn't I experience others' perceptions, and why couldn't they experience mine. I also wondered if others had such thoughts, or if they were simply the deranged thoughts of a weird little kid.

Then today I read an article that made me think that I wasn't so weird after all. "Self-Serve Brains: Personal identity veers to the right hemisphere," by Bruce Bower, is a Science News Online article available only to subscrbers, so most of you won't be able to access it.

The article talks about how the sense of self seems to be centered in the right brain, how this sense can go wrong, and how it can be fooled.

People who have suffered brain damage may not recognize their friends or members of their own families. They may think they are someone else. They may think their doctors and nurses are their siblings, parents, or spouses.

One woman had a paralyzed arm as a result of a stroke. She was convinced the arm was no longer part of her body. She called it, "my pet rock."

Another man who lived half a world away from his family was convinced his paralyzed arm was not his, rather his brother's. His doctor asked him how it felt having his brother's arm. He replied in a chocked voice, "It makes me feel good. Having my brother's arm makes me feel closer to my family."

"Pinocchio illusion" and "Anarchic-hand syndrome" are two terms I learned from this article. The Pinocchio illusion was discovered and named by James R. Lackner of Brandeis University in 1988. He stimulated the wrist tendons of blindfolded people who were touching their noses. They became convinced that their noses were growing. This article reports on a variation of that experiment:

A young woman stands in neuroscientist J. Henrik Ehrsson's laboratory at London's University College and places her palms on her waist. Cuffs placed over her wrists begin to vibrate tendons just under the skin, creating the sensation that her hands are bending inward. At the same time, the woman feels her waist and hips shrink by several inches to accommodate the imagined hand movements. Dr. Ehrsson's illusory instant-waist-loss program lasts only about 30 seconds.

Ehrsson and his coworkers used a brain-imaging machine to measure blood flow in the brains of 24 people as they experienced this illusion. Parts of the left parietal cortex, located near the brain's midpoint, displayed especially intense activity as volunteers felt their waists contract, the scientists report in the December 2005 PloS Biology.

The greater the parietal response, the more waist shrinkage the individual reported.

The scientists suspect that the activated parietal areas integrate sensory information from different body parts, a key step in constructing an internal image of one's body size and shape. When the brain receives a message that the hands are bending into the waist, it adjusts the internal body image accordingly, Ehrsson's team hypothesizes.

The brain can adjust its internal body map in a matter of minutes, the experiment demonstrates. Researchers who similarly induced illusions of expanding fingers came to that same conclusion (SN: 7/30/05, p. 69: Available to subscribers at http://www.sciencenews.org/articles/20050730/fob5.asp).

You should be able to get the PloS Biology link. It gives this explanation under Discussion:

This illusion is elicited when the hands are in contact with the waist and the tendons of both hands are vibrated. Thus in this situation the brain receives conflicting sensory information from the vibrated wrists and the contact surfaces between the hands and waist. The input from the vibrated wrist muscles signals to the brain that the hands are flexing, whereas the tactile signals from the palms remained stable, signalling that the hands were in contact with the waist and hips. This conflict is resolved by recalibrating the size and shape of the waist and hips, so that it feels as if the waist/hip region is shrinking as the hands are bending inwards.

Anarchic-hand syndrome occured in people who had motor areas damaged on one side of the brain, leaving them unable to control the actions of the hand on the other side of the body. As one patient passed by doors, his errant hand would grab the doorknob. He'd have to pry it off with his good hand. Another man would try to soap up a washcloth in his right hand, while his left hand put the soap back in the soap dish.

Chris Frith, a neuroscientist at University College London, "suspects that anarchic-hand syndrome and schizophrenia's delusions of being controlled by others share a neural defect that makes it seem like one's movements occur passively. However, people with schizophrenia mistakenly perceive the passive movements as having been intentional."

I don't really understand that last part very well.

Comments?

Tinman

This message has been edited. Last edited by: tinman,

Tinman, how interesting! I haven't heard of either of these, though I know that many strange consequences can occur from brain damage. I was able to access 2 of your 3 links, and they were just fascinating. The discussion of schizophrenics as analyzing movements to a greater extent than mentally healthy people was interesting, as was the discussion of whether there is really a sense of self, or Freud's ego, in the brain.

There was a mention of people who have had limbs amputated and how they can feel that limb. We call that phantom pain, though it's really not a pain. I have seen that with patients, and it's quite eery.

BTW, I found this interesting Wikipedia article on anarchic hand syndrome. The cultural references at the end I thought were good.

This message has been edited. Last edited by: Kalleh,

Thanks for that link, Kalleh. I'd never heard of those before today, either. Anarchic-hand syndrome in the artcle I cited sounded incredible and extremely frustrating for the victim, but not dangerous. However, the Wikipedia article on Alien Hand Syndrome (AHS - another name for Anarchic-hand syndrome) you cited sounds downright scary.

Here's an article from the Pennsylvania Gazette which talks about a woman who woke up at night to find her left hand choking her. This was from a 1908 study in Germany.

The Happy Hippy thinks the two sides of the brain each have a separate personality. The differences in these personalities show up occasionally in normal people, but rarely cause a major problem. In people with schizophrenia or brain damage, through, the dissociation between the two halves of the brain, and the personalities, is greater and potentially dangerous. Scary stuff.

Some of the stories, though frustrating and scary to the victims, are funny to read about, especially this one.

Tinman

This message has been edited. Last edited by: tinman,

Sorry, didn't mean to do that, I'm just not in my right mind today.

or

I'm of two minds on this subject.

Fascinating.

I'm reminded of Oliver Sacks's books, such as "The Man Who Mistook His Wife For A Hat," and "Awakenings." While Sacks investigated different brain anomalies, there are similarities.

Science fiction has long considered "empaths," those who could, as Slick Willie Clinton said, "feel your pain."

I wonder if similar parts of the brain are responsible for normal feelings of empathy.

Perhaps this is irrelevant, but there may be a developmental aspect here.

Fill a familiar cereal box and fill it with ribbons, show it to a young child and ask, "What is in this box?" He will answer, "Breakfast," or, "Food." You then open the box, and show him the real contents, and close it and ask again, "What is in this box?" He'll remember his newly learned knowledge and say, "Pretty ribbons."

But now ask, "What would John say if I asked him what's in the box?" A young child will still answer, "Pretty ribbons." He is unable to distinguish "what I know" from "what other people know". That ability doesn't come until a certain age (3? 4?).

Interestingly, intelligent animals (monkeys, apes) have this ability.

Wordnerd, would this have anything to do with the concept of object permanence? Young humans don't get this connection until much later than chimps or gorillas, from what I've read. This is where the fun comes from in "peek-a-boo" games with little kids. When they can't see someone, they're gone!