In the mind's eye, an arm or hand changes shape, study finds,,
THURSDAY, June 25 (HealthDay News) -- Pick up a golf club and your brain may do more than look for an easy par three.
New research suggests that the brain considers tools to be extensions of the body.
The mere act of holding a mechanical grasping tool "temporarily modifies the cerebral representation of a subject's arm," said Lucilla Cardinali, a graduate student in France and lead author of the study.
In other words, people think their arm is longer, at least for a moment.
It's not immediately clear what this new knowledge about the "schema" -- people's internal representation of themselves in the world -- could mean in terms of treatment of illness.
But it could potentially help people with conditions that have disrupted their view of their place in space, such as amputees who receive hand transplants, said Cardinali, who studies at Claude Bernard University in Lyon, France.
Scientists have discussed the concept of schema since the 19th century as they've tried to figure out how the brain comprehends where someone is and where that person wants to go.
To move around, people must understand their position in the space around them and also have to anticipate what will happen when they move their bodies or a body part. Usually that's done with ease.
"You know exactly where that toothbrush needs to go to fit your teeth -- as if it's an extension of your arm," said Paul Sanberg, a professor of neurosurgery at the University of South Florida College of Medicine.
Some people with neurological problems have difficulty with that process, however, and tests have shown they can't imagine rotating their hands, Cardinali said.
In the French study, published in the June 23 issue of Current Biology, researchers used measurements to show that people acted as if their arms had extended after using a mechanical grasping tool.
"People move their hands as if their arms were longer," Cardinali said. And when asked to point to their elbow and middle fingertip, the two points they indicated were further apart after using the tool.
The study proves for the first time that people extend their representation of themselves when using tools, Cardinali said.
Of course, people don't notice that they're continually creating an idea of where they are in relation to space and things. That makes sense, Cardinali said, because the brain doesn't have the resources to make someone aware of the entire body's place in space when the person wants to move.
But the schema system is still in place, she said, meaning that "you don't need to pay attention to your feet at every step or visually look in the mirror and visually control your movements while you brush your teeth."
Understanding more about the human body's schema could lead to better understanding of such diseases as anorexia, in which people think they're heavy when they're not, said Sanberg, the Florida neurosurgeon.
"How they perceive their body may not be exactly what is in the real world," he said. How we position ourselves in space could play a role.
The Lundbeck Institute has more about the brain.
SOURCES: Lucilla Cardinali, graduate student, Claude Bernard University, Lyon, France; Paul Sanberg, Ph.D., distinguished professor, neurosurgery, University of South Florida College of Medicine, Tampa; June 23, 2009, Current Biology
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