missing limbs, still atingle, are clues to changes in the brain - straight line laser

by:UMeasure     2020-03-13
missing limbs, still atingle, are clues to changes in the brain  -  straight line laser
Sandra in Brax Lionel
1992 this is a digital version of an article from The Times Print Archive, before it starts online in 1996.
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A month after losing his left arm in a car accident, Victor kuitro sat there with his eyes closed.
A scientist poked his cheek with a cotton swab.
"Where do you think it is? " asked Dr. Vilayanur S.
A neuropsychologist at the University of California, San Diego, Ramachandran.
"On my left cheek, on the back of my missing hand," said the 17-year-oldyear-
Old high school students. Dr.
Ramachandran is in Mr.
Left nostrils of Quintero
"Where do you think this is?
"On my little finger on the left. It tingles. "Eventually Dr.
Ramachandran found some points on the young man's left face and chin, which caused the feeling on his intercepted hands and arms.
The advertisement when the scientist touched the cotton swab on the right side of the gentleman
Quintero's face and body, the young man felt nothing on the Phantom's body.
But when he did
Quinterro's left shoulder is right above the stump, and the young man feels again that there are discrete points on his lost hand and arm.
Finally, advertising.
Mr. Ramachandran dropped the water.
Quintero's left cheek
Both were surprised.
"I think it runs down my arm . "
Quinterro blinks to check if the body is still there.
This strange experiment reveals a new feature of the adult brain that is changing the way neuroscientists think about brain damage and everyday cognition.
Until recently, scientists believe that if the body part of the brain connected to it is lost, nerve cells in the brain will die.
They believe that the sensation of the "phantom" limbs is caused by the lack of nerve stimulation near the end of the limb.
Now, however, it seems that the brain does not have a fixed circuit.
On the contrary, the adult brain seems to be able to restructure and rewire in a very large distance in an unknown way ---
Thus, brain cells that accept facial and shoulder inputs can trigger brain cells that no longer accept arm inputs.
This rapid dynamic change is the characteristic of the healthy adult brain and the injured brain, Dr.
Charles Gilbert, a neurologist at Rockefeller University in New York.
As people look at each new world by moving their eyes from scene to scene, the cells in the visual cortex go through extensive restructuring, he said.
"We are just beginning to realize that the adult brain is more dynamic than static.
Michael Merzenich, a neuroscientist at the University of California, San Francisco.
It constantly shapes and reshapes itself from the experience of a lifetime.
"Most of the things we don't know about the brain may be explained from these dynamics. " he said.
Once you understand the dynamic properties, Dr
Merzenich said it should be possible to help people recover from a lot of tension
Systemic diseases and this understanding may lead to changes in treatment of spinal cord injury and diseases such as paralysis, stroke, depression, mental illness and various brain injuries.
Questioning the old theory, understanding the dynamics may also explain strange phenomena such as why the feet are eroded and how the brain forms visual illusion.
It has explained the phantom limb sensation, why some people recover after a stroke, and why deaf people with cochlear implants hear clearer sounds over time.
Finally, this new view of the adult brain "provides basic insights for learning and memory," the doctor said.
Vernon Monta Castle, an outstanding neurologist from Johns Hopkins University.
"Most brains never reach their full potential," he said . "
"Maybe we didn't train them properly.
We can learn to emphasize certain circuits and go
So as to improve education.
The new findings, many of which were first reported at a recent meeting of the Neuroscience Society, are subverting the traditional view of the human adult brain.
Previously it was thought that the brain was highly dynamic during infancy and childhood, especially during critical periods of development, but after a certain age, brain cells "knew what they should do, they have been doing it all their lives. "Merzenich said.
The brain structure is considered fixed, especially in areas where raw information is received from the eyes, ears and skin.
In the visual cortex, each cell has its own receptor field, corresponding to the fixed space region of the external world, so different points in the three regions
Dimension space triggers different brain cells.
Cells also specifically detect specific stimuli in this space, such as edges, colors, horizontal lines, and contrast.
When stimulation is detected by the cell, its receptive field is activated and the visual space is mapped to the cortex.
Images are processed by at least 30 layers of visual cortex, each with its own architecture and rules.
Most of the unexplored auditory cortex is believed to contain at least four maps of different frequency ranges.
In the somatosensory cortex, adjacent points on the skin map to adjacent cells in the brain.
Each half of the body is represented on the other side of the brain, and the lips, tongue, fingers, and all other parts of the body correspond to areas.
In the 1980s, Dr.
Merzenich is the first researcher to work with Dr to question the fixed nature of these maps
Jon Cass of the University of van der Burg
He cut a finger from an adult monkey. The fixed-
Brain Theory predicts that cells mapped to the fingers will die.
Merzenich said a hole was left on the map.
But tests have shown that these cells are not dead and, in fact, can be activated by touching adjacent fingers.
But when the researchers cut off two fingers, the phenomenon of diffusion or "filling" disappeared, so they inferred that the cells were only reconnected at a very short distance.
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They were quickly proved wrong.
A few years ago, doctor.
Tim Pons, a senior scientist at the neuropsychology laboratory at the National Institute of Mental Health, examined monkeys with arm paralysis 12 years ago, cutting off nerve connections to the brain.
