University College London scientists produce the first map showing how the ability to feel pain varies across the body
The forehead and fingertips are the most sensitive parts to pain, according to the first map created by scientists of how the ability to feel pain varies across the human body.
It is hoped that the study, in which volunteers had pain inflicted without touching them, could help the estimated 10 million people in the UK who suffer from chronic pain by allowing physicians to use lasers to monitor nerve damage across the body. This would offer a quantitative way to monitor the progression or regression of a condition.
Lead author Dr Flavia Mancini, of the UCL Institute of Cognitive Neuroscience, said: "Acuity for touch has been known for more than a century, and tested daily in neurology to assess the state of sensory nerves on the body. It is striking that until now nobody had done the same for pain."
In the study, a pair of lasers were used to cause brief sensation of pinprick pain to 26 blindfolded healthy volunteers on various parts of their body without any touch, in order to define our ability to identify where it hurts, known as "spatial acuity".
Sometimes only one laser would be activated, and sometimes both. The participants were asked whether they felt one sting or two, at varying distances between the two beams and researchers recorded the minimum distance between the beams at which people were able to accurately say whether it was one sting or two.
"This measure tells us how precisely people can locate the source of pain on different parts of their body," said senior author Dr Giandomenico Iannetti, of the UCL department of neuroscience, physiology and pharmacology. "Touch and pain are mediated by different sensory systems."