Thinking of something else is a time-honored method for coping with pain. Indeed, psychologists have demonstrated repeatedly that what you think about can modulate the pain you experience. But what's less clear is how exactly that effect plays out in the body. In a study published today in Current Biology, neuroscientists have found that distraction does more than merely divert your mind; it actually sends signals that bar pain from reaching the central nervous system.

"This study connects two important fields of pain research," says lead author Christian Sprenger, a physician and neuroscientist at the University Medical Center Hamburg–Eppendorf in Germany. "There are many studies describing the sensitization processes of the spinal cord. On the other hand, it is well known that certain psychological factors are good predictors of the development of pain."

Sprenger and his colleagues told 20 male volunteers they would be participating in an experiment that would study concentration and memory. Each subject, while undergoing functional magnetic resonance imaging (fMRI) to map their neural activity, used a computer screen to take a memory test called an "n-back test." In such a test, subjects recall a specific letter either one or two letters back from the end of a series. As initial sessions confirmed, remembering a letter two-back is more challenging than a letter one-back. Researchers gave volunteers either the one- or two-back test so that they could study the nervous system under two levels of cognitive load.

While taking the test, each subject received a burning sensation on the forearm, courtesy of a heating element that reached a little over 47 degrees Celsius—hot enough to hurt but not enough to damage the skin. After completing the test and heat stimulus session, each man rated the sensation of pain on a scale of 0 (no pain) to 100 (unbearable). On average, the amount of heat should have produced a pain level of about 60. In line with previous studies, individuals taking the tricky two-back test described less pain than those taking the simpler one-back test.

But the effect wasn't just in their heads. The fMRI revealed differences in each group taking place in their spinal cords. For those unfortunate subjects taking a one-back test, pain signals successfully reached nerve fibers along the spinal cord, creating the experience of pain. But in subjects preoccupied by the more challenging test, pain receptors were blocked. The researchers concluded that the brain sends some kind of signal to the rest of the body, which enables the nervous system to ignore most pain and focus on the task at hand.

Intrigued, the researchers decided to repeat the test but add an extra variable. As some individuals received an injection of harmless saline, others received naloxone, a drug that blocks the action of opioids. Those receiving saline showed the same pattern as before as did subjects taking a one-back test with naloxone. For subjects taking a two-back test with naloxone, however, the pain-relieving effects of a distracted brain diminished by 40 percent. The finding suggests the concentrating brain doesn't just divert attention from the agony, it also triggers a release of opioid-based compounds.

"I think this is very novel," says Tor D. Wager, a psychologist and neuroscientist at the University of Colorado at Boulder. "It has not been clear whether attention works at an output stage or modifies a higher level or even interferes with memory for pain." Wager, who is also studying the interaction of working memory and pain, explains that Sprenger's study is nearly unprecedented in its look at the spinal cord.

7 Comments

1. 1. ASGMc 08:20 AM 5/18/12

   I think this would explain the preoccupation inherent with addictions as well. A busy brain dampens external stimuli, and probably internal pain as well in order to maintain focus. Relief from pain is even more rewarding than satiation, which would explain why addiction never leads to satiation. Thinking itself is addictive for the brain.

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2. 2. Stagnaro 08:37 AM 5/19/12

   To corroborate this fascinating research results, and especially to ascertain the possible mechanism for the brain's inhibition of the pain response - a mechanism that can be measured and further studied, eventually leading to clinical applications such as therapies, I suggest a clinical method, I have created 25 years ago, based on bedside assessing endogenous endorphynes:Stagnaro S., Stagnaro-Neri M., Valutazione percusso-ascoltatoria del sistema degli oppioidi endogeni nei pazienti cefalalgici. Contributo alla definizione della costituzione emicranica. Epat. 33, 35, 1987. In addition, we must remember also that endogenous endorphynes prompt antibody synthesis.

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3. 3. Stagnaro 08:38 AM 5/19/12

   To corroborate this fascinating research results, and especially to ascertain the possible mechanism for the brain's inhibition of the pain response - a mechanism that can be measured and further studied, eventually leading to clinical applications such as therapies, I suggest a clinical method, I have created 25 years ago, based on bedside assessing endogenous endorphynes:Stagnaro S., Stagnaro-Neri M., Valutazione percusso-ascoltatoria del sistema degli oppioidi endogeni nei pazienti cefalalgici. Contributo alla definizione della costituzione emicranica. Epat. 33, 35, 1987. In addition, we must remember also that endogenous endorphynes prompt antibody synthesis.

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4. 4. stargene 08:40 PM 5/19/12

   Disregarding any mechanism, I can imagine that
   if our species had not evolved some way to think
   and plan while not being too distracted by mental
   or physical pain, we might not have survived as
   a species. Ie: a being which is routinely pre-
   occupied, even to the point of distraction, with
   the sufferings imposed by simply existing in the
   world, will have less chance of coping and finding
   strategies for avoiding causes of suffering in the
   future. Such coping and planning, however rudi-
   mentary, would be enhanced by any mechanism giving
   the mind a 'breathing space', away from pain.

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5. 5. PatZu 02:35 AM 5/20/12

   Perhaps the brain is merely delighted by engaging in a task, and rewards itself with a little opiod buzz. Pain mitigation is a side-effect.

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6. 6. jtdwyer in reply to stargene 07:14 AM 5/20/12

   I agree with your sentiments, but I strongly suspect the mechanism producing this effect was developed long before modern humans came along. Have you ever seen a rat in a trap? They do not go quietly, but struggle mightily to find a way out of the trap, including ingeniously backing through a space too small for the trap. I suspect they would not be able to attend to their predicament if they had succumbed to the induced pain potential.

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7. 7. jperk82 11:15 PM 9/3/12

   This method could be held true. To me, this is a method of diversion like when two thieves enter a store attempting to steal. One diverts the clerks attention while the other stuffs articles of clothing in a bag. If the brain is focused on something other than pain, the pain may seem a little less intense than it would if the attention was primarily on the pain. When I was a child, I broke my arms and had pins in it until it healed. When it was time for the pins to come out, the doctor told me to look the other way diverting my attention from the procedure at hand. It only made me look but why did the doctor attempt to make me focus on something else? I think the answer would be correlate with this study.

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