Researchers Develop Method to Examine Body’s Pain Control System

When two painful stimuli act on us at the same time, we perceive one of them as less painful. This phenomenon is part of the body’s pain control system. A dysfunction of this inhibition is associated with chronic pain disorders. Researchers from the Berufsgenossenschaftliches Universitätsklinikum Bergmannsheil, clinic of the Ruhr-Universität Bochum (RUB), have developed a method for this. They were able to show that the method works effectively with both painful electrical stimuli and pain due to heat. Two consecutive studies on this subject have been published in the journals Brain science and BMC Neuroscience.

The same stimulus hurts differently

The human perception of pain can vary greatly depending on the situation. It is therefore possible that the same pain stimulus is more or less painful under different conditions. The body’s pain control system is responsible for this. Researchers are studying this system with the research method called Conditioned Pain Modulation, or CPM for short. “This records how much a painful stimulus inhibits the experience of another painful stimulus which is presented at the same time,” explains Assistant Professor Dr. Oliver Höffken, neurologist at Bergmannsheil.

In the first study, the research team compared an established CPM model with a recently introduced variant. With conditioned pain modulation, two pain stimuli always play a role. The first stimulus, also called the test stimulus, is given twice: once on its own and once in conjunction with the second stimulus, the conditioning stimulus. The test person should assess how painful the test stimulus was and how he felt during the delivery of the conditioning stimulus.

An objective criterion

In the current work, the team led by Oliver Höffken, Dr özüm özgül and Professor Elena Enax-Krumova compared two different test stimuli: a proven stimulus caused by pain due to heat and a new one triggered by stimulation. electric skin. In both cases, the conditioning stimulus was generated by cold water. Electrical stimulation of the skin has a decisive advantage over the thermal method previously used: it makes it possible to measure variations in brain activity triggered by electrical stimuli in the skin using EEG recording. This adds an objectively measurable criterion to the subjective assessment of the pain of those tested.

Two mechanisms with the same result

In the second study, the researchers used the previously tested CPM model with electrical stimulation of the skin and compared it to the analgesic effect of cognitive distraction. They found that CPM and cognitive distraction can reduce pain sensation to a similar degree. However, the two methods showed different results in measuring electrical potentials.

Based on our measurements, we assume that the two analgesic effects examined are two different neural mechanisms that simply lead to the same effect. “

Dr Oliver Höffken, Assistant Professor, Neurologist, Bergmannsheil

The researchers conducted their studies on healthy volunteers. However, research on the body’s pain inhibition system is also relevant in order to better understand various pain disorders. “In patients with chronic pain, the development of postoperative pain and the transition from acute pain to chronic pain, altered CPM effects have already been found in the past. In our research group, we therefore use the CPM model as an instrument to study the mechanisms in the processing of painful information ”, explains Höffken.