Posted by: faithful | July 9, 2008

brain pains

Very Nervous

The following is from

Stories of Personal Triumph from the Frontiers of Brain Science (James H. Silberman Books)
The Brain That Changes Itself: Stories of Personal Triumph from the Frontiers of Brain Science (James H. Silberman Books) by Norman Doidge

 

 

THE BRAIN THAT CHANGES ITSELF
by Norman Doidge, M. D.
 

 

 

“Normally, when we make a mistake, three things happen. First, we get a “mistake feeling,” that nagging sense that something is wrong. Second, we become anxious, and that anxiety drives us to correct the mistake. Third, when we have corrected the mistake, an automatic gearshift in our brain allows us to move on to the next thought or activity. Then both the “mistake feeling” and the anxiety disappear.But the brain of the obsessive-compulsive does not move on or “turn the page.” Even though he has corrected his spelling mistake, washed the germs off his hands, or apologized for forgetting his friend’s birthday, he continues to obsess. His automatic gearshift does not work, and the mistake feeling and its pursuant anxiety build in intensity.

 

We now know, from brain scans, that three parts of the brain are involve in obsessions.

We detect mistakes with our orbital frontal cortex, part of the frontal lobe, on the underside of the brain, just behind our eyes. Scans show that the more obsessive a person is, the more activated the orbital frontal cortex is.

Once the orbital frontal cortex has fired the “mistake feeling,” it sends a signal to the cingulate gyrus, located in the deepest part of the cortex. The cingulate triggers the dreadful anxiety that something bad is going to happen unless we correct the mistake and sends signals to both the gut and the heart, causing the physical sensations we associate with dread.

The “automatic gearshift,” the caudate nucleus, sits deep in the center of the brain and allows our thoughts to flow from one to the next unless, as happens in OCD, the caudate becomes extremely “sticky.”

Brain scans of OCD patients show that all three brain areas are hyperactive. The orbital frontal cortex and the cingulate turn on and stay on as though locked in the “on position” together — one reason that Schwartz calls OCD “brain lock.” because the caudate doesn’t “shift the gear” automatically, the orbital frontal cortex and the cingulate continue to fire off their signals, increasing the mistake feeling and the anxiety. Because the person has already corrected the mistake, these are, of course, false alarms. The malfunctioning caudate is probably overactive because it is stuck and is still being inundated with signals from the orbital frontal cortex.

–p.170

**
“Pain and body image are closely related. We always experience pain as projected into the body. When you throw your back out, you say, “My back is killing me!” and not, “My pain system is killing me.” But as phantoms show, we don’t need a body part or even pain receptors to feel pain. We need only a body image, produced by our brain maps. People with actual limbs don’t usually realize this, because the body images of our limbs are perfectly projected onto our actual limbs, making it impossible to distinguish our body image from our body. “You own body is a phantom,” say Ramachandran, “one that your brain has constructed purely for convenience.”

p. 188

**
“According to Ramachandran, pain, like the body image, is created by the brain and projected onto the body. This assertion is contrary to common sense and the traditional neurological view of pain that says that when we are hurt, our pain receptors send a one-way signal to the brain’s pain center and that the intensity of pain perceived is proportional to th seriousness of the injury. We assume that pain always files an accurate damage report. This traditional view dates back to the philosopher Descartes, who saw the brain as a passive recipient of pain. But that view was overturned in 1965, when neuroscientists Ronald Melzack (a Canadian who studied phantom limbs and pin) and Patrick Wall (an Englishman who studied pain and plasticity) wrote the most important article in the history of pain. Wall and Melzack’s theory asserted that the pain system is spread throughout the brain and spinal cord, and far from being a passive recipient of pain, the brain always controls the pain signals we feel.

Their “gate control theory of pain” proposed a series of controls, or “gates,” between the site of injury and the brain. When pain messages are sent from damaged tissue through the nervous system, they pass through several “gates,” starting in the spinal cord, before they get to the brain. But these messages travel only if the brain gives them “permission,” after determining they are important enough to be let through. If permission is granted, a gate will open and increase the feeling of pain by allowing certain neurons to turn on and transmit their signals. The brain can also close a gate and block the pain signal by releasing endorphins, the narcotics made by the body to quell pain.

***
Wall and Melzack showed that the neurons in our pain system are far more plastic than we ever imagined, that important pain maps in the spinal cord can change following injury, and that a chronic injury can make the cells in the pain system fire more easily — a plastic alteration — making a person hypersensitive to pain. Maps can also enlarge their receptive field, coming to represent more of the body’s surface, increasing pain sensitivity. As the maps change, pain signals in one map can”spill” into adjacent pain maps, and we may develop “referred pain,” when we are hurt in one body part but feel the pain in another. Sometimes a single pain signal reverberates throughout the brain, so that pain persists even after its original stimulus has stopped.

**
Extending the gate theory, Ramachandran developed his next idea: that pain is a complex system under the plastic brain’s control. He summed this up as follows: “pain is an opinion on the organism’s state of health rather than a mere reflexive response to injury.” The brain gather evidence from many sources before triggering pain. He has also said that “pain is an illusion” and that “our mind is a virtual reality machine,” which experiences the world indirectly and processes it at one remove, constructing a model in our head. So pain, like the body image, is a construct of our brain.”

 

 

 

 

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