The power of touch to take away pain
Sitting by a sick person's bedside and stroking their hand is a natural impulse for most human beings, but a new study by researchers at the Sahlgrenska Academy in Sweden has proved that as well as creating a pleasurable sensation, stroking the skin can actually help relieve pain. The researchers carried out tests on a group of healthy people using a technique called microneurography. The tests showed that signals from stroking the skin have a direct route to the brain and can therefore help to relieve pain. The results are published in the journal Nature Neuroscience. 'Basically, the signals that tell the brain that we are being stroked have their own direct route to the brain, and are not blocked even if the brain is receiving pain impulses from the same area,' said Line Löken, postgraduate student in neurophysiology at the Sahlgrenska Academy. 'In fact,' he added, 'it's more the opposite - that the stroking impulses are able to deaden the pain impulses.' Each nerve fibre in the body is responsible for touch signals from approximately one square centimetre of skin. The researchers tested different areas of skin for nerve responses by using a specially designed robot which continually brushed the area of skin for which a particular nerve fibre is responsible. The subjects were asked to rate how pleasant the sensation felt. 'By inserting a thin electrode into a nerve in the forearm we can listen in on the nerve and pick up signals from one of the thousands of nerve fibres that make up a nerve,' explained Associate Professor Hakan Olausson, who is leading the research group behind the discovery together with fellow researcher Johan Wessberg. The specialised nerve fibres in the skin are called CT nerves (C-tactile). These travel directly to areas of the brain that are responsible for feelings and sensations. 'As the nerve signals that were sent in the CT nerves became more frequent, the subjects reported the experience as being increasingly pleasant,' Johan Wessberg explained. 'Of the skin nerves that we studied, it was only the CT nerves that had this strong link between the frequency of the signals and how pleasant it felt.' Until now, the role of the peripheral nervous system in pleasurable sensations has not received great attention from the scientific world. The research team believes that the results of the study are the first demonstration of a relationship between positive pleasurable stroking sensations and coding at the level of the peripheral afferent nerve.
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