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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: one experienced stimulus caused by heat pain 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,” Höffken explains.
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.
Original publication
Elena Enax-Krumova, Ann-Christin Plaga, Kimberly Schmidt, Özüm S. Ozgül, Lynn B. Eitner, Martin Tegenthoff and Oliver Höffken: Painful cutaneous electrical stimulation vs thermal pain as test stimuli in conditioned pain modulation, by: Brain science, 2020, DOI: 10.3390 / brainsci10100684
AT Lisa Do, Elena Enax-Krumova, Özüm Özgül, Lynn B. Eitner, Stefanie Heba, Martin Tegenthoff, Christoph Maier, Oliver Höffken: Distraction by a cognitive task has a higher impact on electrophysiological measurements than the modulation of pain conditioned, in: BMC Neuroscience, 2020, DOI: 10.21203 / rs.3.rs-26882 / v3
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