When the brain says don't get too close

chas smith R.I.P. · Post by **chas smith R.I.P.** » 13 Jul 2004 4:41 pm

When the Brain Says, Don't Get Too Close;

July 13, 2004
By SANDRA BLAKESLEE

A century ago, neurologists noticed that when ladies
wearing big feathered hats ducked through entryways, they
would align their bodies just so. It was as if they could
feel the tops of doors with the tips of the feathers.

From this and other observations, the scientists concluded
that each person holds within the brain a mental
representation of the body and its parts - even the
clothing it wears - as it moves through space.

Those early scientists could not explain how the brain
creates such sensations, or body schemas. But using modern
methods for probing brains, researchers are uncovering the
cells and circuits that are responsible.

For example, research has found that brain cells become
active as objects approach the space around the body. These
cells will fire when, say, you see an insect fly toward
your face. This so-called peripersonal space extends to
arm's length; people with longer arms have a bigger
peripersonal space. And when they use a tool, a rake, a
joystick or an automobile, their body schema and
peripersonal space expand to include it.

Moreover, perceptions change as the body schema changes in
response to outside stimuli. A hill looks steeper when you
wear a backpack than when you do not.

The findings, from laboratories worldwide, offer
tantalizing biological explanations for many phenomena,
including anorexia and syndromes in which stroke patients
neglect one side of the body. They may explain why people
are sucked into video games, and even why drivers get so
upset when their car is dented.

"To act efficiently, we need to locate objects in the space
around our bodies," said Dr. Angelo Maravita, a psychology
professor at the University of Milan. "We need to hold a
constantly updated report on the body's shape and posture."

The new research draws on the principle that the brain
forms internal maps of the external world; groups of cells
hold mental models of everything a person sees, hears,
feels and knows. The brain also forms a mental map of the
body itself. Clumps of brain tissue represent each hand,
foot, trunk or lip. If someone touches your hand, cells in
the brain's "hand area" become active.

Neurons respond to both vision and touch in at least six
brain areas. For example, a cell will fire when the right
hand is touched, or when the person sees an object moving
toward it. The closer the object, the faster the cell
fires.

Such cells encode the space around the body, within arm's
reach. It is as if you walked around in your own private
soap bubble. But the brain also has cells to map space
farther away.

Dr. Atsushi Iriki, a cognitive neuroscientist at the Riken
Institute in Japan, was one of the first to explore body
schema using modern techniques. He inserted single
electrodes into monkey brains and identified single cells
that responded to both a touch on the hand and visual space
next to the hand. Then he gave the monkeys a rake and for
three weeks trained them to pull in food pellets with the
tool. After training, he found that the cells that
represented the hand and arm, as well as space around the
arm, changed their firing pattern to include the rake and
the space around it.

The moving tool was incorporated into the monkey's body
schema, Dr. Iriki said. When the monkey held the tool
passively, its body schema shrank to normal size.

In another experiment, Dr. Iriki allowed the monkeys to see
a virtual hand on a video monitor while the monkey's real
hand, hidden from view, operated a joystick. When he made
the image of the hand larger, the monkey's brain treated
the virtual hand as if it were an enlarged version of its
own; the brain's hand area blew up like a cartoon
character's hand. When he put the image of a spider or
snake on the screen and made it approach the image of the
hand in the monitor, the monkey suddenly retracted its own
hand.

These neurons may constitute the neural basis of a person's
feeling a sense of reality when playing video games, Dr.
Iriki said. People say they can feel the joystick touching
objects in the monitor as they extend their bodies into far
space.

Stroke patients who neglect one side of their body also
reveal changes in body maps. Dr. Anna Berti, a psychologist
and physician at the University of Turin in Italy, asked a
patient to indicate the midpoint of a line held in front of
her body. She put the mark way to the right of the
midpoint. But when the same line was shown to her in far
space, beyond her reach, she found the midpoint with a
laser pointer. The neglect caused by the stroke extended
only to the space around her body.

But when Dr. Berti asked the patient to find the midpoint
with a stick in the distant line, she made the earlier
mistake. Using a tool extended her neglect further into
space.

Dr. Berti also tested a stroke patient who denied that the
wedding rings on her left hand were hers. But when she was
shown the rings in front of her or on her right hand, she
described how she came to own them. Dr. Berti concluded
that objects closely associated with a hand are part of the
body map.

People do not notice they have a body schema until they
lose it or feel it is permanently altered, said Dr. Michael
S. A. Graziano, a psychology professor at Princeton.
Certain kinds of brain damage result in a sensation of
floating outside one's body. The feeling can be induced in
healthy people by bombarding a region of their brains with
a powerful magnetic force.

In a condition called body dysmorphic disorder, people
perceive a normal part of their body, like the nose, ears
or buttocks, as grotesquely large. And there is recent
evidence that anorexia is partly a disorder of the body
schema, Dr. Graziano said.

Social psychologists have long studied how personal space
expands or shrinks depending on personality, culture and
circumstances, although they do not know the underlying
mechanisms. For example, when a person is threatened or
anxious, body space expands in an effort to keep others
away. A conversation with someone from a different culture
can produce the feeling that his face is uncomfortably
close, though it may be the same distance as that of
someone from the same culture. Dr. Dennis Proffitt, a
psychologist at the University of Virginia, studies how the
body schema affects our perception of the environment. For
example, just about everyone overestimates the inclines of
hills so that a 5-degree hill looks like a 20-degree hill.
But people who are encumbered, tired, out of shape or
elderly and in declining health may perceive the incline as
25 or 30 degrees.