The brain tissue that is expected to map the arm is not only alive, Dr.
Pons said, but it responded to the face.
"We are shocked," he said . "
"There's a huge fill. "Last year, Dr.
Ramachandran decided to test like Mr. Quintero.
In the tactile brain map, he says, the arms and hands lie between the face and the shoulders.
If there is a filling, the cut-off limb should be felt on the face and shoulders, which is exactly what happens.
Within a month, the cells reconnect at a very large distance, Dr.
Said Lamar.
To understand the speed at which this happens, he hopes to test amputees in the first few hours and days after the operation.
Doctor, there's a clue that the repositioning process is dynamic and fast.
Said Lamar.
In test 45-year-
The 16-year-old woman's entire middle finger was cut off, and he found that the contact point on the adjacent fingers caused sensation at the same point on the phantom finger.
Cold or warm water drops evoke warmth or cold in phantom fingers.
When he grabbed her index finger, she felt the phantom finger caught together with the index finger.
When he released the pressure, she felt the phantom finger feeling gone in 7 to 8 seconds.
"We have found an explanation for the sensation of the phantom limb . "
Said Lamar.
He said it was thought to be caused by nerve stimulation near the stump, "but we now know it started with the brain," when the map after reorganization was stimulated, the feeling is wrongly interpreted as coming from the missing limb.
These findings led to some strange predictions.
Said Lamar.
Since the area corresponding to the foot and genitals is adjacent to the sensory brain map, a man with a cancer penis removed should produce the sensation of a virtual penis by stimulating his foot.
This proximity can also explain why some people think feet are sexy, he said.
Experiments reported at the neuroscience conference show that many parts of the sensory brain map are being rewired.
As an adult, people who fused their fingers to separate through surgery quickly developed a new map of the brain with the location of individual fingers.
Monkeys trained to pick up small balls will expand areas of the brain specifically used to catch muscles and fingers of small objects.
People who read Braille have a bigger onethan-
Normal brain map of their index finger
Doctor, the visual cortex will also be filled. Gilbert said.
Many people, especially those with diabetes, have very little damage to the retina, creating blind spots on their visual maps.
He said that if such a person is staring at a friend in the background of the wallpaper, the head of the friend may disappear, but the wallpaper will fill the gap.
That is, the cells that get the signal share their stimuli with the neighboring cells that are not stimulated, so the blind spots are not perceived.
Advertising in an ongoing experiment
Gilbert used a laser to create minor damage in the monkey's eyes and to record the activity of the affected cortical cells.
Within minutes, he said, the cortical regions that damaged the "silent" began to share inputs from the adjacent receptive regions.
A clue to the activisionsit may be that this activity occurs in milliseconds
"It allows us to adapt to the changing visual environment," Gilbert said.
This can also explain the optical illusion.
A straight line relative to the tilt line appears to be tilted in the opposite direction, he said.
Perhaps the cells that respond to the oblique line will enter the cells that detect the line and drown it.
There is a similar filling in the auditory cortex. Merzenich said.
Many deaf people have cochlear implants, an artificial hearing device that replaces the sensory cells of the ear with an electronic sensor.
At first, he said, they reported hearing speeches that sounded mechanical and impersonal.
But a few months later, they began to say that the speech sounded natural and distinctive.
Doctor, it's been filled out. Merzenich said.
The scientists who studied the filling proposed several mechanisms for this phenomenon.
Cells in the sensory map can be connected through horizontal neural trajectories that send information over long distances.
Or they may be connected through a large, loose network of synapses.
New connections may sprout after injury, or existing connections may be unblocked.
The answer is in the air, doctor.
Said Lamar.
But when it is discovered, the return can be huge.
Neurologists believe that people can recover from the wind because some damaged parts of the brain are not dead. Gilbert said.
But the study suggests that healthy parts of the brain replace the dead.
This puts forward new strategies for the rehabilitation of stroke. Merzenich said.
A person with weak fingers but good arm and shoulder movements is often told to exercise the arm to help strengthen the finger, he said.
But he said the fingers were weaker because of the filling.
A better strategy is to exercise the fingers and limit the movement of the arms so that the strong do not drown the weak. Merzenich said.
Mapping of CortexAdvertisementDr.
The researchers are on the edge of the injured spinal cord to produce a new connection, Pons noted.
But if the brain reconstructs its sensory map, it may not be enough to reconnect the cable, he says.
The second part of the treatment may include the prevention of changes in the cortical map.
In fact, Dynamic Cortical maps may be the basis for learning and memory, Dr. Merzenich said.
The same process happens in the advanced areas of the brain, so who we are and what we know is constantly being changed by experience.
In the end, new sensory processing models may help researchers understand and may improve emotional difficulties, depression, mental illness, and brain aging.
But the most immediate reward is the amputees who have the sensation of a phantom limb.
After Cottonswab test, Mr.
Quintero vs Dr. Ramachandran.
"I'm glad you told me about it.
My "fingers" itch like crazy.
"Now I know where to scrape," he said, reaching out to touch his left cheek.
A version of this article appears on page C00001 of the national edition of November 10, 1992, with the title: missing limbs are still beating, a clue to brain changes.
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