To me, this is one of the ultimate questions. I spend many an hour pondering the meaning of pain and of course the bottom line is that pain has a unique meaning to each and every one of us. There are a wide range of influences upon our thinking as to what the pain experience means including our belief system and the context of the injury.
In the early or acute stages of an injury or sensitisation, the pain indicates that there is something wrong in the body and that we need to consciously address the problem. This is a vital part of survival and the mechanism is magnificent. Pain yes, unpleasant yes, normal yes. The consequential meaning in many cases is that the tissues are injured or heading in that direction (a warning shot across the bow so to speak) and the pain signifies a healing process that itself is potent and incredibly efficient. These are wanted mechanisms and we can understand their use.
What about the persisting pain case? What is the meaning of a pain that feels like you have just injured your back for example, yet you know that in fact the tissue basis for the pain is poor? We know very well that pain is not an accurate indicator of tissue damage–one need only study phantom limb pain to understand that pain is emergent from the body or virtual body in the phantom case, but underpinned by neural networks in the brain that allocate pain to the said and ‘felt’ location.
The meaning that the individual generates, and only the individual can generate, will affect the pain perception. Salience is another word being used to describe the importance and significance of the pain experience as determined by a neuroimmune system. The two recent studies below highlight the effect of changing the meaning of pain and how this changes the experience of pain.
One of the first interventions must be to work with the patient’s understanding of their pain, condition and the influences upon their experience, e.g./ stress, fatigue, health. By listening to the patient’s narrative, making sense of the story and the pain by explaining the mechanisms reduces the threat value by changing the meaning. Or in fact, actually providing a meaning for the on-going pain by explaining the experience fully, describing the inter-related physical, cognitive and emotional dimensions.
Pain as a reward: changing the meaning of pain from negative to positive co-activates opioid and cannabinoid systems.
Benedetti F, Thoen W, Blanchard C, Vighetti S, Arduino C.
Department of Neuroscience, University of Turin Medical School, Turin, Italy. firstname.lastname@example.org
Pain is a negative emotional experience that is modulated by a variety of psychological factors through different inhibitory systems. For example, endogenous opioids and cannabinoids have been found to be involved in stress and placebo analgesia. Here we show that when the meaning of the pain experience is changed from negative to positive through verbal suggestions, the opioid and cannabinoid systems are co-activated and these, in turn, increase pain tolerance. We induced ischemic arm pain in healthy volunteers, who had to tolerate the pain as long as possible. One group was informed about the aversive nature of the task, as done in any pain study. Conversely, a second group was told that the ischemia would be beneficial to the muscles, thus emphasizing the usefulness of the pain endurance task. We found that in the second group pain tolerance was significantly higher compared to the first one, and that this effect was partially blocked by the opioid antagonist naltrexone alone and by the cannabinoid antagonist rimonabant alone. However, the combined administration of naltrexone and rimonabant antagonized the increased tolerance completely. Our results indicate that a positive approach to pain reduces the global pain experience through the co-activation of the opioid and cannabinoid systems. These findings may have a profound impact on clinical practice. For example, postoperative pain, which means healing, can be perceived as less unpleasant than cancer pain, which means death. Therefore, the behavioral and/or pharmacological manipulation of the meaning of pain can represent an effective approach to pain management.
The importance of context: when relative relief renders pain pleasant.
Leknes S, Berna C, Lee MC, Snyder GD, Biele G, Tracey I.
Centre for Functional Magnetic Resonance Imaging of the Brain, Nuffield Department of Clinical Neurosciences (Nuffield Division of Anaesthetics), University of Oxford, Oxford, UK. Siri.email@example.com
Context can influence the experience of any event. For instance, the thought that “it could be worse” can improve feelings towards a present misfortune. In this study we measured hedonic feelings, skin conductance, and brain activation patterns in 16 healthy volunteers who experienced moderate pain in two different contexts. In the “relative relief context,” moderate pain represented the best outcome, since the alternative outcome was intense pain. However, in the control context, moderate pain represented the worst outcome and elicited negative hedonic feelings. The context manipulation resulted in a “hedonic flip,” such that moderate pain elicited positive hedonics in the relative relief context. Somewhat surprisingly, moderate pain was even rated as pleasant in this context, despite being reported as painful in the control context. This “hedonic flip” was corroborated by physiological and functional neuroimaging data. When moderate pain was perceived as pleasant, skin conductance and activity in insula and dorsal anterior cingulate were significantly attenuated relative to the control moderate stimulus. “Pleasant pain” also increased activity in reward and valuation circuitry, including the medial orbitofrontal and ventromedial prefrontal cortices. Furthermore, the change in outcome hedonics correlated with activity in the periacqueductal grey (PAG) of the descending pain modulatory system (DPMS). The context manipulation also significantly increased functional connectivity between reward circuitry and the PAG, consistent with a functional change of the DPMS due to the altered motivational state. The findings of this study point to a role for brainstem and reward circuitry in a context-induced “hedonic flip” of pain.
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