Pitt, Carnegie Mellon Researchers Shed Light On 'The Nature Of The Self'

February 19, 1998

PITTSBURGH, Feb. 18 -- Researchers at the University of Pittsburgh and Carnegie Mellon University have taken an important step toward determining how the body comes to be identified as part of the self. The results of their unusual experiment appear in Thursday's scientific journal Nature.

According to the researchers, the concept of body self-identification arises out of the way humans perceive their bodies versus other objects in the world around them.

"Our mind represents our own bodies as different from other worldly objects," explained Matthew Botvinick, M.D., a psychiatrist at the University of Pittsburgh School of Medicine. "We're suggesting that this is because the body participates in intersensory matches in a way that other objects don't. When something touches our hand, we both see it and feel it. This gives us a dual perspective, sight and touch. The brain makes a match between the two perspectives. This match leads the brain to identify that part of the self. When we see another object like a chair or table being touched, we have only one perspective, sight, with no corresponding tactile perception. This is what makes the body and other objects different, and this difference counts for the brain."

Dr. Botvinick and Jonathan Cohen, Ph.D., professor of psychology at Carnegie Mellon University and professor of psychiatry at Pitt, developed an experiment through which they could observe how the brain integrates multiple sensory modalities in representing the body. Each of 10 subjects was seated with his or her left arm resting on a small table just left of the body midline. A screen was placed beside the arm to hide it from the subject's view. Then, the researchers placed a rubber model of a left hand and arm on a table directly in front of the subject. The participant was instructed to sit still and focus on the rubber hand while the experimenter used two small paintbrushes to simultaneously stroke the rubber hand and the subject's hidden left hand. The procedure was carried out so as to create as close a match as possible between what the subject saw and what the subject felt.

After ten minutes, each participant completed a questionnaire. The subjects' responses indicated they had experienced an illusion in which they seemed to feel not the touch of the hidden brush, but the touch of the brush they could see, as if sensed by the rubber hand. Eight out of 10 subjects who reported this illusion also reported that they had experienced the rubber hand as if it were their own. The subjects described the rubber hand with phrases like "It felt like the rubber hand was my own."

"This suggests that one of the ways our mind comes to determine the body as its own is the correlation of sensory experiences such as touch and sight," commented Dr. Cohen. "This is an important step in determining what defines us as ourselves."

"We humans have a sense of inhabiting our bodies," said Dr. Botvinick. "This sense of ownership depends on multiple senses and the continuing matches our brain makes between them. In this experiment the subjects felt the brush on their real hand and saw it on the artificial hand and their brain brought these two things together in space. As a result, our subjects developed a sense of inhabiting the rubber hand.

"The effect is surprisingly compelling," continued Dr. Botvinick. "If you ask someone to describe the sensation, they tell you the rubber hand felt like it was their own."

"This is not a subtle finding that will create a lot of debate," commented Dr. Cohen. "It is a really robust effect. It's possible that this is the beginning of how our mind says 'that's mine, that's yours'."

According to Dr. Botvinick, the illusion of ventriloquism is created in much the same way. "In both cases, the brain puts together two things that belong together. In ventriloquism, it's the voice and the dummy's moving mouth. In the rubber hand experiment, a touch is felt in one place, but seen in another. In order to make sense of this, the brain puts the two together. We think we hear the dummy talk, we think we feel through the rubber hand."

The researchers have developed a computational model of what is happening within the brain as the illusion occurs. The next step will be to relate this to such clinical conditions as phantom limb and "alienation phenomenon," where brain damaged patients fail to recognize parts of their bodies as belonging to themselves.

For additional information about UPMC Health System, please access http://www.upmc.edu.

For additional information about Carnegie Mellon University, please access http://whatsnew.andrew.cmu.edu.

University of Pittsburgh Medical Center

Related Brain Articles from Brightsurf:

Glioblastoma nanomedicine crosses into brain in mice, eradicates recurring brain cancer
A new synthetic protein nanoparticle capable of slipping past the nearly impermeable blood-brain barrier in mice could deliver cancer-killing drugs directly to malignant brain tumors, new research from the University of Michigan shows.

Children with asymptomatic brain bleeds as newborns show normal brain development at age 2
A study by UNC researchers finds that neurodevelopmental scores and gray matter volumes at age two years did not differ between children who had MRI-confirmed asymptomatic subdural hemorrhages when they were neonates, compared to children with no history of subdural hemorrhage.

New model of human brain 'conversations' could inform research on brain disease, cognition
A team of Indiana University neuroscientists has built a new model of human brain networks that sheds light on how the brain functions.

Human brain size gene triggers bigger brain in monkeys
Dresden and Japanese researchers show that a human-specific gene causes a larger neocortex in the common marmoset, a non-human primate.

Unique insight into development of the human brain: Model of the early embryonic brain
Stem cell researchers from the University of Copenhagen have designed a model of an early embryonic brain.

An optical brain-to-brain interface supports information exchange for locomotion control
Chinese researchers established an optical BtBI that supports rapid information transmission for precise locomotion control, thus providing a proof-of-principle demonstration of fast BtBI for real-time behavioral control.

Transplanting human nerve cells into a mouse brain reveals how they wire into brain circuits
A team of researchers led by Pierre Vanderhaeghen and Vincent Bonin (VIB-KU Leuven, Université libre de Bruxelles and NERF) showed how human nerve cells can develop at their own pace, and form highly precise connections with the surrounding mouse brain cells.

Brain scans reveal how the human brain compensates when one hemisphere is removed
Researchers studying six adults who had one of their brain hemispheres removed during childhood to reduce epileptic seizures found that the remaining half of the brain formed unusually strong connections between different functional brain networks, which potentially help the body to function as if the brain were intact.

Alcohol byproduct contributes to brain chemistry changes in specific brain regions
Study of mouse models provides clear implications for new targets to treat alcohol use disorder and fetal alcohol syndrome.

Scientists predict the areas of the brain to stimulate transitions between different brain states
Using a computer model of the brain, Gustavo Deco, director of the Center for Brain and Cognition, and Josephine Cruzat, a member of his team, together with a group of international collaborators, have developed an innovative method published in Proceedings of the National Academy of Sciences on Sept.

Read More: Brain News and Brain Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.