Pain perception can vary greatly. Sometimes, we feel pain more intensely than expected due to an injury or physical ailment, but we can feel less intense pain in other similar cases. This variability indicates that our perception of pain depends largely on our expectations and uncertainty.
Two hypotheses have been proposed to explain how the brain perceives pain. One is the estimation hypothesis, where the brain estimates the intensity of pain based on predictions. The other is the surprise hypothesis, where the brain perceives pain as the difference between prediction and reality, also known as the prediction error. In this study, the mechanism underlying pain perception was investigated. In the experiment, healthy participants received painful thermal stimuli and reported that they felt pain intensity while watching painful or non -painful visual stimuli in virtual reality. The researchers found that the participants strongly perceived the pain when the prediction error was great, which shows that the surprise hypothesis more adequately explains the mechanism of perception of pain in the brain. The study also confirmed that the pain was extended when unexpected events occurred.
People with chronic pain often experience vague fears and anxieties related to pain. Possibly, this uncertain gap between expectation and reality further increases the perceived intensity of pain. Therefore, reducing the gap between the expectation of pain and reality or “surprise” is important to reduce pain. A better understanding of the perception of pain would facilitate the development of new treatments that would improve the recovery of chronic pain and trauma.
This work was supported by JSPS Kakenhi (subsidy numbers 19H05729 and 23KJ0261).