London -
A new study by British researchers has called into question previous theories about how we experience pain.
The study, conducted by scientists from University College London (UCL) and the University of Reading, was intended to test the nature of the ‘‘pain matrix’’, a particular pattern of brain activity that is believed to be a reliable indicator for pain.
By scanning test participants’ brains while subjecting them to pain, scientists in past studies have consistently observed the same parts of the brain ‘‘lighting up’’, leading to the idea of the pain matrix becoming widely accepted.
However, the new study, published in the journal JAMA Neurology has called this belief into question. For their tests, the scientists recruited two people with a rare condition that makes them unable to feel pain. They also recruited four healthy volunteers who were roughly the same age.
Each of the six participants was exposed to a painful pinprick while having their brains monitored in an fMRI machine. Oddly, the people with no sense of pain showed the same pattern of brain activity as the healthy participants – calling the assertion that the pain matrix actually represents the sensation of pain into question.
As Reading’s Dr. Tim Salomons explains: ‘‘Our results suggest that these patterns are not in fact ‘pain responses’ but responses to attention-grabbing stimuli regardless of whether a person feels pain.’’
‘‘By testing people with no sense of pain, we can categorically rule out that these are pain-specific responses. These people still retain all other senses including non-painful touch, so the brain activity that has been dubbed the pain matrix is likely to represent these senses rather than actual pain.’’
In other words, while the pain matrix may represent painful stimuli, and could well be involved in processing pain, it's wrong to make an explicit link between the pattern and the feeling of pain.
According to UCL's Professor John Wood, the team's findings highlight the importance of not associating correlation with causation.
‘‘We should not forget this when interpreting brain scans,’’ he said.
The study may have dispelled a myth, but it sheds no light on where the feeling of pain actually comes from.
Professor Wood said: ‘‘Just like a sense of beauty or happiness, the precise location of pain sensation in the brain remains elusive for now.’’
The Independent