"This measure tells us how precisely people can locate the source of pain on different parts of their body," explains senior author Dr Giandomenico Iannetti of the UCL Department of Neuroscience, Physiology and Pharmacology. "Touch and pain are mediated by different sensory systems. While tactile acuity has been well studied, pain acuity has been largely ignored, beyond the common textbook assertion that pain has lower acuity than touch. We found the opposite: acuity for touch and pain are actually very similar. The main difference is in their gradients across the body. For example, pain acuity across the arm is much higher at the shoulder than at the wrist, whereas the opposite is true for touch."
Acuity for both touch and pain normally correlates with the density of the relevant nerve fibres in each part of the body. However, the fingertips remain highly sensitive despite having a low density of pain-sensing nerve cells.
"The high pain acuity of the fingertips is something of a mystery that requires further investigation," says Dr Mancini. "This may be because people regularly use their fingertips, and so the central nervous system may learn to process the information accurately."
The findings have important implications for the assessment of both acute and chronic pain. Dr Roman Cregg of the UCL Centre for Anaesthesia, who was not involved in the research, is a clinical expert who treats patients with chronic pain.
"Chronic pain affects around 10 million people in the UK each year according to the British Pain Society, but we still have no reliable, reproducible way to test patients' pain acuity," says Dr Cregg. "This method offers an exciting, non-invasive way to test the state of pain networks across the body. Chronic pain
|Contact: Harry Dayantis|
University College London