Scientists have found that areas of the brain that respond to feelings of pleasure also react to the sensation of pain. The findings could lead to a better understanding of the effects of pain within the brain and to new ways to diagnose and treat pain. The new research carried out by the USA's Massachusetts General Hospital (MGH) backs up previous studies. The MGH's Dr David Borsook said: "Pain is a complex experience that includes both a sensation and an emotional reaction. Understanding this emotional component would be key to developing new approaches to helping chronic pain in patients, who are at increased risk for anxiety, depression and suicide."

Researchers used a technique called functional magnetic resonance imaging (fMRI) to take pictures of the brains of eight study volunteers. The eight young men had a thermode or small heat pad attached to their hands, which administered warm or hot temperatures for brief periods, alternating with normal skin temperatures. Brain images focused both on areas previously identified as being involved with the sensory experience of pain and on those found in earlier studies to be activated by response to such stimuli as cocaine, food and money.

Objective pain tests

The results showed the painful "hot" temperatures caused activation not only of the classic pain circuitry in the brain, but also some of the areas previously described as reward circuitry. The reward circuits responded more quickly than the pain circuits during the administration of hot temperatures. The pain circuits were active towards the end of the heat administration period.

Lino Becerra, one of the authors of the study, said: "These are two systems that were never associated in the past and it's the first time we have seen something aversive activating these reward structures." Co-author Dr Hans Breiter said: "It would appear the philosophers Spinoza and Bentham, who proposed that pleasure and pain were part of the same spectrum, were right."

The scientists go on to suggest this response is due to circuits in the brain that handle reward trying to analyse stimuli and judge which are important to survival. It is hoped these conclusions could pave the way for developing objective tests to measure pain and pain relief and the creation of pain-relieving drugs that target the structures previously associated with reward.

This strategy could lead to the treatment of pain that does not respond to traditional medications. British pain imaging expert Dr Irene Tracey from Oxford University believes such findings could bring hope of developing alternative pain remedies, which do not involve drugs. She said: "This research provides information which is critical for future studies that will pave the way for pain sufferers being given alternative therapies to combat their suffering."