Expectations underlie the effects of unpredictable pain: a behavioral and electroencephalogram study

Abstract

Previous studies on the potential effects of unpredictability on pain perception and its neural correlates yielded divergent results. This study examined whether this may be explained by differences in acquired expectations. We presented 41 healthy volunteers with laser heat stimuli of different intensities. The stimuli were preceded either by predictable low, medium, or high cues or by unpredictable low–medium, medium–high, or low–high cues. We recorded self-reports of pain intensity and unpleasantness and laser-evoked potentials (LEPs). Furthermore, we investigated whether dynamic expectations that evolved throughout the experiment based on past trials were better predictors of pain ratings than fixed (nonevolving) expectations. Our results replicate previous findings that unpredictable pain is higher than predictable pain for low-intensity stimuli but lower for high-intensity stimuli. Moreover, we observed higher ratings for the medium–high unpredictable condition than the medium–low unpredictable condition, in line with an effect of expectation. We found significant interactions (N1, N2) for the LEP components between intensity and unpredictability. However, the few significant differences in LEP peak amplitudes between cue conditions did not survive correction for multiple testing. In line with predictive coding perspectives, pain ratings were best predicted by dynamic expectations. Surprisingly, expectations of reduced precision (increased variance) were associated with lower pain ratings. Our findings provide strong evidence that (dynamic) expectations contribute to the opposing effects of unpredictability on pain perception; therefore, we highlight the importance of controlling for them in pain unpredictability manipulations. We also suggest to conceptualize pain expectations more often as dynamic constructs incorporating previous experiences.

The effect of unpredictability on the perception of breathlessness: a narrative review

“…For pain, another aversive bodily sensation, evidence has shown that unpredictability does not always directly enhance pain perception ( 62 – 64 ). Instead, several variables including pain expectations can partially explain the relationship between unpredictability and pain perception ( 62 – 64 ).…”

“…For pain, another aversive bodily sensation, evidence has shown that unpredictability does not always directly enhance pain perception ( 62 – 64 ). Instead, several variables including pain expectations can partially explain the relationship between unpredictability and pain perception ( 62 – 64 ). Such effects have not yet been systematically confirmed for breathlessness, although research has already repeatedly suggested comparable influences of expectations on breathlessness perception in both clinical and non-clinical samples ( 22 , 65 – 70 ).…”

“…However, effects of unpredictable intensities of breathlessness have not yet been investigated. According to research with other aversive bodily sensations such as pain ( 63 , 64 ), this type of manipulation of unpredictability is more likely to create differences in pain perception between the predictable and unpredictable conditions because of underlying differences in expected pain intensities. In the absence of clear differences in expectations, a recent meta-analysis revealed that unpredictability did not significantly influence pain perception, and that for all types of unpredictability (onset, duration, intensity, location) ( 72 ).…”