The Brain Can Learn To Decrease Pain

New research led by Raymonde Scheuren from the University of Luxembourg has brought some new insights into the world of pain. It’s generally known that a pain present in one part of the body can be attenuated by painfully stimulating a different part of the body. This is known as diffuse noxious inhibitory control (DNIC) and is thought to take place to allow the body to focus on the new, and potentially more important, threat to the body.

In their experiments, Scheuren et al. caused pain in subjects by electrically stimulating a foot. They then created a second source of pain by placing the opposite hand in a bucket of ice-cold water. As predicted, after the hand was immersed in cold water, the pain from the foot decreased. The interesting part of the experiment was when the insertion of the hand into cold water was repeatedly coupled with a phone ring tone. Afterwards, simply playing the ring tone (without placing a hand in cold water) was enough to decrease foot pain from the electrical stimulation! Conditioning had taken place. Conditioning is a form of learning where the physiological effect of a stimulus (ice-cold water) is reproduced by an unrelated stimulus (phone ring tone) by having the two repeatedly happen simultaneously. The one takes on the effect of the other.

The reverse effect possibly plays a part in chronic pain. Sights, sounds, smells and other sensations that were present during the traumatic incident that caused the injury can unconsciously become triggers for pain long after the injury has healed.