When people expect to feel intense pain, they do—even if the stimuli isn’t so painful, according to brain imaging research.
These false perceptions of pain can persist even when reality demonstrates otherwise. It may have an impact on a person’s recovery from painful conditions and can explain why, for some, chronic pain lingers for a long while after healing has taken place, note researchers, in a media release from the University of Colorado at Boulder.
“We discovered that there is a positive feedback loop between expectation and pain,” says senior author Tor Wager, a professor of psychology and neuroscience at the University of Colorado Boulder. “The more pain you expect, the stronger your brain responds to the pain. The stronger your brain responds to the pain, the more you expect.”
The study, published recently in Nature Human Behaviour, aims to directly model the dynamics of the feedback loop between expectations and pain and the neural mechanisms underlying it, according to the release.
“We wanted to get a better understanding of why pain expectations are so resistant to change,” says lead author Marieke Jepma, who launched the study when she was a postdoctoral researcher in Wager’s lab. She is now a researcher at the University of Amsterdam.
In the study, the release explains, the researchers recruited 34 subjects and taught them to associate one symbol with low heat and another with high, painful heat.
Then, the subjects were placed in a functional magnetic resonance imaging (fMRI) machine, which measures blood flow in the brain as a proxy for neural activity. For 60 minutes, subjects were shown low or high pain cues (the symbols, the words Low or High, or the letters L and W), then asked to rate how much pain they expected.
Then varying degrees of painful but non-damaging heat were applied to their forearm or leg, with the hottest reaching “about what it feels like to hold a hot cup of coffee” Wager explains.
The participants were then asked to rate their pain. Unbeknownst to them, heat intensity was not actually related to the preceding cue.
The study found that when subjects expected more heat, brain regions involved in threat and fear were more activated as they waited. Regions involved in the generation of pain were more active when they received the stimulus. Participants reported more pain with high-pain cues, regardless of how much heat they actually got.
“This suggests that expectations had a rather deep effect, influencing how the brain processes pain,” Jepma adds, the release continues.
Surprisingly, their expectations also highly influenced their ability to learn from experience. Many subjects demonstrated high “confirmation bias”—the tendency to learn from things that reinforce our beliefs and discount those that don’t. For instance, if they expected high pain and got it, they might expect even more pain the next time. But if they expected high pain and didn’t get it, nothing changed.
“You would assume that if you expected high pain and got very little you would know better the next time. But interestingly, they failed to learn,” Wager says.
This phenomenon could have tangible impacts on recovery from painful conditions, Jepma suggests.
“Our results suggest that negative expectations about pain or treatment outcomes may in some situations interfere with optimal recovery, both by enhancing perceived pain and by preventing people from noticing that they are getting better,” Jepma says. “Positive expectations, on the other hand, could have the opposite effects.”
The research also may shed light on why, for some, chronic pain can linger long after damaged tissues have healed.
Whether in the context of pain or mental health, the authors suggest that it may do us good to be aware of our inherent eagerness to confirm our expectations.
“Just realizing that things may not be as bad as you think may help you to revise your expectation and, in doing so, alter your experience,” Jepma concludes.
[Source(s): University of Colorado at Boulder, Science Daily]