Finally, researchers say that large machines can become
part of the body map. The lines between parking spaces
appear closer together from a Humvee than from a Miata, Dr.
Graziano said. An automobile is automatically absorbed into
peripersonal space. And that helps explain why a minor dent
in a fender can provoke a major blowup. The driver's body
space has been harmed.

Meanwhile, expert riders describe how their body space
becomes integrated with the horse's. Imagine what that does
to the ego.
http://www.nytimes.com/2004/07/13/science/13body.html?ex=1090766183&ei=1&en=4a59eabd4d07cfeb

Ken Lang · Post by **Ken Lang** » 13 Jul 2004 7:01 pm

..........................................
The lines between parking spaces
appear closer together from a Humvee than from a Miata.
..........................................

Uh, yeh.

The lines between parking spaces
appear closer together from a 747 than from a skateboard.

Not to dis Dr. Irike, but in this instance aren't we talking talking, uh, duh.

Donna Dodd · Post by **Donna Dodd** » 14 Jul 2004 12:57 am

Chas - interesting reading!
Helps explain the overly-aggressive road hog whose own personal space includes the interstate highway system!

<a href='http://www.smileycentral.com/?partner=ZSzeb008' target='_blank'><img src='http://smileys.smileycentral.com/cat/7/7_2_125v.gif' border=0></a> "Anybody seen JFK Airport?"[This message was edited by Donna Dodd on 14 July 2004 at 02:01 AM.]

Dave Boothroyd · Post by **Dave Boothroyd** » 14 Jul 2004 4:13 am

And does it explain why I, and many other bikers, say "We" when referring to themselves riding the bike?

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Cheers!
Dave

Erv Niehaus · Post by **Erv Niehaus** » 14 Jul 2004 6:13 am

Gee,
I thought we were going to hear what happens when a 350 pound fan hovers over your guitar when you are playing steel guitar rag!

Uff-Da!

David Mason · Post by **David Mason** » 14 Jul 2004 6:43 am

Does this mean I can "feel" a pretty girl in the crowd through my amplifier?

Bill Llewellyn · Post by **Bill Llewellyn** » 14 Jul 2004 6:46 am

Bringing this back to the PSG, does the guitar become part of one's personal space when playing?

Prob'ly does.....

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Bill, steelin' since '99 | Steel page | My music | Steelers' birthdays | Over 50?[This message was edited by Bill Llewellyn on 14 July 2004 at 07:46 AM.]

chas smith R.I.P. · Post by **chas smith R.I.P.** » 14 Jul 2004 8:04 am

Having had mixed emotions when an attractive woman dancer, spinning out of control, sprawled across the top of my Bigsby....

Pat Burns · Post by **Pat Burns** » 14 Jul 2004 12:10 pm

..the steel definately becomes part of my personal space when playing...

..drunken slobbering incoherent steel guitar fans are politely encouraged to wait until break time to ask what it is, so we can put some distance between us...

...attractive well-endowed young females are tolerated when they lean in too close, regardless of sobriety...

Erv Niehaus · Post by **Erv Niehaus** » 14 Jul 2004 12:54 pm

You may not be able to "feel" a pretty girl in the crowd through your amplifier but she can "feel" YOU through your amplifier. Especially those low bass notes

Erv

erik · Post by **erik** » 14 Jul 2004 2:33 pm

This is very interesting reading. This probably explains the phenomena of non-touch massage. Similarly, when i stay in my truck when it's getting washed and the person sprays the windows my body reacts as if it were hitting me. I get tinglely like a massage.

I don't think the center focal point test is so unusual. Even people with 2 good eyes can find a center point at a distance better than close. Try lining up headlights, same concept.

-johnson

Ray Minich · Post by **Ray Minich** » 14 Jul 2004 4:03 pm

Posting deleted, could be misinterpreted.

A woman's space extends for 100's of yards.[This message was edited by Ray Minich on 15 July 2004 at 09:08 PM.]

erik · Post by **erik** » 14 Jul 2004 5:27 pm

I think perhaps you are joking?

that could not possibly see me as they were walking away from me.

Maybe, you don't realize that at some point they see you and pegged you as someone up to no good. They can't be walking away from you unless they were either going by or coming perpendicular. In either case you're in their field of vision.

-johnson

Paul Graupp · Post by **Paul Graupp** » 14 Jul 2004 11:15 pm

Chas: It's around three AM and I was laying there trying to sleep when I realized I have been watching this occur in my 2 year old grandson, Caleb. With little boys, food and toys are the prominent items rather than girls or tools. He is a Burger King subject and loves "King's House !

I have watched him as he has learned to deal with catsup. At first, it was all over his hands and face as he began to learn how to manipulate it but now he has learned these parameters as you have laid them out for our examination. He only wants so much catsup on his fries or chicken strips; his favorite King's menu items. He isn't even watching half the time when he applies the catsup to said food items. He's watching other things such as big 18 wheelers in the parking lot or other kids at play.

It's as if I have watched him learn this talent without even being aware of it. It seems perfectly obvious to me that the thinkings and workings as they have been written and noted in the article, are indeed true. Now all I have to understand is why it wasn't so obvious to me before you posted ?!

Regards, Paul