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 impact of emotion on respiratory-related evoked potentials

Emotion influences the perception of respiratory sensations, although the specific mechanism underlying this modulation is not yet clear. We examined the impact of viewing pleasant, neutral, and unpleasant affective pictures on the respiratory-related evoked potential (RREP) elicited by a short inspiratory occlusion in healthy volunteers. Reduced P3 amplitude of the RREP was found for respiratory probes presented when viewing pleasant or unpleasant series, when compared to those presented during the neutral series. Earlier RREP components, such as Nf, P1, N1, and P2, showed no modulation by emotion. The results suggest that emotion impacts the perception of respiratory sensations by reducing the attentional resources available for processing afferent respiratory sensory signals.

The impact of emotions on the perception of dyspnea in pediatric asthma

Inadequate symptom perception is increasingly recognized as a contributing factor in asthma morbidity. Recent research has shown that psychological factors can influence the perception of asthmatic symptoms such as dyspnea, but little is known, about the impact of emotions on the perception of dyspnea in pediatric asthma. Therefore, we examined the impact of viewing affective film clips of positive, neutral, and negative valence on perceived dyspnea during resistive load breathing in children with stable mild asthma. Perceived dyspnea decreased during the positive film compared to baseline and neutral film whereas the level of respiratory loading and respiratory resistance (R5) remained unchanged across conditions. The results underline the potential impact of psychological factors such as emotions on the perception of dyspnea in children with asthma.